Osteoinductive activity of biphasic calcium phosphate with different rhBMP-2 doses in rats

3D printed PLGA scaffold with nano-hydroxyapatite carrying linezolid for treatment of infected bone defects

BACKGROUND

Linezolid has been reported to protect against chronic bone and joint infection. In this study, linezolid was loaded into the 3D printed poly (lactic-co-glycolic acid) (PLGA) scaffold with nano-hydroxyapatite (HA) to explore the effect of this composite scaffold on infected bone defect (IBD).

METHODS

PLGA scaffolds were produced using the 3D printing method. Drug release of linezolid was analyzed by elution and high-performance liquid chromatography assay. PLGA, PLGA-HA, and linezolid-loaded PLGA-HA scaffolds, were implanted into the defect site of a rabbit radius defect model. Micro-CT, H&E, and Masson staining, and immunohistochemistry were performed to analyze bone infection and bone healing. Evaluation of viable bacteria was performed. The cytocompatibility of 3D-printed composite scaffolds in vitro was detected using human bone marrow mesenchymal stem cells (BMSCs). Long-term safety of the scaffolds in rabbits was evaluated.

RESULTS

The linezolid-loaded PLGA-HA scaffolds exhibited a sustained release of linezolid and showed significant antibacterial effects. In the IBD rabbit models implanted with the scaffolds, the linezolid-loaded PLGA-HA scaffolds promoted bone healing and attenuated bone infection. The PLGA-HA scaffolds carrying linezolid upregulated the expression of osteogenic genes including collagen I, runt-related transcription factor 2, and osteocalcin. The linezolid-loaded PLGA-HA scaffolds promoted the proliferation and osteogenesis of BMSCs in vitro via the PI3K/AKT pathway. Moreover, the rabbits implanted with the linezolid-loaded scaffolds showed normal biochemical profiles and normal histology, which suggested the safety of the linezolid-loaded scaffolds.

CONCLUSION

Overall, the linezolid-loaded PLGA-HA scaffolds fabricated by 3D printing exerts significant bone repair and anti-infection effects.

Osteogenic Potential of Nano-Hydroxyapatite and Strontium-Substituted Nano-Hydroxyapatite

Nanohydroxyapatite (nanoHA) is the major mineral component of bone. It is highly biocompatible, osteoconductive, and forms strong bonds with native bone, making it an excellent material for bone regeneration. However, enhanced mechanical properties and biological activity for nanoHA can be achieved through enrichment with strontium ions. Here, nanoHA and nanoHA with a substitution degree of 50 and 100% of calcium with strontium ions (Sr-nanoHA_50 and Sr-nanoHA_100, respectively) were produced via wet chemical precipitation using calcium, strontium, and phosphorous salts as starting materials. The materials were evaluated for their cytotoxicity and osteogenic potential in direct contact with MC3T3-E1 pre-osteoblastic cells. All three nanoHA-based materials were cytocompatible, featured needle-shaped nanocrystals, and had enhanced osteogenic activity in vitro. The Sr-nanoHA_100 indicated a significant increase in the alkaline phosphatase activity at day 14 compared to the control. All three compositions revealed significantly higher calcium and collagen production up to 21 days in culture compared to the control. Gene expression analysis exhibited, for all three nanoHA compositions, a significant upregulation of osteonectin and osteocalcin on day 14 and of osteopontin on day 7 compared to the control. The highest osteocalcin levels were found for both Sr-substituted compounds on day 14. These results demonstrate the great osteoinductive potential of the produced compounds, which can be exploited to treat bone disease.

Enhanced Biocompatibility and Osteogenic Activity of Marine-Plankton-Derived Whitlockite Bone Granules through Bone Morphogenetic Protein 2 Incorporation

Whitlockite (WH) is a calcium-phosphate-based Mg-containing ceramic with good mechanical properties, rapid resorption, and good osteogenicity. Recently, we successfully synthesized highly porous WH granules using a marine plankton exoskeleton (MP-WH). In the present study, we improved the osteoinductive activity of MP-WH granules by bone morphogenetic protein2 (BMP2) (MP-WH/BMP2). The surface morphology and composition of the fabricated MP-WH/BMP2 granules were characterized using scanning electron microscopy (SEM), X-ray diffraction, and Fourier transform infrared (FT-IR) spectroscopy. The biocompatibility and osteogenic effects were evaluated using human mesenchymal stem cells (hMSCs). BMP2 was absorbed on the surfaces of the MP-WH/BMP2 granules. Immobilized BMP2 was released at a moderate rate over 30 days. hMSCs seeded on MP-WH/BMP2 granules became biocompatible, with a better proliferation and adhesion for MP-WH/BMP2, compared with MP-WH. Bone-specific markers Runx2, type I collagen, osteocalcin, and osteopontin were significantly upregulated following BMP2 incorporation. Similar observations were made regarding the alkaline phosphatase activity. This study suggests that BMP2 incorporation improves the osteoinductive activity of marine-plankton-derived WH granules for bone tissue repair.

The Granule Size Mediates the In Vivo Foreign Body Response and the Integration Behavior of Bone Substitutes

The physicochemical properties of synthetically produced bone substitute materials (BSM) have a major impact on biocompatibility. This affects bony tissue integration, osteoconduction, as well as the degradation pattern and the correlated inflammatory tissue responses including macrophages and multinucleated giant cells (MNGCs). Thus, influencing factors such as size, special surface morphologies, porosity, and interconnectivity have been the subject of extensive research. In the present publication, the influence of the granule size of three identically manufactured bone substitute granules based on the technology of hydroxyapatite (HA)-forming calcium phosphate cements were investigated, which includes the inflammatory response in the surrounding tissue and especially the induction of MNGCs (as a parameter of the material degradation). For the in vivo study, granules of three different size ranges (small = 0.355-0.5 mm; medium = 0.5-1 mm; big = 1-2 mm) were implanted in the subcutaneous connective tissue of 45 male BALB/c mice. At 10, 30, and 60 days post implantationem, the materials were explanted and histologically processed. The defect areas were initially examined histopathologically. Furthermore, pro- and anti-inflammatory macrophages were quantified histomorphometrically after their immunohistochemical detection. The number of MNGCs was quantified as well using a histomorphometrical approach. The results showed a granule size-dependent integration behavior. The surrounding granulation tissue has passivated in the groups of the two bigger granules at 60 days post implantationem including a fibrotic encapsulation, while a granulation tissue was still present in the group of the small granules indicating an ongoing cell-based degradation process. The histomorphometrical analysis showed that the number of proinflammatory macrophages was significantly increased in the small granules at 60 days post implantationem. Similarly, a significant increase of MNGCs was detected in this group at 30 and 60 days post implantationem. Based on these data, it can be concluded that the integration and/or degradation behavior of synthetic bone substitutes can be influenced by granule size.

Bone Morphogenetic Proteins, Carriers, and Animal Models in the Development of Novel Bone Regenerative Therapies

Bone morphogenetic proteins (BMPs) possess a unique ability to induce new bone formation. Numerous preclinical studies have been conducted to develop novel, BMP-based osteoinductive devices for the management of segmental bone defects and posterolateral spinal fusion (PLF). In these studies, BMPs were combined with a broad range of carriers (natural and synthetic polymers, inorganic materials, and their combinations) and tested in various models in mice, rats, rabbits, dogs, sheep, and non-human primates. In this review, we summarized bone regeneration strategies and animal models used for the initial, intermediate, and advanced evaluation of promising therapeutical solutions for new bone formation and repair. Moreover, in this review, we discuss basic aspects to be considered when planning animal experiments, including anatomical characteristics of the species used, appropriate BMP dosing, duration of the observation period, and sample size.

Three-Dimensionally-Printed Bioactive Ceramic Scaffolds: Construct Effects on Bone Regeneration

BACKGROUND/PURPOSE

The utilization of three-dimensionally (3D)-printed bioceramic scaffolds composed of beta-tricalcium phosphate in conjunction with dipyridamole have shown to be effective in the osteogenesis of critical bone defects in both skeletally immature and mature animals. Furthermore, previous studies have proven the dura and pericranium's osteogenic capacity in the presence of 3D-printed scaffolds; however, the effect galea aponeurotica on osteogenesis in the presence of 3D scaffolds remains unclear.

METHOD/DESCRIPTION

Critical-sized (11 mm) bilateral calvarial defects were created in 35-day old rabbits (n = 7). Two different 3D scaffolds were created, with one side of the calvaria being treated with a solid nonporous cap and the other with a fully porous cap. The solid cap feature was designed with the intention of preventing communication of the galea and the ossification site, while the porous cap permitted such communication. The rabbits were euthanized 8 weeks postoperatively. Calvaria were analyzed using microcomputed tomography, 3D reconstruction, and nondecalcified histologic sectioning in order assess differences in bone growth between the two types of scaffolding.

RESULTS

Scaffolds with the solid (nonporous) cap yielded greater percent bone volume (P = 0.012) as well as a greater percent potential bone (P = 0.001) compared with the scaffolds with a porous cap. The scaffolds with porous caps also exhibited a greater percent volume of soft tissue (P < 0.001) presence. There were no statistically significant differences detected in scaffold volume.

CONCLUSION

A physical barrier preventing the interaction of the galea aponeurotica with the scaffold leads to significantly increased calvarial bone regeneration in comparison with the scaffolds allowing for this interaction. The galea's interaction also leads to more soft tissue growth hindering the in growth of bone in the porous-cap scaffolds.

Osteogenic Peptides and Attachment Methods Determine Tissue Regeneration in Modified Bone Graft Substitutes

The inclusion of biofunctional molecules with synthetic bone graft substitutes has the potential to enhance tissue regeneration during treatment of traumatic bone injuries. The clinical use of growth factors has though been associated with complications, some serious. The use of smaller, active peptides has the potential to overcome these problems and provide a cost-effective, safe route for the manufacture of enhanced bone graft substitutes. This review considers the design of peptide-enhanced bone graft substitutes, and how peptide selection and attachment method determine clinical efficacy. It was determined that covalent attachment may reduce the known risks associated with growth factor-loaded bone graft substitutes, providing a predictable tissue response and greater clinical efficacy. Peptide choice was found to be critical, but even within recognised families of biologically active peptides, the configurations that appeared to most closely mimic the biological molecules involved in natural bone healing processes were most potent. It was concluded that rational, evidence-based design of peptide-enhanced bone graft substitutes offers a pathway to clinical maturity in this highly promising field.

Enhancing osteoregenerative potential of biphasic calcium phosphates by using bioinspired ZIF8 coating

Biphasic calcium phosphate ceramics (BCPs) have been extensively used as a bone graft in dental clinics to reconstruct lost bone in the jaw and peri-implant hard tissue due to their good bone conduction and similar chemical structure to the teeth and bone. However, BCPs are not inherently osteoinductive and need additional modification and treatment to enhance their osteoinductivity. The present study aims to develop an innovative strategy to improve the osteoinductivity of BCPs using unique features of zeolitic imidazolate framework-8 (ZIF8). In this method, commercial BCPs (Osteon II) were pre-coated with a zeolitic imidazolate framework-8/polydopamine/polyethyleneimine (ZIF8/PDA/PEI) layer to form a uniform and compact thin film of ZIF8 on the surface of BCPs. The surface morphology and chemical structure of ZIF8 modified Osteon II (ZIF8-Osteon) were confirmed using various analytical techniques such as XRD, FTIR, SEM, and EDX. We evaluated the effect of ZIF8 coating on cell attachment, growth, and osteogenic differentiation of human adipose-derived mesenchymal stem cells (hADSCs). The results revealed that altering the surface chemistry and topography of Osteon II using ZIF8 can effectively promote cell attachment, proliferation, and bone regeneration in both in vitro and in vivo conditions. In conclusion, the method applied in this study is simple, low-cost, and time-efficient and can be used as a versatile approach for improving osteoinductivity and osteoconductivity of other types of alloplastic bone grafts.

Comparative analysis of platelet-rich fibrin, platelet-rich fibrin with hydroxyapatite and platelet-rich fibrin with alendronate in bone regeneration: A cone-beam computed tomography analysis

Aim

This clinical study was designed to evaluate the volumetric healing of periapical (PA) bone defect after PA surgery, using platelet-rich fibrin (PRF), and its combination with hydroxyapatite and alendronate.

Subjects and Methods

Twenty male patients of age between 25 and 35 years, having PA pathology (>5 mm on intraoral periapical radiograph (IOPA)) with intraoral sinus opening, were included in this study. Cone-beam computed tomography (CBCT) imaging of all patients was done. Root canal treatment with PA surgery was done. Patients were divided into four groups (5 in each group), on the basis of material placed in PA bone defect. After 1 year, CBCT imaging was done. Linear measurement of maximal dimensions in all three orthogonal planes was done in both pre- and post-CBCT image. These measurements were used to estimate the volume of the lesion healed after 1 year of surgery.

Statistical Analysis

Analysis of variance and Post hoc Tukey's test were used for statistical analysis.

Results

Change in volume were significantly different between Group 1 vs Group 3; Group 2 vs Group 3 and Group 3 vs Group 4. The Group Order for change in volume 1 year post surgery Group 3> Group 4 ≈ Group 2> Group 1.

Conclusions

PA bone healing after surgery is enhanced by placing combination of bone regenerative materials. PRF with hydroxyapatite provides best healing outcomes in comparison to PRF with alendronate or PRF alone.

Autologous bone graft substitute containing rhBMP6 within autologous blood coagulum and synthetic ceramics of different particle size determines the quantity and structural pattern of bone formed in a rat subcutaneous assay

Bone morphogenetic proteins (BMPs) are potent osteoinductive agents for bone tissue engineering. In order to define optimal properties of a novel autologous bone graft substitute (ABGS) containing rhBMP6 within the autologous blood coagulum (ABC) and ceramic particles as a compression resistant matrix (CRM), we explored the influence of their amount, chemical composition and particle size on the quantity and quality of bone formation in the rat subcutaneous assay. Tested ceramic particles included tricalcium phosphate (TCP), hydroxyapatite (HA) and biphasic calcium phosphate ceramic (BCP), containing TCP and HA in 80/20 ratio of different particle sizes (small 74-420 μm, medium 500-1700 μm and large 1000-4000 μm). RhBMP6 was either mixed with ABC or lyophilized on CRM prior to use with ABC. The experiments were terminated on day 21 and implants were analysed by microCT, histology and histomorphometry. Addition of CRM to ABGS containing rhBMP6 in ABC significantly increased the amount of newly formed bone and the optimal CRM/ABC ratio was found to be around 100 mg/500 μL. MicroCT analyses revealed that all tested ABGS formulations induced an extensive new bone formation and there were no differences between the two methods of rhBMP6 application as determined by the bone volume. However, the particle size played a significant role in the quantity and quality of newly formed bone. ABGS containing small particles induced new bone forming a dense trabecular network, cortical bone at the rim, bone and bone marrow in apposition to and in between ceramic particles. ABGS containing medium and large particles also resulted in new bone on the surface of particles as well as inside the pores. Histomorphometric analysis revealed that the ceramics particle size correlated with the quality of trabecular pattern of newly formed bone, bone/bone marrow ratio as observed in apposition and between particles, and the ratio between the cortical and trabecular bone. By employing rat subcutaneous implant assay, we showed for the first time that the size of synthetic ceramics particles affected the osteogenesis as defined by both the quantity and quality of ectopic bone.

rhBMP-2 Pre-Treated Human Periodontal Ligament Stem Cell Sheets Regenerate a Mineralized Layer Mimicking Dental Cementum

The periodontal complex consisting of alveolar bone, cementum, and periodontal ligaments (PDL) supports human teeth through the systematic orchestration of mineralized tissues and fibrous tissues. Importantly, cementum, the outermost mineralized layer of dental roots, plays an essential role by bridging the inner ligaments from the dental root to the alveolar bone. When the periodontal complex is damaged, the regeneration of each component of the periodontal complex is necessary; however, it is still challenging to achieve complete functional regeneration. In this study, we tried to control the regeneration of cementum and PDL by using a human PDL stem cell (hPDLSC) sheet engineering technology with the pretreatment of recombinant human BMP-2 (rhBMP-2). Isolated hPDLSCs obtained from extracted human teeth were pretreated with rhBMP-2 for in vitro osteogenic differentiation and grafted on the micro/macro-porous biphasic calcium phosphate (MBCP) blocks, which represent dental roots. The MBCPs with hPDLSC sheets were implanted in the subcutaneous layer of immune-compromised mice, and rhBMP-2 pretreated hPDLSC sheets showed higher mineralization and collagen ligament deposition than the no-pretreatment group. Therefore, the rhBMP-2-hPDLSC sheet technique could be an effective strategy for the synchronized regeneration of two different tissues: mineralized tissue and fibrous tissues in periodontal complexes.

Recent Advances of Biphasic Calcium Phosphate Bioceramics for Bone Tissue Regeneration

Biphasic calcium phosphate bioceramics consist of an intimate mixture of hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP) in varying ratios. Due to their biocompatibility, osteoconductivity, and safety in in vitro, in vivo, and clinical models, they have become promising bone substitute biomaterials and are recommended for use as alternatives for or as additives in bone tissue regeneration in various orthopedic and dental applications. Many studies have demonstrated the potential uses of BCP bioceramics as scaffolds for tissue engineering. Here, we highlight the recent advances in the uses of BCP bioceramics and functionalized BCPs for bone tissue regeneration.

Microporous polysaccharide multilayer coated BCP composite scaffolds with immobilised calcitriol promote osteoporotic bone regeneration both in vitro and in vivo

Incorporating a biomimetic coating and integrating osteoinductive biomolecules into basic bone substitutes are two common strategies to improve osteogenic capabilities in bone tissue engineering. Currently, the underlying mechanism of osteoporosis (OP)-related deficiency of osteogenesis remains unclear, and few treatments target at OP-related bone regeneration. Herein, we describe a self-assembling polyelectrolyte multilayered (PEM) film coating with local immobilisation of calcitriol (Cal) in biphasic calcium phosphate (BCP) scaffolds to promote osteoporotic bone regeneration by targeting the calcium sensing receptor (CaSR). Methods: The ovariectomy-induced functional changes in bone marrow mesenchymal stem cells (BMSCs), protective effects of Cal, and the potential mechanism were all verified. A PEM film composed of hyaluronic acid (HA) and chitosan (Chi) was prepared through layer-by-layer self-assembly. The morphology, growth behaviour, and drug retention capability of the composite scaffolds were characterised, and their biocompatibility and therapeutic efficacy for bone regeneration were systematically explored in vitro and in vivo.Results: The osteogenic differentiation, adhesion, and proliferation abilities of ovariectomised rat BMSCs (OVX-rBMSCs) decreased, in accordance with the deficiency of CaSR. Cal effectively activated osteogenesis in these OVX-rBMSCs by binding specifically to the active pocket of the CaSR structure, while the biomimetic PEM coating augmented OVX-rBMSCs proliferation and adhesion due to its porous surface structure. The PEM-coated scaffolds showed advantages in Cal loading and retention, especially at lower drug concentrations. HA/Chi PEM synergised with Cal to improve the proliferation, adhesion, and osteogenesis of OVX-rBMSCs and promote bone regeneration and BCP degradation in the critical-size calvarial bone defect model of OVX rats. Conclusion: A composite scaffold based on BCP, created by simply combining a biomimetic PEM coating and Cal immobilisation, could be clinically useful and has marked advantages as a targeted, off-the-shelf, cell-free treatment option for osteoporotic bone regeneration.

Effect of Fluoride Doping in Laponite Nanoplatelets on Osteogenic Differentiation of Human Dental Follicle Stem Cells (hDFSCs)

Bioactive nanosilicates are emerging prominent next generation biomaterials due to their intrinsic functional properties such as advanced biochemical and biophysical cues. Recent studies show interesting dose-dependent effect of fluoride ions on the stem cells. Despite of interesting properties of fluoride ions as well as nanosilicate, there is no reported literature on the effect of fluoride-doped nanosilicates on stem cells. We have systematically evaluated the interaction of fluoride nanosilicate platelets (NS + F) with human dental follicle stem cells (hDFSCs) to probe the cytotoxicity, cellular transport (internalization) and osteogenic differentiation capabilities in comparison with already reported nanosilicate platelets without fluoride (NS − F). To understand the osteoinductive and osteoconductive properties of the nanosilicate system, nanosilicate treated hDFSCs are cultured in three different medium namely normal growth medium, osteoconductive medium, and osteoinductive medium up to 21 d. NS + F treated stem cells show higher ALP activity, osteopontin levels and significant alizarin red staining compared to NS − F treated cells. This study highlights that the particles having fluoride additives (NS + F) aid in enhancing the osteogenic differentiation capabilities of hDFSCs thus potential nanobiomaterial for periodontal bone tissue regeneration.

Spatiotemporal Control Strategies for Bone Formation through Tissue Engineering and Regenerative Medicine Approaches

Global increases in life expectancy drive increasing demands for bone regeneration. The gold standard for surgical bone repair is autografting, which enjoys excellent clinical outcomes; however, it possesses significant drawbacks including donor site morbidity and limited availability. Although collagen sponges delivered with bone morphogenetic protein, type 2 (BMP2) are a common alternative or supplement, they do not efficiently retain BMP2, necessitating extremely high doses to elicit bone formation. Hence, reports of BMP2 complications are rising, including cancer promotion and ectopic bone formation, the latter inducing complications such as breathing difficulties and neurologic impairments. Thus, efforts to exert spatial control over bone formation are increasing. Several tissue engineering approaches have demonstrated the potential for targeted and controlled bone formation. These approaches include biomaterial scaffolds derived from synthetic sources, e.g., calcium phosphates or polymers; natural sources, e.g., bone or seashell; and immobilized biofactors, e.g., BMP2. Although BMP2 is the only protein clinically approved for use in a surgical device, there are several proteins, small molecules, and growth factors that show promise in tissue engineering applications. This review profiles the tissue engineering advances in achieving control over the location and onset of bone formation (spatiotemporal control) toward avoiding the complications associated with BMP2.

Bone Regeneration of Peri-Implant Defects Using a Collagen Membrane as a Carrier for Recombinant Human Bone Morphogenetic Protein-2

This study is designed to determine the effect of collagen membrane (CM) soaked with bone morphogenetic protein-2 (rhBMP-2) for the treatment of peri-implant dehiscence defects. Material and Methods. Three treatment groups were allocated at each defect in 5 dogs: (i) collagenated synthetic bone (OC) and CM soaked with rhBMP-2 (BMP group), (ii) OC and CM soaked with saline (nonBMP group), and (iii) no further treatment (control group). Titanium pins were used to stabilize the membranes in two dogs. Radiographic and histomorphometric analyses were performed 4 weeks later. Results. The median augmented volumes were 4.27 mm³, 6.24 mm³, and 2.75 mm³ in the BMP, nonBMP, and control groups, respectively; the corresponding median first bone-to-implant contact (fBIC) distances were 3.25 mm, 3.08 mm, and 2.56 mm (P > 0.05). The placement of pins (with the BMP and nonBMP groups pooled) significantly improved bone regeneration: the augmented volumes were 17.60 mm³ with pins and 3.68 mm³ without pins (P = 0.024), with corresponding fBIC distances of 2.25 mm and 3.31 mm, respectively (P < 0.001). Conclusions. The addition of rhBMP-2 to CM failed to improve bone regeneration of peri-implant dehiscence defects compared to using an unsoaked CM after 4 weeks. However, the stabilization of CMs using pins positively influenced the outcomes.

Outcomes of Alveolar Ridge Preservation With Recombinant Human Bone Morphogenetic Protein-2: A Systematic Review

PURPOSE

The main focused question of this systematic review was as follows: Does the application of recombinant human bone morphogenetic protein-2 (rhBMP-2) placed in extraction sockets reduce the alveolar ridge changes?

METHODS

A systematic literature search was performed up to February 2017. Clinical studies published in English were included. Outcome variables of interest were as follows: changes in alveolar ridge width and height, the quality of new bone, patient's safety, adverse events, and postoperative complications.

RESULTS

Seven articles were included. Because of the vast heterogeneity and high risk of bias among the studies, performing a meta-analysis deemed not feasible. Application of rhBMP-2 in the extraction socket was more effective in the reduction of ridge width compared with that of ridge height. The superiority of 1.5 mg/mL rhBMP-2/absorbable collagen sponge over the carrier alone on alveolar ridge width/height remodeling was more significant when it was applied in the sockets with ≥50% buccal bone dehiscence. The limited available data showed that rhBMP-2 did not improve the quality of new bone. Antibodies against rhBMP-2 were detected in the serum in 1 trial.

CONCLUSIONS

Within the limits of this review, 1.5 mg/mL rhBMP-2 might be beneficial for preserving the alveolar ridge width within extraction sockets given as to whether the cost-effectiveness is justifiable. Studies with lower risk of bias should be performed to confirm the above findings.

Formulation, Delivery and Stability of Bone Morphogenetic Proteins for Effective Bone Regeneration

Bone morphogenetic proteins (BMPs) are responsible for bone formation during embryogenesis and bone regeneration and remodeling. The osteoinductive action of BMPs, especially BMP-2 and BMP-7, has led to their use in a range of insurmountable treatments where intervention is required for effective bone regeneration. Introduction of BMP products to the market, however, was not without reports of multiple complications and side effects. Aiming for optimization of the therapeutic efficacy and safety, efforts have been focused on improving the delivery of BMPs to lower the administered dose, localize the protein, and prolong its retention time at the site of action. A major challenge with these efforts is that the protein stability should be maintained. With this review we attempt to shed light on how the stability of BMPs can be affected in the formulation and delivery processes. We first provide a short overview of the current standing of the complications experienced with BMP products. We then discuss the different delivery parameters studied in association with BMPs, and their influence on the efficacy and safety of BMP treatments. In particular, the literature addressing the stability of BMPs and their possible interactions with components of the delivery system as well as their sensitivity to conditions of the formulation process is reviewed. In summary, recent developments in the fields of bioengineering and biopharmaceuticals suggest that a good understanding of the relationship between the formulation/delivery conditions and the stability of growth factors such as BMPs is a prerequisite for a safe and effective treatment.

Bone Regenerative Efficacy of Limited-Dose Escherichia Coli-Derived rhBMP-2 With Biphasic Calcium Phosphate Carrier in Rabbit Calvarial Defect Model

PURPOSE

The aim of this study was to characterize the healing in rabbit calvarial bone defects after delivery of limited-dose (1.5 μg) Escherichia coli-derived recombinant human bone morphogenetic protein-2 (ErhBMP-2), and evaluate biphasic calcium phosphate (BCP) as a carrier.

MATERIALS AND METHODS

Four 8-mm diameter circular calvarial bone defects were made in 16 rabbits and filled with one of the following: (1) nothing, (2) BCP alone, (3) ErhBMP-2-loaded absorbable collagen sponge (ACS), or (4) ErhBMP-2-loaded BCP. The animals were allowed to heal for either 2 or 8 weeks and were evaluated in clinical, microcomputed tomographic, histological, and histomorphometric analyses.

RESULTS

Microcomputed tomography revealed extensive new bone formation in both of the limited-dose ErhBMP-2-loaded groups. However, bony collapse of the upper defect borders was found in the ErhBMP-2-loaded ACS group. Histomorphometric examination revealed significantly greater new bone formation at 8 weeks than at 2 weeks in all 4 groups (P < 0.05). Both new bone formation and the size of the augmented area differed significantly between the ErhBMP-2-loaded BCP group (6.88 ± 0.74 and 19.62 ± 0.77) and the ErhBMP-2-loaded ACS group (3.04 ± 0.27 and 5.41 ± 0.43) at 8 weeks of healing.

CONCLUSION

ErhBMP-2 promotes bone regeneration in rabbit calvarial defects, even at a limited dose (1.5 μg). The results of this study suggest that BCP is the more efficient carrier for this protein than ACS.

Calcium phosphate-phosphorylated adenosine hybrid microspheres for anti-osteosarcoma drug delivery and osteogenic differentiation

Biocompatibility, biodegradability and bioactivity are significantly important in practical applications of various biomaterials for bone tissue engineering. Herein, we develop a functional inorganic-organic hybrid system of calcium phosphate-phosphorylated adenosine (CPPA). Both calcium phosphate and phosphorylated adenosine molecules in CPPA are fundamental components in mammalians and play important roles in biological metabolism. In this work, we report our three leading research qualities: (1) CPPA hybrid microspheres with hollow and porous structure are synthesized by a facile one-step microwave-assisted solvothermal method; (2) CPPA hybrid microspheres show high doxorubicin loading capacity and pH-responsive drug release properties, and demonstrate positive therapeutic effects on six osteosarcoma cell lines in vitro and a mouse model of 143B osteosarcoma subcutaneous tumor in vivo; (3) CPPA hybrid microspheres are favorable to promote osteogenic differentiation of human bone mesenchymal stem cells (hBMSCs) by activating the AMPK pathway, with satisfactory evidences from cellular alkaline phosphatase staining, alizarin red staining, real time PCR and western analysis. The as-prepared CPPA hybrid microspheres are promising in anti-osteosarcoma and bone regeneration, which simultaneously display excellent properties on drug delivery and osteogenic differentiation of hBMSCs.

Increased osteoinductivity and mineralization by minimal concentration of bone morphogenetic protein-2 loaded onto biphasic calcium phosphate in a rabbit sinus

Purpose

The purpose of the present study was to evaluate the effectiveness of a minimal concentration of bone morphogenetic protein-2 (BMP-2) in terms of quantitative and qualitative analyses of newly formed bone in a rabbit maxillary sinus model.

Methods

In 7 rabbits, sinus windows were prepared bilaterally. Biphasic calcium phosphate (BCP) loaded with 0.05 mg/mL BMP-2 was grafted into one sinus (the BMP group) and saline-soaked BCP was placed into the other (the control group) in each animal. The animals were allowed an 8-week healing period before being sacrificed. Specimens including the augmented area and surrounding tissues were then removed and evaluated both radiographically and histologically.

Results

There was a difference in the mineralization of new bone between the groups. In the BMP group, the greater part of the new bone consisted of mature lamellar bone with an evident trabecular pattern, whereas the control group showed mostly woven bone, consisting only partially of lamellar bone. Histometrically, the area of new bone was significantly greater (4.55±1.35 mm² vs. 2.99±0.86 mm²) in the BMP group than in the control group (P<0.05); however, the total augmentation volumes were not significantly different between the groups.

Conclusions

Within the limitations of this study, it can be suggested that a minimal concentration of BMP-2 (0.05 mg/mL) had an osteoinductive effect with accelerated mineralization in a rabbit sinus model using a BCP carrier.

The bone regenerative capacity of canine mesenchymal stem cells is regulated by site-specific multilineage differentiation

OBJECTIVES

Mesenchymal stem cells (MSCs) offer a promising therapy in dentistry because of their multipotent properties. Selecting donor MSCs is crucial because Beagle dogs (canines) commonly used in preclinical studies have shown variable outcomes, and it is unclear whether canine MSCs (cMSCs) are skeletal site specific. This study tested whether jaw and long bone cMSCs have disparate in vitro and in vivo multilineage differentiation capabilities.

STUDY DESIGN

Primary cMSCs were isolated from the mandible (M-cMSCs) and femur (F-cMSCs) of four healthy Beagle dogs. The femur served as the non-oral control. Clonogenic and proliferative abilities were assessed. In vitro osteogenic, chondrogenic, adipogenic, and neural multilineage differentiation were correlated with in vivo bone regeneration and potential for clinical applications.

RESULTS

M-cMSCs displayed two-fold increase in clonogenic and proliferative capacities relative to F-cMSCs (P = .006). M-cMSCs in vitro osteogenesis based on alkaline phosphatase (P = .04), bone sialoprotein (P = .05), and osteocalcin (P = .03), as well as adipogenesis (P = .007) and chondrogenesis (P = .009), were relatively higher and correlated with enhanced M-cMSC bone regenerative capacity. Neural expression markers, nestin and βIII-tubulin, were not significantly different.

CONCLUSIONS

The enhanced differentiation and bone regenerative capacity of mandible MSCs may make them favorable donor graft materials for site-specific jaw bone regeneration.

Effects of block bone substitutes loaded with Escherichia Coli-produced recombinant human bone morphogenetic protein-2 on space maintenance and bone formation in rat calvarial onlay model

We aimed to evaluate the effects of onlay-type grafted human freeze-dried corticocancellous bone block (FDBB) and deproteinized bovine bone with collagen (DBBC) loaded with Escherichia coli-produced recombinant human bone morphogenetic protein-2 (ErhBMP-2) on space maintenance and new bone formation in rat calvaria. Collagen sponge (CS), FDBB, or DBBC disks (8×4 mm) with ErhBMP-2 (2.5 μg) were implanted onto the calvaria of male Sprague-Dawley rats, whereas CS with buffer was implanted onto the calvaria as controls (n=20/carrier). Rats were killed at 2 or 8 weeks post-surgery for histologic and histomorphometric analyses; total augmented area, new bone area, and bone density were evaluated. At both time-points, all ErhBMP-2 groups showed significantly higher new bone area and bone density than the control group (p<0.05). ErhBMP-2/FDBB and ErhBMP-2/DBBC groups showed significantly higher total augmented area than ErhBMP-2/CS group (8 weeks), and ErhBMP-2/FDBB group showed significantly higher new bone area and bone density than ErhBMP-2/DBBC group (p<0.05). ErhBMP-2/CS group showed the highest bone density (p<0.05). Combining ErhBMP-2 with FDBB or DBBC could significantly improve onlay graft outcomes, by new bone formation and bone density increase. Moreover, onlay-grafted FDBB and DBBC with ErhBMP-2 could be an alternative to autogenous block onlay bone graft.

Effective healing of chronic rotator cuff injury using recombinant bone morphogenetic protein-2 coated dermal patch in vivo

Biologic augmentation for rotator cuff repair is a challenging treatment in patients with chronic large, massive, and irreparable rotator cuff injuries. Particularly, the use of an extracellular matrix (ECM) patch such as dermal tissue offered improved biomechanical properties in previous studies. Cytokines induce cell chemotaxis, proliferation, matrix synthesis, and cell differentiation. Moreover, osteoinductive growth factors such as bone morphogenetic protein-2 (BMP-2) affect the formation of new bone and fibrocartilage in lesions. However, the effects of using a dermal patch in combination with BMP-2 have not been evaluated to date, although many researchers have recognized the importance thereof. In this study, rhBMP-2-coated dermal patch (1 cm × 2 cm) isolated from human cadaveric donor was inserted in a rabbit model of chronic rotator cuff injury for in vivo evaluation. Bone mineral density and biomechanical strength were tested and histological and histomorphometric analyses were performed. The results showed that insertion of an rhBMP-2-coated acellular dermal patch not only significantly ameliorated new bone formation, it also improved biomechanical properties such as ultimate tensile strength. Thus, the use of this combination may improve the chronic rotator cuff injury-healing rate and clinical outcomes after rotator cuff repair. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1840-1846, 2017.

Restoration of a Critical Mandibular Bone Defect Using Human Alveolar Bone-Derived Stem Cells and Porous Nano-HA/Collagen/PLA Scaffold

Periodontal bone defects occur in a wide variety of clinical situations. Adult stem cell- and biomaterial-based bone tissue regeneration are a promising alternative to natural bone grafts. Recent evidence has demonstrated that two populations of adult bone marrow mesenchymal stromal cells (BMSCs) can be distinguished based on their embryonic origins. These BMSCs are not interchangeable, as bones preferentially heal using cells that share the same embryonic origin. However, the feasibility of tissue engineering using human craniofacial BMSCs was unclear. The goal of this study was to explore human craniofacial BMSC-based therapy for the treatment of localized mandibular defects using a standardized, minimally invasive procedure. The BMSCs' identity was confirmed. Scanning electron microscopy, a cell proliferation assay, and supernatant detection indicated that the nHAC/PLA provided a suitable environment for aBMSCs. Real-time PCR and electrochemiluminescence immunoassays demonstrated that osteogenic markers were upregulated by osteogenic preinduction. Moreover, in a rabbit critical-size mandibular bone defect model, total bone formation in the nHAC/PLA + aBMSCs group was significantly higher than in the nHAC/PLA group but significantly lower than in the nHAC/PLA + preinduced aBMSCs. These findings demonstrate that this engineered bone is a valid alternative for the correction of mandibular bone defects.

BMP-2-transduced human bone marrow stem cells enhance neo-bone formation in a rat critical-sized femur defect

Synthetic graft materials are considered as possible substitutes for cancellous bone, but lack osteogenic and osteoinductive properties. In this study, we investigated how composite scaffolds of βTCP containing osteogenic human bone marrow mesenchymal stem cells (hBMSCs) and osteoinductive bone morphogenetic protein-2 (BMP-2) influenced the process of fracture healing. hBMSCs were loaded into βTCP scaffolds 24 h before implantation in a rat critical-sized bone defect. hBMSCs were either stimulated with rhBMP-2 or transduced with BMP-2 by gene transfer. The effect of both protein stimulation and gene transfer was compared for osteogenic outcome. X-rays were conducted at weeks 0, 1, 3, 6, 9 and 12 post-operatively. In addition, bone-labelling fluorochromes were applied at 0, 3, 6 and 9 weeks. Histological analysis was performed for the amount of callus tissue and cartilage formation. At 6 weeks, the critical-sized defect in 33% of the rats treated with the Ad-BMP-2-transduced hBMSCs/βTCP scaffolds was radiographically bridged. In contrast, in only 10% of the rats treated with rhBMP2/hBMSCs, 12 weeks post-treatment, the bone defect was closed in all treated rats of the Ad-BMP-2 group except for one. Histology showed significantly higher amounts of callus formation in both Ad-BMP-2- and rhBMP-2-treated rats. The amount of neocartilage was less pronounced in both BMP-2-related groups. In summary, scaffolds with BMP-2-transduced hBMSCs performed better than those with the rhBMP2/hBMSCs protein. These results suggest that combinations of osteoconductive biomaterials with genetically modified MSCs capable of secreting osteoinductive proteins may represent a promising alternative for bone regeneration. Copyright © 2015 John Wiley & Sons, Ltd.

Lumbar interbody fusion with porous biphasic calcium phosphate enhanced by recombinant bone morphogenetic protein-2/silk fibroin sustained-released microsphere: an experimental study on sheep model

Biphasic calcium phosphate (BCP) has been investigated extensively as a bone substitute nowadays. However, the bone formation capacity of BCP is limited owing to lack of osteoinduction. Silk fibroin (SF) has a structure similar to type I collagen, and could be developed to a microsphere for the sustained-release of rhBMP-2. In our previous report, bioactivity of BCP could be enhanced by rhBMP-2/SF microsphere (containing 0.5 µg rhBMP-2) in vitro. However, the bone regeneration performance of the composite in vivo was not investigated. Thus, the purpose of this study was to evaluate the efficacy of BCP/rhBMP-2/SF in a sheep lumbar fusion model. A BCP and rhBMP-2/SF microsphere was developed, and then was integrated into a BCP/rhBMP-2/SF composite. BCP, BCP/rhBMP-2 and BCP/rhBMP-2/SF were implanted randomly into the disc spaces of 30 sheep at the levels of L1/2, L3/4 and L5/6. After sacrificed, the fusion segments were evaluated by manual palpation, CT scan, biomechanical testing and histology at 3 and 6 months, respectively. The composite demonstrated a burst-release of rhBMP-2 (39.1 ± 2.8 %) on the initial 4 days and a sustained-release (accumulative 81.3 ± 4.9 %) for more than 28 days. The fusion rates, semi-quantitative CT scores, fusion stiffness in bending in all directions and histologic scores of BCP/rhBMP-2/SF were significantly greater than BCP and BCP/rhBMP-2 at each time point, respectively (P < 0.05). These findings indicate that the SF microspheres containing a very low dose of rhBMP-2 improve fusion in sheep using BCP constructs.

Bone regenerative efficacy of biphasic calcium phosphate collagen composite as a carrier of rhBMP-2

OBJECTIVES

This study compared the bone regenerative effects of a recombinant human bone morphogenetic protein 2 (rhBMP-2)-loaded collagen-based biphasic calcium phosphate composite (BCPC) and rhBMP-2-loaded biphasic calcium phosphate (BCP).

MATERIAL AND METHODS

The in vitro release profiles of rhBMP-2-loaded BCP and BCPC were measured. The animal surgery was performed on ten rabbits. Four 8-mm-diameter circular calvarial defects were made and filled with BCP, BCPC, rhBMP-2-loaded BCP (BMP + BCP) and rhBMP-2-loaded BCPC (BMP + BCPC). The animals were euthanized either 2 or 8 weeks after surgery.

RESULTS

The initial burst release of rhBMP-2 was greater for BCP than for BCPC, and both presented a slow release pattern thereafter. In rabbit calvarial defects, the space maintaining capability and graft resorption of all experimental groups did not show statistical differences at 2 and 8 weeks. New bone formation in the rhBMP-2-loaded groups was greater than in the non-loaded groups at both weeks, but the amount of new bone was comparable between both rhBMP-2-loaded groups at both weeks. There was a distinct histologic difference between the BMP + BCP and BMP + BCPC groups at 2 weeks; the new bone formation occurred more in the intergranular spaces and the BCP-to-bone contact was greater in the BMP + BCPC group, but these differences were no longer discernible at 8 weeks.

CONCLUSIONS

BCP- and BCPC-loaded rhBMP-2 significantly improved bone regeneration and BCPC led to a dense network of new bone and bone particles during the early healing period. BCPC can therefore be considered as a promising candidate for carrying rhBMP-2.

Osteoconduction capacity of human deciduous and permanent teeth ash in a rat calvarial bone defect model

The aim of this study was to confirm the osteoconduction capacities and determine the potential of permanent teeth ash (PTA), and deciduous teeth ash (DTA) as bone substitutes. Rats (n = 71) were divided randomly into four groups: sham, micro macroporous biphasic calcium phosphate (MBCP), PTA, and DTA. A sample of the each group was transplanted into preformed 8-mm calvarial defects (one per rat). The density of new bone was calculated and the crystallinities of the PTA and DTA were analyzed by X-ray diffraction. The degree of new bone formation was high in the MBCP and DTA groups but low in the PTA groups. The DTA was highly crystalline, whereas the PTA was not. The percentages of β-tricalcium phosphate in the DTA and PTA were 10.7 and 3.7%, respectively. DTA has a high osteoconduction capacity, suggesting that it is a useful bone substitute.

Cranial vault reconstruction with bone morphogenetic protein, calcium phosphate, acellular dermal matrix, and calcium alginate in mice

PURPOSE

To evaluate experimental cranial vault reconstructions, by combining bone morphogenetic protein type 2 (BMP-2) and different matrices.

METHODS

Fourty-nine animals were initially included (seven per group). We designed an experimental, open, prospective and comparative study, divided in seven groups: 1 - BMP-2+calcium phosphate (BT); 2 - BMP-2+acellular dermal matrix (BM); 3 - BMP-2+calcium alginate (BA); 4 - TCP; 5 - MDM; 6 - ALG; 7 - Bone autograft (BAG). A bone failure was created in left parietal bone of adult male mice. At the same procedure reconstruction was performed. After five weeks, animals were sacrificed, and reconstruction area was removed to histological analysis. After exclusion due to death or infection, thirty-eight animals were evaluated (BT=5; BM=6; BA=6; TCP=7; MDM=3; ALG=6; BAG=5).

RESULTS

A higher incidence of infection has occurred in MDM group (57%, P=0.037). In cortical fusion, groups BAG, TCP, and BMP-2+TCP (BT) obtained the best scores, comparing to the others (P=0.00846). In new bone formation, groups BT, BAG, and TCP have presented the best scores (P=0.00835). When neovascularization was considered, best groups were BMP-2+MDM (BM), BMP-2+ALG (BA), TCP, and MDM (P=0.001695). BAG group was the best in bone marrow formation, followed by groups BT and TCP (P=0.008317).

CONCLUSIONS

Bone morphogenetic protein type 2 increased bone regeneration in experimental skull reconstruction, especially when combined to calcium phosphate. Such association was even comparable to bone autograft, the gold-standard treatment, in some histological criteria.

Controlled release of granulocyte colony-stimulating factor enhances osteoconductive and biodegradable properties of Beta-tricalcium phosphate in a rat calvarial defect model

Autologous bone grafts remain the gold standard for the treatment of congenital craniofacial disorders; however, there are potential problems including donor site morbidity and limitations to the amount of bone that can be harvested. Recent studies suggest that granulocyte colony-stimulating factor (G-CSF) promotes fracture healing or osteogenesis. The purpose of the present study was to investigate whether topically applied G-CSF can stimulate the osteoconductive properties of beta-tricalcium phosphate (β-TCP) in a rat calvarial defect model. A total of 27 calvarial defects 5 mm in diameter were randomly divided into nine groups, which were treated with various combinations of a β-TCP disc and G-CSF in solution form or controlled release system using gelatin hydrogel. Histologic and histomorphometric analyses were performed at eight weeks postoperatively. The controlled release of low-dose (1 μg and 5 μg) G-CSF significantly enhanced new bone formation when combined with a β-TCP disc. Moreover, administration of 5 μg G-CSF using a controlled release system significantly promoted the biodegradable properties of β-TCP. In conclusion, the controlled release of 5 μg G-CSF significantly enhanced the osteoconductive and biodegradable properties of β-TCP. The combination of G-CSF slow-release and β-TCP is a novel and promising approach for treating pediatric craniofacial bone defects.

Effect of nano-hydroxyapatite coating on the osteoinductivity of porous biphasic calcium phosphate ceramics

Background

Porous biphasic calcium phosphate (BCP) ceramics exhibit good biocompatibility and bone conduction but are not inherently osteoinductive. To overcome this disadvantage, we coated conventional porous BCP ceramics with nano-hydroxyapatite (nHA). nHA was chosen as a coating material due to its high osteoinductive potential.

Methods

We used a hydrothermal deposition method to coat conventional porous BCP ceramics with nHA and assessed the effects of the coating on the physical and mechanical properties of the underlying BCP. Next, its effects on mesenchymal stem cell (MSC) attachment, proliferation, viability, and osteogenic differentiation were investigated.

Results

nHA formed a deposited layer on the BCP surface, and synthesized nHA had a rod-like shape with lengths ranging from ~50–200 nm and diameters from ~15–30 mm. The nHA coating did not significantly affect the density, porosity, flexural strength, or compressive strength of the underlying BCP (P > 0.1). Scanning electron microscopy showed MSC attachment to the scaffolds, with a healthy morphology and anchorage to nHA crystals via cytoplasmic processes. The densities of MSCs attached on BCP and nHA-coated BCP scaffolds were 62 ± 26 cells/mm² and 63 ± 27 cells/mm² (P > 0.1), respectively, after 1 day and 415 ± 62 cells/mm² and 541 ± 35 cells/mm² (P < 0.05) respectively, after 14 days. According to an MTT assay, MSC viability was higher on nHA-coated BCP scaffolds than on BCP scaffolds (P < 0.05). In addition, MSCs on nHA-coated BCP scaffolds produced more alkaline phosphatase, collagen type I, and osteocalcin than MSCs on BCP scaffolds (P < 0.05).

Conclusions

Our results demonstrate that BCP scaffolds coated with nHA were more conducive for MSC adhesion, proliferation, and osteogenic differentiation than conventional, uncoated BCP scaffolds, indicating that nHA coating can enhance the osteoinductive potential of BCP ceramics, making this material more suitable for applications in bone tissue engineering.

Characterization of the enhanced bone regenerative capacity of human periodontal ligament stem cells engineered to express the gene encoding bone morphogenetic protein 2

Human periodontal ligament stem cells (hPDLSCs) are considered an appropriate cell source for therapeutic strategies. The aims of this study were to investigate the sustainability of bone morphogenetic protein 2 (BMP2) secretion and the bone regenerative capacity of hPDLSCs that had been genetically modified to express the gene encoding BMP2 (BMP2). hPDLSCs isolated from healthy third molars were transduced using replication-deficient recombinant adenovirus (rAd) encoding BMP2 (hPDLSCs/rAd-BMP2), and the cellular characteristics and osteogenic potentials of hPDLSCs/rAd-BMP2 were analyzed both in vitro and in vivo. hPDLSCs/rAd-BMP2 successfully secreted BMP2, formed colonies, and expressed immunophenotypes similar to their nontransduced counterparts. As to their osteogenic potential, hPDLSCs/rAd-BMP2 formed greater mineralized nodules and exhibited significantly higher levels of expression of BMP2 and the gene encoding alkaline phosphatase, and formed more and better quality bone than other hPDLSC-containing or recombinant human BMP2-treated groups, being localized at the initial site until 8 weeks. The findings of the present study demonstrate that hPDLSCs/rAd-BMP2 effectively promote osteogenesis not only in vitro but also in vivo. The findings also suggest that hPDLSCs can efficiently carry and deliver BMP2, and that hPDLSCs/rAd-BMP2 could be used in an attractive novel therapeutic approach for the regeneration of deteriorated bony defects.

Bone regenerative medicine: classic options, novel strategies, and future directions

This review analyzes the literature of bone grafts and introduces tissue engineering as a strategy in this field of orthopedic surgery. We evaluated articles concerning bone grafts; analyzed characteristics, advantages, and limitations of the grafts; and provided explanations about bone-tissue engineering technologies. Many bone grafting materials are available to enhance bone healing and regeneration, from bone autografts to graft substitutes; they can be used alone or in combination. Autografts are the gold standard for this purpose, since they provide osteogenic cells, osteoinductive growth factors, and an osteoconductive scaffold, all essential for new bone growth. Autografts carry the limitations of morbidity at the harvesting site and limited availability. Allografts and xenografts carry the risk of disease transmission and rejection. Tissue engineering is a new and developing option that had been introduced to reduce limitations of bone grafts and improve the healing processes of the bone fractures and defects. The combined use of scaffolds, healing promoting factors, together with gene therapy, and, more recently, three-dimensional printing of tissue-engineered constructs may open new insights in the near future.

Bone regenerative medicine: classic options, novel strategies, and future directions

This review analyzes the literature of bone grafts and introduces tissue engineering as a strategy in this field of orthopedic surgery. We evaluated articles concerning bone grafts; analyzed characteristics, advantages, and limitations of the grafts; and provided explanations about bone-tissue engineering technologies. Many bone grafting materials are available to enhance bone healing and regeneration, from bone autografts to graft substitutes; they can be used alone or in combination. Autografts are the gold standard for this purpose, since they provide osteogenic cells, osteoinductive growth factors, and an osteoconductive scaffold, all essential for new bone growth. Autografts carry the limitations of morbidity at the harvesting site and limited availability. Allografts and xenografts carry the risk of disease transmission and rejection. Tissue engineering is a new and developing option that had been introduced to reduce limitations of bone grafts and improve the healing processes of the bone fractures and defects. The combined use of scaffolds, healing promoting factors, together with gene therapy, and, more recently, three-dimensional printing of tissue-engineered constructs may open new insights in the near future.

Ridge preservation using demineralized bone matrix gel with recombinant human bone morphogenetic protein-2 after tooth extraction: a randomized controlled clinical trial

PURPOSE

The aim of the present randomized controlled trial was to determine the safety and efficacy of injectable demineralized bone matrix (DBM) gel combined with recombinant human bone morphogenetic protein-2 (rhBMP-2) on alveolar ridge preservation after tooth extraction.

MATERIALS AND METHODS

A total of 69 patients were randomly assigned to either a test group (n = 35) or a control group (n = 34). In the test group, DBM, together with rhBMP-2 (0.05 mg/mL; rhBMP-2/DBM) was transplanted into the extraction sockets. The control group received DBM alone. The safety of rhBMP-2/DBM was evaluated by oral examination, serum chemistry, and hematologic examination. The radiographic changes in alveolar bone height and width were measured using computed tomography scans performed immediately after transplant and again 3 months thereafter.

RESULTS

Healing was uneventful in all subjects, with no anticipated adverse events and no clinically significant changes in the serum chemistry and hematologic findings. No meaningful immune response was found among the study groups. No significant difference was found in the radiographic changes of alveolar bone height and width (P > .05).

CONCLUSIONS

This new injectable biomaterial can be used easily and safely in clinical applications.