Clinical evaluation of rhBMP-2/ACS in orthopedic trauma: a progress report.

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is an osteoinductive protein that plays a pivotal role in bone growth and regeneration. Studies conducted in many mammalian species and, most recently, human clinical studies, have provided definitive evidence of the ability of rhBMP-2 to induce bone. The findings of these studies provide a rationale for investigating whether rhBMP-2 therapy will be clinically useful in orthopedic practice. Consequently, we have initiated a clinical research program to evaluate the safety and efficacy of rhBMP-2 therapy in open tibial fractures. A prospective observational study (involving no rhBMP-2 treatment) was conducted to define an appropriate patient population for rhBMP-2 clinical trials and has provided critical information related to the design and execution of future studies. The rhBMP-2 clinical trials include a small pilot feasibility study and several larger studies. Data from the pilot feasibility study have demonstrated that implantation of rhBMP-2 (combined with an absorbable collagen sponge) is surgically feasible and safe. Larger, multicenter clinical studies are now ongoing in the United States and abroad.     

A comprehensive clinical review of recombinant human bone morphogenetic protein-2 (INFUSE® Bone Graft)

The combination of recombinant human bone morphogenetic protein-2 (rhBMP-2) on an absorbable collagen sponge (ACS) carrier has been shown to induce bone formation in a number of preclinical and clinical investigations. In 2002, rhBMP-2/ACS at a 1.5-mg/cc concentration (INFUSE Bone Graft, Medtronic Spinal and Biologics, Memphis, TN) was FDA-approved as an autograft replacement for certain interbody spinal fusion procedures. In 2004, INFUSE Bone Graft was approved for open tibial fractures with an intermedullary (IM) nail fixation. Most recently, in March 2007, INFUSE Bone Graft was approved as an alternative to autogenous bone grafts for sinus augmentations, and for localised alveolar ridge augmentations for defects associated with extraction sockets. The culmination of extensive preclinical and clinical research and three FDA approvals makes rhBMP-2 one of the most studied, published and significant advances in orthopaedics. This review article summarises a number of clinical findings of rhBMP-2/ACS, including the FDA-approved investigational device exemption (IDE) studies used in gaining the aforementioned approvals.     

Clinical applications of BMP-7/OP-1 in fractures,nonunions and spinal fusion

Since the identification of the osteogenic protein-1 (OP-1) gene, also called bone morphogenetic protein-7 (BMP-7), almost 20 years ago, OP-1 has become one of the most characteristic members of the BMP family. The biological activity of recombinant human OP-1 has been defined using a variety of animal models. These studies have demonstrated that local implantation of OP-1 in combination with a collagen matrix results in the repair of critical size defects in long bones and in craniofacial bones and the formation of bony fusion masses in spinal fusions. Clinical trials investigating long bone applications have provided supportive evidence for the use of OP-1 in the treatment of open tibial fractures, distal tibial fractures, tibial nonunions, scaphoid nonunions and atrophic long bone nonunions. Clinical studies investigating spinal fusion applications have provided supportive evidence for the use of OP-1 in posterolateral lumbar models and compromised patients as an adjunct or as a replacement for autograft. Both long bone repair and spinal fusion studies have demonstrated the efficacy and safety of OP-1 by clinical outcomes and radiographic measures. Future clinical investigations will be needed to better define variables, such as dose, scaffold and route of administration. Clearly the use of BMPs in orthopaedics is still in its formative stage, but the data suggest an exciting and promising future for the development of new therapeutic applications.     

Recombinant human BMP-2 for the treatment of open tibial fractures

Recombinant human bone morphogenetic protein-2 (rhBMP-2) improves healing of open tibial fractures treated with intramedullary nail fixation. However, routine use has not occurred. The purposes of the current study were to provide a systematic review of the literature using rhBMP-2 in the treatment of acute open tibial fractures treated with intramedullary nail fixation and to provide a meta-analysis of the randomized, controlled trials. Multiple databases, reference lists of relative articles, and main orthopedic journals were searched. The basic information and major results were compared. Four studies with a total of 609 patients were included.The secondary intervention rate in the standard-of-care (SOC) group was significantly higher than in the rhBMP-2 combined with absorbable collagen sponge (rhBMP-2/ACS) group (27.1% vs 17.5%, respectively; P<.01). The treatment failure rate in the SOC group was significantly higher (34.3% vs. 21.4%, respectively; P<.01). No significant differences were found in infection rate, hardware failure rate, fracture healing rate at 20 weeks, and postoperative pain level. For patients treated with reamed intramedullary nail fixation, only the treatment failure rate in the SOC group was significantly higher (21.5% vs 14.2%, respectively; P=.02); no other significant difference was observed. Adding rhBMP-2 to the treatment of Gustilo-Anderson grade IIIA and B open tibial fractures led to net savings of approximately $6000 per case.Recombinant human bone morphogenetic protein-2 added to intramedullary nail fixation of open tibial fractures could reduce the frequency of secondary interventions and total health care costs. For reamed patients, adding rhBMP-2 reduced treatment failure. This analysis supports the clinical efficacy of rhBMP-2/ACS for the treatment of these severe fractures.     

Recombinant human bone morphogenetic protein-2 accelerates healing in a rabbit ulnar osteotomy model

BACKGROUND: Approximately 5% to 20% of fractures have delayed or impaired healing. Therefore, it is desirable to develop new therapies to enhance fracture-healing that can be used in conjunction with traditional treatment methods. The purpose of this study was to evaluate the ability of a single application of recombinant human bone morphogenetic protein-2 to accelerate fracture-healing in a rabbit ulnar osteotomy that heals spontaneously. METHODS: Bilateral mid-ulnar osteotomies (approximately 0.5 to 1.0 mm wide) were created in seventy-two skeletally mature male rabbits. The limbs were assigned to one of three groups: those treated with an absorbable collagen sponge containing recombinant human bone morphogenetic protein-2, those treated with an absorbable collagen sponge containing buffer, and those left untreated. In the first two groups, an 8 20-mm strip of absorbable collagen sponge containing either 40 g of recombinant human bone morphogenetic protein-2 or buffer only was wrapped around the osteotomy site. The rabbits were killed at two, three, four, or six weeks after surgery. In addition, twenty-four age-matched rabbits were used to provide data on the properties of intact limbs. The retention of recombinant human bone morphogenetic protein-2 at the osteotomy site was determined with scintigraphic imaging of (125)I-labeled recombinant human bone morphogenetic protein-2. After the rabbits were killed, the limbs were scanned with peripheral quantitative computed tomography to assess the area and mineral content of the mineralized callus. The limbs were then tested to failure in torsion, and undecalcified specimens were evaluated histologically. RESULTS: Gamma scintigraphy of (125)I-recombinant human bone morphogenetic protein-2 showed that 73% +/- 6% (mean and standard deviation) of the administered dose was initially retained at the fracture site. Approximately 37% +/- 10% of the initial dose remained at the site one week after surgery, and 8% +/- 7% remained after two weeks. The mineralized callus area was similar in all groups at two weeks, but it was 20% to 60% greater in the ulnae treated with recombinant human bone morphogenetic protein-2 than in either the ulnae treated with buffer or the untreated ulnae at three, four, and six weeks (p < 0.05). Biomechanical properties were similar in all groups at two weeks, but they were at least 80% greater in the ulnae treated with recombinant human bone morphogenetic protein-2 at three and four weeks than in either the ulnae treated with buffer (p < 0.005) or the untreated ulnae (p < 0.01). By four weeks, the biomechanical properties of the ulnae treated with recombinant human bone morphogenetic protein-2 were equivalent to those of the intact ulnae, whereas the biomechanical properties of both the ulnae treated with buffer and the untreated ulnae had reached only approximately 45% of those of the intact ulnae. At six weeks, the biomechanical properties were similar in all groups and were equivalent to those of the intact ulnae. The callus geometry and biomechanical properties of the ulnae treated with buffer were equivalent to those of the untreated ulnae at all time-points. CONCLUSIONS AND CLINICAL RELEVANCE: These findings indicate that treatment with an absorbable collagen sponge containing recombinant human bone morphogenetic protein-2 enhances healing of a long-bone osteotomy that heals spontaneously. Specifically, osteotomies treated with recombinant human bone morphogenetic protein-2 healed 33% faster than osteotomies left untreated. The results of this study provide a rationale for testing the ability of recombinant human bone morphogenetic protein-2 to accelerate healing in patients with fractures requiring open surgical management.     

Osteogenesis by recombinant human bone morphogenetic protein-2 at skeletal sites

Osteogenesis was evaluated in the mandibular bone by combinations of various dosages of recombinant human bone morphogenetic protein-2, atelopeptide Type I collagen, and porous hydroxyapatite (four groups: Group I, 2 micrograms recombinant human bone morphogenetic protein-2, atelopeptide Type I collagen, and porous hydroxyapatite; Group II, 10 micrograms recombinant human bone morphogenetic protein-2, atelopeptide Type I collagen, and porous hydroxyapatite; Group III, 50 micrograms recombinant human bone morphogenetic protein-2, atelopeptide Type I collagen, and porous hydroxyapatite; Control Group, only atelopeptide Type I collagen and porous hydroxyapatite). The prepared materials were implanted in the mandibular bone hole (7 mm in diameter, 2 mm deep). Three weeks later, the alkaline phosphatase activity in the implanted region was determined, and the histologic features of the excised tissue were examined. There were significant differences in histologic and biochemical findings among the four groups. In the recombinant human bone morphogenetic protein-2 implanted groups, osteogenesis increased with the dosage of recombinant human bone morphogenetic protein-2, as assessed by alkaline phosphatase activity and histologic findings. The results suggest that atelopeptide Type I collagen is an effective carrier for recombinant human bone morphogenetic protein-2 and that porous hydroxyapatite would be advantageous for clinical application as a material to maintain its original form after implantation.     

Bone marrow and recombinant human bone morphogenetic protein-2 in osseous repair

Bone marrow stem cells and recombinant human bone morphogenetic protein-2 each has the capacity to repair osseous defects. Recombinant human bone morphogenetic proteins require the presence of progenitor cells to function. It is hypothesized that a composite graft of recombinant human bone morphogenetic protein-2 and marrow would be synergistic and could result in superior grafting to autogenous bone graft. Syngeneic Lewis rats with a 5-mm critical sized femoral defect were grafted with recombinant human bone morphogenetic protein-2 and marrow, recombinant human bone morphogenetic protein-2, marrow, syngeneic cancellous bone graft, or carrier alone (control). Serial radiographs (3, 6, 9, 12 weeks) and torque testing (12 weeks) were performed. Bone formation and union were determined. The recombinant human bone morphogenetic protein-2 and marrow composite grafts achieved 100% union at 6 weeks. Recombinant human bone morphogenetic protein alone achieved 80% union by week 12. Both groups yielded a higher union rate and superior mechanical properties than did either syngeneic bone graft (38%) or marrow (47%) alone. The superior performance of recombinant human bone morphogenetic protein-2 combined with bone marrow in comparison with each component alone strongly supports a biologic synergism. This experimentation shows the clinical importance of establishing operative site proximity for the osteoinductive factors and responding progenitor cells.     

Recombinant human bone morphogenetic protein-2 in open tibial fractures. A subgroup analysis of data combined from two prospective randomized studies

BACKGROUND: The use of recombinant human bone morphogenetic protein-2 (rhBMP-2) to improve the healing of open tibial shaft fractures has been the focus of two prospective clinical studies. The objective of the current study was to perform a subgroup analysis of the combined data from these studies. METHODS: Two prospective, randomized clinical studies were conducted. A total of 510 patients with open tibial fractures were randomized to receive the control treatment (intramedullary nail fixation and routine soft-tissue management) or the control treatment and an absorbable collagen sponge impregnated with one of two concentrations of rhBMP-2. The rhBMP-2 implant was placed over the fracture at the time of definitive wound closure. For the purpose of this analysis, only the control treatment and the Food and Drug Administration-approved concentration of rhBMP-2 (1.50 mg/mL) were compared. Patients who anticipated receiving planned bone-grafting as part of a staged treatment were excluded from enrollment. RESULTS: Fifty-nine trauma centers in twelve countries participated, and patients were followed for twelve months postoperatively. Two subgroups were analyzed: (1) the 131 patients with a Gustilo-Anderson type-IIIA or IIIB open tibial fracture and (2) the 113 patients treated with reamed intramedullary nailing. The first subgroup demonstrated significant improvements in the rhBMP-2 group, with fewer bone-grafting procedures (p = 0.0005), fewer patients requiring invasive secondary interventions (p = 0.0065), and a lower rate of infection (p = 0.0234), compared with the control group. The second subgroup analysis of fractures treated with reamed intramedullary nailing demonstrated no significant difference between the control and the rhBMP-2 groups. CONCLUSIONS: The addition of rhBMP-2 to the treatment of type-III open tibial fractures can significantly reduce the frequency of bone-grafting procedures and other secondary interventions. This analysis establishes the clinical efficacy of rhBMP-2 combined with an absorbable collagen sponge implant for the treatment of these severe fractures.     

Recombinant bone morphogenetic protein (BMP)-2 regulates costochondral growth plate chondrocytes and induces expression of BMP-2 and BMP-4 in a cell maturation-dependent manner

This study examined the effect of recombinant human bone morphogenetic protein-2 on several parameters of growth, differentiation, and matrix synthesis and on the endogenous production of mRNA of bone morphogenetic proteins 2 and 4 by growth plate chondrocytes in culture. Chondrocytes from resting and growth zones were obtained from rat costochondral cartilage and cultured for 24 or 48 hours in medium containing 0.05-100 ng/ml recombinant human bone morphogenetic protein-2 and 10% fetal bovine serum. Incorporation of [³H]thymidine, cell number, alkaline phosphatase specific activity, incorporation of [³H]proline into collagenase-digestible protein and noncollagenase-digestible protein, and incorporation of [³⁵S]sulfate were assayed as indicators of cell proliferation, differentiation, and extracellular matrix synthesis. mRNA levels T for bone morphogenetic proteins 2 andv4 were determined by Northern blot analysis. Recombinant human bone morphogenetic protein-2 increased the incorporation of [³H]thymidine by quiescent resting-zone and growth-zone cells in a similar manner, whereas it had a differential effect on nonquiescent cultures. At 24 and 48 hours, 12.5-100 ng/ml recombinant human bone morphogenetic protein-2 caused a dose-dependent increase in cell number and DNA synthesis in resting-zone chondrocytes. No effect was seen in growth-zone cell Recombinant human bone morphogenetic protein-2 stimulated alkaline phosphatase specific activity in resting-zone chondrocytes in a bimodal manner, causing significant increases between 0.2 and 0.8 ng/ml and again between 25 and 100 ng/ml. In contrast, alkaline phosphatase specific activity in growth-zone chondrocytes was significantly increased only between 12.5 and 100 ng/ml. Recombinant human bone morphogenetic protein-2 increased the production of both collagenase-digestible protein and noncollagenase-digestible protein by resting-zone and growth-zone cells, but incorporation of [³⁵S]sulfate was unaffected. Administration of recombinant human bone morphogenetic protein-2 also increased incorporation of [³H]uridine in both resting-zone and growth-zone chondrocytes; these cells produced mRNA for bone morphogenetic proteins 2 and 4. Bone morphogenetic protein-2 mRNA levels in both resting-zone and growth-zone chondrocytes increased in the presence of recombinant human bone morphogenetic protein-2; however, bone morphogenetic protein-4 mRNA levels in growth-zone cells decreased under its influence, and those in resting-zone cells were upregulated only with a dose of 10 ng/ml. This indicates that recombinant human bone morphogenetic protein-2 regulates chondrocyte proliferation, differentiation, and matrix production, and the effects are dependent on the stage of cell maturation. Resting-zone chondrocytes were more sensitive, suggesting that they are targeted by bone morphogenetic protein-2 and that this growth factor may have autocrine effects on these cells.     

Biomaterial Scaffolds for Treating Osteoporotic Bone

Healing fractures resulting from osteoporosis or cancer remains a significant clinical challenge. In these populations, healing is often impaired not only due to age and disease, but also by other therapeutic interventions such as radiation, steroids, and chemotherapy. Despite substantial improvements in the treatment of osteoporosis over the last few decades, osteoporotic fractures are still a major clinical challenge in the elderly population due to impaired healing. Similar fractures with impaired healing are also prevalent in cancer patients, especially those with tumor growing in bone. Treatment options for cancer patients are further complicated by the fact that bone anabolic therapies are contraindicated in patients with tumors. Therefore, many patients undergo surgery to repair the fracture, and bone grafts are often used to stabilize orthopedic implants and provide a scaffold for ingrowth of new bone. Both synthetic and naturally occurring biomaterials have been investigated as bone grafts for repair of osteoporotic fractures, including calcium phosphate bone cements, resorbable polymers, and allograft or autograft bone. In order to re-establish normal bone repair, bone grafts have been augmented with anabolic agents, such as mesenchymal stem cells or recombinant human bone morphogenetic protein-2. These developing approaches to bone grafting are anticipated to improve the clinical management of osteoporotic and cancer-induced fractures.     

Recombinant human bone morphogenetic proteins-2 and -4 induce several mesenchymal phenotypes in culture

Bone morphogenetic protein has previously been shown to induce the formation of cartilage and bone in vivo. We have isolated a population of mesenchymal stem cells from rat skeletal muscle capable of forming multiple mesodermal morphologies in vitro. These cells were treated with recombinant human bone morphogenetic proteins-2 and -4 to determine the differentiation-inducing activities of bone morphogenetic protein on these cells. The mesenchymal stem cells were cultured in medium with 10% preselected horse serum containing 0 to 100 ng/ml recombinant human bone morphogenetic proteins-2 or -4 for a maximum of 4 weeks. Control cultures maintained the stellate morphology of mesenchymal stem cells. Cultures treated with recombinant human bone morphogenetic protein-2 exhibited discrete cartilage nodules and mineralized bone nodules. The first increase in chondrogenesis was seen at 0.5 ng/ml. Cultures treated with recombinant human bone morphogenetic protein-4 also exhibited an increase in chondrogenesis at the higher concentration of 2 ng/ml. Skeletal myotubes and adipocytes also appeared in cultures treated with either bone morphogenetic protein. Mesenchymal stem cells do respond to inductive factors, but bone morphogenetic proteins-2 and -4 were not specific for the induction of cartilage and bone.     

Effect of bone morphogenetic protein-12 gene transfer on mesenchymal progenitor cells

Recombinant adenovirus mediated human bone morphogenetic protein-12 gene transfer induced tendon and cartilage-like tissue formation in vivo. The recombinant adenovirus with the human bone morphogenetic protein-12 gene was constructed, and mature human bone morphogenetic protein-12 expression mediated by adenovirus gene transfer was detected by specific antibody. Unlike bone morphogenetic protein-2 gene transfer, bone morphogenetic protein-12 gene transferred mesenchymal progenitor cell line C3H 10T1/2 showed no change of alkaline phosphatase activity, which is the mark of cell differentiation into osteoblastic phenotype. Injection of bone morphogenetic protein-12 gene transferred C3H 10T1/2 cells into nude mice thigh muscles induced tendon and cartilage-like tissue formation. The results indicate bone morphogenetic protein-12 has different effects on mesenchymal progenitor cell differentiation, and it may influence the cell differentiation into a nonosteoblast lineage.     

Bone morphogenetic proteins in clinical applications

The role of bone morphogenetic proteins (BMPs) in bone healing has been shown in numerous animal models. To date, at least 20 BMPs have been identified, some of which have been shown in vitro to stimulate the process of stem cell differentiation into osteoblasts in human and animal models. Having realized the osteoinductive properties of BMPs and having identified their genetic sequences, recombinant gene technology has been used to produce BMPs for clinical application - most commonly, as alternatives or adjuncts in the treatment of cases in which fracture healing is compromised. BMP-2 and BMP-7 are approved for clinical use in open fractures of long bones, non-unions and spinal fusion. However, despite significant evidence of their potential benefit to bone repair and regeneration in animal and preclinical studies, there is, to date, a dearth of convincing clinical trials. The purpose of this paper is to give a brief overview of BMPs and to critically review the clinical data currently available on the use of BMP-2 and BMP-7 in fracture healing.     

Regional gene therapy with a BMP-2-producing murine stromal cell line induces heterotopic and orthotopic bone formation in rodents

The ability to continuously deliver osteoinductive proteins to a specific anatomic site would facilitate the treatment of fracture nonunions and other clinical problems associated with bone loss. We have developed a murine model of regional gene therapy. A bone-marrow stromal cell line infected with an adenovirus expressing recombinant bone morphogenetic protein-2 cDNA secreted biologically active bone morphogenetic protein-2. These bone morphogenetic protein-2-producing cells were able to induce abundant heterotopic bone formation when implanted into the quadriceps muscle of severe combined immune deficient mice and also successfully healed large segmental femoral defects in nude rats. These studies demonstrate that regional gene therapy with continuous delivery of osteoinductive factors to a specific anatomic site can enhance the formation and repair of bone.     

Recombinant human bone morphogenetic protein-2 maintains the articular chondrocyte phenotype in long-term culture

Bone morphogenetic proteins have been shown to increase matrix synthesis by articular chondrocytes in short-term cultures. Members of this family of proteins have also been shown to induce endochondral ossification in vivo. The present study was performed to determine if the addition of human recombinant bone morphogenetic protein-2 to a long-term monolayer articular chondrocyte cell culture system affected the ability of the chondrocytes to divide in vitro, whether the cytokine altered expression of the articular chondrocyte phenotype and synthesis of matrix proteoglycans, and whether the cytokine was capable of inducing differentiation to a hypertrophic chondrocyte. Human recombinant bone morphogenetic protein-2 did not alter cell proliferation. It caused 3.5–6.2 times more proteoglycan synthesis by articular chondrocytes during each of the time points tested after 4 days in culture. Total proteoglycan accumulation in the extracellular matrix after 28 days in culture was 6.7 times as great in the treated cultures as in the control. Treatment with human recombinant bone morphogenetic protein-2 maintained the articular chondrocyte phenotype of cells in culture as demonstrated by Northern blot analysis: the expression of type-I collagen genes was increased and that of type-II collagen and aggrecan mRNA was lost in untreated chondrocyte cultures after 14–21 days in culture. In contrast, exposure to 100 ng/ml human recombinant bone morphogenetic protein-2 maintained expression of type-II collagen and increased expression of aggrecan compared with controls during the 28-day culture period. Northern blot analysis of the expression of type-X collagen and osteocalcin by chondrocytes treated with human recombinant bone morphogenetic protein-2 showed a lack of expression of these genes, indicating no alteration in phenotype. These experiments demonstrated the ability of human recombinant bone morphogenetic protein-2 to promote the articular chondrocyte phenotype and matrix synthesis in long-term culture. Characteristics of cell growth were not affected, and the cytokine did not induce differentiation to a hypertrophic chondrocyte.     

Structural characteristics of repair tissue of cricoid cartilage defects treated with recombinant human bone morphogenetic protein-2

We examined the structural characteristics of repair tissue induced by recombinant human bone morphogenetic protein-2 in a rabbit model of laryngotracheal reconstruction. Twenty-four New Zealand White rabbits were randomly divided into four groups of six rabbits. Two groups were treated with recombinant human bone morphogenetic protein-2 delivered on an absorbable collagen sponge, while two groups were used as controls. Rabbits were euthanized at 1 and 4 weeks after surgery. The larynx was removed, fixed, and sectioned. The sections were stained with hematoxylin-eosin, safranine O/fast green, and immunostained with an antibody for tissue inhibitor of metalloproteinases-1. In rabbits treated with bone morphogenetic protein-2, the defects were filled with new cartilage and bone at 4 weeks after surgery. There were no discontinuities or gaps at the margins of the cartilage defects. Proteoglycans were synthesized in new cartilage in rabbits treated with bone morphogenetic protein-2, and were present 4 weeks after surgery. The general aspects of the vascular pattern and the pattern of tissue inhibitor of metalloproteinases-1 expression were similar in control and treated rabbits, both 1 week and 4 weeks after surgery. The repair tissue induced by recombinant human bone morphogenetic protein-2 consisted of new cartilage and bone perfectly integrated with host tissue at the site of the cricoid cartilage defects. This new cartilage was able to mature and produce proteoglycans.     

Evaluation of carriers of bone morphogenetic protein for spinal fusion

STUDY DESIGN: Posterolateral lumbar transverse process fusion in a rabbit model was performed using two different carriers for recombinant human morphogenetic protein-2, one having a porous structure and the other being a Type I collagen sheet. OBJECTIVES: To compare the effectiveness of two different carriers for recombinant human morphogenetic protein-2 in achieving lumbar intertransverse process arthrodesis. SUMMARY OF BACKGROUND DATA: The application of osteoinductive growth factors at various anatomic sites, such as in long bones and spinal segments, has been performed experimentally by many researchers. Although many carriers of osteoinductive factors have been reported, the most effective carrier has not been established. We have reported the efficacy of sintered bovine bone, True Bone Ceramics, which is coated with Type I collagen as a carrier of recombinant human bone morphogenetic protein-2 in achieving lumbar intertransverse process arthrodesis. True Bone Ceramics is a crystallized form of bone minerals made from sintering bovine bone at high temperatures and possesses natural trabecular structure. The crystalline character of True Bone Ceramics is similar to that of artificial hydroxyapatite. In this study we focused on the structure of two different carriers to facilitate osteosynthesis in lumbar arthrodesis. METHODS: Fifty-four adult rabbits underwent bilateral lumbar intertransverse process arthrodesis at L4-L5. The animals were divided into five groups and had implants placed as follows: Group 1, autograft group, harvested autologous corticocancellous bone from the posterior iliac crest; Group 2, TBC group, True Bone Ceramics alone; Group 3, TBC-TBMP group, True Bone Ceramics coated with Type I collagen infiltrated with 100 microg of recombinant human bone morphogenetic protein-2; Group 4, collagen group, Type I collagen sheet; and Group 5, collagen-BMP group, implanted collagen sheet containing 100 microg of recombinant human bone morphogenetic protein-2. Spinal fusion was evaluated by radiographic analysis, manual palpation, biomechanical testing, and histologic examination at both 3 and 6 weeks after surgery. RESULTS: Radiographs in the TBC-TBMP group showed a continuous trabecular pattern within the intertransverse area at 3 weeks after surgery. The fusion mass in the intertransverse area was more prominent than in the other groups. At 3 weeks after surgery the TBC-TBMP group had higher fusion rates based on manual palpation, and the fusions showed significantly higher tensile strength and stiffness. The histologic findings in the TBC-TBMP group at 3 weeks after surgery showed a cortical bone rim around the edge of the fusion mass, and contiguous new bone appearing between the recipient bone and the matrix of TBC without evidence of foreign body formation. In the collagen-BMP group, less mature bone formation was present within the grafted area and the new bone was not contiguous, even at 6 weeks after surgery. CONCLUSIONS: As a carrier for recombinant human bone morphogenetic protein-2, True Bone Ceramics, possessing a bony or porous structure, was more effective than a Type I collagen sheet in achieving a faster and stronger lumbar spinal fusion in a rabbit model.     

骨形态发生蛋白治疗开放性胫骨骨折的Meta分析

目的:系统评价骨形态发生蛋白(BMP)治疗开放性胫骨骨折的疗效。方法:计算机检索Cochrane Library、PubMed、EMBASE、中国生物医学文献数据库、中国期刊全文数据库和维普数据库,并手工检索相关领域杂志。检索不受语种限制,时间均从建库至2012年4月,收集骨形态发生蛋白治疗开放性胫骨骨折的所有随机对照试验。根据Cochrane协作网推荐的"风险评估工具"进行偏倚风险评估,用RevMan 5.1软件进行统计学分析。结果:最终纳入3个随机对照试验,共851例患者。研究结果显示:和对照组相比,BMP治疗开放性胫骨骨折未提高其骨折愈合率[RR=1.16,95%CI(0.95,1.41),P=0.15],但是可减少二次干预发生情况[RR=0.72,95%CI(0.58,0.89),P=0.003];在不良事件发生率方面,BMP治疗开放性胫骨骨折后发生感染[RR=1.31,95%CI(0.94,1.81),P=0.11]和疼痛的不良事件[RR=0.92,95%CI(0.79,1.08),P=0.30]与对照组差异无统计学意义。结论:骨形态发生蛋白治疗开放性胫骨骨折有一定的效果。由于纳入研究质量和病例数量的局限,上述结论尚需要更多高质量的随机对照试验进一步验证。     

Combination of growth factors inhibits bone ingrowth in the bone harvest chamber

Previous studies using bone harvest chambers have shown that bone morphogenetic protein-2 inhibits bone ingrowth. The authors hypothesized that the combination of bone morphogenetic protein-2 and a potent angiogenic factor, basic fibroblast growth factor, would result in increased bone formation in this model. Five New Zealand White rabbits were surgically implanted with bone harvest chambers in the proximal metaphyseal region of both tibias. The right leg of each rabbit was implanted with a bovine collagen sponge that was impregnated with recombinant human bone morphogenetic protein-2, basic fibroblast growth factor, or a combination of these factors. The left leg chamber was implanted with the collagen sponge with no growth factors as a control. The bone that grew into the chambers was harvested after 2 weeks, and histomorphologic analysis was performed to determine the amount of tissue and bone ingrowth. The tissue chambers were left empty for 2 weeks between test implants, and this tissue also was harvested, analyzed, and compared with the other samples. The results showed decreased bone formation for the bone morphogenetic protein-2, basic fibroblast growth factor, and combination of bone morphogenetic protein-2 and basic fibroblast growth factor treated groups when compared with the control and empty groups. The combination of bone morphogenetic protein-2 and basic fibroblast growth factor showed inhibition of bone formation that was greater than either growth factor individually. The reason for the inhibition of bone formation with the combination of factors is unknown.     

Gene therapy: adenovirus-mediated human bone morphogenetic protein-2 gene transfer induces mesenchymal progenitor cell proliferation and differentiation in vitro and bone formation in vivo.

This study reports that recombinant adenovirus-mediated human bone morphogenetic protein-2 gene transfer can induce mesenchymal progenitor cell differentiation and bone formation. The recombinant adenovirus with the human bone morphogenetic protein-2 gene was constructed, and mature human bone morphogenetic protein-2 expression mediated by adenovirus gene transfer was detected by specific antibody. Under adenovirus-mediated bone morphogenetic-protein gene transfer, mesenchymal progenitor cell line C3H/10T 1/2 showed cell proliferation dependent on adenovirus bone morphogenetic-protein dose. The C3H/10T 1/2 cells transduced by adenovirus bone morphogenetic protein also exhibited differentiation to osteoblast phenotype, which indicates alkaline phosphatase activity. Injection of the C3H/10T 1/2 cells into the thigh muscles of nude mice led to ossicle development detectable on radiographs. Histological analysis indicated that the new ossicles that developed in the thigh muscles of the mice had different osseous components including bone trabeculae, bone marrow, and chondrified tissue. The results of this study demonstrate the potential for gene therapy by adenovirus-mediated bone morphogenetic-protein gene transfer.