Simultaneous gene transfer of bone morphogenetic protein (BMP) -2 and BMP-7 by in vivo electroporation induces rapid bone formation and BMP-4 expression

Background  

Transcutaneous in vivo electroporation is expected to be an effective gene-transfer method for promoting bone regeneration using the BMP-2 plasmid vector. To promote enhanced osteoinduction using this method, we simultaneously transferred cDNAs for BMP-2 and BMP-7, as inserts in the non-viral vector pCAGGS.     

Mechanical tension-stress induces expression of bone morphogenetic protein (BMP)-2 and BMP-4, but not BMP-6, BMP-7, and GDF-5 mRNA, during distraction osteogenesis.

Bone lengthening with osteotomy and gradual distraction was achieved in 57 rats, and the effect of mechanical tension-stress on gene expression of bone morphogenetic proteins (BMPs) was investigated by in situ hybridization and Northern blot analysis using probes of BMP-2, BMP-4, BMP-6, BMP-7, and growth/differentiation factor (GDF)-5. There was a lag phase for 7 days after femoral osteotomy until gradual distraction was carried out for 21 days at a rate of 0. 25 mm/12 h using a small external fixator. The signals of the above BMPs mRNA were not detected in the intact rat bone but they were induced after osteotomy except those for BMP-7. By 4 days after osteotomy, BMP-2 and BMP-4 mRNAs were detected in chondrogenic precursor cells in the subperiosteal immature callus. BMP-6 and GDF-5 mRNA were detected in more differentiated cells in chondroid bone. By 7 days after osteotomy, cartilaginous external callus and bony endosteal callus were formed. Meanwhile, the signals of BMP-2 and BMP-4 mRNAs declined to preoperative levels, whereas the signals of BMP-6 and GDF-5 mRNAs were rather elevated. As distraction was started, the callus elongated and eventually separated into proximal and distal segments forming a fibrous interzone in the middle. Expression of BMP-2 and BMP-4 mRNAs was markedly induced at this stage. Their signals were detected widely among chondrogenic and osteogenic cells and their precursor cells sustaining mechanical tension-stress at the fibrous interzone. BMP-6 and GDF-5 mRNAs were detected exclusively in chondrogenic cells at both ends of the fibrous interzone, where endochondral ossification occurred. But neither mRNA was detected in terminally differentiated hypertrophic chondrocytes. As distraction advanced, the cartilage was progressively resorbed from both ends and new bone was formed directly by intramembranous ossification. There was no new cartilage formation in the advanced stage of distraction. The signals of BMP-6 and GDF-5 mRNA declined by this stage, while those of BMP-2 and BMP-4 were maintained at high level for as long as distraction was continued. After completion of distraction, the fibrous interzone fused and the lengthened segment was consolidated. BMP-2, BMP-4, BMP-6, nor GDF-5 was expressed at this stage. The signals of BMP-7 were not detected throughout the experiment. The present results suggest that excellent and uninterrupted bone formation during distraction osteogenesis owes to enhanced expression of BMP-2 and BMP-4 genes by mechanical tension-stress. Abundant gene products of BMP-2 and BMP-4 could induce in situ bone formation by paracrine and autocrine mechanisms.     

Prostaglandins mediate the effects of 1,25-(OH)2D3 and 24,25-(OH)2D3 on growth plate chondrocytes in a metabolite-specific and cell maturation-dependent manner.

Prior studies have shown that 1,25-(OH)2D3 stimulates alkaline phosphatase, phospholipase A2 (PLA2), and protein kinase C (PKC)-specific activities, and production of prostaglandin E2 (PGE2) in growth zone chondrocytes. In contrast, 24,25-(OH)2D3 stimulates alkaline phosphatase and PKC-specific activities but inhibits PLA2-specific activity and PGE2 production in resting zone cells. This indicates that different mechanisms are involved in the action of 1,25-(OH)2D3 and 24,25-(OH)2D3 on their respective target cells. In this study, we examined the hypothesis that differential regulation of prostaglandin production modulates the activity of PKC and alkaline phosphatase. To do this, we examined the effect of the cyclooxygenase inhibitor indomethacin (Indo) on alkaline phosphatase, PLA2, and PKC-specific activities in growth plate chondrocytes treated with these two vitamin D metabolites. In addition, we examined whether inhibition of PKC altered PGE2 production. In growth zone cells, Indo inhibited basal alkaline phosphatase and blocked the 1,25-(OH)2D3-dependent increase in alkaline phosphatase. This effect was due to inhibition of both plasma membrane and matrix vesicle alkaline phosphatase. In resting zone cells, Indo increased basal alkaline phosphatase activity in a dose-dependent manner, but it did not further enhance the 24,25-(OH)2D3-dependent stimulation of this enzyme. The effect of Indo was found in both plasma membranes and matrix vesicles. These data indicate that 1,25-(OH)2D3-dependent increases in alkaline phosphatase-specific activity in growth zone cells are mediated through increased prostaglandin production, whereas 24,25-(OH)2D3-mediated changes in enzyme activity in resting zone cells are mediated through decreased prostaglandin production. Regulation of PLA2 by either 1,25-(OH)2D3 or 24,25-(OH)2D3 in their target cells was unaffected by Indo, indicating that the effect of the vitamin D metabolites on this enzyme is not dependent on changes in PGE2 production. The rapid increase in 1,25-(OH)2D3-dependent PKC-specific activity in growth zone cells was inhibited by Indo, whereas there was a potentiation of the effect of 24,25-(OH)2D3 on PKC activity in resting zone cells. In addition, inhibition of PKC blocked the 1,25-(OH)2D3-dependent increase in PGE2 production in growth zone cells and the 24,25-(OH)2D3-dependent decrease in PGE2 production by resting zone cells. These data indicate that prostaglandins are involved in mediating the rapid effects of 1,25-(OH)2D3 on growth zone cells, and contribute to the effects of 24,25-(OH)2D3 on resting zone cells; in both instances, the vitamin D metabolites exert their effects on PKC through changes in arachidonic acid via the action of PLA2. In addition, PKC by itself may mediate the production of PGE2.     

Direct stimulation of osteoclastic bone resorption by bone morphogenetic protein (BMP)-2 and expression of BMP receptors in mature osteoclasts

Bone morphogenetic proteins (BMPs) play an important role in various kinds of pattern formation and organogenesis during vertebrate development. In the skeleton, BMPs induce the differentiation of cells of chondrocytic and osteoblastic cell lineage and enhance their function. However, the action of BMPs on osteoclastic bone resorption, a process essential for pathophysiological bone development and regeneration, is still controversial. In this study, we examine the direct effect of BMPs on osteoclastic bone-resorbing activity in a culture of highly purified rabbit mature osteoclasts. BMP-2 caused a dose- and time-dependent increase in bone resorption pits excavated by the isolated osteoclasts. BMP-4 also stimulated osteoclastic bone resorption. The increase in osteoclastic bone resorption induced by BMP-2 was abolished by the simultaneous addition of follistatin, a BMP/activin binding protein that negates their biological activity. Just as it increased bone resorption, BMP-2 also elevated the messenger RNA expressions of cathepsin K and carbonic anhydrase II, which are key enzymes for the degradation of organic and inorganic bone matrices, respectively. Type IA and II BMP receptors (BMPRs), and their downstream signal transduction molecules, Smad1 and Smad5, were expressed in isolated osteoclasts as well as in osteoblastic cells, whereas type IB BMPR was undetectable. BMPs directly stimulate mature osteoclast function probably mediated by BMPR-IA and BMPR-II and their downstream molecules expressed in osteoclasts. The results presented here expand our understanding of the multifunctional roles of BMPs in bone development.     

Bone morphogenetic protein (BMP)-2 enhances the expression of type II collagen and aggrecan in chondrocytes embedded in alginate beads

OBJECTIVE: For autologous chondrocyte transplantation (ACT) chondrocytes are expanded in vitro. During expansion these cells may dedifferentiate. This change in phenotype is characterized by a raised expression of type I collagen and a decrease in type II collagen expression. Since high expression of type II collagen is of central importance for the properties of hyaline cartilage, we investigated if the growth factor bone morphogenetic protein-2 (BMP-2) may modulate the chondrogenic phenotype in monolayer cell cultures and in three-dimensional culture systems. DESIGN: Chondrocytes from articular knee cartilage of 11 individuals (average age: 39.8 years) with no history of joint disease were isolated and seeded either in monolayer cultures or embedded in alginate beads in presence or absence of human recombinant BMP-2 (hr-BMP-2). Then, cells were harvested and analysis of the chondrogenic phenotype was performed using quantitative RT-PCR, immunocytochemistry and ELISA. RESULTS: Addition of BMP-2 to chondrocytes expanded in two-dimensional (2D) cultures during the first subculture (P1) had no effect on mRNA amounts encoding type II collagen and interleukin-1beta (IL-1beta). In contrast, seeding chondrocytes in three-dimensional (3D) alginate cultures raised type II collagen expression significantly and addition of BMP-2 enhanced this effect. CONCLUSIONS: We conclude that chondrocytes during expansion for ACT may benefit from BMP-2 activation only when seeded in an appropriate 3D culture system.     

BMP-2联合BMP-7在截骨延长时促进成骨的实验研究

目的 探究在截骨延长成骨过程中联合应用BMP-2和BMP-7对成骨的促进作用.方法 采用健康成年日本大耳白兔30只,完全随机分为三组.A组作为对照组正常牵拉不做其他处理;B组在截骨后于截骨处加入rhBMP-2药片;C组在截骨后于截骨处加入rhBMP-2药片,7d后在延长区经皮注射rhBMP-7溶解液.在术后第7天、第3...     

Complications with the use of bone morphogenetic protein 2 (BMP-2) in spine surgery

Background contextRecombinant human bone morphogenetic protein 2 (rhBMP-2) is a very potent osteogenic growth factor that has been used successfully in various spine fusions, obviating the need for autologous iliac crest bone graft harvest and therefore avoiding the associated morbidities.PurposeIn the past few years, a tremendous increase in rhBMP-2 usage was noted, and concerns regarding costs, benefits, and safety issues were raised by many. The goal of this work was to provide a comprehensive review of the adverse events and complications associated with use of rhBMP-2.Study designLiterature review.MethodsThis is a review of the current literature on the reported adverse events, complications, and concerns associated with rhBMP-2 use.ResultsThis article discusses the wide spectrum of adverse outcomes related to rhBMP-2 use in the lumbar and the cervical spine; retrograde ejaculation, antibodies formation, postoperative radiculitis, postoperative nerve root injury, ectopic bone formation, vertebral osteolysis/edema, dysphagia and neck swelling, hematoma formation, interbody graft lucency, and wound healing complications are reviewed. Cost-related concerns, dosage considerations, carrier types, and theoretical carcinogenesis concerns were also presented.ConclusionsDespite the excellent spinal fusion rates promoted by this powerful molecule, the increasingly reported adverse outcomes associated with bone morphogenetic protein usage have created real concerns. This article will provide the reader with a good understanding of the reported complications associated with rhBMP-2 use and ultimately help recognize its safety spectrum and limits for better clinical application.     

Nature of bone morphogenetic protein (BMP) from decalcified rabbit bone matrix

Rabbit bone morphogenetic protein (BMP) from demineralized and defatted rabbit bone matrix was partially purified. BMP activity was examined by the implantation of fractionated materials into the thigh muscle pouch of the mouse. Rabbit BMP was solubilized by both 4M guanidine hydrochloride (GuHCl) and 6M urea solutions. Crude BMP had isoelectric point precipitation at pH 3 in 6M urea and showed bone morphogenesis. Fractions eluted with 0 and 0.2 N NaCl in DEAE CL-6B ion exchange chromatography showed bone morphogenesis in each individual pH of pH 4 to pH 7 but the fraction eluted with 1.0 N NaCl did not show any activity. Sephadex G-75 filtration separated the crude material into three peaks and the peak of about 23,000 showed bone morphogenesis. In sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis and isoelectric focusing, rabbit BMP was thought to be an acidic protein having a molecular weight of 24,000 with an isoelectric point around 4.85.     

调控骨形态发生蛋白诱导成骨的相关转录因子

骨形态发生蛋白（Bone morphogenetic protein,BMPs）是一种确切具有诱导成骨活性的生长因子,其主要生物学作用是诱导未分化的间充质细胞分化形成软骨和骨。迄今为止,至少发现了15种BMP,除BMP1外,其他BMPs均属于转化生长因子β（transforming growth factor-beta,TGF-β）超家族成员,它们可通过旁分泌和自分泌的形式诱导骨、软骨及与骨有关的结缔组织的形成,还能诱导骨源和非骨源性细胞的成骨分化。转录因子是一种核蛋白,是一类可以通过与下游靶基因DNA结合,从而调控下游基因转录的分子。随着对BMPs诱导成骨研究的深入,一些与BMPs相关的转录因子日益受到关注,对它们的研究也成为热点。根据目前的研究结果发现,调控BMPs诱导成骨的相关转录因子可分为两类,包括正调控因子（如Cbfαl、Osterix、Dlx5、Hoxc8和Msx2等）和负调控因子（如CIZ、AJ18、Tob和c-Ski等）,本综述对它们的研究进展分别作以介绍。     

Induced regeneration of calvaria by bone morphogenetic protein (BMP) in dogs

In the adult dog, a 14-mm skull trephine defect regenerates only incompletely in the lifetime of the individual. Only about half of the defect is repaired; the regenerated part develops by extension of growth from the bony rim. Correlated roentgenographic and histomorphometric methods demonstrate that new bone develops by proliferation of preexisting osteoprogenitor cells lining the diplo? and perivascular cells of the bone marrow stroma. An autogeneic bone graft, including bone marrow, provides a supplementary supply of cells in a homostructural framework and generally completes the repair process. Transplants of bone marrow alone fail to repair the defect. Implants of bovine bone morphogenetic protein (bBMP) and a carrier consisting of matrix gamma-carboxyglutamic acid rich protein (without any additional bone or bone marrow) induce repair almost as completely as an autograft. BMP-induced bone regeneration is incomplete in the thin lateral temporal marrow-deficient part of the cranium. Implants of BMP plus bone marrow induce complete repair, suggesting that calvarial bone regeneration is bone marrow stroma-dependent for a supply of target cells. The target for BMP in cranial bone regeneration is the perivascular connective tissue cells (pericyte) of the host bed marrow stroma and endosteum. The molecular mechanism of differentiation of pericytes into osteoprogenitor cells is not known, but the process is irreversible, heritable, and presents a solvable problem.     

Solubilization and purification of bone morphogenetic protein (BMP) from Dunn osteosarcoma

The 4 M GuHCl soluble proteins of Dunn osteosarcoma were fractionated in two steps by means of CsCl density gradient centrifugation. Further purification of bone morphogenetic protein (BMP) was accomplished by molecular sieve techniques utilizing thin-channel diafiltration (Amicon), Sepharose CL-6B and Sephacryl S-200 gel filtration. Partially purified BMP fractions were analyzed by electrophoresis on 7.5% SDS polyacrylamide gel. The molecular weight of BMP active fractions ranges from 30,000 to a few thousand daltons. BMP may be one of the two proteins of MW of 12,500 and 16,000 daltons.     

Analysis of bone morphogenetic protein (BMP) derived from human and bovine bone matrix

Recently, Bone Morphogenetic Protein (BMP) has attracted the attention of a number of investigators, but its elucidation remains incomplete. At present, the determination of its amino acid sequence, which is necessary for its synthesis, and screening for a carrier that allows BMP to be effective in small amounts are unsolved problems. Bone morphogenetic protein is studied here to clarify its clinical applications. BMP was extracted from human and bovine bone matrix with 4 M guanidine-HCl and purified by liquid chromatography. Acrylamide electrophoresis (SDS-PAGE) and isoelectric focusing (IEF) showed that the purified BMP was homogeneous. We used type I collagen as the carrier in the bioassay. This BMP induced new bone in situ three weeks after implantation in muscle pouches in Wistar rats. The molecular weights of human and bovine bone matrix-derived BMP are 17.0 and 18.0 kDa by SDS-PAGE, and pI values for both are 4.9 by IEF. Human and bovine bone matrix-derived BMP are peptides containing 165 and 163 amino acids, respectively, according to amino acid analysis. The NH2-terminal sequence of bovine bone matrix-derived BMP was obtained from the bovine band, electroblotted onto polyvinylidene difluoride membrane, that corresponded to the final purified fraction. The sequence differs from previously designated BMPs25 and other proteins reported to have similar activity, but the physicochemical characteristics are comparable to the native preparations.     

Noggin regulation of bone morphogenetic protein (BMP) 2/7 heterodimer activity in vitro

Bone morphogenic proteins (BMPs) are growth factors important for skeletal development and bone growth. Noggin, one of the soluble BMP antagonists, regulates the action of BMPs on mesenchymal precursor cells, partially through a feedback type of inhibition. In this study, we constructed a novel BMP2/7 'fusion gene' that encodes both BMP2 and BMP7 genes in tandem by a linker. Polymerase chain reaction (PCR) and Western blotting showed that the BMP2/7 fusion gene construct led to the production of BMP2/7 heterodimers in A549 'producer' cells. When applied to C2C12 myoblastic cells, BMP2/7 heterodimers increased alkaline phosphatase (ALP) activity and osteocalcin (OCN) expression (markers of osteoblastic differentiation) more effectively than either BMP2 or BMP7 homodimers. Moreover, this heterodimer induced significantly lower levels of Noggin expression in C2C12 cells than respective homodimers at similar doses. The addition of Noggin did not affect the heterodimer's activities in increasing osteoblastic differentiation in C2C12 cells. In contrast, BMP2 and BMP7 homodimers were largely inhibited by Noggin. Our finding suggests that the 'fusion gene' construct led to the production of bioactive BMP2/7 heterodimers, which were not antagonized by Noggin as effectively as it to BMP homodimers. The weaker Noggin antagonism on BMP heterodimers compared to homodimers may contribute to increased osteogenic potency of heterodimers in vitro and in vivo.     

Solubilized bone morphogenetic protein (BMP) from mouse osteosarcoma and rat demineralized bone matrix

A selection of proteins including bone morphogenetic protein (BMP) was extracted in a disaggregated form from Dunn osteosarcoma or rat demineralized bone matrix by 4M guanidine hydrochloride (GuHCl) solution without losing its biological activity. The GuHCl extracts of Dunn osteosarcoma were divied into 4 different fractions by cesium chloride (CsCl) density gradients. Under a dissociative condition, the highest new bone yield was obtained in the low dense top one-third fraction, and BMP acitivity declined with increase in the density of each fraction. No BMP potential was observed in the surface-gel fraction under dissociative conditions. Under an associative condition (low GuHCl concentrations), BMP activity appears in the surface-gel fraction, while under a dissociative condition (high concentrations of GuHCl) BMP appears in the fraction below the surface gel. These facts suggest that under associative conditions, BMP aggregates with other low dense proteins in the surface-gel fraction and that this may be the state of aggregation of BMP in cells and matrix in nature. Present observations support the assumption that BMP is a relatively low density protein and excludes the idea of BMP activity in the collagen molecule, per se. A specific protein, with an apparent molecular weight of 63,000 daltons, is present in all fractions that exhibit BMP activity, and absent in fractions that do not exhibit this activity. BMP is not species-specific; rat BMP induces bone formation in mice. CsCl density-gradient centrifugation is an efficient tool for further purification and isolation of BMP.     

BMP binding peptide: a BMP-2 enhancing factor deduced from the sequence of native bovine bone morphogenetic protein/non-collagenous protein.

Forty years ago, Marshall Urist described a partially purified extract of demineralized bone matrix which induced the formation of ectopic bone. This substance, bone morphogenetic protein/non-collagenous protein (BMP/NCP), was never purified to homogeneity but other investigators used similar starting materials to clone a number of recombinant BMPs. Urist recognized that his material probably contained the BMPs which had been cloned by others but always contended that it contained another, more potent, bone inducing material which differed significantly in its physical and chemical properties from the known BMPs. We have used Urist's protocol to isolate a protein that has the chemical and physical properties of Urist's "BMP". It is an 18.5 kD fragment of the bone matrix protein, SPP-24. This fragment contains the cystatin-like domain of SPP-24. We have located a 19 amino acid region which is similar to the TGF-beta/BMP-binding region of fetuin, a member of the cystatin family of protease inhibitors. A cyclic peptide, which we call BMP binding peptide (BBP) was generated using this sequence. The peptide avidly bound rhBMP-2 with a KD of 3 x 10(-5) M. When implanted alone in mouse muscle, the peptide frequently induced dystrophic calcification. When implanted with rhBMP-2, the peptide enhanced the osteogenic activity of the recombinant molecule. We hypothesize that Urist's "BMP" was a fragment of SPP-24 which influenced bone induction by binding to bone morphogenetic proteins. BBP may be clinically useful because of its effects on other bone-inducing substances.     

Low dose fibroblast growth factor-2 (FGF-2) enhances bone morphogenetic protein-2 (BMP-2)-induced ectopic bone formation in mice

To examine how fibroblast growth factor-2 (FGF-2) affects the BMP signaling pathway during bone morphogenetic protein-2 (BMP-2)-induced ectopic bone formation, we implanted type I collagen disks containing constant amounts of BMP-2 (5 micrograms) and varying amounts of FGF-2 onto the back muscles of adult male mice. We then performed histological analyses and histomorphometry, and measured bone mineral density and radiopaque area on the discs 1, 2, and 3 weeks after implantation. We also determined the expression profiles of several genes involved in bone formation and the BMP signaling pathway in the muscle that had been adjacent to the implanted disc and in muscle-derived primary culture cells that had similarly been treated with a constant concentration of BMP-2 and a varying concentration of FGF-2. In the presence of a constant amount of BMP-2, we confirmed that low doses of FGF-2 increased ectopic bone formation in vivo and high doses inhibited bone formation. Northern and/or Western blots of recovered muscle from the in vivo experiment and treated muscle-derived primary culture cells from the in vitro experiment revealed that low doses of FGF-2, but not high doses, increased the expression BMP receptor (BMPR)-1B, phosphorylated Smad1, Noggin, and Osteocalcin. Our results indicate that low-dose FGF-2 may facilitate BMP-2-induced ectopic bone formation by altering the expression of BMPRs on the surface of bone forming progenitor cells. They also indicate that the inhibitory effect of high-dose FGF-2 is not mediated via increased expression of the BMP inhibitor Noggin.     

大段同种异体骨移植复合BMP2和TGF-β2对兔桡骨中段骨缺损愈合的影响

[目的]探讨外源性TGF-β2和BMP2复合同种异体骨对骨缺损愈合的作用。[方法]用兔桡骨骨缺损模型,在骨缺损局部单独或联合应用TGF-β2和BMP2与同种异体骨复合,A组:同种异体骨与BMP2复合;B组(对照组):自体骨;C组:同种异体骨与TGF-β2复合;D组:同种异体骨与TGF-β2、BMP2复合;通过不同时间X线片、生物力学、骨密度和骨痂钙含量的检测对骨缺损愈合情况进行评估。[结果]B组的骨痂钙含量、骨缺损愈合情况和愈合后的力学强度明显优于A、C、D组(P<0.01),D组优于A、C组(P<0.05),C组优于A组(P<0.01)。[结论]TGF-β2和BMP2在骨缺损愈合过程中均发挥了重要的作用。在兔骨缺损周围局部应用外源性TGF-β2和BMP2与同种异体骨复合,可明显促进骨缺损愈合,使骨痂量增加,增强骨折愈合后的力学强度。并且在骨折愈合时间上接近自体骨移植骨折愈合的时间,从而在临床上缩短了需要大段植骨患者治疗时间,减轻了患者痛苦。单用TGF-β2的作用强于BMP2。它们联合应用时,这种作用进一步增强,在促进骨缺损愈合方面具有协同作用。同时也为异体骨复合何种因子及因子的剂量提供可靠的参考指标。     

A possible role of bone morphogenetic protein (BMP) in the regulation of bone remodeling

Bone morphogenetic protein (BMP) from an osteosarcoma powder was found to be solubilized in weak acid (pH 2.6–3.0), but not in acidic solutions of a lower or higher pH. This indicates that the solubility of BMP strictly depends on the hydrogen ion concentration of the solution. Ectopic osteogenesis induced by the osteosarcoma powder was greatly enhanced by treating the powder with acid solutions below pH 3.0. The acid-treated preparations were neutralized before bioassay. Acid treatment resulted in almost a five-fold increase in the amount of new bone formation. This finding suggests that a high concentration of hydrogen ion is important in regulating the activity of BMP. Lyophilized cultured cells of the osteosarcoma preserved the osteogenic activity even after incubation in acidic and neutral buffers at 37°C for six days. This observation suggests that BMP is stable to endogenous enzymes such as lysosomal or proteolytic enzymes. Based on these results, the role possibly played by BMP in the regulation of bone remodeling is discussed.     

人工骨腰椎后外侧融合过程中BMP基因的表达

目的研究利用人工骨做脊柱后外侧融合时局部BMP的表达情况,探讨人工骨在此过程中是否具备骨诱导作用。方法选用36只健康成年雄性新西兰白兔,制作L4、L5双侧横突间植骨融合模型,一侧采用磷酸钙人工骨(CPC),另一侧采用自体骨作为对照。按术后动物不同处死时间(0、2、4d、1、2、3、4、5、6、10周、6、10个月)随机平分为12组。采用RTPCR法检测融合组织BMP2mRNA、BMP4mRNA的表达水平。结果CPC材料内部在融合的各个时间段均未检测到BMP2mRNA和BMP4mRNA的表达。与紧密结合的植骨床及融合交界面中BMP2mRNA和BMP4mRNA的表达水平随时间变化均没有明显的增高,与自体骨相比,CPC融合过程中不同时间段内BMP2mRNA、BMP4mRNA的表达水平均明显低于自体骨(P<0.05)。结论单纯利用CPC做脊柱融合时,局部缺乏BMP的有效表达,可能导致融合失败率的增加。