大肠杆菌表达的重组人骨形成蛋白-7的复性

带有pBV221-hBMP-7的E．coli表达得到的rhBMP-7以不溶的包涵体形式存在,用高浓度的变性利溶解后,经过DEAE-FF纯化,得到高纯度的目的蛋白,达95％以上。分别用尿素浓度梯度降低法、添加促复性剂及人工分子伴侣法对蛋白质进行复性,并通过不同方法对复性结果进行比较。Western blot中辉度扫描结果显示,GSH／GSSG法样品二聚体／单体比例为79．5／20．5,尿素浓度梯度降低法二聚体／单体比例为73．6／26．4,表明GSH／GSSG法复性样品溶液上清中含较高比例的蛋白质二聚体。根据不同复性样品对NIH3T3细胞ALP活性影响大小的比较结果,氧化还原剂最有助于二聚体的形成,蛋白质活性最高。     

重组骨形态发生蛋白-7在骨损伤疾病治疗中的研究进展

骨形态发生蛋白-7(BMP-7)是具有强诱骨活性的蛋白质因子,已通过基因工程技术在体外得到表达,较长时间以来不断被应用于骨损伤疾病的研究,得到了确切的治疗效果。通过载体将BMP-7基因转入真核细胞,与生物聚合载体复合后植入体内,能表达并分泌活性的BMP-7,诱导骨细胞的生成,促进骨组织的修复,成为一种新的有效的治疗手段。     

离子交换色谱法对大肠杆菌表达的人重组骨形态发生蛋白-7的纯化

重组大肠杆菌高量表达重组人骨形态发生蛋白-7(rhBMP-7),每升培养液约得到湿菌体3g,其中目的蛋白约占菌体总蛋白量的40％。裂解离心,用低浓度变性剂洗涤初步纯化包涵体,上清中无目的蛋白损失;将包涵体溶解于高浓度变性剂溶液中,目的蛋白纯度提高到60％;然后在不同条件下用离子交换色谱法对变性状态下的蛋白质进行纯化,绝大部分杂蛋白被除去,目的蛋白纯度达95％以上;改变条件,可以减少rhBMP-7损失;用Western blot对目的蛋白进行特异性鉴定。     

Bone morphogenetic protein-7 expression in human pyelonephritis

Bone morphogenetic protein 7 (BMP- 7) is a member of the transforming growth factor (TGF) beta superfamily and is involved in regeneration, repair, and development of specific tissues, for example kidney and skeleton. The experimental studies have shown its protective role against fibrotic processes. Tubulointerstitial changes are present in the pyelonephritic kidney which progresses to fibrosis. Renal fibrosis may lead to the loss of renal function. The aim of this study was to investigate BMP-7 expression in acute and chronic pyelonephritis in humans. Seven patients with acute pyelonephritis and 7 with chronic pyelonephritis were treated in Department of Nephrology Clinical Hospital, Rijeka. Tissue biopsy was taken and renal tissue was studied histopathologically by use of hematoxylin and eosin and scored for diagnosis of pyelonephritis. BMP-7 expression was studied by immunohistochemical staining. BMP-7 expression was observed in the tubular area of the pyelonephritic kidneys. The expression of BMP- 7 was stronger in the acute pyelonephritic group and less in the chronic pyelonephritic group of patients. The results imply that BMP-7 has a role in chronic pyelonephritis. Tubular BMP-7 expression had a negative correlation with fibrosis and tubular, atrophy. Our results are suggesting that BMP- 7 plays an important protective role in renal inflammatory diseases preventing greater damage and fibrosis.     

Expression and secretion of human bone morphogenetic protein-7 in pichia pastoris

The synonymous codons are used in a highly nonrandom manner in hosts of widely divergent species, which is termed ‘codon usage bias’. Several reports suggest that codon usage bias sometimes obstructs attempts to express high levels of exogenous genes. In this study, an attempt was made to express mature peptide of human bone morphogenetic protein-7 with optimized codons in P. pastoris expression system. Three low-usage ARG codons (CGG or CGA) in hBmp7 mature domain have been successfully transformed into P. pastoris-preferred ARG codons (AGA) with overlap extension PCR-based multiple-site-directed mutagenesis for a high level expression of hBMP7 mature peptide. The results of this study showed that the production level (25.45 mg/L) of a codon-optimized strain increased 4.6-fold in comparison with that (5.5 mg/L) of noncodon-optimized strain. A strain harboring multicopy of codon-optimized hbmp7 expression cassette showed an even higher expression level, which was about 2-fold compared with that of the single-copy one. These recombinant hBMP7 mature peptides were produced as 18-kD monomer proteins and were easily purified from culture supernatants using ion-exchange chromatography. Functional assay demonstrated that rhBMP7 could induce ectopic cartilage formation, although its inductive ability was much less active than that of CHO cell-derived hBMP7.     

Heparan sulfate is required for bone morphogenetic protein-7 signaling

Although genetic studies have suggested that heparan sulfate (HS) is involved in bone morphogenetic protein (BMP)-mediated embryonic morphogenesis, it is unclear whether HS is directly involved in BMP-mediated signaling. Here, we investigate the involvement of HS in BMP-7 signaling. We show that HS and heparin chains specifically bind to BMP-7. Digestion of cell-surface HS with heparitinase interferes with BMP-7-mediated Smad phosphorylation in ROS 17/2.8 osteoblastic cells. Inhibiting sulfation of cell-surface HS with chlorate also causes interruption of Smad phosphorylation. Addition of exogenous heparin to ROS 17/2.8 cells prevents BMP-7-mediated Smad phosphorylation rather than enhances the BMP-7 signal, suggesting that HS should be anchored on the plasma membrane for BMP signaling. Moreover, BMP-7 binding to ROS 17/2.8 cells is inhibited by chlorate treatment and exogenous application of heparin. These results demonstrate that BMP-7 specifically binds to cell-surface HS and the BMP-7-HS interaction is required for BMP-7 signaling.     

Crystal structure of human bone morphogenetic protein-2 at 2.7 A resolution

Homodimeric bone morphogenetic protein-2 (BMP-2) is a member of the transforming growth factor beta (TGF-beta) superfamily that induces bone formation and regeneration, and determines important steps during early stages of embryonic development in vertebrates and non-vertebrates. BMP-2 can interact with two types of receptor chains, as well as with proteins of the extracellular matrix and several regulatory proteins. We report here the crystal structure of human BMP-2 determined by molecular replacement and refined to an R-value of 24.2 % at 2.7 A resolution. A common scaffold of BMP-2, BMP-7 and the TGF-betas, i.e. the cystine-knot motif and two finger-like double-stranded beta-sheets, can be superimposed with r. m.s. deviations of around 1 A. In contrast to the TGF-betas, the structure of BMP-2 shows differences in the flexibility of the N terminus and the orientation of the central alpha-helix as well as two external loops at the fingertips with respect to the scaffold. This is also known from the BMP-7 model. Small secondary structure elements in the loop regions of BMP-2 and BMP-7 seem to be specific for the respective BMP-subgroup. Two identical helix-finger clefts and two distinct cavities located around the central 2-fold axis of the dimer show characteristic shapes, polarity and surface charges. The possible function of these specific features in the interaction of BMP-2 with its binding partners is discussed.     

Weekly intra-articular injections of bone morphogenetic protein-7 inhibits osteoarthritis progression

Introduction  

We investigated the ability of a weekly intra-articular injection of bone morphogenetic protein (BMP)-7 to prevent osteoarthritis in rabbits with anterior cruciate ligament transections.     

Changes in bone morphogenetic protein receptor-IB localisation regulate osteogenic responses of human bone cells to bone morphogenetic protein-2

Cell responses to bone morphogenetic proteins (BMP) depend on the expression and surface localisation of transmembrane receptors BMPR-IA, -IB and -II. The present study shows that all three antigens are readily detected in human bone cells. However, only BMPR-II was found primarily at the plasma membrane, whereas BMPR-IA was expressed equally in the cytoplasm and at the cell surface. Notably, BMPR-IB was mainly intracellular, where it was associated with a number of cytoplasmic structures and possibly the nucleus. Treatment with transforming growth factor β1 (TGF-β1) caused rapid translocation of BMPR-IB to the cell surface, mediated via the p38 mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) pathways. The TGF-β1-induced increase in surface BMPR-IB resulted in significantly elevated BMP-2 binding and Smad1/5/8 phosphorylation, although the receptor was subsequently internalised and the functional response to BMP-2 consequently down-regulated. The results show, for the first time, that BMPR-IB is localised primarily in intracellular compartments in bone cells and that TGF-β1 induces rapid surface translocation from the cytoplasm to the cell surface, resulting in increased sensitivity of the cells to BMP-2.     

Effects of bone morphogenetic protein-7 stimulation on osteoblasts cultured on different biomaterials

The objective of the present study was to investigate the effects of an in vitro stimulation of human osteoblasts by recombinant human bone morphogenetic protein-7 (rhBMP-7) on the collagen types and the quantity of the collagen cross-links synthesized in a three-dimensional culture on various biomaterials for bone replacement. Trabecular bone chips were harvested from human iliac crests, and cell cultures were established at standard conditions. One hundred and fifty nanograms per milliliter of rhBMP-7 was added. For the second passage a cell scraper was used to bring the cells into suspension, and 100 microl osteoblasts (at a density of 3.3 x 10(5)) were transferred onto nine blocks of either Bio-Oss, Tutoplast, or PepGen p-15. Blocks incubated with cells that were not treated with rhBMP-7 served as controls. Cell colonization of the biomaterials was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) after a period of 2, 4, and 6 weeks. Throughout the experiment medium, supernatants were collected and collagen was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Finally, the collagen cross-link residues hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) were quantified by HPLC. Within 4 weeks the cells became confluent on all of the studied biomaterials. All samples synthesized bone specific LP and collagen type I. However, in rhBMP-7-stimulated samples, the amount of HP and LP found was increased by 45% compared to non-stimulated samples. Cell proliferation and collagen synthesis was similar on the different biomaterials, but was consistently reduced in specimen not stimulated with rhBMP-7. In vitro stimulation of osteoblasts on Bio-Oss, Tutoplast, or PepGen p-15 with rhBMP-7 and subsequent transplantation of the constructs might lead to an enhanced osseointegration of the biomaterials in vivo.     

Roles and regulation of bone morphogenetic protein-7 in kidney development and diseases

The gene encoding bone morphogenetic protein-7(BMP7) is expressed in the developing kidney in embryos and also in the mature organ in adults. During kidney development, expression of BMP7 is essential to determine the final number of nephrons in and proper size of the organ. The secreted BMP7 acts on the nephron progenitor cells to exert its dual functions: To maintain and expand the progenitor population and to provide them with competence to respond to differentiation cues, each relying on distinct signaling pathways. Intriguingly, in the adult organ, BMP7 has been implicated in protection against and regeneration from injury. Exogenous administration of recombinant BMP7 to animal models of kidney diseases has shown promising effects in counteracting inflammation, apoptosis and fibrosis evoked upon injury. Although the expression pattern of BMP7 has been well described, the mechanisms by which it is regulated have remained elusive and the processes by which the secretion sites of BMP7 impinge upon its functions in kidney development and diseases have not yet been assessed. Understanding the regulatory mechanisms will pave the way towards gaining better insight into the roles of BMP7, and to achieving desired control of the gene expression as a therapeutic strategy for kidney diseases.     

Effect of bone morphogenetic protein-7 on folliculogenesis and ovulation in the rat

We have previously established the presence of a functional bone morphogenetic protein (BMP) system in the ovary by demonstrating the expression of BMP ligands and receptors as well as novel cellular functions. Specifically, BMP-4 and BMP-7 are expressed in theca cells, and their receptors by granulosa cells. These BMPs enhanced and attenuated the stimulatory action of FSH on estradiol and progesterone production, respectively. To investigate the underlying mechanism of the differential regulation, we analyzed mRNA levels for key regulators in the steroid biosynthetic pathways by RNase protection assay. BMP-7 enhanced P450 aromatase (P450(arom)) but suppressed steroidogenic acute regulatory protein (StAR) mRNAs induced by FSH, whereas mRNAs encoding further-downstream steroidogenic enzymes, including P450 side-chain cleavage enzyme and 3beta-hydroxysteroid dehydrogenase, were not significantly altered. These findings suggest that BMP-7 stimulation and inhibition of P450(arom) and StAR mRNA expression, respectively, may play a role in the mechanisms underlying the differential regulation of estradiol and progesterone production. To establish the physiological relevance of BMP functions, we investigated the in vivo effects of injections of recombinant BMP-7 into the ovarian bursa of rats. Ovaries treated with BMP-7 had decreased numbers of primordial follicles, yet had increased numbers of primary, preantral, and antral follicles, suggesting that BMP-7 may act to facilitate the transition of follicles from the primordial stage to the pool of primary, preantral, and antral follicles. In this regard, we have also found that BMP-7 caused an increase in DNA synthesis and proliferation of granulosa cells from small antral follicles in vitro. In contrast to the stimulatory activity, BMP-7 exhibited pronounced inhibitory effects on ovulation rate and serum progesterone levels. These findings establish important new biological activities of BMP-7 in the context of ovarian physiology, including folliculogenesis and ovulation.     

Follistatin regulates bone morphogenetic protein-7 (BMP-7) activity to stimulate embryonic muscle growth

Bone morphogenetic proteins (BMPs) can either promote growth of embryonic muscle by expanding the Pax-3-expressing muscle precursor population or restrict its development by inducing apoptosis. Follistatin, a proposed BMP antagonist, is expressed in embryonic muscle. Deficiency in Follistatin results in muscle defects and postnatal asphyxia. Here, we report that during chick limb development Follistatin enhances BMP-7 action to induce muscle growth but prevents the ability of BMP-7 to induce apoptosis and muscle loss. Follistatin, unlike another BMP-binding protein, Noggin, promotes Pax-3 expression and transiently delays muscle differentiation and thus exerts proliferative signalling during muscle development. We provide data which show that Follistatin binds BMP-7 and BMP-2 at low affinities and that the binding is reversible. These data suggest that Follistatin acts to present BMPs to myogenic cells at a concentration that permits stimulation of embryonic muscle growth.     

Effects of bone morphogenetic protein-2 on human neonatal calvaria cell differentiation

Bone morphogenetic proteins (BMPs) are factors that promote osteoblastic cell differentiation and osteogenesis. It is unknown whether BMPs may act on human osteoblastic cells by increasing immature cell growth and/or differentiation. We investigated the short- and long-term effects of recombinant human (rh)BMP-2 on cell growth and osteoblast phenotype in a new model of human neonatal pre-osteoblastic calvaria cells (HNC). In short-term culture, rhBMP-2 (20-100 ng/ml) inhibited DNA synthesis and increased alkaline phosphatase (ALP) activity without affecting osteocalcin (OC) production. When cultured for 3 weeks in the presence of ascorbic acid and inorganic phosphate to induce cell differentiation, HNC cells initially proliferated, type 1 collagen mRNA and protein levels rose, and then decreased, whereas OC mRNA and protein levels, and calcium accumulation into the extracellular matrix increased at 2 to 3 weeks. A transient treatment with rhBMP-2 (50 ng/ml) for 1 to 7 days which affected immature HNC cells, decreased cell growth, increased ALP activity and mRNA, and induced cells to express ALP, osteopontin, and OC at 7 days, as shown by immunocytochemistry. At 2 to 3 weeks, matrix mineralization was markedly increased despite cessation of treatment, and although OC and Col 1 mRNA and protein levels were not changed. A continuous treatment with rhBMP-2 for 3 weeks which affected immature and mature cells reduced cell growth, increased ALP activity and mRNA at 1 week and increased OC mRNA and protein levels and calcium content in the matrix at 3 weeks, indicating complete osteoblast differentiation. These results indicate that the differentiating effects of BMP-2 on human neonatal calvaria are dependent on duration of exposure. Although long-term exposure led to complete differentiation of OC-synthesizing osteoblasts, the primary effect of rhBMP-2 was to promote osteoblast marker expression in immature cells, which was sufficient to induce optimal matrix mineralization independently of cell growth and type 1 collagen expression.     

人骨形态发生蛋白-2重组腺病毒的构建与制备

将人BMP-2的编码区cDNA克隆至穿梭载体pShuttle,以PI-SceI和I-CeuI切下含BMP-2编码区cDNA的片断,在体外与PI-SceI/I-CeuI切开的腺病毒DNA连接,构建重组有BMP-2全长编码区基因的腺病毒DNA,PCR鉴定正确后,经PacI酶切线性化,在脂质体介导下转染HEK293细胞,反复冻融制备重组腺病毒,空斑形成试验测定病毒滴度约为7.5×106～1.5×107pfu/ml。以BMP-2重组腺病毒感染体外培养的小鼠成肌细胞C2C12,Westernblot检测证实有BMP-2表达。     

Hypergonadotropic ovarian failure associated with an inherited mutation of human bone morphogenetic protein-15 (BMP15) gene

Hypergonadotropic ovarian failure is a common cause of female infertility. It is a heterogeneous disorder that, in the most severe forms, is a result of ovarian dysgenesis (OD). Most OD cases are associated with major X-chromosome abnormalities, but the pathogenesis of this disorder is still largely undefined in patients with a normal karyotype. Animal models showed the important role in female reproduction played by the product of a gene located at Xp11.2 in humans (BMP15). BMP15 is an oocyte-specific growth/differentiation factor that stimulates folliculogenesis and granulosa cell (GC) growth. We report two sisters with a normal karyotype who are affected with hypergonadotropic ovarian failure due to OD. The familial presentation suggested a genetic origin, and candidate genes were screened for mutations. A heterozygous nonconservative substitution in the pro region of BMP15 (Y235C) was identified in both sisters but not in 210 control alleles. This mutation was inherited from the father. Mutant BMP15 appears to be processed abnormally, is associated with reduced GC growth, and antagonizes the stimulatory activity of wild-type protein on GC proliferation. In conclusion, the first natural mutation in human BMP15 is associated with familial OD, indicating that the action of BMP15 is required for the progression of human folliculogenesis. This condition represents an exceptional example of X-linked human disease exclusively affecting heterozygous females who inherited the genetic alteration from the unaffected father. BMP15 defects are involved in the pathogenesis of hypergonadotropic ovarian failure in humans.     

Effect of elcatonin on osteoinduction by recombinant human bone morphogenetic protein-2

To evaluate the effect of elcatonin on osteoinduction by recombinant human bone morphogenetic protein-2 (rhBMP-2), 5 microg of rhBMP-2 was implanted into intramuscular sites of rats. For 14 days after the implantation, elcatonin was administered intraperitoneally with total dosage of 80 U, 8 U, and 0.8 U, respectively. For the control group, only physiological saline was administered. At 21 days after implantation, the area of the oval shadow in the radiologic findings depended on the elcatonin dose and the amount of trabecular bone and the number of osteoblasts observed in the histologic findings depended on the dosage of elcatonin. The values of ALP activity and Ca content also showed an elcatonin dose dependency. These results suggested that elcatonin is effective in enhancing osteoinduction by rhBMP-2 within the dose range of this study, and that elcatonin has an anabolic effect on osteoblasts in addition to an antiresorptive effect.