Bone regeneration by recombinant human bone morphogenetic protein-2 and a novel biodegradable carrier in a rabbit ulnar defect model

The effects of recombinant human bone morphogenetic protein (rhBMP)-2 and a novel carrier, PLGA-coated gelatin sponge (PGS), on bone defect repair was examined. A 1.5 cm unilateral segmental bone defect was created in the ulnar diaphysis of a Japanese white rabbit. In an initial study, defects were either treated with PGS impregnated with various concentrations of rhBMP-2 (0, 0.1, 0.4 and 1 mg/cm(3)) or left untreated. Defect healing was assessed by radiographic union rate, and biomechanical properties of regenerated bones were determined at 16 weeks postoperatively. In a second study, defects were implanted with PGS with or without rhBMP-2, and histologically observed at postoperative weeks 8 and 16. Radiographic union rate increased the dose-dependently at an early time point. All defects treated with rhBMP-2 (0.4 and 1 mg/cm(3)) were radiographically repaired. Mechanical properties of regenerated bones were restored in a dose-dependent manner. Neither ulnae left untreated nor implanted PGS alone showed radiographic union. Longitudinal alignment of lamellar structure was observed histologically at 16 weeks, indicating that remodeling of regenerated bone was complete. Implanted PGS was almost completely resorbed by 8 weeks, and no abnormalities were observed in the surrounding soft tissue. These results suggest that PGS is a promising carrier for rhBMP-2.     

Long-term stability of bone tissues induced by an osteoinductive biomaterial, recombinant human bone morphogenetic protein-2 and a biodegradable carrier

The long-term stability of bone tissues induced by recombinant human bone morphogenetic protein-2 (rhBMP-2) and poly[L-lactide-co-glycolide] copolymer-coated gelatin sponge (PGS) was examined. In 16 dogs, 2.5 cm unilateral bone defects were created in the left tibial diaphyses. Tibia was fixed with metal plate, and PGS impregnated with (0.4 mg/cm(3)) or without rhBMP-2 was implanted into 15 or one defects, respectively. The metal plates of rhBMP-2-treated limbs were removed 16 weeks after the implantation. The bilateral tibiae of five animals each of the rhBMP-2-treated group were harvested at 32, 52 or 104 weeks, and served for biomechanical testing and histology. Although the defect that received PGS alone resulted in nonunion at 16 weeks, all defects treated with rhBMP-2 achieved radiographic bony union by 8 weeks. Biomechanical properties of the regenerated bones restored to the levels of intact tibiae at 32 weeks, but torsional stiffness was significantly higher. No statistical significances were detected in all parameters between regenerated and intact tibiae at 104 weeks. No radiographic and histological findings suggesting enhanced resorption to the regenerated bones were observed. These results suggest the long-term stability of the bone tissues induced by rhBMP-2, and the usefulness of rhBMP-2-impregnated PGS as a biomaterial for long bone defect filling.     

Biodegradable composite scaffolds incorporating an intramedullary rod and delivering bone morphogenetic protein-2 for stabilization and bone regeneration in segmental long bone defects

In this study, a two-part bone tissue engineering scaffold was investigated. The scaffold consists of a solid poly(propylene fumarate) (PPF) intramedullary rod for mechanical support surrounded by a porous PPF sleeve for osseointegration and delivery of poly(dl-lactic-co-glycolic acid) (PLGA) microspheres with adsorbed recombinant human bone morphogenetic protein-2 (rhBMP-2). Scaffolds were implanted into critical size rat segmental femoral defects with internal fixation for 12 weeks. Bone formation was assessed throughout the study via radiography, and following euthanasia, via microcomputed tomography and histology. Mechanical stabilization was evaluated further via torsional testing. Experimental implant groups included the PPF rod alone and the rod with a porous PPF sleeve containing PLGA microspheres with 0, 2 or 8 μg of rhBMP-2 adsorbed onto their surface. Results showed that presence of the scaffold increased mechanical stabilization of the defect, as evidenced by the increased torsional stiffness of the femurs by the presence of a rod compared to the empty defect. Although the presence of a rod decreased bone formation, the presence of a sleeve combined with a low or high dose of rhBMP-2 increased the torsional stiffness to 2.06 ± 0.63 and 1.68 ± 0.56 N·mm, respectively, from 0.56 ± 0.24 N·mm for the rod alone. The results indicate that, while scaffolds may provide structural support to regenerating tissues and increase their mechanical properties, the presence of scaffolds within defects may hinder overall bone formation if they interfere with cellular processes.     

The role of recombinant human bone morphogenetic protein-2 in PLGA capsules at an extraskeletal site of the rat.

Bone morphogenetic protein-2 (BMP-2) is a member of the transforming growth factor-beta (TGF-beta) superfamily and has strong bone-inductive activity in vivo. To examine the role of BMP-2 in an extraskeletal site of rat using a controlled release system of peptides, we encapsulated the recombinant human BMP-2 (rhBMP-2) with poly(DL-lactide-co-glycolide) (PLGA) and implanted the rhBMP-2/PLGA capsules in the subcutaneous area of rats. Upon histochemical examination, it was found that bone-inducing cells having alkaline phosphatase (ALP) activity appeared around the capsules by the suitably released rhBMP-2. In addition, the temporal histological examination showed that direct bone formation without cartilage occurred in the process of this ectopic bone induction. These data indicate that the role of rhBMP-2 in the extraskeletal site of rats is to induce the differentiation of mesenchymal cells into the osteoblasts.Copyright 1999 John Wiley & Sons, Inc.     

Repair of long intercalated rib defects in dogs using recombinant human bone morphogenetic protein-2 delivered by a synthetic polymer and beta-tricalcium phosphate

Long intercalated defects in canine ribs can be repaired successfully using porous beta-tricalcium phosphate (beta-TCP) cylinders, infused with a biodegradable polymer (poly D,L-lactic acid-polyethylene block copolymer) containing recombinant human bone morphogenetic protein-2 (rhBMP-2). We previously reported the successful regeneration of bony rib and periosteum defects using beta-TCP cylinders containing 400 microg of rhBMP-2. To reduce the amount of rhBMP-2 and decrease the time required for defect repair, we utilized a biodegradable polymer carrier, in combination with rhBMP-2 and the porous beta-TCP cylinders. An 8 cm long section of rib bone was removed and replaced with an implant comprised of the porous beta-TCP cylinders and the polymer containing 80 microg of rhBMP-2. Six weeks after surgical placement of the beta-TCP cylinder/polymer/BMP-2 implants, new rib bone with an anatomical configuration and mechanical strength similar to the original bone was regenerated at the defect site. The stiffness of the regenerated ribs at 3, 6, and 12 weeks after implantation of the composite implant was significantly higher than that of ribs regenerated by implantation of rhBMP-2/beta-TCP implants. Thus, addition of the synthetic polymer to the drug delivery system for BMP potentiated the bone-regenerating ability of the implant and enabled the formation of mechanically competent rib bone. This new method appears to be applicable to the repair of intercalated long bone defects often encountered in clinical practice.     

Experimental studies on bone induction using low-molecular-weight poly (DL-lactide-co-glycolide) as a carrier for recombinant human bone morphogenetic protein-2

An appropriate carrier acting as a slow delivery vehicle for the BMPs is required for maximal clinical effectiveness of these bone-inductive proteins. The purpose of this study was to evaluate a low-molecular-weight PLGA copolymer as a synthetic, biodegradable carrier for rhBMP-2 implantation in vivo. Two, 10, or 50 microg of recombinant human BMP-2 were mixed with 10 mg of a poly (DL-lactide-co-glycolide) (PLGA) 50:50 copolymer and implanted into the calf muscles of Wistar rats. Soft X-ray analysis and histologic examination indicated that new bone formation occurred at all rhBMP-2-implanted sites within 3 weeks after implantation. Correlation of rhBMP-2 concentration with the amount of bone induction was confirmed by specific alkaline phosphatase activity and calcium content assay. In vitro analysis indicated that 78.5% of the PLGA copolymer was degraded to smaller molecular weight material after 14 days in PBS solution. It is suggested that rhBMP-2 was released in an active form at the implant site during the degradation of the copolymer, resulting in the induction of new bone formation. Thus this low-molecular-weight PLGA copolymer material represents a promising delivery vehicle for BMPs, and possibly other growth factors, around dental and orthopedic implants.     

Segmental bone regeneration using a load-bearing biodegradable carrier of bone morphogenetic protein-2

Segmental defect regeneration has been a clinical challenge. Current tissue-engineering approach using porous biodegradable scaffolds to delivery osteogenic cells and growth factors demonstrated success in facilitating bone regeneration in these cases. However, due to the lack of mechanical property, the porous scaffolds were evaluated in non-load bearing area or were stabilized with stress-shielding devices (bone plate or external fixation). In this paper, we tested a scaffold that does not require a bone plate because it has sufficient biomechanical strength. The tube-shaped scaffolds were manufactured from poly(propylene) fumarate/tricalcium phosphate (PPF/TCP) composites. Dicalcium phosphate dehydrate (DCPD) were used as bone morphogenetic protein-2 (BMP-2) carrier. Twenty-two scaffolds were implanted in 5mm segmental defects in rat femurs stabilized with K-wire for 6 and 15 weeks with and without 10 microg of rhBMP-2. Bridging of the segmental defect was evaluated first radiographically and was confirmed by histology and micro-computer tomography (microCT) imaging. The scaffolds in the BMP group maintained the bone length throughout the duration of the study and allow for bridging. The scaffolds in the control group failed to induce bridging and collapsed at 15 weeks. Peripheral computed tomography (pQCT) showed that BMP-2 does not increase the bone mineral density in the callus. Finally, the scaffold in BMP group was found to restore the mechanical property of the rat femur after 15 weeks. Our results demonstrated that the load-bearing BMP-2 scaffold can maintain bone length and allow successfully regeneration in segmental defects.     

Tissue-engineered bone biomimetic to regenerate calvarial critical-sized defects in athymic rats.

A tissue-engineered bone biomimetic device was developed to regenerate calvaria critical-sized defects (CSDs) in athymic rats. Well-documented evidence clearly confirms that left untreated, CSDs will not spontaneously regenerate bone. To accomplish regeneration, four candidate treatments were assessed: porous poly(D,L-lactide) and type I collagen (PLC), PLC and human osteoblast precursor cells (OPCs) at 2 x 10(5) (PLC/OPCs), PLC and 50 microg of recombinant human bone morphogenetic protein-2 (PLC/rhBMP-2), and PLC/OPCs/rhBMP-2 (the bone biomimetic device). The hypotheses for this study were PLC/OPCs/rhBMP-2 would promote more new bone formation in CSDs than the other treatments and the amount of bone formation would be time dependent. To test the hypotheses, outcomes from treatments were measured at 2 and 4 weeks postoperatively by radiomorphometry for percent radiopacity and by histomorphometry for square millimeters of new bone formation. Data were analyzed by analysis of variance and Fisher's protected least significant difference for multiple comparisons with p < or = 0.05. At 2 and 4 weeks, radiomorphometric data revealed PLC/rhBMP-2 and PLC/OPCs/rhBMP-2 promoted significantly more radiopacity than either PLC or PLC/OPCs. Histomorphometry data at 2 and 4 weeks indicated significantly more new bone formation for PLC/rhBMP-2, PLC/OPCs/rhBMP-2, and PLC/OPCs compared to PLC. By 4 weeks, PLC/OPCs/rhBMP-2 and PLC/rhBMP-2 had regenerated the CSDs with more new bone than the other treatments; the quantity of bone at 4 weeks for these treatments was greater than at 2 weeks.     

Hierarchically biomimetic bone scaffold materials: nano-HA/collagen/PLA composite

A bone scaffold material (nano-HA/ collagen/PLA composite) was developed by biomimetic synthesis. It shows some features of natural bone both in main composition and hierarchical microstructure. Nano-hydroxyapatite and collagen assembled into mineralized fibril. The three-dimensional porous scaffold materials mimic the microstructure of cancellous bone. Cell culture and animal model tests showed that the composite material is bioactive. The osteoblasts were separated from the neonatal rat calvaria. Osteoblasts adhered, spread, and proliferated throughout the pores of the scaffold material within a week. A 15-mm segmental defect model in the radius of the rabbit was used to evaluate the bone-remodeling ability of the composite. Combined with 0.5 mg rhBMP-2, the material block was implanted into the defect. The segmental defect was integrated 12 weeks after surgery, and the implanted composite was partially substituted by new bone tissue. This scaffold composite has promise for the clinical repair of large bony defects according to the principles of bone tissue engineering.     

Repair of an intercalated long bone defect with a synthetic biodegradable bone-inducing implant

Recombinant human bone morphogenetic protein (rhBMP)-2 in a block copolymer composed of poly-D,L-lactic acid with randomly inserted p-dioxanone and polyethylene glycol (PLA-DX-PEG) as a carrier and porous beta-tricalcium phosphate (beta-TCP) blocks were used to generate a new fully absorbable osteogenic biomaterial. The bone regenerability of the rhBMP-2/PLA-DX-PEG/beta-TCP composite was studied in a critical-sized rabbit bone defect model. In an initial study, a composite of PLA-DX-PEG (250 mg) and beta-TCP (300 mg) loaded with or without rhBMP2 (50 microg) was implanted into a 1.5 cm intercalated bone defect created in a rabbit femur. Defects were assessed by biweekly radiography until 8 weeks postoperatively. The bony union of the defect was recognized only in the BMP-loaded group. To obtain further data on biomechanical and remodeling properties, another BMP-loaded composites group was made and observed up to 24 weeks. All defects were completely repaired without residual traces of implants. Anatomical and mechanical properties of the repaired bone examined by histology, 3-dimensional CT (3D-CT) and mechanical testing were essentially equivalent to the nonoperated-on femur at 24 weeks. These experimental results indicate that fully absorbable rhBMP-2/PLA-DX-PEG/beta-TCP is a promising composite having osteogenicity efficient enough for repairing large bone defects.     

The effects of rhBMP-2 released from biodegradable polyurethane/microsphere composite scaffolds on new bone formation in rat femora

Scaffolds prepared from biodegradable polyurethanes (PUR) have been investigated as a supportive matrix and delivery system for skin, cardiovascular, and bone tissue engineering. While previous studies have suggested that PUR scaffolds are biocompatible and moderately osteoconductive, the effects of encapsulated osteoinductive molecules, such as recombinant human bone morphogenetic protein (rhBMP-2), on new bone formation have not been investigated for this class of biomaterials. The objective of this study was to investigate the effects of different rhBMP-2 release strategies on new bone formation in PUR scaffolds implanted in rat femoral plug defects. In the simplest approach, rhBMP-2 was added as a dry powder prior to the foaming reaction, which resulted in a burst release of 35% followed by a sustained release for 21 days. Encapsulation of rhBMP-2 in either 1.3-micron or 114-micron PLGA microspheres prior to the foaming reaction reduced the burst release. At 4 weeks post-implantation, all rhBMP-2 treatment groups enhanced new bone formation relative to the scaffolds without rhBMP-2. Scaffolds incorporating rhBMP-2 powder promoted the most extensive new bone formation, while scaffolds incorporating rhBMP-2 encapsulated in 1.3-micron microspheres, which exhibited the lowest burst release, promoted the least extensive new bone formation. Thus our observations suggest that an initial burst release followed by sustained release is better for promoting new bone formation.     

Healing of segmental bone defects in rats induced by a beta-TCP-MCPM cement combined with rhBMP-2.

A beta-tricalcium phosphate-monocalcium phosphate monohydrate (beta-TCP-MCPM) cement was evaluated as an effective carrier of recombinant human bone morphogenetic protein-2 (rhBMP-2) in rat femoral critical-size defects. Hard cement cylinders (4 x 5 mm) impregnated with two different doses of rhBMP-2 (1.26 or 6.28 microg) were implanted into each defect, and the results were compared with those in rats that had implantations of cylinders only. Implantation of the 6.28 microg dose of rhBMP-2 caused a large bone shell to form around the defect, resulting in osseous union in all cases within 3 weeks. Except for beta-TCP granules, the cement was resorbed and replaced by bone tissue at 6 weeks. A torsion test at 9 weeks showed that the failure torque and bone stiffness had recovered 99% and 141%, respectively, compared with the intact contralateral femur. The defects that received 1.26 microg of rhBMP-2 resulted in 40% union and 41% of the failure torque at 9 weeks. However, no instances of union were observed in the defects implanted with cylinders only. In conclusion, the beta-TCP-MCPM cement was shown to be effective as a rhBMP-2 carrier. Combined with rhBMP-2, this cement was rapidly resorbed and completely healed the defects.     

重组人骨形态发生蛋白2修饰的组织工程化骨修复眼眶骨折的实验研究

目的 探讨组织工程化骨修复眼眶骨折缺损的治疗效果.方法 体外构建以自体骨髓基质干细胞(BMSC)为种子细胞、可降解吸收的生物材料聚乳酸羟基乙酸聚合物(PLGA)为载体、重组人骨形态发生蛋白2(rhBMP-2)为生长因子的组织工程化骨,将实验动物分为对照组(植入PLGA/rhBMP-2复合物)和实验组(植入组织工程化骨),观察术后1个月、3个月和6个月伤口愈合情况、并发症及眼眶外观、CT影像学和组织学变化.结果 术后所有动物伤口愈合良好,无并发症和眼球凹陷.CT三维成像显示术后3个月实验组的缺损范围[(25.1±6.8) mm2]小于对照组[(55.3±7.7)mm2];术后6个月,实验组的眼眶骨折缺损消失,而对照组仍存在.组织学结果显示,术后1个月即可观察到实验组植入区边缘植入物开始缓慢吸收,少量成骨细胞沿支架长人材料内,而对照组未观察到;术后3个月可见实验组形成条带状新生骨长入将其分割包绕呈交叉排列,材料降解吸收明显高于对照组;术后6个月实验组植人材料完全被降解吸收,同时被新生骨组织取代,植入物与自身骨组织紧密结合,融为一体.而对照组仅部分降解吸收.结论 重组人骨形态发生蛋白2修饰的组织工程化骨具有较强的传导成骨和诱导成骨活性,生物相容性好,材料可完全降解,为骨组织取代,对眼眶骨折缺损具有较好的修复效果.     

Synergism between interleukin-11 and bone morphogenetic protein-2 in the healing of segmental bone defects in a rabbit model.

Recombinant human interleukin-11 (rHuIL-11) and recombinant human bone morphogenetic protein-2 (rHuBMP-2) have been shown to act synergistically in the induction of osteoblast differentiation. To determine whether these two proteins can be used clinically in fracture healing and reconstructive surgery, we investigated whether rHuIL-11 and rHuBMP-2 act synergistically to heal segmental bone defects in a rabbit model. A 1.5-cm segmental defect was created in the right ulnar diaphysis of 20 Japanese white rabbits. Polylactic-co-glycolic acid (PLGA)-coated gelatin sponges (PGS) permeated with rHuBMP-2 (n = 8), rHuIL-11 plus rHuBMP-2 (n = 8), or rHuIL-11 (n = 4) were implanted into the bone defects. Radiographs were scored by two independent observers for bone formation and union rates after 2, 3, 4, and 8 weeks. Bone formation was higher in rabbits implanted with rHuBMP-2 plus rHuIL-11 than in those implanted with rHuBMP-2 alone, reaching statistical significance after 4 weeks. At early time points, the union rate in rabbits implanted with rHuBMP-2 plus rHuIL-11 was higher than in rabbits implanted with rHuBMP-2. At 2, 4, and 8 weeks, new bone volume was significantly higher in rabbits administered rHuIL-11 plus rHuBMP-2 than in those given rHuBMP-2 alone. In contrast, mechanical testing after 8 weeks showed that bone strength in the two groups of rabbits was equivalent. These findings show that rHuIL-11 and rHuBMP-2 act synergistically to accelerate bone formation without affecting bone strength. Treatment with a combination of rHuIL-11 and rHuBMP-2 may thus be of great benefit in fracture healing and for patients undergoing reconstructive surgery.     

Repair of diaphyseal bone defects with calcitriol-loaded PLGA scaffolds and marrow stromal cells

Calcitriol (1,25(OH)2D3)-loaded porous poly(D,L-lactide-co-glycolide) (PLGA) scaffolds prepared by solvent casting/salt leaching method were used to repair a 1.5 cm diaphyseal segmental bone defect as a fully absorbable osteogenic biomaterial. The in vitro release of sulforhodamine B (SRB) from PLGA scaffold was measured using spectrophotometer, considering SRB as a model drug. The SRB released from SRB-incorporated PLGA scaffold during 3 months was with relatively low initial burst. The calcitriol-loaded PLGA scaffolds with or without marrow stromal cells (MSCs) were implanted in a critical-sized intercalated bone defect in rabbit femur. Defects were assessed by radiographs until 9 weeks. The bony union of the defect was observed only in the calcitriol-loaded groups. RT-PCR results indicated that MSCs, which were seeded into calcitriol-loaded scaffold, expressed an increased level of alkaline phosphatase, osteonectin, and type I collagen mRNA at day 10. After 2 and 4 weeks, the implanted scaffolds were evaluated by histology. New osteoid matrix and direct calcium deposits were more evident in calcitriol/PLGA/MSC group. Three-dimensional computed tomography and frontal tomographic images of repaired femur showed that normal femur anatomy had been restored with cortical bone with no implanted PLGA remnants at 20 weeks. It can be concluded that the porous calcitriol-loaded PLGA scaffold combined with MSCs may be a novel method for repairing the large loaded bone defect.     

Improving bone formation in a rat femur segmental defect by controlling bone morphogenetic protein-2 release

Nonunion is a common complication in open fractures and other severe bone injuries. Recombinant human bone morphogenetic protein-2 (rhBMP-2) delivered on a collagen sponge enhances healing of fractures. However, the burst release of rhBMP-2 necessitates supra-physiological doses of rhBMP-2 to achieve a robust osteogenic effect, which introduces risk of ectopic bone formation and severe inflammation and increases the cost. Although the concept that the ideal pharmacokinetics for rhBMP-2 includes both a burst and sustained release is generally accepted, investigations into the effects of the release kinetics on new bone formation are limited. In the present study, biodegradable polyurethane (PUR) and PUR/microsphere [PUR/poly(lactic-co-glycolic acid)] composite scaffolds with varying rhBMP-2 release kinetics were compared to the collagen sponge delivery system in a critical-sized rat segmental defect model. Microcomputed tomography analysis indicated that a burst followed by a sustained release of rhBMP-2 from the PUR scaffolds regenerated 50% more new bone than the collagen sponge loaded with rhBMP-2, whereas a sustained release without the burst did not form significantly more bone than the scaffold without rhBMP-2. This study demonstrated that the putative optimal release profile (i.e., burst followed by sustained release) for rhBMP-2 can be achieved using PUR scaffolds, and that this enhanced pharmacokinetics regenerated more bone than the clinically available standard of care in a critical-sized defect in rat femora.     

Mineral apposition rates provide significant information on long-term effects in BMP-induced bone regeneration

In this study, a CaP biomaterial was used as a carrier for rhBMP-2. Biomaterials were investigated in calvarial and femoral defects using a rabbit animal model, with unloaded biomaterials serving as control. Fluorochrome labels were administered at days 14 and 70. Specimens were retrieved after 12 weeks for histological analysis. When area fractions were assessed by conventional histomorphometry, no significant effect of rhBMP-2 on the amounts of regenerated bone and residual biomaterial were seen by 12 weeks. After mineral appositional rate (MAR) measurement using double labels, calculation yielded significantly higher MARs for defects at both implantation sites, when compared with surrounding bone, whether or not biomaterials were loaded with rhBMP-2. Analyzing the effect of rhBMP-2, both defect sites showed significantly higher MARs in the rhBMP-2 group. MARs of bone surrounding the defects had also been elevated significantly by rhBMP-2 at calvarial and femoral implantation sites. It is concluded that MAR measurement is suitable to identify long-term effects of rhBMP-2 on bone formation at a time when conventional histomorphometry using fractional area determination is inadequate. Also, by MAR assessment, effects of rhBMP-2 on surrounding bone can be documented.     

Ectopic bone formation associated with recombinant human bone morphogenetic proteins-2 using absorbable collagen sponge and beta tricalcium phosphate as carriers

The ectopic bone formation of recombinant human bone morphogenetic protein-2(rhBMP-2) was evaluated using absorbable collagen sponges (ACS) and beta tricalcium phosphate (beta-TCP) as carriers in a rat subcutaneous assay model. Subcutaneous pockets were created on the back of rats. The pockets were implanted with rhBMP-2/ACS, rhBMP-2/beta-TCP, ACS alone, and beta-TCP alone. The rats were sacrificed at 2 or 8 weeks for histological and immunohistochemical evaluation. At 2 weeks, bone formation was evident in both the rhBMP-2/ACS and rhBMP-2/beta-TCP sites. At 8 weeks, the quantity of the new bone with a more advanced stage of remodeling had increased further in the rhBMP-2/beta-TCP sites. However, the newly formed bone observed at 2 weeks was not found in the rhBMP-2/ACS sites. On immunohistochemical observation, osteopontin staining was observed on both the rhBMP-2/ACS (2 weeks) and rhBMP-2/beta-TCP (2 and 8 weeks) sites. Osteocalcin was not detected in any of the samples. The lack of space-providing capacity of ACS may be one of the major factors responsible for its failure to maintain the newly induced bone. Therefore, a carrier for BMPs should provide space for bone formation and maturation during the more advanced healing stages.     

纤维蛋白胶复合重组人骨形态发生蛋白2微球对犬骨髓基质细胞增殖与分化的影响

背景：前期实验证实聚乳酸-聚乙醇酸微球/纤维蛋白胶能作为重组人骨形态发生蛋白2的良好可注射性缓释载体。 目的：观察可注射性骨形态发生蛋白缓释体系对犬骨髓基质细胞增殖与分化的影响。 方法：采用复乳-溶剂挥发法制备重组人骨形态发生蛋白2/聚乳酸-聚乙醇酸共聚物载药微球,然后将微球与纤维蛋白胶复合制备出重组人骨形态发生蛋白2/聚乳酸-聚乙醇酸共聚物/纤维蛋白胶复合材料,采用细胞培养及组织化学等方法观察微球对犬骨髓基质细胞的增殖与分化的影响。 结果与结论：重组人骨形态发生蛋白2/聚乳酸-聚乙醇酸共聚物/纤维蛋白胶微球对骨髓基质细胞的增殖无明显影响,但对细胞的分化功能有明显的促进作用。说明纤维蛋白胶复合重组人骨形态发生蛋白2微球能够提高骨髓基质细胞的体外成骨能力,可作为骨形态发生蛋白的良好载体。     

重组人骨形成蛋白-2-珊瑚人工骨复合物在拔牙窝牙槽骨修复中的作用

目的:探讨重组人骨形成蛋白-2与珊瑚人工骨复合物(复合骨 )在拔牙窝修复中的作用。方法:拔除 12只成年狗两侧上颌第二及第三切牙,并去除牙槽窝之间的牙槽间隔,一侧随即植入复合骨,对侧植入珊瑚人工骨(珊瑚骨 )作为对照。并于植入后 4、8、12周取材,采用组织学观察、图像分析和 [⁹⁹Tc^m]-MDP核素骨显像等方法比较两种植入材料在牙槽窝中的骨修复能力。结果:复合骨植入牙槽骨后,材料被逐渐降解吸收,新骨不断生成,12周后,植入材料完全被成熟的骨组织取代;图像分析结果显示不同时间复合骨组新骨形成的比值显著高于珊瑚骨组(P <0.05 );4和 8周复合骨组核素浓聚程度高于珊瑚骨组,12周两组核素浓聚程度差异不明显。结论:复合骨在牙槽骨缺损中的骨修复能力和修复效果明显优于珊瑚骨.