Next Article in Journal
The Pivotal Role of Quantum Dots-Based Biomarkers Integrated with Ultra-Sensitive Probes for Multiplex Detection of Human Viral Infections
Next Article in Special Issue
Therapeutic Effect of Benidipine on Medication-Related Osteonecrosis of the Jaw
Previous Article in Journal
Dexamethasone Increases the Anesthetic Success in Patients with Symptomatic Irreversible Pulpitis: A Meta-Analysis
Previous Article in Special Issue
Development of Astaxanthin-Loaded Nanosized Liposomal Formulation to Improve Bone Health
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:

Bone Tissue Engineering in the Treatment of Bone Defects

Jiangsu Provincial Engineering Research Center of Traditional Chinese Medicine External Medication Development and Application, Nanjing University of Chinese Medicine, Nanjing 210023, China
Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, National and Local Collaborative Engineering Center of Chinese Medicinal Resources Industrialization and Formulae Innovative Medicine, Jiangsu Key Laboratory for High Technology Research of TCM Formulae, Nanjing University of Chinese Medicine, Nanjing 210023, China
Burns Injury and Reconstructive Surgery Research, ANZAC Research Institute, University of Sydney, Concord Repatriation General Hospital, Concord 2137, Australia
Authors to whom correspondence should be addressed.
Pharmaceuticals 2022, 15(7), 879;
Submission received: 21 June 2022 / Revised: 12 July 2022 / Accepted: 15 July 2022 / Published: 17 July 2022
(This article belongs to the Special Issue Development of Bone Targeted Drug Delivery Technologies)


Bones play an important role in maintaining exercise and protecting organs. Bone defect, as a common orthopedic disease in clinics, can cause tremendous damage with long treatment cycles. Therefore, the treatment of bone defect remains as one of the main challenges in clinical practice. Today, with increased incidence of bone disease in the aging population, demand for bone repair material is high. At present, the method of clinical treatment for bone defects including non-invasive therapy and invasive therapy. Surgical treatment is the most effective way to treat bone defects, such as using bone grafts, Masquelet technique, Ilizarov technique etc. In recent years, the rapid development of tissue engineering technology provides a new treatment strategy for bone repair. This review paper introduces the current situation and challenges of clinical treatment of bone defect repair in detail. The advantages and disadvantages of bone tissue engineering scaffolds are comprehensively discussed from the aspect of material, preparation technology, and function of bone tissue engineering scaffolds. This paper also summarizes the 3D printing technology based on computer technology, aiming at designing personalized artificial scaffolds that can accurately fit bone defects.

Graphical Abstract

1. Introduction

Hard bone constitutes approximately 15% of the total body weight and is known to be the largest organ system in the human body [1]. Bone tissue has a double-layered structure: The outer layer is cortical bone, which accounts for approximately 80% of the total adult bone mass and has a relatively dense porosity of 3–5%. It has high resistance to bending and torsion, and it is essential for physical support, structural integrity, and weight bearing. The cancellous bone formed by the inner layer of honeycomb-shaped trabecular connection accounts for about 20% of the total bone mass in adults with a high porosity of approximately 80–90% [2]. As an internal supporting system, the bone forms the skeleton of a human body and also plays an important role in maintaining motor function, hematopoietic function, and protecting the internal organs and nervous system [3].
Bone can regulate the metabolic requirements through calciotropic hormones (vitamin D3, parathyroid hormone, and calcitonin). In addition, better bone quality can improve the structure strength to better prevent fracture damage [4]. Contrary to societal misconceptions, bone tissue responds positively to high rates or frequency of stimulation [5]. A study found that regular walking did not significantly preserve the mineral density of the spinal bone in postmenopausal women [6]. In contrast, Watson et al. demonstrated that high-intensity impact training can preserve bone mass in postmenopausal women than low-intensity training [7]. Therefore, available data strongly suggest that exercise characterized by impact load is able to promote and maintain a person’s bone health throughout life.
Bone regeneration is the process of re-forming bone tissue with essential shape and function post partial bone tissue loss [8]. Such defects are caused by trauma, infection, tumor, or functional atrophy, and it is known as one of the most common injuries in clinical practice. Bone tissue can be self-repaired and regenerated, therefore, small defects normally heal without additional treatment [9]. However, when bone defect exceeds the critical size threshold (approximately > 2 cm) or greater than 50% loss of circumference of bone [10], it will cause nonunion, malunion, or pathological fracture [11]. According to the latest data, bone transplantation is second to blood transfusion in the world, and it is the second most common tissue transplantation [12]. Globally, 4 million people require bone transplantation or bone replacement surgery each year, while in the United States, the number of age-related bone disorders is expected to increase from 2.1 million in 2005 to 3 million in 2025 [13]. In Europe, the fracture cases raised about 28% from 2010 to 2025, with increased population [14]. Therefore, effective treatment and therapeutical of bone diseases has great clinical significance.
In this review, we overviewed bone tissue engineering scaffolds, including the current clinical treatment status, challenges, and future prospects. Moreover, advantages and disadvantages of various functional materials including organic materials, inorganic materials, and biological composite materials in bone tissue engineering were discussed, and the developmental direction of bone tissue engineering scaffolds was prospected.

2. Advances and Challenges of Bone Defect Treatment

2.1. Clinical Treatment

Clinical treatment of bone defects includes non-invasive and invasive therapies. Non-invasive therapeutical methods mainly refer to biophysical stimulation, pulsed electromagnetic field (PEMF), etc. Clinically used exogenous stimulation therapy, including electromagnetic field therapy, low-intensity ultrasound therapy, and hyperthermia can stimulate bone tissue re-growth with faster bone repair and minimal pain. Surgical treatment is the most commonly used method for reconstructing bone defects, and the most important treatment method includes bone graft, which refers to the graft from the common site to the recipient site, accounting for about a quarter of the surgical treatment of bone defects. Prosthetic surgery can be used to reconstruct or improve the process of defective, damaged, or lost structures. In addition, surgical treatment methods for bone defect repair include: Ilizarov technique, Masquelet technique, Arthroplasty, replacement, etc. (Figure 1).

2.1.1. Bone Grafting

Bone grafting is widely used in clinical practice. It can be sub-grouped to autologous bone grafting and allogeneic bone grafting. Autologous bone has dual effects of osteo-induction and osteo-conduction, and it is the “gold standard” for bone repair with proved osteogenesis [15]. However, because of a lack of donor tissue together with additional secondary defects, it is not appropriate for children or elderly patients. Allogeneic and xenografting bone grafting are limited in use due to their insufficient integration and vascularization in the host area and potential risks of immune rejection and pathogen transmission. Cryogenic treatment can reduce the occurrence of immune rejection, but its mechanical strength and bone-induced activity is known to be correspondingly reduced.

2.1.2. Ilizarov Technique

Ilizarov technique was proposed and named after a former soviet doctor in 1951 [16]. The core biomechanical theory of this technique is the “law of tension stress” (LTS), which states that continuous slow traction stimulation can promote tissue regeneration and active growth of biological tissue similar to embryonic tissue [17]. This rule is referred to as distraction osteogenesis (DO) in orthopedics, which Dr. Ilizarov first described in a canine model. Despite advantages of Ilizarov technology, it is undeniable that the technology also has disadvantages, such as complex operations and extremely long treatment and recovery [18]. In comparison with traditional methods, Ilizarov technique shows better outcomes in the treatment of fracture complicated with infection and large bone defects [19].

2.1.3. Masquelet Technique

Membrane induction regeneration technique (Masquelet technique) is effective for the treatment of bone defects. Masquelet technique has two steps: Firstly, bone cement is filled in the defect area, aiming to induce the formation of local pseudoperiostium. Thereafter, cement filler is removed and replaced with autologous or allogeneic cancellous bone [20]. This technique can restore functional activity of bone tissue in a short time. However, due to the high cost, secondary surgery, and the limitation of bone graft volume, it cannot meet all requirements for large-segment bone defects.

2.1.4. Bone Graft Substitutes

Bone graft substitutes can be made from synthetic or natural biomaterials. Various biomaterials are currently under developed or studied as bone graft scaffolds, including collagen, hydroxyapatite (HA), β-tricalcium phosphate (β-TCP), calcium phosphate cement, and ceramic glass. At present, the reconstruction of large bone defects is the goal in clinical practice, while titanium alloy is commonly used. Titanium is non-toxic, harmless, and has good corrosion resistance, and its elastic modulus is closer to human hard tissue. However, the surface of titanium alloy is relatively smooth resulting in poor osseointegration performance [21]. The introduction of 3D-printed titanium alloy can solve this problem via precisely controlled construction that mimics natural bone tissue at both macro and micro levels. Porous titanium alloy structure is also utilized to promote the adhesion of osteoblasts, providing enough space for the growth of bone tissue and promoting the growth of new bone tissue into the gap [22].

2.2. Challenges of Bone Defect Treatment

2.2.1. Angiogenesis and Vascularization

The integrity of bone, as a highly vascularized tissue, relies on angiogenesis and the tight connection of bone cells in time and space. Therefore, sufficient angiogenesis plays a key role in bone development and repair [23]. Local vascularization in the early stages post grafting provides various essential nutrients for osteogenesis activity, but also plays an indispensable role between bone and adjacent tissues and organs [24]. In adults, the vascular endothelium is usually in a state of silence due to cell-to-cell contact and inhibition of cell proliferation. Only under certain stimulation, endothelial cells can be triggered for angiogenesis, such as: hypoxia environment, cell morphological changes, and changes in the sensitivity of angiogenic factors [25]. At present, common tissue engineering scaffolds are still greatly restricted in terms of material transfer exchange and neovascularization [25,26]. Findings showed that angiogenesis is mainly concentrated around the surface of scaffolds, leading to low nutrients and oxygen transfer to the internal area of the scaffold. Such insufficient oxygen supply can result in death of cells and necrotic-tissue due to hypoxia, hindering the growth of host bone cells, and cavitation or necrosis inside the scaffold [27].

2.2.2. Osteoinduction and Osteoconduction

Bone induction refers to the process of stem cell differentiation into osteoblast cell lines under stimulation via the microenvironment. Bone induction process directly determines the success or failure of the bone regeneration process. Bone scaffolds can promote stem cell-directed differentiation by producing differentiation-inducing substances in the microenvironment, mainly ions and scaffolds. The ions that are precipitated from the scaffold material itself [28], and the scaffold as a delivery carrier, transporting growth factors or drugs, can induce stem cell differentiation. Bone morphogenetic proteins and vascular endothelial growth factor have also been found to promote bone induction in scaffolds [29,30].
Osteoconduction is the frame structure required for the growth of bone cells, and it provides a track for integration and migration of bone tissue. Bone tissue, capillaries, and surrounding tissue can gradually grow into the pores and form new bone tissue. Osteo-conduction is highly dependent on tissue interaction with biomaterials. This process involves cellular behaviors such as cell adhesion, attachment, proliferation, and migration. Scaffolds properties in terms of physicochemical strength and structural characteristics effect the osteoconductivity of the scaffolds.

2.2.3. Osseointegration

The concept of bone integration was proposed by Brånemark, indicating direct connection of the non-fibrous connective tissue interface layer between implanted scaffold materials and the bone tissue [31]. Osteoblasts are allowed to form clusters on the surface of implants with an extracellular matrix, initiating the formation of new bone. Due to bone conversion and repair process, osteogenesis occurs at all stages of life. Thus, osseointegration can be described as the final step in the healing process of bone surrounding the implant. To promote osseointegration, modification of prosthesis materials surface via sand spraying, acid etching, laser treatment [32,33], together with alteration of bone metabolism around the prosthesis, can be both utilized.

3. Tissue Engineering Technologies in Bone Regeneration and Repair

The concept of “tissue engineering” was firstly introduced in 1996, while bone tissue engineering has become the most rapidly developed research field in tissue engineering [34]. Bone tissue engineering uses scaffolds, well-integrated cells, and bioactive growth factors to promote bone repair and regeneration, providing an innovative platform for regenerative medicine. The hydrophilicity, hydrophobicity, and biochemical structure of scaffold can affect cell adhesion, arginine–glycine–aspartate (RGD), and varying biological domains on scaffold surface are known to improve cell adhesion [35]. In addition, literature on different biomaterials and cell sources indicates a wide range of average pore sizes from 20 to 1500 µm for optimal cell attachment and successful bone regeneration [36,37,38]. Other studies have shown that pores ≥ 300 µm are critical for inducing direct osteogenesis and allow higher cell infiltration, migration, capillaries, and bone ingrowth [38,39,40]. The pore size and porosity of the scaffold determines total surface area in supporting tissue regeneration, but if the pore size is below 100 µm, cell migration and nutrient diffusion will be limited, resulting in a dead cavity in the internal area of the scaffolds [41]. In contrast, when pore size is over 750 µm, the specific surface area of the scaffold will decrease, and the mechanical properties of the scaffold will be reduced [42].

3.1. Biomaterials in Bone Tissue Engineering

Biomaterial is one of three key elements in bone tissue engineering, and it forms the skeleton for tissue regeneration. Biomaterials in bone regeneration can be sub-characterized into inorganic materials, organic materials, and composite materials.

3.1.1. Inorganic Materials

Inorganic materials include medical metal materials and non-metal materials, which are characterized by high mechanical strength and are not easily deformed and degraded. Some require secondary surgery to remove.
Metal materials are ideal for bone repair in terms of load-bearing bone defects due to their remarkable mechanical properties. Metal-based biomaterials include titanium-based alloys, tantalum-based alloys, cobalt-based alloys, and magnesium-based alloys. Currently, titanium and its alloys are widely accepted in clinical application. The titanium-based alloys used in clinics are represented by pure Ti and titanium alloy Ti6Al4V [43]. Pure Ti has sufficient corrosion resistance in a physiological environment, but its poor strength and resistance limit its further clinical utilization. Compared with pure Ti, Ti6Al4V has optimal mechanical strength, flexibility, and fatigue resistance. Compared with various other metal materials, the elastic modulus of titanium-based alloy is highly relative to native bone, which is appropriate for applications in the field of orthopedics [44]. However, titanium lacks the ability to resist corrosion and bind to bone, so it is often required to add surface coatings to enhance its biological activity and corrosion resistance, including bio-adhesive coatings and composite coatings [21,45].
In 1940, Werman invested pure tantalum in the field of orthopedics as the pioneered biological material after titanium [46]. Pure tantalum was reported with no adverse reactions as a human implant. However, as its elastic modulus differs greatly compared to the host bone tissue, poor osseointegration is a result. Thereafter, porous tantalum was developed, and results showed outstanding capability to promote bone fusion and favorable orthopaedic capability [47,48,49,50]. Porous tantalum has an interconnected structure, and its particular porous architecture greatly contribute to its comparable elastic modulus to human cancellous bone and cortical bone. Porous tantalum is suitable for bone and joint replacement. Compared with titanium alloys, porous tantalum can promote cell adhesion and proliferation of bone marrow mesenchymal stem cells (BMSCs) and regulate the expression of osteogenic genes such as alkaline phosphatase (ALP), type I collagen, osteonectin and osteocalcin via activation of MAPK/ERK signaling pathway, and BMSCs osteogenic differentiation in vitro [51].
Both magnesium-based alloys and zinc-based alloys are biodegradable bone repair materials [52]. Magnesium is an essential element in the human body that is involved in cell metabolism [53]. Magnesium alloys have been extensively studied in repairing bone defects, attributing to their favorable degradability, plasticity, and mechanical strength, and it can avoid secondary surgery post implantation [54]. In a previous study, Mg2+ scaffold and hydroxyapatite scaffold were implanted into rabbit femur, respectively. Findings showed that both scaffolds had ideal biocompatibility [55]. The degree of degradation is rapid, and the ingrowth of new bone is obviously promoted, suggesting magnesium is a promising candidate for the treatment of bone defects.
In the group of medical metal materials, other types of materials are stainless steel, titanium, titanium alloys, and cobalt-based alloys. At present, many issue are presenting prior to clinical application. Difficulty in tissue integration was a major concern because the composition of metal materials varies from the composition of human tissue. In addition, most metal materials have an extremely low degradation rate, which requests additional operation for removal. Over the past 20 years, the modification of current medical metal materials with more stiffness, corrosion resistance, and biocompatibility was the goal in the research field of biodegradable metal and biological functionalization metal [56]. Using surface bioactive coating, drug coating and other related surface modification technologies was also found to further develop metal medical treatment appliance products.
Bioceramic has been studied in bone research based on their favorable biocompatibility, biodegradability, osteo-conductivity, and osteo-induction [57]. In bone tissue engineering research, bioceramics include hydroxyapatite (HA), β-tricalcium phosphate (β-TCP), biphasic calcium phosphate (BCP), bioglass, etc. Blank bioceramic powder cannot be directly used in repairing bone defects due to fast degradation and loss. Therefore, various porous three-dimensional tissue engineering scaffolds were prepared and proved to have sufficient mechanical support, nutrient exchange, and induction of tissue ingrown, suggesting bioceramics in treating large-size bone defects [58].
The doping of metal ions or bioactive ions opens a new avenue for the utilization of bioceramics. Human bone morphogenetic protein-2 (BMP-2)-coated bioceramic scaffolds promotes osteo-induction and bone remodeling. A calcium silicate/calcium phosphate scaffold was developed with macropores and micropores and loaded BMP-2 [59]. In this study, authors found that the microporous scaffold retained the secondary structure and biological activity of RhBMP-2, and the local release of BMP-2 promoted the formation of new bone. Another study used biphasic calcium phosphate combined with BMP2-precipitated layer-by-layer assembled biomimetic calcium phosphate particles (bone morphogenetic protein-2 coprecipitated biomimetic calcium phosphate particles, BMP2-cop-BioCaP) for repairing rat calvarial defects [60]; BMP2-cop-BioCaP in improving bone formation was comparable to the most often used osteoinducer in clinical practice—autologous bone.

3.1.2. Natural Biomaterials

Natural biomaterials, including collagen, chitosan, sodium alginate silk fibroin, and hyaluronic acid can simulate natural bone extracellular matrix, followed by biodegradation into carbon dioxide and water in vivo. Natural biomaterial is widely used in the preparation of bone tissue engineering scaffolds based on its convenient material acquisition, good plasticity, and good biocompatibility.
Collagen is the major component in skin, bone, tendon, and ligament, and has high swelling rate and low antigenicity, which is ideal natural material in bone tissue engineering. However, its poor mechanical properties limit its direct use as a substitute for bone, therefore, composite scaffolds of collagen together with high physical strength has received attention [61]. Chitosan is a natural cationic carbohydrate material that is partially deacetylated from chitin. It is a non-antigenic, non-toxic, biodegradable material with certain biological functions. However, as chitosan is insoluble in water, has fast biodegradation in vivo, and has poor compatibility with blood, its potential for bone regeneration is limited. Researchers realized the function of chitosan structure by compounding chitosan with various other materials, such as HA [62]. Such a combination solves the limitation of its application in bone defect repair. Fibrin is the major component of the extracellular matrix, and it has been proved to mediate intercellular signal transduction and interaction [63]. A 3D fibrin/sodium alginate scaffold was successfully constructed on a titanium plate and the finding showed that such modification is capable of improving cell adhesion, proliferation, and subsequent differentiation of human mesenchymal stem cells into osteoblasts [64]. At present, most of the studies on the preparation of fibrin in bone tissue engineering scaffolds have failed in pre-clinical test via small and large animal models.
Deproteinized bovine mineral matrix (Bio-Oss) is naturally deproteinized from the mineral fraction of bovine cancellous and cortical bone, which retains fine trabecular structure and internal pores, providing favorable conditions for osteoblast ingrowth and angiogenesis [65,66]. Bio-Oss bone contains more carbonate to facilitate autologous osseointegration to achieve the required mechanical strength and stiffness [67]. Clinically, Bio-Oss bone powder is mixed with normal saline or the patient’s own blood to form a paste on the bone defect, and it can be precisely sized with easy operational purpose. However, few studies demonstrated that Bio-Oss materials are difficult to be absorbed over time [68], while it needs to be mixed with normal saline or venous blood for use. Over bleeding with the flow dispersion of Bio-Oss can increase surgical difficulties, resulting in severe loss of bone meal over the bone grafting process and osteogenesis [69].
Autologous tooth graft material (AutoBT) and autologous dentin particles can be prepared via extracting unretained teeth from host patient, followed by implantation into the patient’s bone defect as a graft. Due to its favorable biocompatibility, osteoconductivity and osteoinductive effects, and no immune rejection, it is expected to have a promising clinical outcome compared to many other commercial products [70]. However, the mechanism of how dentin induced osteogenesis is unclear, while preparation processing is cumbersome and time-consuming, which may limit its wide application in clinical practice [71].

3.1.3. Synthetic Polymer

Synthetic polymer materials are widely studied for bone regeneration, including commonly used polylactic acid (PLA), polyglycolic acid (PGA) and polylactic acid-glycolic acid copolymer (PLGA). Polymethyl methacrylate (PMMA) bone cement was the bone cement utilized in clinical practice, due to its fast-setting speed and better mechanical strength. However, it is known to cause mild damage to bone surrounding tissue, and its monomer has proven biological toxicity [72,73,74,75]. Additionally, the low biodegradation rate of PMMA in the defect area can negatively affect the growth of new bone, resulting in being non-conducive to the regeneration and repair of bone defect in the future clinical use [73].
In recent years, due to the rapid development of polymer materials, polyetherketone ketone (PEEK), as a new biocompatible high-performance polymer, has been approved by FDA as an implant device and gradually applied in the biomedical field. Within the elastic modulus of 4.5 GPa, PEEK is closer to that of human bone, which can meet the normal physiological needs of the human body [76]. PEEK is an organic thermoplastic polymer with good biocompatibility, heat resistance, corrosion resistance, etc. leading to “the most promising material in the 21st century”. Few organic synthetic polymer materials, such as: polymethyl methacrylate, polyurethane, polylactide, polyglycolide, polycaprolactone, etc., are remaining as the research hotspots of bone tissue engineering scaffolds, but these materials are not widely used in biological applications. Degradability, biocompatibility, and other aspects cannot meet the requirements of an ideal scaffold, so the research on the modification of materials is particularly important [77].
Over 20 new bone graft substitutes have been used to treat different types of bone defects in the last decade (Table 1). Most bone graft substitutes are hydroxyapatite and deproteinized mineral matrix materials.

3.2. Cells and Stem Cells in Bone Repair

In the field of tissue engineering and regenerative medicine, stem cells that can be isolated from tissues such as bone marrow or adipose tissue [103] have been used for the treatment of bone defects for years.
Bone marrow mesenchymal stem cells (BMSCs) are a heterogeneous population of cells obtained from the bone marrow stromal fraction [104]. They have high self-proliferation and multi-directional differentiation potential, which are recognized as favorable cell types in bone tissue engineering [105,106,107]. In in-vitro studies, BMSCs can rapidly amplify and differentiate into various mesodermal lineages, such as adipocyte, chondrocytes, and osteocytes, greatly contributing to the regeneration of osteochondral tendon, fat, and muscle [108,109]. In 2001, three patients having large bone defects were successfully treated as BMSCs for the first clinical trial [110]. However, a relatively low abundance of BMSCs in vitro expansion reduced post-translational survival and immunomodulatory BMSCs, which are regulatory and logical challenges [111]. In addition, the age of donors is a key factor for cell survival and differentiation that should be considered in both basic and clinical evaluations [112].
Adipose-derived stem cells (ADSCs) are a population of stromal cells that can be isolated from adipose tissue, with comparable morphology and phenotype to BMSCs. ADSCs extraction is easy, and cell proliferation is not affected by patient’s age with multi-functional differentiation. ADSCs are capable to differentiate into osteoblasts, chondrocytes, and adipocytes [113,114,115]. Post being implanted into the body, adipose-derived mesenchymal stem cells can adapt to the physiological, pathological, stress, and other microenvironments of the local area and maintain osteogenic activity [116]. In a study, a 7-year-old pediatric patient having post-traumatic calvarial defects was successfully treated with autologous ADSCs, fibrin glue, and biodegradable scaffold. Postoperative new bone formation as well as relatively complete calvarial continuity was formed based on computed tomography analysis [117,118].
With the continuing development of bone tissue engineering, researchers are seeking for other potential seed cells to repair bone defects. At present, many seed cells with osteogenic activity are still in experimental stage, such as embryonic stem cells (ESCs) [119], periosteum-derived cells (PDCs) [120], dental pulp stem cells (DPSCs) [121], human amniotic mesenchymal stem cells (HAMSCs), etc. Moreover, aiming to achieve the best repair outcomes, researchers are also working on the combination of varying stem cells. HAMSCs and HBMSCs were used together, of which having osteogenic ability but different advantages [122]. Results of co-culture showed that the mineralized nodules formed in the co-culture system were more significant compared to that in single culture, while all osteogenic markers were also significantly up regulated [122].

3.3. Active Factors of Bone Tissue Engineering

Growth factors play an auxiliary role in bone tissue engineering. Nowadays, viral or non-viral vectors are widely used to deliver growth factors and promote osteogenesis with accelerated vascularization in the defect areas [123]. Growth factors used for bone defect repair include bone morphogenetic protein-2 (BMP-2), fibroblast growth factor-2 (FGF-2), and vascular endothelial growth factor (vascular endothelial growth factor, VEGF) etc. BMP-2 is a member from the transforming growth factor-β protein family, responding for osteogenesis in vivo. BMP-2 simultaneously promotes bone regeneration and stimulates angiogenesis in the defect area, while it is approved by FDA as osteoinductive growth factor in clinical practice. FGF-2, also known as basic fibroblast growth factor, is a canonical FGF that belongs to the FGF-1 subfamily [124]. FGF is involved in osteoblasts proliferation and differentiation [125], angiogenesis, and in signal transduction within the cell membrane of bone progenitor [126]. However, concentrations of FGF can alter its effects: A high dose of FGF was found to inhibit bone formation while a low dose increase bone formation [127,128]. VEGF promotes angiogenesis and can also regulate the osteogenic process. Osteoblast-derived VEGF can stimulate cell differentiation of mesenchymal stem cells into osteoblasts and inhibit its differentiation into adipocytes, as a key role maintaining bone homeostasis [129].
In bone tissue engineering, researchers attempt to combine two or multiple materials, aiming for multi-functions and overcoming disadvantages of a single material. Scientists use bionics to improve the biological properties via loading bioactive factors, as well as incorporating varying materials to develop composites with more gradient and a controllable degradation rate. For example, a biocompatible and resorbable scaffold is produced with minimal tissue rejection and better bone tissue growth [130]. Naudot et al. [131] prepared honeycomb polycaprolactone (PCL)-nano-hydroxyapatite (nHA) composite scaffold via 3D electrospinning and printing technology. The combination of BMSCs with such scaffold was found to significantly improve bone regeneration and bone mineralization in a rat calvarial defect model [131]. Moreover, mixed polymethyl methacrylate together with nano-scale tricalcium phosphate and hydroxyethyl methacrylate in different proportions was investigated to produce novel porous tricalcium phosphate/hydroxyethyl methacrylate/polymethyl methacrylate [132]. It is pre-clinically proved to be a new bone substitute prior to clinical tests.
Silk fibroin/chitosan/nanohydroxyapatite (SF/CS/nHA) 3D scaffolds combined with bone marrow stromal cells were used to repair the rabbit radius defect model [133]. In comparison with blank SF/CS/nHA scaffolds, BMSCs-loaded SF/CS/nHA scaffolds had a better stiffness on the repair of radial bone defect [133]. Adipose-derived mesenchymal stem cells on 3D-printed titanium scaffolds showed significantly faster cell proliferation and osteogenicity [134]. BMP-2 combined with a scaffold is an effective method to promote osteoinduction and bone remodeling. Zhang et al. [59] developed a calcium silicate/calcium phosphate scaffold with macropores and micropores, loaded with human bone morphogenetic protein-2, which could maintain its structural integrity and biological activity, as well as controlled release. In addition, local delivery of BMP-2 loaded with microporous calcium phosphate can further accelerate osteoclast resorption and promote new bone formation [135]. BMP-2-loaded PLGA nanoparticles coating on the surface of HA scaffolds were found to be uniformly distributed on the surface of the scaffold, with sustained release of BMP-2 over 30 days. Additionally, PCL-BMP-2/PLGA nanoparticles can improve cell proliferation, adhesion, and osteogenic differentiation both in vitro and in vivo [136].

3.4. Preparation of Bone Tissue Scaffolds

In bone tissue engineering, novel approaches in terms of scaffold preparation methods are widely investigated. Hydroxyapatite/chitosan (SrHAP/CS) nanocomposite scaffolds with different concentrations of strontium were reported to be prepared by freeze-drying method [137]. Results showed that the different composites had good cytocompatibility and promoted cell adhesion, integration, and proliferation of hBMSCs. Delivery of Sr2+ can significantly enhance cell proliferation and osteogenic differentiation. In addition, due to the synergistic effect of Ca2+ and Sr2+, a high-concentration Sr-loaded scaffold was found to be optimal in osteogenic induction. Nano-hydroxyapatite/chitosan scaffolds loaded with slow-release microspheres of Mutong saponin D were also reported to be prepared by freeze-drying. Findings also demonstrated that scaffolds improve cell adhesion, proliferation, and osteogenic differentiation of osteoblasts [138]. Recently, a co-culture of rabbit adipose-derived mesenchymal stem cells (ADSCs) together with double-cell sheet DCS complexes was carried out. DCS-PLL-CHA, a coral hydroxyapatite (CHA) composite scaffold modified with DCS and polylysine (PLL), was prepared by soaking and vacuum freeze drying. Results show that PLL can effectively promote the proliferation and differentiation of ADSCs, and DCS-PLL-CHA vascularized tissue engineered bone has the potential to promote bone regeneration and bone remodeling, which can be used to repair large bone defects [139].
Thermally induced phase separation is a method to prepare polymeric nanofibrous materials that resemble natural extracellular matrices. The first step is to mix a polymer with a liquid or solid diluent of high boiling point and low molecular mass to form a homogeneous solution at high temperature, followed by casting a mixture solution into the desired shape, while lowering the temperature enables solution phase-separation. These solvents were extracted to remove the diluent and finally freeze-dried to obtain the pore structure. Macroporous nanofiber scaffolds-polylactic acid-glycolic acid copolymer microspheres/nanofibers (BMP-2@MS/NF) loaded with human bone morphogenetic protein 2 using cloud point thermally induced phase-separation method was recently reported [140]. Studies have shown that the composite scaffold can enhance the adhesion and proliferation of mouse primary osteoblasts and promote the repair of rat calvarial defects. PLLA/1,4-dioxane/H2O ternary system was used to prepare macroporous PLLA scaffolds, via treating with acetone and immersed in chitosan solution for modification [141].
Electrospinning technology is a direct and continuous method for preparing polymer nanofibers [142]. Due to its simple production process, scaffold materials with nanoscale fibers can be synthesized, and the morphology of the fiber surface can be adjusted by changing the conditions of electrospinning. Electrospun PCL scaffolds have been widely investigate based on their great potential in mimicking the structure of a native extracellular matrix (ECM). However, relatively small pore size and low bioactivity of the scaffolds limit tissue regeneration. PCL (polycaprolactone), PCL/PEG (polyethylene glycol), and PCL/PEG/ATP (nano-attapulgite) scaffolds were produced by electrospinning, and water-soluble PEG fibers were removed by washing to increase scaffold pores rate [143]. This study was the first to show that scaffolds after PEG removal had better cell infiltration compared to non-washed scaffolds. Compared with PCL scaffolds, ATP-doped electrospun PCL scaffolds further improved bone regeneration in rat calvarial defects [143]. Enhanced osteogenesis and bone repair were found to be associated with PCL/ATP-activated BMP/Smad signaling pathway [143]. Electrospinning also provides an opportunity to prepare nanofibrous scaffolds that mimic the structure of a natural extracellular matrix (ECM) with high porosity and large specific surface area. However, the small pore size in the range of 10~50 µm in traditional electrospinning-prepared scaffolds normally limits cell infiltration and tissue regeneration. To achieve satisfactory results in tissue engineering, it is necessary to combine conventional, coaxial electrospinning and advanced techniques to produce better 3D structures with larger pores and open space. Fabricating 3D structures for bone tissue regeneration remains challenging.
Within the rapid development of 3D-printing technology in the last decade, this technology has been widely used in tissue engineering. 3D printing, also known as “additive manufacturing”, is an advanced manufacturing process. Based on the 3D model data of computer-aided design, it can quickly manufacture entities that are highly consistent with the design model [144].
Controlled internal macroscopic structure and the design of the shape matching are always considered as challenges. Scientists use the characteristics of 3D printing to produce different organs and tissues, which can largely solve the problem of insufficient organ donors [145]. At present, the application of 3D printing technology in orthopedics mainly focuses on the preparation of orthopedic scaffolds and macroscopic skeleton with a modified internal porous structure [146]. Advanced methods such as indirect 3D printing and 4D printing are also considered to be utilized in bone tissue engineering. Additionally, 3D-printing technologies can be divided into laser or high-energy-density heat source, including photo-curing (Stereo lithography appearance, SLA), and selected laser sintering (Selected laser sintering, SLS). Jet-based forming technology such as fused deposition modeling (Fused deposition modeling, FDM), 3D printing (3D printing, 3DP), and direct ink 3D printing (DIW) is in another group of 3D printing (Table 2) [144]. However, now existing 3D printing technology is known to enable cell fusion during the printing process, other than 3D bioprinting to produce cell-laden hydrogel structures. Therefore, advanced 3D-printing techniques should be invented to enable simultaneous scaffold fabrication and cell fusion.

4. Adjuvant Therapy

4.1. Physiotherapy

Physical intervention and promotion of the bone repair through exogenous stimuli such as light, heat, electricity, and magnetic fields are also widely investigated in basic science and clinical therapy (Figure 2).
Photothermal therapy (PTT) has been used to promote tissue regeneration as it has low destructiveness, superior tissue penetration, non-invasiveness, and controllability. Mild heat (40~43 °C) is proved to effectively promote bone regeneration. A study synthesized porous AuPd alloy nanoparticles as a hyperthermia agent and conducted in-situ bone regeneration of critical calvarial defect in rats by photothermal therapy. Results found that after being swallowed by cells, almost 97% of the cranial defect area (8 mm in diameter) was covered by the newly formed bone after 6 weeks of PTT [156]. Exogenous electrical stimulation produces progressive cell attachment, proliferation, and differentiation through cell–cell and cell–scaffold interactions [157,158,159]. Therefore, the introduction of appropriate electrical stimulation may have a positive significance for bone repair and regeneration. Maharjan et al. [160] found that the electrical stimulation on PCL/polypyrrole (PPy) scaffolds enhanced cell adhesion, growth, and proliferation of MC3T3-E1, while calcium and phosphorus deposition on the scaffold surface was also found significantly increased. This finding provides a new strategy for preparing conductive scaffolds with higher bioactivity and osteogenic differentiation ability under electrical stimulation. Another important role in the regulation of cellular responses is magnetic field. A study found that the polycaprolactone/magnetic nanoparticle magnetic nanocomposite scaffold, which was assisted by an external static magnetic field (SMF), can synergistically act on primary mouse calvarial osteoblasts and stimulate angiogenesis [161]. Magnetic field stimulation was also found to accelerate tissue binding of the scaffold to host bone with increased calcium deposition and bone density, thereby accelerating the healing of critical defects in the mouse calvaria.

4.2. Other Techniques Involved in Bone Tissue Engineering

4.2.1. Exosome

Exosomes (Exos) were first discovered in the late 1980s, when sheep reticulocytes secreted membrane proteins through exocytosis during maturation, which were named “Exosomes” as the existence of extracellular space [162]. Exosomes, with a diameter of 30 ~150 nm, are now known to be secreted by a variety of cells (such as mesenchymal stem cells, dendritic cells, epithelial cells, adipocytes and B cells) and widely exist in blood, urine, saliva, and other body fluids [163]. Exosomes are mainly composed of phospholipid bilayers containing (mRNA, miRNA, DNA, lipids, and proteins) [164]. Proteomics showed that exosomes contained tetraspnin proteins (CD63, CD81, CD9) and antigen presenting proteins (MHCI and MHCII) involved in immune response [165]. Exosomes can transport their contents to target cells, thus playing a role in intercellular communication, influencing microenvironment, and regulating physiological functions of cells. Current studies have shown that exosomes participate in tissue repair and regeneration, disease diagnosis, tumor invasion and metastasis, immune regulation, and drug-targeted transport (Table 3) [166].

4.2.2. Microneedling

Microneedle (MN) is micron-scale needle that can penetrate the skin cuticle, form microporous channels, and promote drug penetration. Recently, MN has attracted great attention in application thanks to its low pain, high safety, and outstanding therapeutic effects [184]. MNs are used to treat many bone disorders [185,186,187]. Studies have shown that microneedles can be used for the delivery of alendronate and improve the bioavailability of the drug. Katsumi et al. designed a self-dissolving ALN microneedle patch based on hydroxyapatite. Alendronate was loaded in the whole microneedle made of hyaluronic acid. Through the application of the microneedle array in the rat model of osteoporosis, findings showed that transdermal administration of alendronate can modulate bone resorption of osteoclasts in treating osteoporosis and achieve approximately 90% bioavailability [188]. In order to avoid skin irritation and reduce the loss of drug residues at the base of MNs, alendronate microneedle was further modified by immersing alendronate onto the tip of the needle only [189]. Human parathyroid hormone (1-34) (PTH) is a polypeptide that can be used to treat osteoporosis and promote bone healing [190]. However. frequent injection is not always accepted by patients. Therefore, alternative administration methods using PTH (1-34)-coated microneedle patch was investigated in the treatment of osteoporosis [191] with phase II trial completed [192].
Clinical pharmacokinetics and pharmacodynamics of PTH (1-34)-coated microneedle patch were examined [186]. Scientists found that ZP-PTH patch had sustained, rapid, and efficient delivery of PTH with short plasma exposure time and significantly increased bone mineral density in the lumbar spine and hip. Interestingly, ZP-PTH also increased hip bone mineral density over 6 months, and this effect was not observed with subcutaneous injections [186]. Some studies have used hyaluronic acid as a microneedle shell to prepare soluble microneedle for efficient percutaneous delivery of PTH [193]. Microneedle has sufficient mechanical strength and penetrates the stratum corneum, epidermis, and upper dermis. At the same time, drugs in the microneedle have high stability. PTH (1-34) with pharmacological activity can be effectively transmitted to bone through transdermal absorption. The application of MN loaded with parathyroid hormone enhances bone formation [193]. Abaloparatide (TymlosTM) is a synthetic peptide analogue of human parathyroid hormone-related protein that can increase bone formation and reduce the risk of fracture in postmenopausal women with osteoporosis [194]. At present, Radius is still developing a transdermal preparation of abaloparatide administered by microneedle patch [195]. In addition, a study showed that the cyclic peptide drug salmon calcitonin (SCT)-coated MN transdermal patch can promote osteoblast proliferation and differentiation, thus replacing traditional subcutaneous and nasal administration. The surface of the microneedle is coated with SCT dry powder drug formulations, which can be dissolved when inserted into the skin, improving the bioavailability of the drug [196]. Based on this design, studies have used two dissolving microneedle arrays (DMNAs) to deliver salmon calcitonin, avoiding sharp biological hazards. Compared with the traditional transdermal gel patch, DMNA can significantly improve the therapeutic effect of sCT [197], providing a feasible scheme for the treatment of bone diseases in the future. In addition, a method of combining conductive MN and ITP to achieve local anesthesia of teeth was proposed. The study found that under the rabbit-inhibitor model, the drug can quickly pass through the oral mucosa and alveolar bone to reach the tooth sensory supply nerve to produce an anesthetic effect [198]. Compared with the traditional needle, the micro needle overcomes people’s fear of the needle. In conclusion, MN has great potential in the treatment of bone diseases.

5. Conclusions and Future Perspectives

In conclusion, bone defect repair is still a challenge faced by orthopedics. The etiology of bone defects mainly includes two aspects, one is congenital factors, the other is acquired factors, and how to prevent bone defects is mainly caused by acquired factors. Acquired factors can be skeletal injuries caused by external forces or the sequelae of various diseases and operations. The prevention and management of these injuries is mainly to reduce the risk of bone stress injury. The management of bone stress injuries depends on their location and the risk of healing complications. Bone stress injuries in low-risk sites can usually be adjusted for healing with physical exercise, followed by a gradual reintroduction of the activity [199]. Treatment options for bone stress injury at high-risk sites include non-weight-bearing immobilization, medical therapy, or surgery. Although the underlying mechanism of bone stress injury is currently unclear, the prevailing theory is that maintaining a balance of bone metabolism is beneficial to reduce the accumulation of bone damage [200]. These skeletal injuries result in damage to the plasma membrane of skeletal muscle cells, while mitochondrial function plays a crucial role in the self-repair of such plasma membrane [201]. Few studies reported that aging of mitochondria in skeletal muscle can be prevented by limiting the caloric intake in animal models; it can also accelerate the internal ability of skeletal muscle to repair by supplementing some endogenous proteins, such as BMP-2 [202,203].
The emergence of bone tissue engineering technology made remarkable progress in the study of new materials and significantly promoted the progress of bone defect treatment. However, low bionic materials, poor biocompatibility, cell migration, adhesion, and proliferation are still remaining as the issues. The precise control of cell differentiation, genes expression and growth factors, as well as safety of clinical applications are still needed to be further investigated. With the cross-integration and development of multidisciplinary concepts and technologies in the field of bone repair, such as cell biology, immunology, materials science, and manufacturing, bioactive bone-like tissues can be constructed by constructing new bone repair substitutes or directly in vitro. Regenerative repair of bone defects is believed to apply in clinical practice in the near future.

Author Contributions

Conceptualization, N.X., P.L. and Y.W.; investigation, H.H., X.P.; writing—original draft preparation, N.X., X.D., R.H. and R.J.; writing—review and editing, W.M., J.C., J.-A.D., P.L. and Y.W.; visualization, N.X.; supervision, J.C., J.-A.D. and Y.W.; project administration, Y.W.; All authors have read and agreed to the published version of the manuscript.


This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

There are no conflict of interest to declare.


  1. Han, Y.; You, X.; Xing, W.; Zhang, Z.; Zou, W. Paracrine and endocrine actions of bone-the functions of secretory proteins from osteoblasts, osteocytes, and osteoclasts. Bone Res. 2018, 6, 16. [Google Scholar] [CrossRef] [PubMed]
  2. Parfitt, A.M. Misconceptions (2): Turnover is always higher in cancellous than in cortical bone. Bone 2002, 30, 807–809. [Google Scholar] [CrossRef]
  3. Clarke, B. Normal bone anatomy and physiology. Clin. J. Am. Soc. Nephrol. 2008, 3 (Suppl. 3), S131–S139. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  4. Eckstein, F.; Hudelmaier, M.; Putz, R. The effects of exercise on human articular cartilage. J. Anat. 2006, 208, 491–512. [Google Scholar] [CrossRef] [PubMed]
  5. Turner, C.H. Three rules for bone adaptation to mechanical stimuli. Bone 1998, 23, 399–407. [Google Scholar] [CrossRef]
  6. Martyn-St James, M.; Carroll, S. Meta-analysis of walking for preservation of bone mineral density in postmenopausal women. Bone 2008, 43, 521–531. [Google Scholar] [CrossRef]
  7. Watson, S.L.; Weeks, B.K.; Weis, L.J. High-intensity resistance and impact training improves bone mineral density and physical function in postmenopausal women with osteopenia and osteoporosis: The LIFTMOR randomized controlled trial. J. Bone Miner. Res. 2018, 33, 211–220. [Google Scholar] [CrossRef]
  8. Masquelet, A.C.; Begue, T. The concept of induced membrane for reconstruction of long bone defects. Orthop. Clin. N. Am. 2010, 41, 27–37. [Google Scholar] [CrossRef]
  9. Rioja, A.Y.; Daley, E.L.H.; Habif, J.C.; Putnam, A.J.; Stegemann, J.P. Distributed vasculogenesis from modular agarose-hydroxyapatite-fibrinogen microbeads. Acta Biomater. 2017, 55, 144–152. [Google Scholar] [CrossRef]
  10. Keating, J.F.; Simpson, A.H.; Robinson, C.M. The management of fractures with bone loss. J. Bone Jt. Surg. Br. 2005, 87, 142–150. [Google Scholar] [CrossRef] [Green Version]
  11. Annamalai, R.T.; Hong, X.; Schott, N.G.; Tiruchinapally, G.; Levi, B.; Stegemann, J.P. Injectable osteogenic microtissues containing mesenchymal stromal cells conformally fill and repair critical-size defects. Biomaterials 2019, 208, 32–44. [Google Scholar] [CrossRef] [PubMed]
  12. Campana, V.; Milano, G.; Pagano, E.; Barba, M.; Cicione, C.; Salonna, G.; Lattanzi, W.; Logroscino, G. Bone substitutes in orthopaedic surgery: From basic science to clinical practice. J. Mater. Sci. Mater. Med. 2014, 25, 2445–2461. [Google Scholar] [CrossRef] [PubMed]
  13. Quarto, R.; Giannoni, P. Bone Tissue Engineering: Past-Present-Future. Methods Mol. Biol. 2016, 1416, 21–33. [Google Scholar] [PubMed]
  14. Hernlund, E.; Svedbom, A.; Ivergård, M.; Compston, J.; Cooper, C.; Stenmark, J.; McCloskey, E.V.; Jönsson, B.; Kanis, J.A. Osteoporosis in the European Union: Medical management, epidemiology and economic burden. A report prepared in collaboration with the International Osteoporosis Foundation (IOF) and the European Federation of Pharmaceutical Industry Associations (EFPIA). Arch. Osteoporos. 2013, 8, 136. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  15. Salamanca, E.; Hsu, C.C.; Huang, H.M.; Teng, N.C.; Lin, C.T.; Pan, Y.H.; Chang, W.J. Bone regeneration using a porcine bone substitute collagen composite in vitro and in vivo. Sci. Rep. 2018, 8, 984. [Google Scholar] [CrossRef] [Green Version]
  16. Selhi, H.S.; Mahindra, P.; Yamin, M.; Jain, D.; De Long, W.G., Jr.; Singh, J. Outcome in patients with an infected nonunion of the long bones treated with a reinforced antibiotic bone cement rod. J. Orthop. Trauma 2012, 26, 184–188. [Google Scholar] [CrossRef]
  17. Malkova, T.A.; Borzunov, D.Y. International recognition of the Ilizarov bone reconstruction techniques: Current practice and research (dedicated to 100(th) birthday of G. A. Ilizarov). World J. Orthop. 2021, 12, 515–533. [Google Scholar] [CrossRef]
  18. Magadum, M.P.; Basavaraj Yadav, C.M.; Phaneesha, M.S.; Ramesh, L.J. Acute compression and lengthening by the Ilizarov technique for infected nonunion of the tibia with large bone defects. J. Orthop. Surg. 2006, 14, 273–279. [Google Scholar] [CrossRef]
  19. Rohilla, R.; Sharma, P.K.; Wadhwani, J.; Das, J.; Singh, R.; Beniwal, D. Prospective randomized comparison of bone transport versus Masquelet technique in infected gap nonunion of tibia. Arch. Orthop. Trauma Surg. 2021. [Google Scholar] [CrossRef]
  20. Walker, M.; Sharareh, B.; Mitchell, S.A. Masquelet Reconstruction for Posttraumatic Segmental Bone Defects in the Forearm. J. Hand Surg. Am. 2019, 44, 342.e1–342.e8. [Google Scholar] [CrossRef]
  21. Wang, L.J.; Ni, X.H.; Zhang, F.; Peng, Z.; Yu, F.X.; Zhang, L.B.; Li, B.; Jiao, Y.; Li, Y.K.; Yang, B.; et al. Osteoblast Response to Copper-Doped Microporous Coatings on Titanium for Improved Bone Integration. Nanoscale Res. Lett. 2021, 16, 146. [Google Scholar] [CrossRef] [PubMed]
  22. Bertollo, N.; Da Assuncao, R.; Hancock, N.J.; Lau, A.; Walsh, W.R. Influence of electron beam melting manufactured implants on ingrowth and shear strength in an ovine model. J. Arthroplast. 2012, 27, 1429–1436. [Google Scholar] [CrossRef] [PubMed]
  23. Pezzotti, G.; Enomoto, Y.; Zhu, W.; Boffelli, M.; Marin, E.; McEntire, B.J. Surface toughness of silicon nitride bioceramics: I, Raman spectroscopy-assisted micromechanics. J. Mech. Behav. Biomed. Mater. 2016, 54, 328–345. [Google Scholar] [CrossRef] [PubMed]
  24. Jin, L.; Li, P.; Wang, Y.C.; Feng, L.; Xu, R.; Yang, D.B.; Yao, X.H. Studies of Superb Microvascular Imaging and Contrast-Enhanced Ultrasonography in the Evaluation of Vascularization in Early Bone Regeneration. J. Ultrasound Med. 2019, 38, 2963–2971. [Google Scholar] [CrossRef]
  25. Kanczler, J.M.; Oreffo, R.O. Osteogenesis and angiogenesis: The potential for engineering bone. Eur. Cell Mater. 2008, 15, 100–114. [Google Scholar] [CrossRef]
  26. Novosel, E.C.; Kleinhans, C.; Kluger, P.J. Vascularization is the key challenge in tissue engineering. Adv. Drug Deliv. Rev. 2011, 63, 300–311. [Google Scholar] [CrossRef]
  27. Thevenot, P.; Nair, A.; Dey, J.; Yang, J.; Tang, L. Method to Analyze Three-Dimensional Cell Distribution and Infiltration in Degradable Scaffolds. Tissue Eng. Part C Methods 2008, 14, 319–331. [Google Scholar] [CrossRef] [Green Version]
  28. Wu, Q.; Wang, X.; Jiang, F.; Zhu, Z.; Wen, J.; Jiang, X. Study of Sr-Ca-Si-based scaffolds for bone regeneration in osteoporotic models. Int. J. Oral Sci. 2020, 12, 25. [Google Scholar] [CrossRef]
  29. Van Houdt, C.I.A.; Koolen, M.K.E.; Lopez-Perez, P.M.; Ulrich, D.J.O.; Jansen, J.A.; Leeuwenburgh, S.C.G.; Weinans, H.H.; van den Beucken, J. Regenerating Critical Size Rat Segmental Bone Defects with a Self-Healing Hybrid Nanocomposite Hydrogel: Effect of Bone Condition and BMP-2 Incorporation. Macromol. Biosci. 2021, 21, e2100088. [Google Scholar] [CrossRef]
  30. Gurel Pekozer, G.; Abay Akar, N.; Cumbul, A.; Beyzadeoglu, T.; Torun Kose, G. Investigation of Vasculogenesis Inducing Biphasic Scaffolds for Bone Tissue Engineering. ACS Biomater. Sci. Eng. 2021, 7, 1526–1538. [Google Scholar] [CrossRef]
  31. Guglielmotti, M.B.; Olmedo, D.G.; Cabrini, R.L. Research on implants and osseointegration. Periodontology 2000 2019, 79, 178–189. [Google Scholar] [CrossRef] [PubMed]
  32. Qiu, L.; Zhu, Z.; Peng, F.; Zhang, C.; Xie, J.; Zhou, R.; Zhang, Y.; Li, M. Li-Doped Ti Surface for the Improvement of Osteointegration. ACS Omega 2022, 7, 12030–12038. [Google Scholar] [CrossRef] [PubMed]
  33. Ocaña, R.P.; Rabelo, G.D.; Sassi, L.M.; Rodrigues, V.P.; Alves, F.A. Implant osseointegration in irradiated bone: An experimental study. J. Periodontal. Res. 2017, 52, 505–511. [Google Scholar] [CrossRef] [PubMed]
  34. Langer, R.; Vacanti, J. Advances in tissue engineering. J. Pediatr. Surg. 2016, 51, 8–12. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  35. Hasan, A.; Saxena, V.; Pandey, L.M. Surface Functionalization of Ti6Al4V via Self-assembled Monolayers for Improved Protein Adsorption and Fibroblast Adhesion. Langmuir 2018, 34, 3494–3506. [Google Scholar] [CrossRef] [PubMed]
  36. Murphy, C.M.; O’Brien, F.J. Understanding the effect of mean pore size on cell activity in collagen-glycosaminoglycan scaffolds. Cell Adh. Migr. 2010, 4, 377–381. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  37. Nehrer, S.; Breinan, H.A.; Ramappa, A.; Young, G.; Shortkroff, S.; Louie, L.K.; Sledge, C.B.; Yannas, I.V.; Spector, M. Matrix collagen type and pore size influence behaviour of seeded canine chondrocytes. Biomaterials 1997, 18, 769–776. [Google Scholar] [CrossRef]
  38. Zhao, Y.; Tan, K.; Zhou, Y.; Ye, Z.; Tan, W.S. A combinatorial variation in surface chemistry and pore size of three-dimensional porous poly(ε-caprolactone) scaffolds modulates the behaviors of mesenchymal stem cells. Mater. Sci. Eng. C Mater. Biol. Appl. 2016, 59, 193–202. [Google Scholar] [CrossRef]
  39. Oh, S.H.; Park, I.K.; Kim, J.M.; Lee, J.H. In vitro and in vivo characteristics of PCL scaffolds with pore size gradient fabricated by a centrifugation method. Biomaterials 2007, 28, 1664–1671. [Google Scholar] [CrossRef]
  40. Xia, H.; Dong, L.; Hao, M.; Wei, Y.; Duan, J.; Chen, X.; Yu, L.; Li, H.; Sang, Y.; Liu, H. Osteogenic Property Regulation of Stem Cells by a Hydroxyapatite 3D-Hybrid Scaffold with Cancellous Bone Structure. Front. Chem. 2021, 19, 798299. [Google Scholar] [CrossRef]
  41. Karageorgiou, V.; Kaplan, D. Porosity of 3D biomaterial scaffolds and osteogenesis. Biomaterials 2005, 26, 5474–5491. [Google Scholar] [CrossRef] [PubMed]
  42. Sobral, J.M.; Caridade, S.G.; Sousa, R.A.; Mano, J.F.; Reis, R.L. Three-dimensional plotted scaffolds with controlled pore size gradients: Effect of scaffold geometry on mechanical performance and cell seeding efficiency. Acta Biomater. 2011, 7, 1009–1018. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  43. Albrektsson, T. Osseointegrated dental implants. Dent. Clin. N. Am. 1986, 30, 151. [Google Scholar] [CrossRef]
  44. Wang, C.; Xu, D.; Li, S.; Yi, C.; Zhang, X.; He, Y.; Yu, D. Effect of Pore Size on the Physicochemical Properties and Osteogenesis of Ti6Al4V Porous Scaffolds with Bionic Structure. ACS Omega 2020, 5, 28684–28692. [Google Scholar] [CrossRef]
  45. Doi, K.; Kobatake, R.; Makihara, Y.; Oki, Y.; Umehara, H.; Kubo, T.; Tsuga, K. The development of novel bioactive porous titanium as a bone reconstruction material. RSC Adv. 2020, 10, 22684–22690. [Google Scholar] [CrossRef]
  46. Werman, B.S.; Rietschel, R.L. Chronic urticaria from tantalum staples. Arch. Dermatol. 1981, 117, 438–439. [Google Scholar] [CrossRef] [PubMed]
  47. Edelmann, A.R.; Patel, D.; Allen, R.K.; Gibson, C.J.; Best, A.M.; Bencharit, S. Retrospective analysis of porous tantalum trabecular metal-enhanced titanium dental implants. J. Prosthet. Dent. 2019, 121, 404–410. [Google Scholar] [CrossRef]
  48. Wauthle, R.; van der Stok, J.; Amin Yavari, S.; Van Humbeeck, J.; Kruth, J.P.; Zadpoor, A.A.; Weinans, H.; Mulier, M.; Schrooten, J. Additively manufactured porous tantalum implants. Acta Biomater. 2015, 14, 217–225. [Google Scholar] [CrossRef]
  49. Sagomonyants, K.B.; Hakim-Zargar, M.; Jhaveri, A.; Aronow, M.S.; Gronowicz, G. Porous tantalum stimulates the proliferation and osteogenesis of osteoblasts from elderly female patients. J. Orthop. Res. 2011, 29, 609–616. [Google Scholar] [CrossRef]
  50. Black, J. Biological performance of tantalum. Clin. Mater. 1994, 16, 167–173. [Google Scholar] [CrossRef]
  51. Dou, X.; Wei, X.; Liu, G.; Wang, S.; Lv, Y.; Li, J.; Ma, Z.; Zheng, G.; Wang, Y.; Hu, M.; et al. Effect of porous tantalum on promoting the osteogenic differentiation of bone marrow mesenchymal stem cells in vitro through the MAPK/ERK signal pathway. J. Orthop. Translat. 2019, 15, 81–93. [Google Scholar] [CrossRef] [PubMed]
  52. Yang, A.; He, A.; Dianyu, E.; Yang, W.; Qi, F.; Xie, D.; Shen, L.; Peng, S.; Shuai, C. Mg bone implant: Features, developments and perspectives. Mater. Des. 2020, 185, 108259. [Google Scholar]
  53. Khare, D.; Basu, B.; Dubey, A.K. Electrical stimulation and piezoelectric biomaterials for bone tissue engineering applications. Biomaterials 2020, 258, 120280. [Google Scholar] [PubMed]
  54. Qi, T.; Weng, J.; Yu, F.; Zhang, W.; Li, G.; Qin, H.; Tan, Z.; Zeng, H. Insights into the Role of Magnesium Ions in Affecting Osteogenic Differentiation of Mesenchymal Stem Cells. Biol. Trace Elem. Res. 2021, 199, 559–567. [Google Scholar] [CrossRef] [PubMed]
  55. Liu, Y.J.; Yang, Z.Y.; Tan, L.L.; Li, H.; Zhang, Y.Z. An animal experimental study of porous magnesium scaffold degradation and osteogenesis. Braz. J. Med. Biol. Res. 2014, 47, 715–720. [Google Scholar] [CrossRef]
  56. Zakhireh, S.; Barar, J.; Adibkia, K.; Beygi-Khosrowshahi, Y.; Fathi, M.; Omidain, H.; Omidi, Y. Bioactive Chitosan-Based Organometallic Scaffolds for Tissue Engineering and Regeneration. Top Curr. Chem. 2022, 380, 13. [Google Scholar] [CrossRef]
  57. Tanaka, T.; Komaki, H.; Chazono, M.; Kitasato, S.; Kakuta, A.; Akiyama, S.; Marumo, K. Basic research and clinical application of beta-tricalcium phosphate (β-TCP). Morphologie 2017, 101, 164–172. [Google Scholar] [CrossRef]
  58. Qin, H.; Wei, Y.; Han, J.; Jiang, X.; Yang, X.; Wu, Y.; Gou, Z.; Chen, L. 3D printed bioceramic scaffolds: Adjusting pore dimension is beneficial for mandibular bone defects repair. J. Tissue Eng. Regen. Med. 2022, 16, 409–421. [Google Scholar] [CrossRef]
  59. Zhang, J.; Zhou, H.; Yang, K.; Yuan, Y.; Liu, C. RhBMP-2-loaded calcium silicate/calcium phosphate cement scaffold with hierarchically porous structure for enhanced bone tissue regeneration. Biomaterials 2013, 34, 9381–9392. [Google Scholar] [CrossRef]
  60. Wang, D.; Tabassum, A.; Wu, G.; Deng, L.; Wismeijer, D.; Liu, Y. Bone regeneration in critical-sized bone defect enhanced by introducing osteoinductivity to biphasic calcium phosphate granules. Clin. Oral Implants. Res. 2017, 28, 251–260. [Google Scholar] [CrossRef]
  61. Montalbano, G.; Borciani, G.; Pontremoli, C.; Ciapetti, G.; Mattioli-Belmonte, M.; Fiorilli, S.; Vitale-Brovarone, C. Development and Biocompatibility of Collagen-Based Composites Enriched with Nanoparticles of Strontium Containing Mesoporous Glass. Materials 2019, 12, 3719. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  62. LogithKumar, R.; KeshavNarayan, A.; Dhivya, S.; Chawla, A.; Saravanan, S.; Selvamurugan, N. A review of chitosan and its derivatives in bone tissue engineering. Carbohydr. Polym. 2016, 20, 172–188. [Google Scholar] [CrossRef]
  63. Banihashemi, M.; Mohkam, M.; Safari, A.; Nezafat, N.; Negahdaripour, M.; Mohammadi, F.; Kianpour, S.; Ghasemi, Y. Optimization of Three-Dimensional Culturing of the HepG2 Cell Line in Fibrin Scaffold. Hepat. Mon. 2015, 15, e22731. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  64. Soumya, S.; Sreerekha, P.R.; Menon, D.; Nair, S.V.; Chennazhi, K.P. Generation of a biomimetic 3D microporous nano-fibrous scaffold on titanium surfaces for better osteointegration of orthopedic implants. J. Mater. Chem. 2012, 22, 1725–1733. [Google Scholar] [CrossRef]
  65. Van Houdt, C.I.A.; Ulrich, D.J.O.; Jansen, J.A.; van den Beucken, J. The performance of CPC/PLGA and Bio-Oss (®) for bone regeneration in healthy and osteoporotic rats. J. Biomed. Mater. Res. B Appl. Biomater. 2018, 106, 131–142. [Google Scholar] [CrossRef]
  66. Rombouts, C.; Jeanneau, C.; Camilleri, J.; Laurent, P.; About, I. Characterization and angiogenic potential of xenogeneic bone grafting materials: Role of periodontal ligament cells. Dent. Mater. J. 2016, 35, 900–907. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  67. Ma, X.J.; Bian, Y.F.; Wu, D.; Chen, N.; Wang, L.J. A comparative study of two kinds of artificial bone powder for tooth extraction site preservation. Oral Biomed. 2019, 10, 139–142. [Google Scholar]
  68. Dong, Y.; Dong, F.J.; Pan, L.F. Effect of Bio-oss bone meal combined with platelet-rich fibrin on mucosal healing and bone defect regeneration after oral implant-guided bone regeneration. Chin. Gen. Pract. 2017, 20, 152–154. [Google Scholar]
  69. Xu, M.Y.; Liu, Y.H.; Wang, P.S.; Hu, Y.C. Research progress of bioactive glass-based bone repair materials. Chin. J. Orthop. 2019, 12, 440–448. [Google Scholar]
  70. Jin, S.Y.; Kim, S.G.; Oh, J.S.; You, J.S.; Lim, S.C.; Jeong, M.A.; Kim, J.S. Histomorphometric Analysis of Contaminated Autogenous Tooth Graft Materials after Various Sterilization. Implant Dent. 2016, 25, 83–89. [Google Scholar] [CrossRef]
  71. Kim, E.S. Autogenous fresh demineralized tooth graft prepared at chairside for dental implant. Maxillofac. Plast. Reconstr. Surg. 2015, 37, 8. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  72. Sas, A.; Helgason, B.; Ferguson, S.J.; van Lenthe, G.H. Mechanical and morphological characterization of PMMA/bone composites in human femoral heads. J. Mech. Behav. Biomed. Mater. 2021, 115, 104247. [Google Scholar] [CrossRef] [PubMed]
  73. Hoess, A.; López, A.; Engqvist, H.; Ott, M.K.; Persson, C. Comparison of a quasi-dynamic and a static extraction method for the cytotoxic evaluation of acrylic bone cements. Mater. Sci. Eng. C Mater. Biol. Appl. 2016, 62, 274–282. [Google Scholar] [CrossRef] [PubMed]
  74. Lewis, G. Properties of nanofiller-loaded poly (methyl methacrylate) bone cement composites for orthopedic applications: A review. J. Biomed. Mater. Res. B Appl. Biomater. 2017, 105, 1260–1284. [Google Scholar] [CrossRef]
  75. Xu, D.; Song, W.; Zhang, J.; Liu, Y.; Lu, Y.; Zhang, X.; Liu, Q.; Yuan, T.; Liu, R. Osteogenic effect of polymethyl methacrylate bone cement with surface modification of lactoferrin. J. Biosci. Bioeng. 2021, 132, 132–139. [Google Scholar] [CrossRef]
  76. Lin, Y.; Umebayashi, M.; Abdallah, M.N.; Dong, G.; Roskies, M.G.; Zhao, Y.F.; Murshed, M.; Zhang, Z.; Tran, S.D. Combination of polyetherketoneketone scaffold and human mesenchymal stem cells from temporomandibular joint synovial fluid enhances bone regeneration. Sci. Rep. 2019, 9, 472. [Google Scholar] [CrossRef] [Green Version]
  77. Hakkarainen, M.; Albertsson, A.C. Degradation Products of Aliphatic and Aliphatic–Aromatic Polyesters; Springer: Berlin/Heidelberg, Germany, 2008. [Google Scholar]
  78. Ciobanu, P.; Panuta, A.; Radu, I.; Forna, N.; Arcana, S.; Tudor, R.; Covaciu, A.; Niculescu, V.; Poroch, V.; Puha, B. Treatment of Bone Defects Resulted after Excision of Enchondroma of the Hand in 15 Patients, Comparing the Techniques of Autologous Bone Graft, Injectable Bone Substitute and Spontaneous Healing. Appl. Sci. 2022, 12, 1300. [Google Scholar] [CrossRef]
  79. Jain, G.; Blaauw, D.; Chang, S. A Comparative Study of Two Bone Graft Substitutes—InterOss® Collagen and OCS-B Collagen®. J. Funct. Biomater. 2022, 13, 28. [Google Scholar] [CrossRef]
  80. Kim, J.-S.; Jang, T.-S.; Kim, S.-Y.; Lee, W.-P. Octacalcium Phosphate Bone Substitute (Bontree®): From Basic Research to Clinical Case Study. Appl. Sci. 2021, 11, 7921. [Google Scholar] [CrossRef]
  81. Hofmann, A.; Gorbulev, S.; Guehring, T.; Schulz, A.P.; Schupfner, R.; Raschke, M.; Huber-Wagner, S.; Rommens, P.M.; on behalf of the CERTiFy Study Group. Autologous Iliac Bone Graft Compared with Biphasic Hydroxyapatite and Calcium Sulfate Cement for the Treatment of Bone Defects in Tibial Plateau Fractures: A Prospective, Randomized, Open-Label, Multicenter Study. J. Bone Jt. Surgery. 2020, 102, 179–193. [Google Scholar] [CrossRef] [Green Version]
  82. Fuchs, K.F.; Heilig, P.; McDonogh, M.; Boelch, S.; Gbureck, U.; Meffert, R.H.; Hoelscher-Doht, S.; Jordan, M.C. Cement-augmented screw fixation for calcaneal fracture treatment: A biomechanical study comparing two injectable bone substitutes. J. Orthop. Surg. Res. 2020, 15, 533. [Google Scholar] [CrossRef] [PubMed]
  83. Westhauser, F.; Karadjian, M.; Essers, C.; Senger, A.S.; Hagmann, S.; Schmidmaier, G.; Moghaddam, A. Osteogenic differentiation of mesenchymal stem cells is enhanced in a 45S5-supplemented β-TCP composite scaffold: An in-vitro comparison of Vitoss and Vitoss BA. PLoS ONE 2019, 14, e0212799. [Google Scholar] [CrossRef] [PubMed]
  84. Kent, N.W.; Blunn, G.; Karpukhina, N.; Davis, G.; de Godoy, R.F.; Wilson, R.M.; Coathup, M.; Onwordi, L.; Quak, W.Y.; Hill, R. In vitro and in vivo study of commercial calcium phosphate cement HydroSetTM. J. Biomed. Mater. Res. B 2018, 106, 21–30. [Google Scholar] [CrossRef] [PubMed]
  85. Shih, J.T.; Kuo, C.L.; Yeh, T.T.; Shen, H.C.; Pan, R.Y.; Wu, C.C. Modified Essex-Lopresti procedure with percutaneous calcaneoplasty for comminuted intra-articular calcaneal fractures: A retrospective case analysis. BMC Musculoskelet. Dis. 2018, 19, 77. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  86. Frasca, S.; Norol, F.; Le Visage, C.; Collombet, J.M.; Letourneur, D.; Holy, X.; Sari Ali, E. Calcium-phosphate ceramics and polysaccharide-based hydrogel scaffolds combined with mesenchymal stem cell differently support bone repair in rats. J. Biomed. Mater. Res. B Appl. Biomater. 2017, 28, 35. [Google Scholar] [CrossRef] [Green Version]
  87. Duan, R.; Barbieri, D.; Luo, X.; Weng, J.; Bao, C.; de Bruijn, J.D.; Yuan, H. Variation of the bone forming ability with the physicochemical properties of calcium phosphate bone substitutes. Biomater. Sci. 2017, 6, 136–145. [Google Scholar] [CrossRef]
  88. Mellier, C.; Lefèvre, F.X.; Fayon, F.; Montouillout, V.; Despas, C.; Le Ferrec, M.; Boukhechba, F.; Walcarius, A.; Janvier, P.; Dutilleul, M.; et al. A straightforward approach to enhance the textural, mechanical and biological properties of injectable calcium phosphate apatitic cements (CPCs): CPC/blood composites, a comprehensive study. Acta Biomater. 2017, 62, 328–339. [Google Scholar] [CrossRef]
  89. Nusselt, T.; Hofmann, A.; Wachtlin, D.; Gorbulev, S.; Rommens, P.M. CERAMENT treatment of fracture defects (CERTiFy): Protocol for a prospective, multicenter, randomized study investigating the use of CERAMENT™ BONE VOID FILLER in tibial plateau fractures. Trials 2014, 15, 75. [Google Scholar] [CrossRef] [Green Version]
  90. Kassim, B.; Ivanovski, S.; Mattheos, N. Current perspectives on the role of ridge (socket) preservation procedures in dental implant treatment in the aesthetic zone. Aust. Dent. J. 2014, 59, 48–56. [Google Scholar] [CrossRef] [Green Version]
  91. Gohil, S.V.; Adams, D.J.; Maye, P.; Rowe, D.W.; Nair, L.S. Evaluation of rhBMP-2 and bone marrow derived stromal cell mediated bone regeneration using transgenic fluorescent protein reporter mice. J. Biomed. Mater. Res. A 2014, 102, 4568–4580. [Google Scholar] [CrossRef] [Green Version]
  92. Dallari, D.; Savarino, L.; Albisinni, U.; Fornasari, P.; Ferruzzi, A.; Baldini, N.; Giannini, S. A prospective, randomised, controlled trial using a Mg-hydroxyapatite—Demineralized bone matrix nanocomposite in tibial osteotomy. Biomaterials 2012, 33, 72–79. [Google Scholar] [CrossRef] [PubMed]
  93. Feng, Y.; Wang, S.; Jin, D.; Sheng, J.; Chen, S.; Cheng, X.; Zhang, C. Free vascularised fibular grafting with OsteoSet®2 demineralised bone matrix versus autograft for large osteonecrotic lesions of the femoral head. Int. Orthop. 2011, 35, 475–481. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  94. Hieu, P.D.; Chung, J.H.; Yim, S.B.; Hong, K.S. A radiographical study on the changes in height of grafting materials after sinus lift: A comparison between two types of xenogenic materials. J. Periodontal. Implant Sci. 2010, 40, 25–32. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  95. Kobayashi, H.; Fujishiro, T.; Belkoff, S.M.; Kobayashi, N.; Turner, A.S.; Seim, H.B., 3rd; Zitelli, J.; Hawkins, M.; Bauer, T.W. Long-term evaluation of a calcium phosphate bone cement with carboxymethyl cellulose in a vertebral defect model. J. Biomed. Mater. Res. A 2009, 88, 880–888. [Google Scholar] [CrossRef]
  96. Van Lieshout, E.M.; Van Kralingen, G.H.; El-Massoudi, Y.; Weinans, H.; Patka, P. Microstructure and biomechanical characteristics of bone substitutes for trauma and orthopaedic surgery. BMC Musculoskelet. Disord. 2011, 12, 34. [Google Scholar] [CrossRef] [Green Version]
  97. Huber, F.X.; McArthur, N.; Heimann, L.; Dingeldein, E.; Cavey, H.; Palazzi, X.; Clermont, G.; Boutrand, J.P. Evaluation of a novel nanocrystalline hydroxyapatite paste Ostim in comparison to Alpha-BSM—More bone ingrowth inside the implanted material with Ostim compared to Alpha BSM. BMC Musculoskelet. Disord. 2009, 10, 164. [Google Scholar] [CrossRef] [Green Version]
  98. Rauschmann, M.A.; Wichelhaus, T.A.; Stirnal, V.; Dingeldein, E.; Zichner, L.; Schnettler, R.; Alt, V. Nanocrystalline hydroxyapatite and calcium sulphate as biodegradable composite carrier material for local delivery of antibiotics in bone infections. Biomaterials 2005, 26, 2677–2684. [Google Scholar] [CrossRef]
  99. Sanus, G.Z.; Tanriverdi, T.; Ulu, M.O.; Kafadar, A.M.; Tanriover, N.; Ozlen, F. Use of Cortoss as an alternative material in calvarial defects: The first clinical results in cranioplasty. J. Craniofacial Surg. 2008, 19, 88–95. [Google Scholar] [CrossRef]
  100. Boszczyk, B. Prospective study of standalone balloon kyphoplasty with calcium phosphate cement augmentation in traumatic fractures (G. Maestretti et al.). Eur. Spine J. 2007, 16, 611. [Google Scholar] [CrossRef] [Green Version]
  101. Welch, R.D.; Zhang, H.; Bronson, D.G. Experimental tibial plateau fractures augmented with calcium phosphate cement or autologous bone graft. J. Bone Jt. Surg. Am. 2003, 85, 222–231. [Google Scholar] [CrossRef]
  102. Zimmermann, R.; Gabl, M.; Lutz, M.; Angermann, P.; Gschwentner, M.; Pechlaner, S. Injectable calcium phosphate bone cement Norian SRS for the treatment of intra-articular compression fractures of the distal radius in osteoporotic women. Arch. Orthop. Trauma Surg. 2003, 123, 22–27. [Google Scholar] [CrossRef] [PubMed]
  103. Yousefi, A.M.; James, P.F.; Akbarzadeh, R.; Subramanian, A.; Flavin, C.; Oudadesse, H. Prospect of Stem Cells in Bone Tissue Engineering: A Review. Stem Cells Int. 2016, 2016, 6180487. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  104. Elsafadi, M.; Manikandan, M.; Atteya, M.; Hashmi, J.A.; Iqbal, Z.; Aldahmash, A.; Alfayez, M.; Kassem, M.; Mahmood, A. Characterization of Cellular and Molecular Heterogeneity of Bone Marrow Stromal Cells. Stem Cells Int. 2016, 2016, 9378081. [Google Scholar] [CrossRef] [Green Version]
  105. Bai, H.; Zhao, Y.; Wang, C.; Wang, Z.; Wang, J.; Liu, H.; Feng, Y.; Lin, Q.; Li, Z.; Liu, H. Enhanced osseointegration of three-dimensional supramolecular bioactive interface through osteoporotic microenvironment regulation. Theranostics 2020, 10, 4779–4794. [Google Scholar] [CrossRef] [PubMed]
  106. Shang, F.; Yu, Y.; Liu, S.; Ming, L.; Zhang, Y.; Zhou, Z.; Zhao, J.; Jin, Y. Advancing application of mesenchymal stem cell-based bone tissue regeneration. Bioact. Mater. 2021, 6, 666–683. [Google Scholar] [CrossRef] [PubMed]
  107. Ju, T.; Zhao, Z.; Ma, L.; Li, W.; Li, S.; Zhang, J. Cyclic Adenosine Monophosphate-Enhanced Calvarial Regeneration by Bone Marrow-Derived Mesenchymal Stem Cells on a Hydroxyapatite/Gelatin Scaffold. ACS Omega 2021, 6, 13684–13694. [Google Scholar] [CrossRef]
  108. Pittenger, M.F.; Mackay, A.M.; Beck, S.C.; Jaiswal, R.K.; Douglas, R.; Mosca, J.D.; Moorman, M.A.; Simonetti, D.W.; Craig, S.; Marshak, D.R. Multilineage potential of adult human mesenchymal stem cells. Science 1999, 284, 143–147. [Google Scholar] [CrossRef] [Green Version]
  109. Almubarak, S.; Nethercott, H.; Freeberg, M.; Beaudon, C.; Jha, A.; Jackson, W.; Marcucio, R.; Miclau, T.; Healy, K.; Bahney, C. Tissue engineering strategies for promoting vascularized bone regeneration. Bone 2016, 83, 197–209. [Google Scholar] [CrossRef] [Green Version]
  110. Quarto, R.; Mastrogiacomo, M.; Cancedda, R.; Kutepov, S.M.; Mukhachev, V.; Lavroukov, A.; Kon, E.; Marcacci, M. Repair of large bone defects with the use of autologous bone marrow stromal cells. N. Engl. J. Med. 2001, 344, 385–386. [Google Scholar] [CrossRef]
  111. Hutton, D.L.; Grayson, W.L. Stem cell-based approaches to engineering vascularized bone. Curr. Opin. Chem. Eng. 2014, 3, 75–82. [Google Scholar] [CrossRef]
  112. Li, Y.; Charif, N.; Mainard, D.; Stoltz, J.F.; Isla, N.D. The importance of mesenchymal stem cell donor’s age for cartilage engineering. Osteoarthr. Cartil. 2014, 22, S61. [Google Scholar] [CrossRef] [Green Version]
  113. Sheykhhasan, M.; Wong, J.K.L.; Seifalian, A.M. Human Adipose-Derived Stem Cells with Great Therapeutic Potential. Curr. Stem Cell Res. Ther. 2019, 14, 532–548. [Google Scholar] [CrossRef]
  114. Cho, J.H.; Lee, J.H.; Lee, K.M.; Lee, C.K.; Shin, D.M. BMP-2 Induced Signaling Pathways and Phenotypes: Comparisons Between Senescent and Non-senescent Bone Marrow Mesenchymal Stem Cells. Calcif. Tissue Int. 2022, 110, 489–503. [Google Scholar] [CrossRef] [PubMed]
  115. Mitra, D.; Whitehead, J.; Yasui, O.W.; Leach, J.K. Bioreactor culture duration of engineered constructs influences bone formation by mesenchymal stem cells. Biomaterials 2017, 146, 29–39. [Google Scholar] [CrossRef] [PubMed]
  116. Fukunishi, T.; Best, C.A.; Ong, C.S.; Groehl, T.; Reinhardt, J.; Yi, T.; Miyachi, H.; Zhang, H.; Shinoka, T.; Breuer, C.K.; et al. Role of Bone Marrow Mononuclear Cell Seeding for Nanofiber Vascular Grafts. Tissue Eng. Part A 2018, 24, 135–144. [Google Scholar] [CrossRef]
  117. Mizuno, H. Adipose-derived stem cells for tissue repair and regeneration: Ten years of research and a literature review. J. Nippon Med. Sch. 2009, 76, 56–66. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  118. Mizuno, H.; Itoi, Y.; Kawahara, S.; Ogawa, R.; Akaishi, S.; Hyakusoku, H. In vivo adipose tissue regeneration by adipose-derived stromal cells isolated from GFP transgenic mice. Cells Tissues Organs 2008, 187, 177–185. [Google Scholar]
  119. Tang, M.; Chen, W.; Weir, M.D.; Thein-Han, W.; Xu, H.H. Human embryonic stem cell encapsulation in alginate microbeads in macroporous calcium phosphate cement for bone tissue engineering. Acta Biomater. 2012, 8, 3436–3445. [Google Scholar] [CrossRef] [Green Version]
  120. Sui, B.; Chen, C.; Kou, X.; Li, B.; Xuan, K.; Shi, S.; Jin, Y. Pulp Stem Cell-Mediated Functional Pulp Regeneration. J. Dent. Res. 2019, 98, 27–35. [Google Scholar] [CrossRef]
  121. Gronthos, S.; Mankani, M.; Brahim, J.; Robey, P.G.; Shi, S. Postnatal human dental pulp stem cells (DPSCs) in vitro and in vivo. Proc. Natl. Acad. Sci. USA 2000, 97, 13625–13630. [Google Scholar] [CrossRef] [Green Version]
  122. Jiang, F.; Zhang, W.; Zhou, M.; Zhou, Z.; Shen, M.; Chen, N.; Jiang, X. Human amniotic mesenchymal stromal cells promote bone regeneration via activating endogenous regeneration. Theranostics 2020, 10, 6216–6230. [Google Scholar] [CrossRef] [PubMed]
  123. Zhou, J.L.; Li, D.X.; Zhao, Z.J.; Zhang, C.Y. Research progress of bone tissue engineering in skull repair. Med. Recapitul. 2021, 26, 4817–4823. [Google Scholar]
  124. Novais, A.; Chatzopoulou, E.; Chaussain, C.; Gorin, C. The Potential of FGF-2 in Craniofacial Bone Tissue Engineering: A Review. Cells 2021, 10, 932. [Google Scholar] [CrossRef]
  125. Yun, Y.R.; Won, J.E.; Jeon, E.; Lee, S.; Kang, W.; Jo, H.; Jang, J.H.; Shin, U.S.; Kim, H.W. Fibroblast growth factors: Biology, function, and application for tissue regeneration. J. Tissue Eng. 2010, 2010, 218142. [Google Scholar] [CrossRef] [PubMed]
  126. Ornitz, D.M.; Marie, P.J. FGF signaling pathways in endochondral and intramembranous bone development and human genetic disease. Genes Dev. 2002, 16, 1446–1465. [Google Scholar] [PubMed] [Green Version]
  127. Nakamura, Y.; Tensho, K.; Nakaya, H.; Nawata, M.; Okabe, T.; Wakitani, S. Low dose fibroblast growth factor-2 (FGF-2) enhances bone morphogenetic protein-2 (BMP-2)-induced ectopic bone formation in mice. Bone 2005, 36, 399–407. [Google Scholar] [CrossRef]
  128. Gronowicz, G.; Jacobs, E.; Peng, T.; Zhu, L.; Hurley, M.; Kuhn, L.T. Calvarial Bone Regeneration Is Enhanced by Sequential Delivery of FGF-2 and BMP-2 from Layer-by-Layer Coatings with a Biomimetic Calcium Phosphate Barrier Layer. Tissue Eng. Part A 2017, 23, 1490–1501. [Google Scholar] [CrossRef]
  129. García, J.R.; Clark, A.Y.; García, A.J. Integrin-specific hydrogels functionalized with VEGF for vascularization and bone regeneration of critical-size bone defects. J. Biomed. Mater. Res. A 2016, 104, 889–900. [Google Scholar] [CrossRef] [Green Version]
  130. Walsh, D.P.; Raftery, R.M.; Murphy, R.; Chen, G.; Heise, A.; O’Brien, F.J.; Cryan, S.A. Gene activated scaffolds incorporating star-shaped polypeptide-pDNA nanomedicines accelerate bone tissue regeneration in vivo. Biomater. Sci. 2021, 9, 4984–4999. [Google Scholar] [CrossRef]
  131. Naudot, M.; Garcia Garcia, A.; Jankovsky, N.; Barre, A.; Zabijak, L.; Azdad, S.Z.; Collet, L.; Bedoui, F.; Hébraud, A.; Schlatter, G.; et al. The combination of a poly-caprolactone/nano-hydroxyapatite honeycomb scaffold and mesenchymal stem cells promotes bone regeneration in rat calvarial defects. J. Tissue Eng. Regen. Med. 2020, 14, 1570–1580. [Google Scholar] [CrossRef]
  132. Ding, R.; Wu, Z.Z.; Qiu, G.X.; Wu, G.; Wang, H.; Su, X.L.; Yin, B.; Ma, S.; Qi, B. Bone tissue engineering observation of porous titanium alloy scaffolds by selective laser sintering. Natl. Med. J. China 2014, 94, 1499–1502. [Google Scholar]
  133. Ruan, S.Q.; Deng, J.; Yan, L.; Huang, W.L. Composite scaffolds loaded with bone mesenchymal stem cells promote the repair of radial bone defects in rabbit model. Biomed. Pharmacother. 2018, 97, 600–606. [Google Scholar] [CrossRef]
  134. Zhou, X.; Zhang, D.; Wang, M.; Zhang, D.; Xu, Y. Three-Dimensional Printed Titanium Scaffolds Enhance Osteogenic Differentiation and New Bone Formation by Cultured Adipose Tissue-Derived Stem Cells Through the IGF-1R/AKT/Mammalian Target of Rapamycin Complex 1 (mTORC1) Pathway. Med. Sci. Monit. 2019, 25, 8043–8054. [Google Scholar] [CrossRef]
  135. Kakuta, A.; Tanaka, T.; Chazono, M.; Komaki, H.; Kitasato, S.; Inagaki, N.; Akiyama, S.; Marumo, K. Effects of micro-porosity and local BMP-2 administration on bioresorption of β-TCP and new bone formation. Biomater. Res. 2019, 23, 12. [Google Scholar] [CrossRef] [Green Version]
  136. Kim, B.S.; Yang, S.S.; Kim, C.S. Incorporation of BMP-2 nanoparticles on the surface of a 3D-printed hydroxyapatite scaffold using an ε-polycaprolactone polymer emulsion coating method for bone tissue engineering. Colloids Surf. B Biointerfaces 2018, 170, 421–429. [Google Scholar] [CrossRef] [PubMed]
  137. Lei, Y.; Xu, Z.; Ke, Q.; Yin, W.; Chen, Y.; Zhang, C.; Guo, Y. Strontium hydroxyapatite/chitosan nanohybrid scaffolds with enhanced osteoinductivity for bone tissue engineering. Mater. Sci. Eng. C Mater. Biol. Appl. 2017, 72, 134–142. [Google Scholar] [CrossRef] [PubMed]
  138. Yun, X.; Ding, T.; Yang, W.Q.; Guo, X.J. Repair of bone defect by nano-hydroxyapatite/chitosan scaffold loaded with xylosaponin D. J. Clin. Rehabil. Tissue Eng. Res. 2022, 26, 4293–4299. [Google Scholar]
  139. Zhang, H.; Zhou, Y.; Yu, N.; Ma, H.; Wang, K.; Liu, J.; Zhang, W.; Cai, Z.; He, Y. Construction of vascularized tissue-engineered bone with polylysine-modified coral hydroxyapatite and a double cell-sheet complex to repair a large radius bone defect in rabbits. Acta Biomater. 2019, 91, 82–98. [Google Scholar] [CrossRef]
  140. Wang, W.; Miao, Y.; Zhou, X.; Nie, W.; Chen, L.; Liu, D.; Du, H.; He, C. Local Delivery of BMP-2 from Poly (lactic-co-glycolic acid) Microspheres Incorporated into Porous Nanofibrous Scaffold for Bone Tissue Regeneration. J. Biomed. Nanotechnol. 2017, 13, 1446–1456. [Google Scholar] [CrossRef]
  141. Chen, S.; Zhao, X.; Du, C. Macroporous poly (l-lactic acid)/chitosan nanofibrous scaffolds through cloud point thermally induced phase separation for enhanced bone regeneration. Eur. Polym. J. 2018, 109, 303–316. [Google Scholar] [CrossRef]
  142. Guo, Z.; Xu, J.; Ding, S.; Li, H.; Zhou, C.; Li, L. In vitro evaluation of random and aligned polycaprolactone/gelatin fibers via electrospinning for bone tissue engineering. J. Biomater. Sci. Polym. Ed. 2015, 26, 989–1001. [Google Scholar] [CrossRef] [PubMed]
  143. Dai, T.; Ma, J.; Ni, S.; Liu, C.; Wang, Y.; Wu, S.; Liu, J.; Weng, Y.; Zhou, D.; Jimenez-Franco, A.; et al. Attapulgite-doped electrospun PCL scaffolds for enhanced bone regeneration in rat cranium defects. Mater. Sci. Eng. C Mater. Biol. Appl. 2022, 133, 112656. [Google Scholar] [CrossRef] [PubMed]
  144. Wang, C.; Huang, W.; Zhou, Y.; He, L.; He, Z.; Chen, Z.; He, X.; Tian, S.; Liao, J.; Lu, B.; et al. 3D printing of bone tissue engineering scaffolds. Bioact. Mater. 2020, 5, 82–91. [Google Scholar] [CrossRef] [PubMed]
  145. Ramiah, P.; Toit, L.; Choonara, Y.E.; Kondia, H.P.; Pillay, V. Hydrogel-Based Bioinks for 3D Bioprinting in Tissue Regeneration. Front. Mater. 2020, 7, 76. [Google Scholar] [CrossRef]
  146. Ashammakhi, N.; Hasan, A.; Kaarela, O.; Byambaa, B.; Sheikhi, A.; Gaharwar, A.K.; Khademhosseini, A. Advancing Frontiers in Bone Bioprinting. Adv. Healthc. Mater. 2019, 8, e1801048. [Google Scholar] [CrossRef] [PubMed]
  147. Chen, Q.; Zou, B.; Lai, Q.; Wang, Y.; Xue, R.; Xing, H.; Fu, X.; Huang, C.; Yao, P. A study on biosafety of HAP ceramic prepared by SLA-3D printing technology directly. J. Mech. Behav. Biomed. Mater. 2019, 98, 327–335. [Google Scholar] [CrossRef]
  148. Yz, A.; Hs, A.; Tao, L.A.; Jiang, P.; Awb, C.; Zz, A.; Lw, A.; Sl, A.; Xy, A. Effect of Ca/P ratios on porous calcium phosphate salt bioceramic scaffolds for bone engineering by 3D gel-printing method—ScienceDirect. Ceram. Int. 2019, 45, 20493–20500. [Google Scholar]
  149. Zeng, Y.; Zhou, M.; Mou, S.; Yang, J.; Yuan, Q.; Guo, L.; Zhong, A.; Wang, J.; Sun, J.; Wang, Z. Sustained delivery of alendronate by engineered collagen scaffold for the repair of osteoporotic bone defects and resistance to bone loss. J. Biomed. Mater. Res. A 2020, 108, 2460–2472. [Google Scholar] [CrossRef]
  150. Chua, C.K.; Leong, K.F.; Tan, K.H.; Wiria, F.E.; Cheah, C.M. Development of tissue scaffolds using selective laser sintering of polyvinyl alcohol/hydroxyapatite biocomposite for craniofacial and joint defects. J. Mater. Sci. Mater. Med. 2004, 15, 1113–1121. [Google Scholar] [CrossRef]
  151. Liu, C.G.; Zeng, Y.T.; Kankala, R.K.; Zhang, S.S.; Chen, A.Z.; Wang, S.B. Characterization and Preliminary Biological Evaluation of 3D-Printed Porous Scaffolds for Engineering Bone Tissues. Materials 2018, 11, 1832. [Google Scholar] [CrossRef] [Green Version]
  152. Yan, Y.; Chen, H.; Zhang, H.; Guo, C.; Yang, K.; Chen, K.; Cheng, R.; Qian, N.; Sandler, N.; Zhang, Y.S.; et al. Vascularized 3D printed scaffolds for promoting bone regeneration. Biomaterials 2019, 190–191, 97–110. [Google Scholar] [CrossRef] [PubMed]
  153. Zhang, B.; Xuan, P.; Ping, S.; Sun, H.; Li, H.; Fan, Y.; Jiang, Q.; Zhou, C.; Zhang, X. Porous bioceramics produced by inkjet 3D printing: Effect of printing ink formulation on the ceramic macro and micro porous architectures control. Compos. B Eng. 2018, 155, 112–121. [Google Scholar] [CrossRef]
  154. Lin, K.; Sheikh, R.; Romanazzo, S.; Roohani, I. 3D Printing of Bioceramic Scaffolds-Barriers to the Clinical Translation: From Promise to Reality, and Future Perspectives. Materials 2019, 12, 2660. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  155. Zuo, M.; Pan, N.; Liu, Q.; Ren, X.; Liu, Y.; Huang, T.S. Three-dimensionally printed polylactic acid/cellulose acetate scaffolds with antimicrobial effect. RSC Adv. 2020, 10, 2952–2958. [Google Scholar] [CrossRef] [Green Version]
  156. Zhang, X.; Cheng, G.; Xing, X.; Liu, J.; Cheng, Y.; Ye, T.; Wang, Q.; Xiao, X.; Li, Z.; Deng, H. Near-Infrared Light-Triggered Porous AuPd Alloy Nanoparticles To Produce Mild Localized Heat To Accelerate Bone Regeneration. J. Phys. Chem. Lett. 2019, 10, 4185–4191. [Google Scholar] [CrossRef]
  157. 1Isaacson, B.M.; Bloebaum, R.D. Bone bioelectricity: What have we learned in the past 160 years? J. Biomed. Mater. Res. A 2010, 95, 1270–1279. [Google Scholar] [CrossRef]
  158. Kuzyk, P.R.; Schemitsch, E.H. The science of electrical stimulation therapy for fracture healing. Indian J. Orthop. 2009, 43, 127–131. [Google Scholar]
  159. Darendeliler, M.A.; Darendeliler, A.; Sinclair, P.M. Effects of static magnetic and pulsed electromagnetic fields on bone healing. Int. J. Adult Orthodon Orthognath. Surg. 1997, 12, 43–53. [Google Scholar]
  160. Maharjan, B.; Kaliannagounder, V.K.; Jang, S.R.; Awasthi, G.P.; Bhattarai, D.P.; Choukrani, G.; Park, C.H.; Kim, C.S. In-situ polymerized polypyrrole nanoparticles immobilized poly(ε-caprolactone) electrospun conductive scaffolds for bone tissue engineering. Mater. Sci. Eng. C Mater. Biol. Appl. 2020, 114, 111056. [Google Scholar] [CrossRef]
  161. Yun, H.M.; Ahn, S.J.; Park, K.R.; Kim, M.J.; Kim, J.J.; Jin, G.Z.; Kim, H.W.; Kim, E.C. Magnetic nanocomposite scaffolds combined with static magnetic field in the stimulation of osteoblastic differentiation and bone formation. Biomaterials 2016, 85, 88–98. [Google Scholar] [CrossRef]
  162. Johnstone, R.M.; Adam, M.; Hammond, J.R.; Orr, L.; Turbide, C. Vesicle formation during reticulocyte maturation. Association of plasma membrane activities with released vesicles (exosomes). J. Biol. Chem. 1987, 262, 9412–9420. [Google Scholar] [CrossRef]
  163. Skotland, T.; Sandvig, K.; Llorente, A. Lipids in exosomes: Current knowledge and the way forward. Prog. Lipid Res. 2017, 66, 30–41. [Google Scholar] [CrossRef] [PubMed]
  164. Liu, J.; Li, D.; Wu, X.; Dang, L.; Lu, A.; Zhang, G. Bone-derived exosomes. Curr. Opin. Pharmacol. 2017, 34, 64–69. [Google Scholar] [CrossRef]
  165. Raposo, G.; Nijman, H.W.; Stoorvogel, W.; Liejendekker, R.; Harding, C.V.; Melief, C.J.; Geuze, H.J. B lymphocytes secrete antigen-presenting vesicles. J. Exp. Med. 1996, 183, 1161–1172. [Google Scholar] [CrossRef] [PubMed]
  166. Phinney, D.G.; Pittenger, M.F. Concise Review: MSC-Derived Exosomes for Cell-Free Therapy. Stem Cells 2017, 35, 851–858. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  167. Fan, J.; Lee, C.S.; Kim, S.; Chen, C.; Aghaloo, T.; Lee, M. Generation of Small RNA-Modulated Exosome Mimetics for Bone Regeneration. ACS Nano 2020, 14, 11973–11984. [Google Scholar] [CrossRef]
  168. Xu, J.F.; Yang, G.H.; Pan, X.H.; Zhang, S.J.; Zhao, C.; Qiu, B.S.; Gu, H.F.; Hong, J.F.; Cao, L.; Chen, Y.; et al. Altered microRNA expression profile in exosomes during osteogenic differentiation of human bone marrow-derived mesenchymal stem cells. PLoS ONE 2014, 9, e114627. [Google Scholar] [CrossRef]
  169. Qin, Y.; Wang, L.; Gao, Z.; Chen, G.; Zhang, C. Bone marrow stromal/stem cell-derived extracellular vesicles regulate osteoblast activity and differentiation in vitro and promote bone regeneration in vivo. Sci. Rep. 2016, 6, 21961. [Google Scholar] [CrossRef]
  170. Zhang, J.; Liu, X.; Li, H.; Chen, C.; Hu, B.; Niu, X.; Li, Q.; Zhao, B.; Xie, Z.; Wang, Y. Exosomes/tricalcium phosphate combination scaffolds can enhance bone regeneration by activating the PI3K/Akt signaling pathway. Stem Cell Res. Ther. 2016, 7, 136. [Google Scholar] [CrossRef] [Green Version]
  171. Jing, X.; Wang, S.; Tang, H.; Li, D.; Zhou, F.; Xin, L.; He, Q.; Hu, S.; Zhang, T.; Chen, T.; et al. Dynamically Bioresponsive DNA Hydrogel Incorporated with Dual-Functional Stem Cells from Apical Papilla-Derived Exosomes Promotes Diabetic Bone Regeneration. ACS Appl. Mater. Interfaces 2022, 14, 16082–16099. [Google Scholar] [CrossRef]
  172. Li, F.; Wu, J.; Li, D.; Hao, L.; Li, Y.; Yi, D.; Yeung, K.W.K.; Chen, D.; Lu, W.W.; Pan, H.; et al. Engineering stem cells to produce exosomes with enhanced bone regeneration effects: An alternative strategy for gene therapy. J. Nanobiotechnol. 2022, 20, 135. [Google Scholar] [CrossRef] [PubMed]
  173. Han, L.; Liu, H.; Fu, H.; Hu, Y.; Fang, W.; Liu, J. Exosome-delivered BMP-2 and polyaspartic acid promotes tendon bone healing in rotator cuff tear via Smad/RUNX2 signaling pathway. Bioengineered 2022, 13, 1459–1475. [Google Scholar] [CrossRef] [PubMed]
  174. Bin-Bin, Z.; Da-Wa, Z.X.; Chao, L.; Lan-Tao, Z.; Tao, W.; Chuan, L.; Chao-Zheng, L.; De-Chun, L.; Chang, F.; Shu-Qing, W.; et al. M2 macrophagy-derived exosomal miRNA-26a-5p induces osteogenic differentiation of bone mesenchymal stem cells. J. Orthop. Surg. Res. 2022, 17, 137. [Google Scholar] [CrossRef]
  175. Lin, Z.; Xiong, Y.; Meng, W.; Hu, Y.; Chen, L.; Chen, L.; Xue, H.; Panayi, A.C.; Zhou, W.; Sun, Y.; et al. Exosomal PD-L1 induces osteogenic differentiation and promotes fracture healing by acting as an immunosuppressant. Bioact. Mater. 2022, 13, 300–311. [Google Scholar] [CrossRef]
  176. Li, Z.; Wang, Y.; Li, S.; Li, Y. Exosomes Derived From M2 Macrophages Facilitate Osteogenesis and Reduce Adipogenesis of BMSCs. Front. Endocrinol. 2021, 12, 680328. [Google Scholar] [CrossRef] [PubMed]
  177. Wu, D.; Chang, X.; Tian, J.; Kang, L.; Wu, Y.; Liu, J.; Wu, X.; Huang, Y.; Gao, B.; Wang, H.; et al. Bone mesenchymal stem cells stimulation by magnetic nanoparticles and a static magnetic field: Release of exosomal miR-1260a improves osteogenesis and angiogenesis. J. Nanobiotechnol. 2021, 19, 209. [Google Scholar] [CrossRef] [PubMed]
  178. Zhang, Y.; Xie, Y.; Hao, Z.; Zhou, P.; Wang, P.; Fang, S.; Li, L.; Xu, S.; Xia, Y. Umbilical Mesenchymal Stem Cell-Derived Exosome-Encapsulated Hydrogels Accelerate Bone Repair by Enhancing Angiogenesis. ACS Appl. Mater. Interfaces 2021, 13, 18472–18487. [Google Scholar] [CrossRef] [PubMed]
  179. Liu, A.; Lin, D.; Zhao, H.; Chen, L.; Cai, B.; Lin, K.; Shen, S.G. Optimized BMSC-derived osteoinductive exosomes immobilized in hierarchical scaffold via lyophilization for bone repair through Bmpr2/Acvr2b competitive receptor-activated Smad pathway. Biomaterials 2021, 272, 120718. [Google Scholar] [CrossRef]
  180. Zhang, Z.; Xu, R.; Yang, Y.; Liang, C.; Yu, X.; Liu, Y.; Wang, T.; Yu, Y.; Deng, F. Micro/nano-textured hierarchical titanium topography promotes exosome biogenesis and secretion to improve osseointegration. J. Nanobiotechnol. 2021, 19, 78. [Google Scholar] [CrossRef]
  181. Fan, L.; Guan, P.; Xiao, C.; Wen, H.; Wang, Q.; Liu, C.; Luo, Y.; Ma, L.; Tan, G.; Yu, P.; et al. Exosome-functionalized polyetheretherketone-based implant with immunomodulatory property for enhancing osseointegration. Bioact. Mater. 2021, 6, 2754–2766. [Google Scholar] [CrossRef]
  182. Cao, Z.; Wu, Y.; Yu, L.; Zou, L.; Yang, L.; Lin, S.; Wang, J.; Yuan, Z.; Dai, J. Exosomal miR-335 derived from mature dendritic cells enhanced mesenchymal stem cell-mediated bone regeneration of bone defects in athymic rats. Mol. Med. 2021, 27, 20. [Google Scholar] [CrossRef] [PubMed]
  183. Liu, L.; Yu, F.; Li, L.; Zhou, L.; Zhou, T.; Xu, Y.; Lin, K.; Fang, B.; Xia, L. Bone marrow stromal cells stimulated by strontium-substituted calcium silicate ceramics: Release of exosomal miR-146a regulates osteogenesis and angiogenesis. Acta Biomater. 2021, 119, 444–457. [Google Scholar] [CrossRef] [PubMed]
  184. Ma, G.; Wu, C. Microneedle, bio-microneedle and bio-inspired microneedle: A review. J. Control Release 2017, 251, 11–23. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  185. Cao, J.; Su, J.; An, M.; Yang, Y.; Zhang, Y.; Zuo, J.; Zhang, N.; Zhao, Y. Novel DEK-Targeting Aptamer Delivered by a Hydrogel Microneedle Attenuates Collagen-Induced Arthritis. Mol. Pharm. 2021, 18, 305–316. [Google Scholar] [CrossRef] [PubMed]
  186. Daddona, P.E.; Matriano, J.A.; Mandema, J.; Maa, Y.F. Parathyroid hormone (1-34)-coated microneedle patch system: Clinical pharmacokinetics and pharmacodynamics for treatment of osteoporosis. Pharm. Res. 2011, 28, 159–165. [Google Scholar] [CrossRef] [PubMed]
  187. Kelekis, A.; Filippiadis, D.K.; Kelekis, N.L.; Martin, J.B. Percutaneous augmented osteoplasty of the humeral bone using a combination of microneedles mesh and cement. J. Vasc. Interv. Radiol. 2015, 26, 595–597. [Google Scholar] [CrossRef]
  188. Katsumi, H.; Liu, S.; Tanaka, Y.; Hitomi, K.; Hayashi, R.; Hirai, Y.; Kusamori, K.; Quan, Y.S.; Kamiyama, F.; Sakane, T.; et al. Development of a novel self-dissolving microneedle array of alendronate, a nitrogen-containing bisphosphonate: Evaluation of transdermal absorption, safety, and pharmacological effects after application in rats. J. Pharm. Sci. 2012, 101, 3230–3238. [Google Scholar] [CrossRef]
  189. Katsumi, H.; Tanaka, Y.; Hitomi, K.; Liu, S.; Quan, Y.S.; Kamiyama, F.; Sakane, T.; Yamamoto, A. Efficient Transdermal Delivery of Alendronate, a Nitrogen-Containing Bisphosphonate, Using Tip-Loaded Self-Dissolving Microneedle Arrays for the Treatment of Osteoporosis. Pharmaceutics 2017, 9, 29. [Google Scholar] [CrossRef]
  190. Carswell, A.T.; Eastman, K.G.; Casey, A.; Hammond, M.; Shepstone, L.; Payerne, E.; Toms, A.P.; MacKay, J.W.; Swart, A.M.; Greeves, J.P.; et al. Teriparatide and stress fracture healing in young adults (RETURN—Research on Efficacy of Teriparatide Use in the Return of recruits to Normal duty): Study protocol for a randomised controlled trial. Trials 2021, 22, 580. [Google Scholar] [CrossRef]
  191. Cosman, F.; Lane, N.E.; Bolognese, M.A.; Zanchetta, J.R.; Garcia-Hernandez, P.A.; Sees, K.; Matriano, J.A.; Gaumer, K.; Daddona, P.E. Effect of transdermal teriparatide administration on bone mineral density in postmenopausal women. J. Clin. Endocrinol. Metab. 2010, 95, 151–158. [Google Scholar] [CrossRef]
  192. Ameri, M.; Fan, S.C.; Maa, Y.F. Parathyroid hormone PTH(1-34) formulation that enables uniform coating on a novel transdermal microprojection delivery system. Pharm. Res. 2010, 27, 303–313. [Google Scholar] [CrossRef] [PubMed]
  193. Naito, C.; Katsumi, H.; Suzuki, T.; Quan, Y.S.; Kamiyama, F.; Sakane, T.; Yamamoto, A. Self-Dissolving Microneedle Arrays for Transdermal Absorption Enhancement of Human Parathyroid Hormone (1-34). Pharmaceutics 2018, 10, 215. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  194. Arlt, H.; Besschetnova, T.; Ominsky, M.S.; Fredericks, D.C.; Lanske, B. Effects of systemically administered abaloparatide, an osteoanabolic PTHrP analog, as an adjuvant therapy for spinal fusion in rats. JOR Spine 2021, 4, e1132. [Google Scholar] [CrossRef] [PubMed]
  195. Shirley, M. Abaloparatide: First Global Approval. Drugs 2017, 77, 1363–1368. [Google Scholar] [CrossRef] [PubMed]
  196. Tas, C.; Mansoor, S.; Kalluri, H.; Zarnitsyn, V.G.; Choi, S.O.; Banga, A.K.; Prausnitz, M.R. Delivery of salmon calcitonin using a microneedle patch. Int. J. Pharm. 2012, 423, 257–263. [Google Scholar] [CrossRef] [Green Version]
  197. Zhang, L.; Li, Y.; Wei, F.; Liu, H.; Wang, Y.; Zhao, W.; Dong, Z.; Ma, T.; Wang, Q. Transdermal Delivery of Salmon Calcitonin Using a Dissolving Microneedle Array: Characterization, Stability, and In vivo Pharmacodynamics. AAPS PharmSciTech 2020, 22, 1. [Google Scholar] [CrossRef]
  198. Targeted Delivery of Anesthetic Agents to Bone Tissues using Conductive Microneedles Enhanced Iontophoresis for Painless Dental Anesthesia. Adv. Funct. Mater. 2021, 31, 2105686. [CrossRef]
  199. Hourdé, C.; Joanne, P.; Medja, F.; Mougenot, N.; Jacquet, A.; Mouisel, E.; Pannerec, A.; Hatem, S.; Butler-Browne, G.; Agbulut, O.; et al. Voluntary physical activity protects from susceptibility to skeletal muscle contraction-induced injury but worsens heart function in mdx mice. Am. J. Pathol. 2013, 182, 1509–1518. [Google Scholar] [CrossRef]
  200. Kiuru, M.J.; Pihlajamäki, H.K.; Ahovuo, J.A. Bone stress injuries. Acta Radiol. 2004, 45, 317–326. [Google Scholar] [CrossRef]
  201. Horn, A.; Van der Meulen, J.H.; Defour, A.; Hogarth, M.; Sreetama, S.C.; Reed, A.; Scheffer, L.; Chandel, N.S.; Jaiswal, J.K. Mitochondrial redox signaling enables repair of injured skeletal muscle cells. Sci. Signal. 2017, 10, 1978. [Google Scholar] [CrossRef] [Green Version]
  202. Lass, A.; Sohal, B.H.; Weindruch, R.; Forster, M.J.; Sohal, R.S. Caloric restriction prevents age-associated accrual of oxidative damage to mouse skeletal muscle mitochondria. Free Radic. Biol. Med. 1998, 25, 1089–1097. [Google Scholar] [CrossRef] [Green Version]
  203. Cerri, D.G.; Rodrigues, L.C.; Alves, V.M.; Machado, J.; Bastos, V.A.F.; Carmo, K.I.D.; Alberici, L.C.; Costa, M.C.R.; Stowell, S.R.; Cummings, R.D.; et al. Endogenous galectin-3 is required for skeletal muscle repair. Glycobiology 2021, 18, 1295–1307. [Google Scholar] [CrossRef] [PubMed]
Figure 1. Surgical treatment for repairing bone defects. Bone transplantation, prosthetic surgery, reoperation, and fracture fixation are listed as the top four surgical treatments.
Figure 1. Surgical treatment for repairing bone defects. Bone transplantation, prosthetic surgery, reoperation, and fracture fixation are listed as the top four surgical treatments.
Pharmaceuticals 15 00879 g001
Figure 2. Different exogenous stimulation promotes the recovery of bone defects.
Figure 2. Different exogenous stimulation promotes the recovery of bone defects.
Pharmaceuticals 15 00879 g002
Table 1. Bone substitutes used in bone defects.
Table 1. Bone substitutes used in bone defects.
Bone SubstituteCompany and LocationCompositionIndicationPore or Particle SizeIncorporatedReferences
k-IBS®AritMedical, SpainHydroxyapatite (HA) and β-Tricalcium Phosphate (β-TCP) The HA/-TCP ratio was 3/1Solitary enchondroma in the hand bones [78]
InterOss®Sigma, USAMixing bovine hydroxyapatite granules to porcine derived collagen in water in 9:1 ratio (by weight)Fill or reconstruct periodontal and bony defects in the mouth [79]
Bontree®HudensBio Co., Gwangju, KoreaOCP and HA mixed at a weight ratio of 80:20Alveolar ridge or sinus augmentation0.5–1 mm [80]
CustomBone®DePuy Synthes, USA60% calcium sulfate and 40% HAHuman tibial fractures [81]
Traumacem™ V+DePuy Synthes, USAAcrylic bone cement in conjunction with ceramics consisting of 45% PMMA, 40% zirconium dioxide, 14.5% hydroxyapatite, and 0.5% benzoyl peroxideCalcaneal fracture [82]
Vitoss BA®Stryker, Kalamazoo, USAβ-TCP particles bonded on a collagen matrix supplemented with 20 wt% 45S5 bioactive glass particlesMetaphyseal bone defect90–150 μm [83]
HydroSet™ Tetracalcium phosphate (73%), dicalcium phosphate anhydrous (27%) and Na2HPO4, NaH2PO4 and PolyvinylpyrrolidoneBone defect, skeletal fractures, hip replacements [84]
MIIG® X3Wright Medical Technolog, Inc., Arlington, TNCalcium sulfateComminuted calcaneal fractures [85]
Calciresorb C35®Ceraver, USAMacroporous biphasic calcium phosphate ceramic granules (HA/TCP = 65/35)Femoral bone defect6 mmMesenchymal stem cells[86]
ChronOS®Depuy Synthes, Massachusetts, USATCPBone defect5.03 ± 1.90 μm [87]
Graftys®Aix-en-Provence, Franceα-tricalcium phosphate, dicalcium phosphate dihydrate, monocalcium monohydrate, calcium-deficient hydroxyapatite, hydroxypropyl methyl celluloseBone defect [88]
Cerament® 60% calcium sulfate (CS) and 40% HAAcute traumatic depression fractures of the proximal tibia [89]
Bio-Oss®Geistlich, Wolhusen, Switzerland90% DBBM extracted from cattle and 10% highly purified porcine collagen matrixAlveolar bone resorption0.25–1 mm [90]
Healos®DePuy Orthopaedics, Inc.Osteoconductive sponge made of collagen fibers coated with hydroxyapatiteBone defect Recombinant human bone morphogenetic protein-2[91]
SINTlife®Fin-Ceramica, SpA, Faenza, ItalyNano-structured Mg-enriched hydroxyapatiteBone defect30–40 nm [92]
DBSint®Fin-Ceramica, SpA, Faenza, ItalyNano-structured Mg-enriched hydroxyapatite and human demineralized bone matrixBone defect [92]
OsteoSet®2 demineralised bone matrixWright Medical Group Inc., Memphis, Tennessee, USADBM particles homogenously dispersed throughout surgical-grade calcium sulphateLarge osteonecrotic lesions of the femoral head3.5–4.8 mm [93]
OCS-B® Calf bone powder, bone inorganic material in calf boneBone defect0.2–1 mm [94]
BoneSource®Stryker Orthopaedics, Mahwah, New JerseyAn equimolar mixture of tetracalcium phosphate and anhydrous dicalcium phosphateBone defect33.4 ± 6.2 μm [95,96]
Ostim®aap biomaterials GmbH, Dieburg, GermanyNanosized HA and calcium sulphateMetaphyseal osseous volume defects19 nm [97,98]
Cortoss™Orthovita®, Malvern, USAAcrylic resin reinforced with glass ceramic particles, 30% copolymerizing organic components and 70% glass-ceramic fillersCalvarial defects148.4 ± 70.6 μm [96,99]
Calcibon®Biomet-Merck Biomaterials GmbH, Darmstadt, Germany61% alpha-TCP, 26% calcium-hydrogeno-phosphate, 10% calcium-carbonate and 3% hydroxyl-apatiteAcute traumatic compression vertebral fracture without neurological deficit41.6 ± 22.0 μm [96,100]
α-BSM® Apatitic calcium phosphateArticular depression fractures12–14 nm [101]
Norian SRS® Monocalcium phosphate, tricalcium phosphate, calcium carbonate and sodium phosphateDistal radial fracture47.2 ± 21.9 μm [96,102]
Table 2. Principles and applications of 3D printing of bone tissue engineering scaffolds.
Table 2. Principles and applications of 3D printing of bone tissue engineering scaffolds.
PrincipleMethodAdvantageDisadvantageMaterials and Bio-inkApplicationReference
Laser or high energy density heat sourceStereo lithography appearance, SLAFast processing speed; high maturity; high precisionHigh cost; software operation difficulty; high environmental requirementsHydroxyapatite; calcium chloride and diammonium hydrogen phosphateparietal bone; cancellous bone repair;[147,148]
Selected laser sintering, SLSWide selection of materials; without add organic adhesives;High cost and low efficiency;titanium alloy; alendronate-collagen; PVA-HAsegmental bone defects; alveolar bone implant therapy;[132,149,150]
Spray forming technologyFused deposition modeling, FDMLow cost; simple manufacturing; wide application range;Low precision; rough surface; slow speedPLGA; PCL-deferoxaminecancellous bone formation; segmental bone defect[151,152]
3D printing, 3DPPrintable active substance; prepared complex scaffolds;Drying time is long; ink is easy to deteriorateHA powders, air jet milling powders, spherical powderMandibular defect;[153]
Direct ink writing 3D printing (DIW)fast printing speed; easy operation; low cost; high precision;Low molding accuracy; easy to deform [154].PLA/CACraniomaxillofacial Reconstruction[155]
Table 3. Applications and targets of exosomes from different sources in the treatment of bone defects.
Table 3. Applications and targets of exosomes from different sources in the treatment of bone defects.
Origin of ExosomesTargetApplicationReferences
human mesenchymal stem cells exosomesMiR-29amice with nonhealing skull defects[167]
Osteogenic Human exosomesMiR-199b/MiR-218/MiR-148a/MiR-135b/MiR-221human bone marrow-derived mesenchymal stem cells; osteoblast cells[168]
Human bone marrow stromal/stem cell exosomesMiR-196a/MiR-27a/MiR-206bone formation in Sprague Dawley (SD) rats with calvarial defects; osteoblast cells[169]
human-induced pluripotent stem cell-derived mesenchymal stem cells exosomesAkt/p-Akthuman bone marrow-derived mesenchymal stem cells[170]
stem cells from apical papilla-derived exosomesMiRNA-126-5p/MiRNA-150-5pthe mandibular defects of diabetic rats[171]
mesenchymal stem cells exosomesgreen fluorescent protein (GFP)old male C57BL/6 mice[172]
Bone marrow mesenchymal stem cells exosomesSmad/RUNX2acute rotator cuff rupture in rabbits[173]
M2 macrophagy-derived exosomalMiRNA-26a-5pOsteogenic differentiation of BMSCs[174]
Exosomes of human umbilical vein endothelial cellsPd-1 on the surface of T cellscallus formation and fracture healing in a murine model[175]
Exosomes of M2 macrophagesMiR-690 / IRS-1/TAZbone marrow mesenchymal stem cells[176]
Exosomes of bone mesenchymal stem cellsMiR-1260acalvarial defect rat model.[177]
Exosomes derived from mesenchymal stem cellsMiR-21/NOTCH1/DLL4skull defects in rats.[178]
Exosomes derived from mesenchymal stem cellsAcvr2b/Acvr1rat skull defect model[179]
Exosomes derived from bone marrow mesenchymal stem cellsRAB27B/SMPD3Human bone marrow mesenchymal stem cells; osteogenic cells; SD rats[180]
Exosomes derived from bone marrow stem cellsNF-κBBMSC. rat balloon models and rat femoral borehole models[181]
Exosomes of mature dendritic cellslarge tongue suppressor kinase 1 (LATS1)femoral bone defect in athymic rats[182]
Exosomes derived from bone marrow stromal cellsMiR-146ahuman umbilical vein endothelial cells; distal femur defect in rats.[183]
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Xue, N.; Ding, X.; Huang, R.; Jiang, R.; Huang, H.; Pan, X.; Min, W.; Chen, J.; Duan, J.-A.; Liu, P.; et al. Bone Tissue Engineering in the Treatment of Bone Defects. Pharmaceuticals 2022, 15, 879.

AMA Style

Xue N, Ding X, Huang R, Jiang R, Huang H, Pan X, Min W, Chen J, Duan J-A, Liu P, et al. Bone Tissue Engineering in the Treatment of Bone Defects. Pharmaceuticals. 2022; 15(7):879.

Chicago/Turabian Style

Xue, Nannan, Xiaofeng Ding, Rizhong Huang, Ruihan Jiang, Heyan Huang, Xin Pan, Wen Min, Jun Chen, Jin-Ao Duan, Pei Liu, and et al. 2022. "Bone Tissue Engineering in the Treatment of Bone Defects" Pharmaceuticals 15, no. 7: 879.

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop