Calvarial bone response to a tricalcium phosphate-genipin crosslinked gelatin composite

A biodegradable composite which was composed of genipin cross-linked gelatin mixing with tricalcium phosphate ceramic particles (GGT) was developed as a bone substitute. This study was evaluated by the biological response of rabbit calvarial bone to assess the potential of the GGT composite as a biodegradable and osteoconductive bone substitute. Eighteen New Zealand white rabbits were used for cranial implantation. Bone defects (15 x 15 mm) of nine rabbits were filled with the GGT composites, while the others were filled with the de-proteinized bovine bones as controls. Three rabbits were examined for each group in every time period at 4, 8 and 12 weeks post-surgery. The assessment included serial post-operative gross examinations, radiographic analyses and histological evaluations. This study demonstrated that this composite is: (1) malleable, with easily molded to the calvarial bone defect without fracture; (2) biocompatible, with no evidence of adverse tissue reaction; (3) osteoconductive, with progressive growth of new bone into the calvarial bone defect; (4) biodegradable, with progressive replacement of the composite by new bone. Additionally, results of both radiographic analyses and histological evaluations revealed obviously greater new bone ingrowth in the GGT composite compared with the de-proteinized bovine bone at the same implantation time. Therefore, the GGT composite could serve as a useful bone substitute for repairing bone defects.     

Effect of adipose tissue-derived osteogenic and endothelial cells on bone allograft osteogenesis and vascularization in critical-sized calvarial defects

The use of processed bone allograft to repair large osseous defects of the skull has been limited, given that it lacks the osteogenic cellularity and intrinsic vascular supply which are essential elements for successful graft healing and, at the same time, the areas to be targeted through tissue-engineering applications. In this study, we investigated the effect of predifferentiated rat adipose tissue-derived osteoblastic cells (OBs) and endothelial cells (ECs) on calvarial bone allograft healing and vascularization using an orthotopic critical-sized calvarial defect model. For this purpose, thirty-seven 8?mm critical calvarial defects in Lewis rats were treated with bone allografts seeded with no cells, undifferentiated adipose tissue-derived stem cells (ASC), OBs, ECs, and OBs and ECs simultaneously. After 8 weeks, the bone volume and mineral density were calculated using microcomputed tomography and the microvessel formation using immunohistochemical staining and imaging software. The amount of bone within the 8?mm defect was significantly higher for the allografts treated with ECs compared with the allografts treated with OBs (p=0.05) and simultaneously with the two cell lineages (p=0.02). There were no significant differences in bone formation between the latter two groups and the control groups (allografts treated with no cells and undifferentiated ASC). There were no significant differences in bone mineral density among the groups. The amount of microvessels was significantly higher in the group treated with ECs relative to all groups (p=相似文献   

A novel hydroxyapatite ceramic bone substitute transformed by ostrich cancellous bone: characterization and evaluations of bone regeneration activity

Various biomaterials have been used for bone repair and reconstruction of bone defects. Inorganic xenogenic bone substitutes have been intensively studied because they possesses favorable regenerative properties. The purpose of this study was to evaluate the properties of a novel inorganic xenogenic bone substitute, sintered ostrich cancellous bone (SOCB). Bone regeneration capability was also comparing to that of other bone substitutes in rabbit calvarial defects. Biochemical and biomechanical properties of the SOCB ceramic closely resembled those of human bone. Bone regeneration was evaluated by radiograph, histology, and histomorphometry. Bone regeneration was significantly enhanced in defects treated with SOCB when compared with other bone substitutes. The biochemical and biomechanical properties of SOCB are favorable for bone regeneration. SOCB might be a promising biomaterial for the repair of bone defects.     

Electrical stimulation therapy and rotary jet-spinning scaffold to treat bone defects

The combination of electrical stimulation (ES) and bone tissue engineering (BTE) has been successful in treatments of bone regeneration. This study evaluated the effects of ES combined with PCL + β-TCP 5% scaffolds obtained by rotary jet spinning (RJS) in the regeneration of bone defects in the calvaria of Wistar rats. We used 120 animals with induced bone defects divided into 4 groups (n = 30): (C) without treatment; (S) with PCL+ β-TCP 5% scaffold; (ES) treated with ES (10 μA/5 min); (ES + S) with PCL + β-TCP 5% scaffold. The ES occurred twice a week during the entire experimental period. Cell viability (in vitro: Days 3 and 7) and histomorphometric, histochemical, and immunohistochemical (in vivo; Days 30, 60, and 90) analysis were performed. In vitro, ES + S increased cell viability after Day 7 of incubation. In vivo, it was observed modulation of inflammatory cells in ES therapy, which also promoted blood vessels proliferation, and increase of collagen. Moreover, ES therapy played a role in osteogenesis by decreasing ligand kappa B nuclear factor-TNFSF11 (RANKL), increasing alkaline phosphatase (ALP), and decreasing the tartarate-resistant acid phosphatase. The combination of ES with RJS scaffolds may be a promising strategy for bone defects regeneration, since the therapy controlled inflammation, favored blood vessels proliferation, and osteogenesis, which are important processes in bone remodeling.     

Increased new bone formation with a surface magnesium-incorporated deproteinized porcine bone substitute in rabbit calvarial defects

This study investigated the effects of magnesium ion (Mg) incorporation into the surface of deproteinized porcine cancellous bone in the bone healing of rabbit calvarial defects with the expectation of utilizing the integrin-ligand binding enhancement effect of Mg, and compared its bone healing capacity with that of untreated porcine cancellous bone and deproteinized bovine bone (Bio-Oss). Hydrothermal treatment was performed to produce Mg-incorporated porcine bone using an alkaline Mg-containing solution. The surface morphology and chemical composition of the samples were investigated using scanning electron microscopy, energy-dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. Defects 7 mm in diameter were created in the calvaria of 14 adult male New Zealand White rabbits and were filled with (1) untreated porcine bone (PB), (2) Bio-Oss, and (3) Mg-containing porcine bone (MG). The percentage of newly formed bone (NB%) was evaluated histomorphometrically at 2 and 4 weeks after implantation. Hydrothermal treatment resulted in a Mg-containing surface in porcine bone covered with nanostructures ~100 nm in size. The MG group supported better new bone formation compared with the other groups. Osteoconductive new bone formation was observed in the central defect area in the MG group at an early healing time-point. Histomorphometric analysis revealed significantly greater NB% in the MG group when compared with the untreated PB and Bio-Oss groups at 4 weeks (p < 0.05). The Mg-incorporated porcine bone with surface nanostructures achieved rapid new bone formation in the osseous defects of rabbit calvaria compared with untreated xenografts of porcine and bovine origin.     

Single-walled carbon nanotubes functionalized with sodium hyaluronate enhance bone mineralization

The aim of this study was to evaluate the effects of sodium hyaluronate (HY), single-walled carbon nanotubes (SWCNTs) and HY-functionalized SWCNTs (HY-SWCNTs) on the behavior of primary osteoblasts, as well as to investigate the deposition of inorganic crystals on titanium surfaces coated with these biocomposites. Primary osteoblasts were obtained from the calvarial bones of male newborn Wistar rats (5 rats for each cell extraction). We assessed cell viability using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay and by double-staining with propidium iodide and Hoechst. We also assessed the formation of mineralized bone nodules by von Kossa staining, the mRNA expression of bone repair proteins, and the deposition of inorganic crystals on titanium surfaces coated with HY, SWCNTs, or HY-SWCNTs. The results showed that treatment with these biocomposites did not alter the viability of primary osteoblasts. Furthermore, deposition of mineralized bone nodules was significantly increased by cells treated with HY and HY-SWCNTs. This can be partly explained by an increase in the mRNA expression of type I and III collagen, osteocalcin, and bone morphogenetic proteins 2 and 4. Additionally, the titanium surface treated with HY-SWCNTs showed a significant increase in the deposition of inorganic crystals. Thus, our data indicate that HY, SWCNTs, and HY-SWCNTs are potentially useful for the development of new strategies for bone tissue engineering.     

The enhancement of bone regeneration by gene activated matrix encoding for platelet derived growth factor

Gene therapy using non-viral vectors that are safe and efficient in transfecting target cells is an effective approach to overcome the shortcomings of protein delivery of growth factors. The objective of this study was to develop and test a non-viral gene delivery system for bone regeneration utilizing a collagen scaffold to deliver polyethylenimine (PEI)-plasmid DNA (pDNA) [encoding platelet derived growth factor-B (PDGF-B)] complexes. The PEI-pPDGF-B complexes were fabricated at amine (N) to phosphate (P) ratio of 10 and characterized for size, surface charge, and in vitro cytotoxicity and transfection efficacy in human bone marrow stromal cells (BMSCs). The influence of the complex-loaded collagen scaffold on cellular attachment and recruitment was evaluated in vitro using microscopy techniques. The in vivo regenerative capacity of the gene delivery system was assessed in 5 mm diameter critical-sized calvarial defects in Fisher 344 rats. The complexes were ∼100 nm in size with a positive surface charge. Complexes prepared at an N/P ratio of 10 displayed low cytotoxicity as assessed by a cell viability assay. Confocal microscopy revealed significant proliferation of BMSCs on complex-loaded collagen scaffolds compared to empty scaffolds. In vivo studies showed significantly higher new bone volume/total volume (BV/TV) % in calvarial defects treated with the complex-activated scaffolds following 4 weeks of implantation (14- and 44-fold higher) when compared to empty defects or empty scaffolds, respectively. Together, these findings suggest that non-viral PDGF-B gene-activated scaffolds are effective for bone regeneration and are an attractive gene delivery system with significant potential for clinical translation.     

Promotion of bone formation by simvastatin in polyethylene particle-induced osteolysis

The effects of statins on bone formation in periprosthetic osteolysis have not been determined to date. We investigated the effect of the HMG-CoA reductase inhibitor simvastatin on osteoblastic bone formation under conditions of ultra-high molecular weight polyethylene (UHMWPE) particle-induced osteolysis. The murine calvarial osteolysis model was utilized in 21 C57BL/J6 mice randomized to three groups. Group I underwent sham surgery only, group II received UHMWPE particles, and group III, particles and simvastatin treatment. After 2 weeks, calvaria were processed for histomorphometry and stained with Giemsa dye. New bone formation was measured as osteoid tissue area within the midline suture. Bone thickness was quantified as indicator of net bone growth. Statistical analysis was performed using one-way ANOVA and a Student's t-test. New bone formation and bone thickness were significantly enhanced following simvastatin treatment. New bone formation was 0.008+/-0.008 mm2 in sham controls (group I), 0.015+/-0.012 mm2 after particle implantation without further intervention (group II), compared to 0.083+/-0.021 mm2 with particle implantation and simvastatin treatment (group III) (p=0.003). The bone thickness was 0.213+/-0.007 mm in group I, 0.183+/-0.005 mm in group II, and 0.238+/-0.009 mm in group III (p=0.00008). In conclusion, simvastatin treatment markedly promoted bone formation and net bone growth in UHMWPE particle-induced osteolysis in a murine calvarial model. These new findings indicate that simvastatin may have favorable osteoanabolic effects on wear debris-mediated osteolysis after total joint arthroplasty, involving local stimulation of osteoblastic bone formation.     

Bone cell interactions with a granular glass-ionomer bone substitute material: in vivo and in vitro culture models.

The interface between bone and a synthetic bone substitute constructed from glass-ionomer cement (ionomeric microimplant) was studied in diffusion chambers implanted in a primate baboon model (Papio ursinus) and in in vitro primary bone organ cultures derived from neonate rat calvaria. In both models osteoblast-like cells colonized the surface of the implant producing a collagenous extracellular matrix. An electron-dense bonding zone similar to that reported for hydroxyapatite and titanium was seen in both models but was a more constant feature of the tissue/implant interface in calvarial culture.     

Immobilization of alkaline phosphatase on microporous nanofibrous fibrin scaffolds for bone tissue engineering

Alkaline phosphatase (ALP) promotes bone formation by degrading inorganic pyrophosphate (PP_i), an inhibitor of hydroxyapatite formation, and generating inorganic phosphate (P_i), an inducer of hydroxyapatite formation. P_i is a crucial molecule in differentiation and mineralization of osteoblasts. In this study, a method to immobilize ALP on fibrin scaffolds with tightly controllable pore size and pore interconnection was developed, and the biological properties of these scaffolds were characterized both in vitro and in vivo. Microporous, nanofibrous fibrin scaffolds (FS) were fabricated using a sphere-templating method. ALP was covalently immobilized on the fibrin scaffolds using 1-ethyl-3-(dimethylaminopropyl)carbodiimide hydrochloride (EDC). Scanning electron microscopic observation (SEM) showed that mineral was deposited on immobilized alkaline phosphatase fibrin scaffolds (immobilized ALP/FS) when incubated in medium supplemented with β-glycerophosphate, suggesting that the immobilized ALP was active. Primary calvarial cells attached, spread and formed multiple layers on the surface of the scaffolds. Mineral deposition was also observed when calvarial cells were seeded on immobilized ALP/FS. Furthermore, cells seeded on immobilized ALP/FS exhibited higher osteoblast marker gene expression compared to control FS. Upon implantation in mouse calvarial defects, both the immobilized ALP/FS and FS alone treated group had higher bone volume in the defect compared to the empty defect control. Furthermore, bone formation in the immobilized ALP/FS treated group was statistically significant compared to FS alone group. However, the response was not robust.     

Use of high-performance polyethylene fibres as a reinforcing phase in poly(methylmethacrylate) bone cement

First results are presented concerning the elastic and ultimate mechanical behaviour of p(MMA) bone cement reinforced with as-received and surface-modified Spectra 900 polyethylene fibres. Even though the surface chemistry and reactivity of the fibres was modified, the surface oxidation and surface grafting treatments of the polyethylene fibres apparently did not significantly affect the mechanical properties of the polyethylene-reinforced p(MMA) bone cement or improve the interfacial bonding. This may be attributed to the rather unfavourable area-to-volume ratio of PE fibres for such treatments, as well as to the necessarily low content of PE fibres in the bone cement which does not allow a clear differentiation between the various samples.     

Initial adhesion of glass-fiber-reinforced composite to the surface of porcine calvarial bone

The aim of this preliminary study was to compare the initial bond strength of the glass-fiber-reinforced composite veil to the surface of the porcine calvarial compact bone using different adhesives. Fiber-reinforced composite (FRC) made of E-glass fiber veil with the BisGMA-PMMA resin system was used in the study. For the shear bond strength test, porcine calvarial bone cubes were mounted into resin matrix. FRC-veil discs were bonded to compact bone with different types of adhesives: (A) BisGMA-HEMA based (3M-ESPE Scotchbond Multi-Purpose Adhesive), (B) 4-META/UDMA/BisGMA based (Unifil Bond Bonding Agent) and MDP based (Clearfil Se Bond adhesive), (C) UDMA/BisGMA/PMMA-based experimental adhesive, and (D) silane-based (APS, ICS, MPS) experimental adhesives. The surface of the bone was mechanically roughened and was either used as such, treated with dental primers (Unifil Bond Self-etching Primer, Clearfil Se Bond Primer), or treated with an experimental silane mixture (APS, ICS, MPS), or with a mixture of the experimental silane liquid and Clearfil Se Bond Primer. The 3M-ESPE Scotchbond Multi-Purpose Adhesive and UDMA/BisGMA/PMMA experimental adhesive gave poor results in the shear bond test (0.58 and 0.40 MPa, respectively). Unifil Bond Bonding Agent and Clearfil Se Bond adhesive with respective primers markedly improved the shear bond strength; with Unifil the result was 3.40 MPa, and with Clearfil it was 6.19 MPa. When the bone surface was primed with a mixture of Clearfil Se Bond Primer and Clearfil Porcelain Bond Activator, the Clearfil Se Bond adhesive-impregnated FRC veil gave the best adhesion to the bone surface in this test: 9.50 MPa. The addition of bioactive glass granules between the veil and the bone lowered the shear bond strength in the test system described above to 6.72 MPa. The test systems with the silane mixture were also promising. In the SEM study, it was found that the mechanical treatment reveals the pores of the bone surface. Chemical treatments of the bone surface improved the adhesion of the FRC veil to the bone. The results showed that the adhesion of the FRC to the surface of the bone can be significantly improved with mechanical roughening and with special chemical treatments of the bone surface.     

Application of a Novel Resorbable Membrane in the Treatment of Calvarial Defects in Rats

Diplen-Gam (DG) is a novel absorbable guided bone regeneration (GBR) membrane. This study was designed to evaluate the capacity of bone repair of DG compared with that of Bio-Gide (BG). Critical size defects were created in both sides of the calcarium of 36 Sprague–Dawley rats. Defects were assigned to six groups and each group was subjected to one of the following treatments: (A1) unfilled defects, (A2) Bio-Oss (BO) grafts, (B1) DG membrane, (B2) BG membrane, (C1) DG membrane + BO grafts and (C2) BG membrane + BO grafts. The animals were killed at 2, 4, 8 and 12 weeks after the operation. The defects and surrounding tissues were examined by gross observation and X-ray examination. The paraffin sections were subjected to HE (hematoxylin and eosin) staining and IHC (immunohistochemistry) for bone morphogenetic protein-2 (BMP-2). The X-rays showed that, at 12 weeks, the DG and BG group exhibited more new bone formation than CSD blank group did; the BG group exhibited more new bone formation than the DG group did (t = 5.240, P = 0.035), the BG + BO group showed no significant differences in bone formation compared with the DG + BO group (t = 1.246, P = 0.339). By IHC staining, BMP-2-positive results could be seen inside the DG membrane, on the surface of the new bone, and inside the new bone. It can be suggested that BG membrane achieved better effects in guided bone regeneration compared with DG membrane. No significant differences were found between the two membranes in their bone healing ability when they are used with BO. Therefore, DG membrane shows clinical effectiveness, but should be used in combination with bone substitute.     

The inhibitory effect of zoledronate on early-stage osteoinduction by recombinant human bone morphogenetic protein 2 in an osteoporosis model

Abstract

This study evaluated the effect of the combined treatment of intravenous zoledronic acid (ZA, 0.08?mg/kg) and rhBMP-2 (5?µg) on osteogenesis in a calvarial defect model of ovariectomized SD rats. New bone formation was evaluated 4 or 8 weeks after calvarial defect implantation using micro-CT and histology. Micro-CT results revealed that the rhBMP-2 group showed significantly higher calvarial defect coverage ratio compared with the ZA?+?rhBMP-2 group at 4 weeks. In addition, bone formation indices were significantly lower in ZA?+?rhBMP-2 group when compared with the rhBMP-2 group after 4 weeks, which indicates a negative effect of ZA on the initial bone formation and the bone quality. At 8 weeks, the negative effect induced by ZA treatment was alleviated as time passed. Histological examination showed similar results to the micro-CT measurements. In conclusion, although ZA treatment lowered the new bone formation induced by rhBMP-2 initially, as time passed, the negative effect was decreased.     

Effect of low intensity pulsed ultrasound on healing of an ulna defect filled with a bone graft substitute

A 1.5 cm unilateral rabbit ulna defect model was performed in 18 adult NZ white rabbits. The defects were filled with a beta-tricalcium phosphate bone graft substitute (JAX TCP). The surgical site in half the animals was treated daily with 20 min of low intensity pulsed ultrasound (LIPUS). Animals were sacrificed at 4 weeks (n = 3 per group) or 12 weeks (n = 6 per group) following surgery for radiographic and histologic endpoints. Radiography revealed some resorption of the JAX TCP by 12 weeks in the control and LIPUS treated groups. LIPUS treatment did not accelerate this resorption. Some new bone formation was noted in the control groups at the defect margins while little bone formed in the center of the defect at 4 and 12 weeks. In contrast, radiographs revealed more new bone at 4 and 12 weeks in the LIPUS treated animals throughout the section. Bone mineral density (DEXA) revealed a statistically significant difference at 4 weeks with LIPUS while no differences were found at 12 weeks. Histology of the LIPUS treated sections demonstrated new woven bone formation on and between the JAX TCP bone graft substitute particles across the defect. VEGF expression was increased with LIPUS treatment at 4 weeks and remained elevated at 12 weeks compared with controls. CBFA-1 expression levels were elevated with LIPUS treatment at both time points. LIPUS treatment increased bone formation in ulna defect healing with a beta-tricalcium phosphate bone graft substitute.     

Nell-1-induced bone regeneration in calvarial defects

Many craniofacial birth defects contain skeletal components requiring bone grafting. We previously identified the novel secreted osteogenic molecule NELL-1, first noted to be overexpressed during premature bone formation in calvarial sutures of craniosynostosis patients. Nell-1 overexpression significantly increases differentiation and mineralization selectively in osteoblasts, while newborn Nell-1 transgenic mice significantly increase premature bone formation in calvarial sutures. In the current study, cultured calvarial explants isolated from Nell-1 transgenic newborn mice (with mild sagittal synostosis) demonstrated continuous bone growth and overlapping sagittal sutures. Further investigation into gene expression cascades revealed that fibroblast growth factor-2 and transforming growth factor-beta1 stimulated Nell-1 expression, whereas bone morphogenetic protein (BMP)-2 had no direct effect. Additionally, Nell-1-induced osteogenesis in MC3T3-E1 osteoblasts through reduction in the expression of early up-regulated osteogenic regulators (OSX and ALP) but induction of later markers (OPN and OCN). Grafting Nell-1 protein-coated PLGA scaffolds into rat calvarial defects revealed the osteogenic potential of Nell-1 to induce bone regeneration equivalent to BMP-2, whereas immunohistochemistry indicated that Nell-1 reduced osterix-producing cells and increased bone sialoprotein, osteocalcin, and BMP-7 expression. Insights into Nell-1-regulated osteogenesis coupled with its ability to stimulate bone regeneration revealed a potential therapeutic role and an alternative to the currently accepted techniques for bone regeneration.     

Surface-modified poly(lactide-co-glycolide) nanospheres for targeted bone imaging with enhanced labeling and delivery of radioisotope

Surface-modified nanospheres can be utilized for targeting drugs and diagnostic agents to the bone and bone marrow while extending their circulation time in the blood stream. The surface modification of poly(lactide-co-glycolide) (PLGA) nanospheres by radioisotope carrying poly(ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) triblock copolymers (Poloxamer 407) has been assessed by in vitro characterization and in vivo biodistribution studies after intravenous administration of the nanospheres to the mouse. A hydroxyphenylpropionic acid, a ligand for (125)I and (131)I labeling, was conjugated to the hydroxyl group of the Poloxamer 407 by using dicyclohexyl carbodiimide. The ligand-conjugated Poloxamer 407 was adsorbed onto the surface of PLGA nanospheres. Surface coating was confirmed by measuring both size distribution and the surface charge of the nanospheres. Besides, (125)I-labeling efficiency, radiolabeling stability, whole body imaging, and biodistribution of the radioisotope-labeled nanospheres were examined. Ligand-labeled, surface-modified PLGA nanospheres were in 100-nm size ranges, which may be adequate for long-circulation and further bone imaging. (125)I-labeling efficiency was >90% and was more stable at human serum for 24 h. A noticeable decrease in liver or spleen uptake was obtained by the surface-modified nanospheres. (125)I-labeled nanospheres showed higher blood maintenance and bone uptake compared with stannous colloid with the same size distribution. Therefore, a fully biodegradable, radioisotope-carrying, surface-modified nanosphere system has been developed as a promising tool for targeting bone and bone marrows.     

Bone regeneration in a rabbit critical-sized calvarial model using tyrosine-derived polycarbonate scaffolds

Porous three-dimensional tyrosine-derived polycarbonate (TyrPC) scaffolds with a bimodal pore distribution were fabricated to mimic bone architecture using a combination of salt-leaching and phase separation techniques. TyrPC scaffolds degraded in register with bone regeneration during the 6-week study period and compressive moduli of the scaffolds were maintained >0.5 MPa at 6 weeks of incubation in PBS at 37 °C. The TyrPC scaffolds either unsupplemented or supplemented with recombinant human bone morphogenetic protein-2 (rhBMP-2) were implanted in a rabbit calvarial critical-sized defect (CSD) model and the TyrPC scaffolds treated with rhBMP-2 or TyrPC coated with calcium phosphate scaffold alone promoted bone regeneration in a rabbit calvarial CSD at 6 weeks postimplantation. A synthetic TyrPC polymeric scaffold either without a biological supplement or with a minimal dose of rhBMP-2 induced bone regeneration comparable to a commercially available bone graft substitute in a nonrodent CSD animal model.     

Orthotopic bone formation by implantation of apatite-coated poly(lactide-co-glycolide)/hydroxyapatite composite particulates and bone morphogenetic protein-2

Bone morphogenetic proteins (BMPs) are the most potent osteoinductive growth factors. However, a delivery system is essential to take advantage of the osteoinductive effect of BMPs. In the present study, we tested the suitability of apatite-coated poly(D,L-lactide-co-glycolide)/nanohydroxyapatite (PLGA/HA) particulates as carriers for the controlled release of BMP-2. The release of BMP-2 from apatite-coated PLGA/HA particulates was sustained for at least 4 weeks in vitro. A delivery system of apatite-coated PLGA/HA particulates suspended in fibrin gel further slowed the BMP-2 release rate. In vivo implantation of either Fibrin gel + BMP-2 or Fibrin gel + apatite-coated PLGA/HA particulates showed enhanced new bone formation in critical-sized calvarial defects of rats 8 weeks after implantation, compared to implantation of fibrin gel only. Importantly, new bone formation was much higher in the defects treated with BMP-2 delivery using apatite-coated PLGA/HA particulates in fibrin gel (Fibrin gel + PLGA/HA + BMP-2 group) than in the defects treated either with apatite-coated PLGA/HA particulates in fibrin gel (Fibrin gel + BMP-2 group) or with BMP-2 delivery using fibrin gel alone (Fibrin gel + BMP-2 group). BMP-2 and osteoinductive HA had an additive effect on orthotopic bone formation. In conclusion, the apatite-coated PLGA/HA particulates showed good results as carriers for BMP-2. The BMP-2 delivery system showed high osteogenic capability in a rat calvarial bone defect model. The local and sustained delivery system for BMP-2 developed in this study may be useful as a carrier for BMP-2 and would enhance bone regeneration efficacy for the treatment of large bone defects.     

Histological evaluation of an impacted bone graft substitute composed of a combination of mineralized and demineralized allograft in a sheep vertebral bone defect

Demineralized bone matrix (DBMs) preparations are a potential alternative or supplement to autogenous bone graft, but many DBMs have not been adequately tested in clinically relevant animal models. The aim of current study was to compare the efficacy of a new bone graft substitute composed of a combination of mineralized and demineralized allograft, along with hyaluronic acid (AFT Bone Void Filler) with several other bone graft materials in a sheep vertebral bone void model. A drilled defect in the sheep vertebral body was filled with either the new DBM preparation, calcium sulfate (OsteoSet), autologous bone graft, or left empty. The sheep were euthanized after 6 or 12 weeks, and the defects were examined by histology and quantitative histomorphometry. The morphometry data were analyzed by one-way analysis of variance with the post hoc Tukey-Kramer test or the Student's t-test. All of the bone defects in the AFT DBM preparation group showed good new bone formation with variable amounts of residual DBM and mineralized bone graft. The DBM preparation group at 12 weeks contained significantly more new bone than the defects treated with calcium sulfate or left empty (respectively, p < 0.05, p < 0.01). There was no significant difference between the DBM and autograft groups. No adverse inflammatory reactions were associated with any of the three graft materials. The AFT preparation of a mixture of mineralized and demineralized allograft appears to be an effective autograft substitute as tested in this sheep vertebral bone void model.