Effect of recombinant human bone morphogenetic protein-4 with carriers in rat calvarial defects

BACKGROUND: Bone morphogenetic proteins (BMPs) are being evaluated as candidates for periodontal and bone regenerative therapy. However, the research on recombinant human bone morphogenetic protein-4 (rhBMP-4) has been insufficient to evaluate its capacity to enhance bone formation and its carrier system. The purpose of this study was to evaluate the bone regenerative effect of rhBMP-4 delivered with an absorbable collagen sponge (ACS) or beta-tricalcium phosphate (beta-TCP). We also compared the potential of beta-TCP to that of ACS as a carrier system for rhBMP-4. METHODS: Eight-mm calvarial critical-sized defects were created in 100 male Sprague-Dawley rats. The animals were divided into 5 groups of 20 animals each. The defects were treated with rhBMP-4/ACS (rhBMP-4 at 0.05 mg/ml), rhBMP-4/beta-TCP (rhBMP-4 at 0.05 mg/ml), ACS alone, beta-TCP alone, or left untreated for surgical control. The rats were sacrificed at 2 or 8 weeks postsurgery, and the results were evaluated radiodensitometrically, histologically, and histomorphometrically. RESULTS: The results of radiodensitometric analysis were as follows: the rhBMP-4/ACS and the rhBMP-4/beta-TCP groups were more radiopaque than other groups at both 2 and 8 weeks (P < 0.01). The histologic observations were as follows: in the rhBMP-4/ACS and the rhBMP-4/beta-TCP groups, new bone was evident at the defect sites at 2 weeks and 8 weeks. The results of histomorphometric analysis were as follows: the rhBMP-4/ACS and the rhBMP-4/beta-TCP groups had more bone (%) than other groups at both 2 and 8 weeks (P < 0.01). CONCLUSIONS: Surgical implantation of rhBMP-4/ACS may be used to support bone regeneration in the rat calvarial critical-sized defect, and rhBMP-4/beta-TCP may be able to regenerate bone in the rat calvarial critical-sized defect without complication. In addition, both ACS and beta-TCP may be considered as available carriers for rhBMP-4.     

Effect of recombinant human bone morphogenetic protein-4 dose on bone formation in a rat calvarial defect model

BACKGROUND: Bone morphogenetic proteins (BMPs) are being evaluated for periodontal and bone regenerative therapy. The objective of this study was to evaluate the effect of recombinant human bone morphogenetic protein-4 (rhBMP-4) dose on local bone formation in a rat calvaria defect model. METHODS: Calvarial, 8 mm diameter, critical-size osteotomy defects were created in 140 male Sprague-Dawley rats. Seven groups of 20 animals each received either 1) rhBMP-4 (2.5 microg) in an absorbable collagen sponge (ACS) carrier, 2) rhBMP-4 (5 microg)/ACS, 3) rhBMP-4 (2.5 microg) in a beta-tricalcium phosphate (beta-TCP) carrier, 4) rhBMP-4 (5 microg)/beta-TCP, 5) ACS or 6) beta-TCP carrier controls, or 7) a sham-surgery control, and were evaluated by histologic and histometric parameters following a 2- or 8-week healing interval (10 animals/group/healing interval). RESULTS: Surgical implantation of rhBMP-4/ACS and rhBMP-4/beta-TCP resulted in enhanced local bone formation at both 2 and 8 weeks. Within the dose range examined, rhBMP-4 did not exhibit an appreciable dose-dependent response. Defect closure was not significantly different between the rhBMP-4/ACS and rhBMP-4/beta-TCP groups. New bone area of the rhBMP-4/ beta-TCP group was significantly greater than that of the rhBMP-4/ ACS group; however, bone density in the rhBMP-4/ACS group was significantly greater than that in the rhBMP-4/beta-TCP group at 8 weeks (P < 0.05). CONCLUSIONS: rhBMP-4 combined with ACS or beta-TCP has a significant potential to induce bone formation in the rat calvaria defect model. Within the selected rhBMP-4 dose range and observation interval, there appeared to be no meaningful differences in bone formation.     

Effect of a fibrin-fibronectin sealing system as a carrier for recombinant human bone morphogenetic protein-4 on bone formation in rat calvarial defects

BACKGROUND: Bone morphogenetic proteins (BMPs) have been shown to play an important role in bone formation during development and wound healing. Despite there being good prospects for BMP applications, an ideal carrier system for BMPs has yet to be determined. The purpose of this study was to evaluate the possibility of a fibrin-fibronectin sealing system (FFSS) as a carrier for recombinant human BMP-4 (rhBMP-4) and to evaluate the genuine osteoconductive potential of the FFSS in a rat calvarial defect model. METHODS: An 8-mm, calvarial, critical-size osteotomy defect was created in each of 30 male Sprague-Dawley rats. Three groups of 10 animals each received rhBMP-4 (0.025 mg/ml) in the FFSS, FFSS control, or sham-surgery control. The groups were evaluated using histologic and histometric parameters following 2- and 8-week healing intervals (five animals per group per healing interval). RESULTS: Surgical implantation of rhBMP-4/FFSS resulted in enhanced local bone formation at 2 and 8 weeks. New bone formation was also evident in the FFSS control; however, the amount of defect closure, new bone area, and bone density was significantly greater in the rhBMP-4/FFSS group (P < 0.05). At 8 weeks, the quantity of the new bone was greater than that observed at 2 weeks, and the specimens showed a more advanced stage of remodeling and consolidation in both groups (P < 0.05). Only very limited bone formation was observed in the sham-surgery control. CONCLUSION: The results of the present study indicated that the FFSS has osteoconductive potential and may be employed as a carrier for BMPs.     

Effect of recombinant human bone morphogenetic protein-2 on bone formation in alveolar ridge defects in dogs

This study was designed to evaluate the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) combined with poly D, L lactic-co-glycolic acid (PLGA)/gelatin sponge complex (PGS) on the formation of bone in critically sized marginal defects of the mandible in dogs. Three months after extraction of the pre-molar teeth, rectangular bone defects (10 x 8 x 7 mm) were made in both sides of the mandible. A PGS block soaked in rhBMP-2 (400 microgram/ml) was implanted into one defect (BMP (+) group). As control, an untreated PGS block was implanted into the contralateral defect (BMP (-) group). 2, 4, 8, and 12 weeks after implantation, the defects were examined. In the BMP (+) group, newly formed bone was found in all defects from 4 weeks onward and was marked at 12 weeks. In contrast, the BMP (-) group showed no appreciable new bone formation, even at 12 weeks. Moreover, density of newly formed bone in the BMP (+) group was similar to that of the surrounding cortical bone at 12 weeks. These findings suggest that rhBMP-2/PGS is an effective bone substitute for reconstructive surgery of the dog mandible.     

The effect of varying the particle size of beta tricalcium phosphate carrier of recombinant human bone morphogenetic protein-4 on bone formation in rat calvarial defects

BACKGROUND: Beta tricalcium phosphate (beta-TCP) has been developed as one of the carriers of recombinant human bone morphogenetic protein (rhBMP). However, it is not known whether the particle size of beta-TCP is related to its resorption rate and the degree of bone formation. The purpose of this study was to evaluate the effect of using beta-TCP with different particle sizes on the ability of rhBMP-4 to enhance bone formation in the rat calvarial defect model. METHODS: Calvarial, 8-mm-diameter, critical-size defects were created in 100 male Sprague-Dawley rats. Five groups of 20 animals each received either rhBMP-4 (2.5 microg) using beta-TCP with a particle size of 50 to 150 microm, rhBMP-4 (2.5 microg) using beta-TCP with a particle size of 150 to 500 microm, a beta-TCP control with a particle size of 50 to 150 microm, a beta-TCP control with a particle size of 150 to 500 microm, or a sham-surgery control, respectively, and were evaluated by measuring their histologic and histometric parameters following a 2- and 8-week healing interval. RESULTS: There were no significant differences in the defect closure, new bone area, or augmented area between either the two rhBMP-4/beta-TCP groups or between the two beta-TCP control groups at 2 and 8 weeks. CONCLUSIONS: rhBMP-4 combined with either small- or large-particle beta-TCP had a significant effect on the induction of bone formation compared to either a small- or large-particle beta-TCP control or a sham-surgery control. Within the parameters of this study, varying the particle size of beta-TCP did not seem to have a significant effect on bone formation.     

Effect of recombinant human bone morphogenetic protein-2 on bone formation in the acute distraction osteogenesis of rat mandibles

Background: Distraction osteogenesis (DO) is a method of producing new bone directly from the osteotomy site by gradual traction of the divided bone fragments.
Aim: The purpose of the present study was to evaluate histomorphometrically whether acute DO would constitute a viable alternative to the conventional continuous distraction treatment and also to verify the capacity of a recombinant human BMP (rhBMP-2) associated with monoolein gel to stimulate bone formation in the acute distraction process.
Materials and methods: Forty-eight Wistar rats were assigned to three groups: Group 1, treated at a conventional continuous distraction rate (0.5 mm/day), Group 2, treated with acute distraction of 2.5 mm at the time of the surgical procedure, and Group 3, subjected to acute distraction associated with rhBMP-2. The animals from each experimental group were killed at the end of the second or fourth post-operative weeks and the volume fraction of newly formed bone trabeculae was estimated in histological images by a differential point-counting method.
Results: The results showed that after 2 and 4 weeks, bone volumes in the rhBMP-2 group were significantly higher than in the other groups ( P <0.05), but no significant difference was observed in the volume fraction of newly formed bone between the continuous and acute DO groups.
Conclusion: In conclusion, the study indicates that rhBMP-2 can enhance the bone formation at acute DO, which may potentially reduce the treatment period and complications related to the distraction procedure.     

Assay of bone morphogenetic protein-2, -4, and -7 in human demineralized bone matrix

Demineralized bone matrix (DBM) is a widely used bone graft material that derives its osteoinductive potential from matrix-associated bone morphogenetic proteins (BMPs). Prior investigations have shown that the osteoinductive potential can vary widely, with influence from both donor and processing sources. Although it is plausible that donor variance in the BMP profile can be an important consideration, the few published studies available have given inconsistent and incomplete information about this. The goal was to (1) characterize the variance of BMP-2, BMP-4, and BMP-7 in fully demineralized DBM derived from 20 appropriately screened (Food and Drug Administration and the American Association of Tissue Banks criteria) donors (male and female, 17-65 years) and (2) using literature review, infer the potential for this to be an important source of variability in graft function. BMPs were extracted with 4 M guanidine hydrochloride, and levels of BMP-2, BMP-4, and BMP-7 were measured using enzyme-linked immunosorbent assay. Measured levels were as follows: BMP-2 = 21.4 +/- 12.0 ng/g DBM, BMP-4 = 5.45 +/- 2.04 ng/g DBM, and BMP-7 = 84.1 +/- 34.4 ng/g DBM, which were significantly different (P < 0.05). There was a positive linear correlation between BMP-2 and BMP-7 (P = 0.0227). DBM derived from female donors had significantly greater concentrations of BMP-2 and BMP-7 than did that derived from male donors (P = 0.0257 and 0.0245, respectively). There was no significant correlation between donor age and the levels of any of the measured BMPs. The magnitude of variance of BMP profile appears to reasonably well correspond to the variance in osteoinductive potential cited by others, suggesting the possibility of using this as a method of donor screening.     

Enhanced bone formation of calvarial bone defects by low-intensity pulsed ultrasound and recombinant human bone morphogenetic protein-9: a preliminary experimental study in rats

Clinical Oral Investigations - The aim of this study was to evaluate the combined effects of recombinant human bone morphogenetic protein&nbsp;- 9 (rhBMP-9) loaded onto absorbable collagen...     

原核表达重组人骨形态发生蛋白-7对牙槽骨修复再生的实验研究

目的研究原核表达重组人骨形态发生蛋白- 7（rhBMP- 7）对牙槽骨修复再生的影响。方法采用新西兰白兔建立动物模型,以明胶海绵作为载体,将大肠杆菌原核表达的rhBMP- 7与之复合后植入即刻拔除牙齿的牙槽窝内进行干预治疗,术后2、4、8及12周处死动物,取标本进行大体观察、扫描电镜分析、碱性磷酸酶（ALP）活性测定。结果大体观察结果显示,实验组和对照组牙槽嵴高度的吸收差异有显著性;扫描电镜观测显示,实验组的骨创愈合比对照组大约提前4～6周;ALP活性测定显示实验组均明显高于对照组,其差异有统计学意义（P<0.05）。结论原核表达rhBMP- 7具有促进新骨修复再生、防止牙槽骨吸收的作用。     

Bone formation of block and particulated biphasic calcium phosphate lyophilized with Escherichia coli-derived recombinant human bone morphogenetic protein 2 in rat calvarial defects

The objective of this study was to evaluate bone formation in rat calvarial defects after surgical implantation of block or particulated biphasic calcium phosphate (BCP) lyophilized with Escherichia coli-derived recombinant human bone morphogenetic protein 2 (ErhBMP-2). Critical-size calvarial osteotomy defects were created in 5 groups of Sprague-Dawley rats. Each group received one of the following: 1) sham surgery control; 2) biphasic calcium phosphate particles (CPP); 3) biphasic calcium phosphate block (CPB); 4) ErhBMP-2-coated CPP; or 5) ErhBMP-2-coated CPB. ErhBMP was coated on BCP by a stepwise lyophilizing protocol. The new bone formation was significantly greater in ErhBMP-2-treated groups compared with the untreated group. In particular, the ErhBMP-2/CPB group showed stability of augmented areas during the period of healing, due to relevant space-providing capacity. Thus, it can be concluded that CPP and CPB lyophilized with ErhBMP-2 enhance the formation of new bone, and CPB appears to be a suitable carrier for ErhBMP-2 in which a 3-dimensional structural integrity is an important consideration factor.     

Effect of recombinant human bone morphogenetic protein-2 on mandibular distraction osteogenesis

The purpose of this investigation was to study the effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) on bone formation of mandibular distraction osteogenesis. Six skeletally mature sheep underwent 10 mm of bilateral mandibular distraction osteogenesis via a custom-made distractor. Three micrograms of rhBMP-2 with a collagen carrier was implanted in the osteotomy site of one side of the mandible during the osteotomy phase. The contralateral side was used as the control group, and no material was implanted into the distracted area. At 10 days after the end of distraction, all animals were killed, and the distracted calluses were harvested for radiologic and histologic analysis. New bone was generated in the distracted zone in all groups. Histologic and radiologic examination showed that the new bone formation was greater in the rhBMP-2 group than in the control group. Quantitative computed tomography evaluation, however, did not demonstrate a significantly different mean bone density of the regenerates between the 2 groups. The results indicate that application of a rhBMP-2/collagen implant during the osteotomy phase of distraction osteogenesis increased bone formation but did not have a significant effect on bone density of the regenerates.     

Enhancement by recombinant human bone morphogenetic protein-2 of bone formation by means of porous hydroxyapatite in mandibular bone defects.

Hydroxyapatite is osteoconductive and can maintain an original biocompatible form. It is useful, in the reconstruction of bone defects, to enhance the osteoconduction of hydroxyapatite with an osteogenic protein. The aim of this study was to evaluate the bone formation in surgically created defects of rabbit mandibles by a combination of recombinant human bone morphogenetic protein-2 (rhBMP-2), with porous hydroxyapatite and atelopeptide type I collagen used as the carrier for rhBMP-2. A 10-microg rhBMP-2-implanted group (n = 15) and a control group (n = 15), in which only atelopeptide type I collagen and porous hydroxyapatite were implanted, were histologically examined 3, 7, and 21 days after implantation. The alkaline phosphatase activity was also quantitatively analyzed. No new bone formation was observed in either the tested or the control group after 3 days. At 7 days, immature bone tissue was observed in some pores of the rhBMP-2implanted group, while in the control group, immature mesenchymal cells were observed. At 21 days, trabecular bone lined some pore walls. In the central portion, the bone marrow, including angioid tissue, was observed. New trabecular bone formation was observed on portions of the external surface of the hydroxyapatite disk. On the other hand, the control group showed infiltration of immature mesenchymal cells into some pores. Marginal bone formation was found in the pores close to the surface of the disk which opposed mandibular bone. The control group showed a slow, small increase in alkaline phosphatase activity in this study, while the experimental group showed a marked increase at 21 days. This increase was significantly higher in the tested group than in the control group at both 7 and 21 days. The findings indicate that rhBMP-2 accelerated bone formation by osteoconduction from porous hydroxyapatite. The combination of rhBMP-2, atelopeptide type I collagen, and porous hydroxyapatite is suggested to be advantageous for clinical application in reconstructing mandibular bone defects.     

Effect of hyperbaric oxygenation on bone induced by recombinant human bone morphogenetic protein-2

We examined the effect of hyperbaric oxygen (HBO) therapy on the osteoinductive activity of recombinant human bone morphogenetic protein-2 (rhBMP-2), 5mg of which was implanted into the calf muscle of rats using atelopeptide type I collagen as a carrier. Thirty Wistar rats were divided equally to be given HBO or act as controls. New bone formation was measured radiographically, biochemically, and histol ogically 3, 7, and 21 days after implantation. In both groups, new bone formation was found on day 21. However, there was significantly more new bone in the HBO group. In the HBO group, cartilage was present at the outer edge of the implanted material on day 7. On days 7 and 21, the local tissue alkaline phosphatase activity and calcium content in the HBO group were significantly greater than in the control group. These results suggest that HBO accelerated the activity and rate of osteoinduction by rhBM P-2.     

Potential of recombinant human bone morphogenetic protein-2 in bone regeneration

Recombinant human bone morphogenetic protein (rhBMP-2) has been used as a bone substitute. This article describes the rhBMP-2 structure, mechanisms of action, carriers, advantages, safety, and recent clinical studies relevant to dentistry.     

Effect of recombinant human bone morphogenetic protein-2 on bone regeneration and osseointegration of dental implants

Recombinant human bone morphogenetic protein-2 (rhBMP-2) induced bone regeneration and osseointegration was evaluated in bony defects created within the hollow chamber of endosseous dental implants in 14 foxhound dogs. Bilateral extractions of mandibular premolars were performed and surgical implantation of 104 hollow cylinder implants followed after 8 weeks of healing. Experimental implants had their hollow chamber filled with 20 microg of rhBMP-2 delivered with a bovine collagen carrier, whereas the control implants had their apical chamber left empty. Dogs were followed for 2, 4, 8 and 12 weeks. Histomorphometric evaluation and immunohistochemical analysis were performed. Minimal bone was regenerated at 2 weeks for both groups. At 4 weeks, bone fill averaged 23.48% for the rhBMP-2 and 5.98% for the control group (P<0.05). At 8 weeks, mean bone fill was 20.94% and 7.75% for the rhBMP-2 and the controls, respectively (P<0.05). At 12 weeks, mean bone fill was 31.39% and 24.31% for the rhBMP-2 and control implants, respectively (P>0.05). Bone-implant contact (BIC) increased for both groups over time and at 8 weeks the rhBMP-2 BIC value was 18.65% and for the control 7.22% (P<0.05). At 12 weeks, the BIC was 43.78% and 21.05% for the rhBMP-2 and the control group, respectively (P<0.05). Immunohistochemical staining for type II collagen was positive only for parts of the collagen carrier and formation of cartilaginous intermediate was not observed in any of the specimens. The results suggest that, in confined defects adjacent to dental implants, rhBMP-2 can induce bone regeneration in close apposition to the implant surface.     

重组人血管内皮生长因子和重组人骨形态发生蛋白-7对大鼠成骨细胞增殖能力的影响

目的研究重组人血管内皮生长因子（recombinant human vascular endothelial growth factor,rhVEGF）和重组人骨形态发生蛋白-7（recombinant human bone morphogenetic protein-7,rhBMP-7）对成骨细胞增殖能力的影响。方法取大鼠颅盖骨组织块,采用改良组织块混合酶消化法培养成骨细胞,分成4组,第1组、第2组、第3组分别加3．125ng／mL不含血清的rhVEGF培养液、50．000ng／mL不含血清的rhBMP-7培养液、3．125ng／mL不含血清的rhVEGF和50．000ng／mL不含血清的rhBMP-7培养液,第4组加不含血清的培养液作为对照组,采用细胞培养技术,应用光镜、四甲基偶氮唑盐（methyl thiazolyl tetrazotium,MTT）法,分析不同浓度的rhVEGF和rhBMP．7对成骨细胞增殖的影响。结果与对照组相比,3．125ng／mL rhVEGF和50.000ng／mLrhBMP-7单独或者联合作用,在1、3、5d均有促进细胞增殖的作用,与对照组的差异均有统计学意义（P〈0.05）,各组间比较差异也有统计学意义（P〈0．05）。其中,3．125ng／mLrhVEGF和50．000ng／mL rhBMP-7单独或者两者联合作用于第3天时,成骨细胞增殖最显著。结论一定剂量的rhVEGF和rhBMP-7可明显促进成骨细胞的增殖。     

Evaluation of recombinant human bone morphogenetic protein-2 on the repair of alveolar ridge defects in baboons

BACKGROUND: The objective of this study was to evaluate alveolar ridge augmentation following surgical implantation of recombinant human bone morphogenetic protein-2 (rhBMP-2) using two novel space-providing carrier technologies in the baboon (Papio anubis) model. METHODS: Standardized alveolar ridge defects ( approximately 15 x 8 x 5 mm) were surgically produced in maxillary and mandibular edentulous areas in four baboons. The defect sites were implanted with rhBMP-2 (0.4 mg/mL) in a tricalcium phosphate/hydroxyapatite/ absorbable collagen sponge composite (TCP/HA/ACS) or calcium phosphate cement (alpha-BSM). Control treatments were TCP/HA/ACS and ?-BSM without rhBMP-2 and sham surgery. Stainless steel pins were placed at the mid-apical and coronal level of the defect sites to provide landmarks for clinical measurements pre- and post-implantation. Impressions were obtained pre- and postimplantation to determine changes in alveolar ridge volume. Radiographic registrations were obtained pre- and post-implantation. Block sections of the defect sites were harvested at week 16 postimplantation and processed for histometric analysis including new bone area and bone density. Statistical comparisons between treatments were made using a mixed effect generalized linear model using least squares estimation. RESULTS: The carrier systems without rhBMP-2 provided a modest ridge augmentation. The addition of rhBMP-2 resulted in an almost 2-fold increase in alveolar ridge width, including a greater percentage of trabecular bone and a higher bone density compared to controls (P < or =0.05) without significant differences between the two rhBMP-2 protocols. CONCLUSIONS: TCP/HA/ACS and alphaBSM appear to be suitable carrier technologies for rhBMP-2. Alveolar augmentation procedures using either technology combined with rhBMP-2, rather than stand-alone therapies, may provide clinically relevant augmentation of alveolar ridge defects for placement of endosseous dental implants.     

Osteogenic potential of recombinant human bone morphogenetic protein-9/absorbable collagen sponge (rhBMP-9/ACS) in rat critical size calvarial defects

Clinical Oral Investigations - It has been reported that bone morphogenetic protein (BMP)-9 has potent osteoinductive properties among the BMP family by adenovirus-transfection experiments. We very...     

Histological assessment of bioengineered new bone in repairing osteoperiosteal mandibular defects in sheep using recombinant human bone morphogenetic protein-7

Numerous experimental studies have been published about osteoinductive bone morphogenetic proteins (BMPs). However, to our knowledge there has been no detailed histological study of a mandibular defect in a large mammal, reconstructed using BMPs. We describe here the histological features of rhBMP-7-induced bone in mandibular defects in sheep. METHODS: A 35 mm osteoperiosteal defect was created at the parasymphyseal region of the mandible in six adult sheep. The continuity of the mandible was maintained using a bony plate, and rhBMP-7 was applied on a type I collagen carrier. Bone labels were injected at selected time intervals during the follow-up period. The animals were killed after 3 months and bone samples were examined histologically, histomorphometrically, and by fluorescence microscopy. RESULTS AND CONCLUSIONS: We found a mixture of woven and lamellar bone that contained many cells with large nuclei. This had not reorganised to form cortical bone and the rhBMP-7-induced bone was more porous than the native bone. The newly-formed bone restored both endosteal and periosteal layers. rhBMP-7-induced bone was biocompatible and induced no ossification of soft tissue or abnormal growth of nearby vital structures. The mineral apposition rate was 1.98 microm/day (range 0.62-5.63 microm/day), a value close to that reported in humans. This suggests that BMPs have a limited effect in accelerating the rate of mineralisation, but promote the pre-mineralisation processes, and perhaps the formation of woven bone.     

Bone induction by Escherichia coli -derived recombinant human bone morphogenetic protein-2 compared with Chinese hamster ovary cell-derived recombinant human bone morphogenetic protein-2

Most recombinant human bone morphogenetic protein (rhBMP) is currently obtained from Chinese hamster ovary (CHO) cells. If rhBMP with more activity could be derived from Escherichia coli (E. coli), a large quantity of rhBMP could be produced at low cost. The bone-inducing ability of an E. coli -derived rhBMP-2 (ErhBMP-2) variant with an N-terminal sequence was examined and compared with CHO cell-derived rhBMP-2 (CrhBMP-2). Two, 10, or 50 microgram of ErhBMP-2 or CrhBMP-2 was mixed with 3mg of atelopeptide type I collagen as the carrier, and specimens were implanted into the calf muscle pouches of Wistar rats (n= 5 in each group). Three weeks later, new bone had formed in all the ErhBMP-2-implanted and CrhBMP-2-implanted muscles. Radiographic and histological examinations showed that the bone induced by ErhBMP-2 had a large hollow bone matrix with more fatty marrow than the bone induced by CrhBMP-2. Quantitative analysis indicated that the activity of ErhBMP-2 was similar to that of CrhBMP-2, so ErhBMP-2 may be useful for inducing bone formation.