Requirement of a bone morphogenetic protein for the maintenance and stimulation of osteoblast differentiation

Inferring causal cell types of human diseases and risk variants from candidate regulatory elements

The heritability of human diseases is extremely enriched in candidate regulatory elements (cRE) from disease-relevant cell types. Critical next steps are to infer which and how many cell types are truly causal for a disease (after accounting for co-regulation across cell types), and to understand how individual variants impact disease risk through single or multiple causal cell types. Here, we propose CT-FM and CT-FM-SNP, two methods that leverage cell-type-specific cREs to fine-map causal cell types for a trait and for its candidate causal variants, respectively. We applied CT-FM to 63 GWAS summary statistics (average N = 417K) using nearly one thousand cRE annotations, primarily coming from ENCODE4. CT-FM inferred 81 causal cell types with corresponding SNP-annotations explaining a high fraction of trait SNP-heritability (~2/3 of the SNP-heritability explained by existing cREs), identified 16 traits with multiple causal cell types, highlighted cell-disease relationships consistent with known biology, and uncovered previously unexplored cellular mechanisms in psychiatric and immune-related diseases. Finally, we applied CT-FM-SNP to 39 UK Biobank traits and predicted high confidence causal cell types for 2,798 candidate causal non-coding SNPs. Our results suggest that most SNPs impact a phenotype through a single cell type, and that pleiotropic SNPs target different cell types depending on the phenotype context. Altogether, CT-FM and CT-FM-SNP shed light on how genetic variants act collectively and individually at the cellular level to impact disease risk.

miRNA-126 Inhibits Osteogenic Differentiation of Rat Bone Marrow Mesenchymal Stem Cells (BMSCs)

This study was to determine whether microRNA (miRNA)-126 regulates osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Rat BMSCs were extracted and stimulated for osteogenic differentiation. Functional experiments were conducted to assess miR-126’s impact on BMSCs differentiation. Western blot and RT-qPCR determined miR-126 expression. ALP activity detection and alizarin red staining detection were also performed. After osteogenic differentiation of BMSCs, miR-126 expression was gradually decreased over time. Overexpression of miR-26 decreased ALP activity, Notch signaling activity as well as declined Runx2 expression and calcium Salt nodules after treatment. Importantly, we found that Smad4 serves as a target of miR-126 while upregulation of the miRNA was accompanied with the decreased Smad4 protein expression without affecting the Smad4 mRNA level. In conclusion, miR-126 restrains osteogenic differentiation through inhibition of SMAD4 signaling, providing a novel insight into the mechanism.

Recombinant Human Bone Morphogenetic Protein 6 Delivered Within Autologous Blood Coagulum Restores Critical Size Segmental Defects of Ulna in Rabbits

BMP2 and BMP7, which use bovine Achilles tendon-derived absorbable collagen sponge and bovine bone collagen as scaffold, respectively, have been approved as bone graft substitutes for orthopedic and dental indications. Here, we describe an osteoinductive autologous bone graft substitute (ABGS) that contains recombinant human BMP6 (rhBMP6) dispersed within autologous blood coagulum (ABC) scaffold. The ABGS is created as an injectable or implantable coagulum gel with rhBMP6 binding tightly to plasma proteins within fibrin meshwork, as examined by dot-blot assays, and is released slowly as an intact protein over 6 to 8 days, as assessed by ELISA. The biological activity of ABGS was examined in vivo in rats (Rattus norvegicus) and rabbits (Oryctolagus cuniculus). In a rat subcutaneous implant assay, ABGS induced endochondral bone formation, as observed by histology and micro-CT analyses. In the rabbit ulna segmental defect model, a reproducible and robust bone formation with complete bridging and restoration of the defect was observed, which is dose dependent, as determined by radiographs, micro-CT, and histological analyses. In ABGS, ABC scaffold provides a permissive environment for bone induction and contributes to the use of lower doses of rhBMP6 compared with BMP7 in bovine bone collagen as scaffold. The newly formed bone undergoes remodeling and establishes cortices uniformly that is restricted to implant site by bridging with host bone. In summary, ABC carrier containing rhBMP6 may serve as an osteoinductive autologous bone graft substitute for several orthopedic applications that include delayed and nonunion fractures, anterior and posterior lumbar interbody fusion, trauma, and nonunions associated with neurofibromatosis type I.

Effect of Combined Action of Extracellular ATP and Elevated Calcium on Osteogenic Differentiation of Primary Cultures From Rat Calvaria

The in vitro osteogenic differentiation has been intensively studied. However, it is not yet clear precisely how osteogenesis can be optimized. Changes in extracellular Ca(2+) concentration ([Ca(2+) ]e ), as well as modulation of purinergic receptors play an important role in the regulation of osteoblasts differentiation and bone formation. In this study, we investigated the effects of a combined treatment of ATPγ-S and high [Ca(2+) ]e (5.35 mM) on osteogenic differentiation and function of primary cell cultures from rat calvaria. Our results indicate that ATPγ-S stimulates cell transition from the G0 to S phase of cell cycle, involving the PI3K signaling pathway. Treatment with 10 or 100 µM ATPγ-S and [Ca(2+) ]e (ATP-[Ca(2+) ]e ) for 48 h increases cell number significantly above the control. ATPγ-S treatment in osteogenic medium containing [Ca(2+) ]e stimulates the gene expression of BMP-4, BMP-5, and OPN at 16, 48, and 72 h, respectively, above control. In same conditions, treatment for 6 days with 10 µM UTP or 100 µM UDP significantly increased the ALP activity respect to control. Cells grown in osteogenic medium showed a statistically significant increase in calcium deposits at 15 and 18 days, for 10 µM ATPγ-S treatment, and at 18 and 22 days, for [Ca(2+) ]e treatment, respect to control but ATP-[Ca(2+) ]e treatment shown a significant greater mineralization at 15 days respect to ATPγ-S, and at 18 days respect to both agonists. In conclusion, we demonstrated that an osteogenic medium containing 10 µM ATPγ-S and 5.35 mM [Ca(2+) ]e enhance osteogenesis and mineralization by rat primary calvarial cells cultures. J. Cell. Biochem. 117: 2658-2668, 2016. © 2016 Wiley Periodicals, Inc.

Establishment of Immortalized BMP2/4 Double Knock-Out Osteoblastic Cells Is Essential for Study of Osteoblast Growth, Differentiation, and Osteogenesis

Bone morphogenetic proteins 2 and 4 (BMP2/4) are essential for osteoblast differentiation and osteogenesis. Generation of a BMP2/4 dual knock‐out (^ko/ko) osteoblastic cell line is a valuable asset for studying effects of BMP2/4 on skeletal development. In this study, our goal was to create immortalized mouse deleted BMP2/4 osteoblasts by infecting adenoviruses with Cre recombinase and green fluorescent protein genes into immortalized murine floxed BMP2/4 osteoblasts. Transduced BMP2/4^ko/ko cells were verified by green immunofluorescence and PCR. BMP2/4^ko/ko osteoblasts exhibited small size, slow cell proliferation rate and cell growth was arrested in G1 and G2 phases. Expression of bone‐relate genes was reduced in the BMP2/4^ko/ko cells, resulting in delay of cell differentiation and mineralization. Importantly, extracellular matrix remodeling was impaired in the BMP2/4^ko/ko osteoblasts as reflected by decreased Mmp‐2 and Mmp‐9 expressions. Cell differentiation and mineralization were rescued by exogenous BMP2 and/or BMP4. Therefore, we for the first time described establishment of an immortalized deleted BMP2/4 osteoblast line useful for study of mechanisms in regulating osteoblast lineages. J. Cell. Physiol. 231: 1189–1198, 2016. © 2015 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.

Role of rhBMP-2 and rhBMP-7 in the metabolism and differentiation of osteoblast-like cells cultured on chemically modified titanium surfaces

This study analyzed the role of recombinant human bone morphogenetic protein 2 (rhBMP-2) and recombinant human bone morphogenetic protein 7 (rhBMP-7) in the adhesion and differentiation of rat osteoblast-like (osteo-1) cells cultured on chemically modified titanium surfaces. Osteo-1 cells were cultured on chemically modified (modified sandblasted and acid-etched) titanium surfaces in 3 different types of medium: control, medium supplemented with 20 ng/mL rhBMP-2, and medium supplemented with 20 ng/mL rhBMP-7. The following parameters were evaluated: cell adhesion after 24 hours; total protein content; collagen content and alkaline phosphatase (AP) activity after 7, 14, and 21 days; and calcified nodule formation after 21 days. The addition of rhBMP-2 or rhBMP-7 did not influence cell adhesion (P = .1175). Cell differentiation was influenced by rhBMP-2, as demonstrated by a significant increase in collagen content after 7 days of culture (P < .0001) and a significant decrease in AP activity after 21 days (P < .0001). The addition of rhBMP-7 only influenced AP activity, and a significant increase was observed after 21 days (P < .0001). Within the limitations of the study, we conclude that the presence of rhBMP-2 or rhBMP-7 did not influence cell adhesion to chemically modified titanium surfaces but provided an additional stimulus during the differentiation of rat osteo-1 cells cultured on this type of surface.

Identification of a growth factor mimicking the synergistic effect of fetal bovine serum on BMP-9 cell response

The bone morphogenetic proteins (BMPs) are potent osteogenic molecules that are used for bone repair in delivery systems and in regenerative medicine. We studied the responses of murine MC3T3-E1 preosteoblasts to doses of recombinant human (rh)BMP-9 with and without fetal bovine serum (FBS). rhBMP-2 was used as a control since it is currently approved by the Food and Drug Administration for bone application. We analyzed the major cell signaling pathways and the expression of osteogenic markers. Without FBS, BMP-9 had a similar effect on MC3T3-E1 preosteoblast differentiation in comparison to BMP-2. In contrast, FBS reduced the EC50 of BMP-9 fourfold to sixfold, as determined by osterix gene expression and alkaline phosphatase (ALP) activity, while it had no influence on EC50 of BMP-2. As suggested by MAPK inhibitor assays, FBS could induce an intracellular signaling environment that favors cell response to BMP-9 by inhibiting ERK1/2 activation and increasing p38 phosphorylation. Finally, IGF-2 (100 ng/mL) could mimic the effect of FBS on BMP-9 cell response in terms of MAPK signaling and ALP activity. Thus, the action of BMP-9 on preosteoblast differentiation can be greatly improved by IGF-2. This finding may well be critical for developing optimal growth factor delivery systems and bone tissue engineering strategies.

The clinical use of bone morphogenetic proteins revisited: a novel biocompatible carrier device OSTEOGROW for bone healing

PURPOSE

The purpose of this study was to revise the clinical use of commercial BMP2 (Infuse) and BMP7 (Osigraft) based bone devices and explore the mechanism of action and efficacy of low BMP6 doses in a novel whole blood biocompatible device OSTEOGROW.

METHODS

Complications from the clinical use of BMP2 and BMP7 have been systemically reviewed in light of their role in bone remodeling. BMP6 function has been assessed in Bmp6-/- mice by μCT and skeletal histology, and has also been examined in mesenchymal stem cells (MSC), hematopoietic stem cells (HSC) and osteoclasts. Safety and efficacy of OSTEOGROW have been assessed in rats and rabbits.

RESULTS

Clinical use issues of BMP2 and BMP7 have been ascribed to the limited understanding of their role in bone remodeling at the time of device development for clinical trials. BMP2 and BMP7 in bone devices significantly promote bone resorption leading to osteolysis at the endosteal surfaces, while in parallel stimulating exuberant bone formation in surrounding tissues. Unbound BMP2 and BMP7 in bone devices precipitate on the bovine collagen and cause inflammation and swelling. OSTEOGROW required small amounts of BMP6, applied in a biocompatible blood coagulum carrier, for stimulating differentiation of MSCs and accelerated healing of critical size bone defects in animals, without bone resorption and inflammation. BMP6 decreased the number of osteoclasts derived from HSC, while BMP2 and BMP7 increased their number.

CONCLUSIONS

Current issues and challenges with commercial bone devices may be resolved by using novel BMP6 biocompatible device OSTEOGROW, which will be clinically tested in metaphyseal bone fractures, compartments where BMP2 and BMP7 have not been effective.

Estrogen facilitates osteoblast differentiation by upregulating bone morphogenetic protein-4 signaling

Imbalanced functions of osteoclasts and osteoblasts are involved in various types of bone damage including postmenopausal osteoporosis. In the present study, we investigated the cellular mechanism by which estrogen interacts in the process of osteoblastic differentiation regulated by BMP-4 using mouse MC3T3-E1 cells that express estrogen receptors (ER) and BMP-4. Estradiol enhanced BMP-4-induced Runx2, osterix, ALP and osteocalcin expression in MC3T3-E1 cells. BMP-4-induced mineralization shown by Alizarin red staining was also facilitated by estrogen treatment. It was revealed that estrogen upregulated BMP-4-induced Smad1/5/8 phosphorylation, BRE-Luc activity and Id-1 mRNA expression. The expression of BMPRII was increased by estrogen in MC3T3-E1 cells, and inhibition of BMPRII or ALK-2/3 signaling impaired the effect of estrogen on BMP-4 signaling. Of note, the enhanced expression of osterix, ALP and osteocalcin mRNAs induced by BMP-4 and estrogen was reversed in the presence of an ER antagonist. Given that membrane-impermeable estrogen also upregulated BMP-4-induced expression of osteoblastic markers and Id-1 mRNA, non-genomic ER activity is involved in the mechanism by which estrogen enhances BMP-4-induced osteoblast differentiation in MC3T3-E1 cells. On the other hand, the expression of ERα and endogenous BMP-4 was suppressed by BMP-4 treatment regardless of the presence of estrogen, implying the presence of a negative feedback loop for osteoblast differentiation. Thus, estrogen is functionally involved in the process of osteoblast differentiation regulated by BMP-4 through upregulating BMP sensitivity of MC3T3-E1 cells.

Comparative genomics identifies the mouse Bmp3 promoter and an upstream evolutionary conserved region (ECR) in mammals

The Bone Morphogenetic Protein (BMP) pathway is a multi-member signaling cascade whose basic components are found in all animals. One member, BMP3, which arose more recently in evolution and is found only in deuterostomes, serves a unique role as an antagonist to both the canonical BMP and Activin pathways. However, the mechanisms that control BMP3 expression, and the cis-regulatory regions mediating this regulation, remain poorly defined. With this in mind, we sought to identify the Bmp3 promoter in mouse (M. musculus) through functional and comparative genomic analyses. We found that the minimal promoter required for expression in resides within 0.8 kb upstream of Bmp3 in a region that is highly conserved with rat (R. norvegicus). We also found that an upstream region abutting the minimal promoter acts as a repressor of the minimal promoter in HEK293T cells and osteoblasts. Strikingly, a portion of this region is conserved among all available eutherian mammal genomes (47/47), but not in any non-eutherian animal (0/136). We also identified multiple conserved transcription factor binding sites in the Bmp3 upstream ECR, suggesting that this region may preserve common cis-regulatory elements that govern Bmp3 expression across eutherian mammals. Since dysregulation of BMP signaling appears to play a role in human health and disease, our findings may have application in the development of novel therapeutics aimed at modulating BMP signaling in humans.

BMP signaling in rats with TNBS-induced colitis following BMP7 therapy

Beyond stimulating bone formation, bone morphogenetic proteins (BMPs) are important in development, inflammation, and malignancy of the gut. We have previously shown that BMP7 has a regenerative, anti-inflammatory, and antiproliferative effect on experimental inflammatory bowel disease (IBD) in rats. To further investigate the BMP signaling pathway we monitored the effect of BMP7 therapy on the BMP signaling components in the rat colon during different stages of experimentally induced colitis by 2,4,6-trinitrobenzene sulfonic acid (TNBS). The results showed a significantly decreased BMP7 expression in the acute phase, followed by a significantly increased BMP2 and decreased BMP6 expression during the chronic phase of colitis. BMP7 therapy influenced the expression of several BMPs with the most prominent effect on downregulation of BMP2 and upregulation of BMP4 in the chronic phase of colitis. Importantly, connective tissue growth factor and noggin expression were elevated in the acute stage and significantly decreased upon BMP7 therapy. BMP receptor I expression was unchanged, whereas BMP receptor II was decreased at day 2 and increased at days 14 and 30 of TNBS inflammation. However, an opposite pattern of expression following BMP7 therapy has been observed. BMP7 increased the expression of BR-Smad including Smad3 and Smad4. Inhibitory Smads were increased in colitis and significantly decreased following BMP7 therapy at later stages of the disease. We suggest that BMP signaling was altered during TNBS-induced colitis and was recovered with BMP7 administration, suggesting that IBD is a reversible process.

The proteome and gene expression profile of cementoblastic cells treated by bone morphogenetic protein-7 in vitro

AIM

Regenerative periodontal therapy is often unpredictable and limited. Cementum regeneration is necessary for the proper repair of a periodontal ligament. The precise mechanism how bone morphogenetic protein-7 (BMP7) induces differentiation and mineralization of cementoblasts remains undetermined. The purpose of this study was to evaluate the effect of BMP7 on early proteome and gene expression profile of cementoblastic OCCM.30 cells in vitro.

MATERIALS AND METHODS

Immortalized murine cementoblasts (OCCM.30) were exposed to BMP7 and evaluated for: (1) proliferation; (2) mineralization; (3) early proteome profile using liquid chromatography-mass spectrometry (LC-MS); and (4) gene expression by quantitative RT-PCR.

RESULTS

Bone morphogenetic protein-7 increased the cell proliferation at 24 h and 48 h, while higher doses suppressed the cell proliferation at 48 h. BMP7 induced the mineralization of cementoblasts following 8 days of therapy. Using LC-MS we identified 1117 proteins from the cell lysate. Many belonged to extracellular matrix formation such as PCPE1, collagens, annexins and integrin receptors. RT-PCR analyses revealed a BMP7 dose-dependent upregulation of BMP1, TGFβ1, osterix, osteoprotegerin, procollagen I and II, PCPE1, and noggin, while BMP6 and chordin expression were decreased. The high BMP7 dose down regulated most of the genes 24 h following therapy.

CONCLUSION

Bone morphogenetic protein-7 promotes differentiation and mineralization of cementoblasts via inducing PCPE1 and BMP1 responsible for processing of type I collagen.

Co-expression of bone morphogenetic protein 6 with estrogen receptor a in endometriosis

BACKGROUND

Bone morphogenetic protein 6 (BMP-6) has decisive role in controlling multiple organogenetic processes, as well as modulating cell differentiation and proliferation. Considering those pleiotropic effects, we focused on determining expression of that multifunctional growth factor in ectopic endometriotic tissues.

MATERIALS AND METHODS

In this prospective study, 85 consecutive women with endometriosis were included. All patients underwent gynecological operations due to endometriosis associated problems and tissue specimens were collected from ectopic endometriotic lesions. Immunohistochemical staining of paraffin sections for both BMP-6 and estrogen receptors a (ERa) was performed in all 85 cases using an avidin-biotin-peroxidase procedure.

RESULTS

Ectopic endometrium showed intense cytoplastic immunoreactivity to BMP-6 in both epithelium and stroma. In addition, we have demonstrated that BMP-6 expression is highly associated with strong expression of ERa.

DISCUSSION

The availability of BMP-6 in the ectopic endometrium may be at least partly involved in the mechanisms of attachment, survival and expansion of endometriosis. Moreover, the statistically significant correlation in expression of BMP-6 and ERa demonstrated in this study may be associated with the development of rich in estrogen microenvironment, but requires further investigation. In conclusion, this is the first study in our knowledge demonstrating strong expression of BMP-6 in endometriosis.

Boron regulates mineralized tissue-associated proteins in osteoblasts (MC3T3-E1)

The aim of this study was to determine the effects of boron (B) on the cell-survival, proliferation, mineralization and mRNA expression of mineralized tissue-associated proteins. Additionally, determination of the effects of B on the BMP-4, -6 and -7 protein levels of pre-osteoblastic cells (MC3T3-E1) was also intended. The effects of B (pH 7.0) concentrations (0, 0.1, 1, 10, 100, 1000, 2000, 4000, 8000 and 10,000 ng/ml) on the survival of the cells were evaluated at 24 and 96 hrs with MTT assay. To evaluate the proliferation in long term, MC3T3-E1 cells were treated with different concentrations of B (0, 0.1, 1, 10, 100 and 1000 ng/ml) and were counted on days 2, 5, and 14. While in short term, decreased cell survival rate was observed at 1000 ng/ml and above, at long term no statistically significant difference was detected in different B concentrations applied. Slight decreases at the proliferation of the B-treated groups were determined on days 5 and 14 but one-way analysis of variance revealed that the difference was statistically insignificant. In mineralization assay, increased mineralized nodules were apparently observed in B treatment (1 and 10 ng/ml concentrations) groups. Based on quantitative RT-PCR results, remarkable regulation in favor of osteoblastic function for Collagen type I (COL I), Osteopontin (OPN), Bone Sialoprotein (BSP), Osteocalcin (OCN) and RunX2 mRNA expressions were observed in B treatment groups in comparison with untreated control groups. Increased BMP-4, -6 and -7 protein levels were detected at 0.1, 1, 10 and 100 ng/ml B concentrations. Results of the study suggest that at the molecular level B displays important roles on bone metabolism and may find novel usages at the regenerative medicine.

Effects of dexamethasone on the functional properties of cartilage explants during long-term culture

BACKGROUND

Intact articular cartilage tissue is used clinically in the form of osteochondral allografts and experimentally as explants in modeling the physiologic behavior of chondrocytes in their native extracellular matrix. Long-term maintenance of allograft tissue is challenging.

HYPOTHESIS

By carefully modulating the preservation environment, it may be possible to preserve osteochondral allograft tissue over the long term while maintaining its original mechanical and biochemical properties.

STUDY DESIGN

Controlled laboratory study.

METHODS

In this study, juvenile bovine, mature bovine, and canine cartilage explants were cultured in chemically defined media with or without supplementation of dexamethasone for up to 4 weeks.

RESULTS

The mechanical properties and biochemical content of juvenile bovine explants cultured in the presence of dexamethasone were significantly enhanced after 2 weeks in culture and remained stable with sustained cell viability thereafter. In contrast, the mechanical properties and biochemical content of juvenile bovine explants cultured in the absence of the dexamethasone significantly decreased after 2 weeks of culture. The mechanical and biochemical content of mature bovine and canine explants were not significantly affected by the presence of dexamethasone and maintained initial (day 0) mechanical and biochemical properties throughout the entire culture period with or without supplementation of dexamethasone.

CONCLUSION

These results suggest that juvenile and mature cartilage explants respond differently to dexamethasone. The functional properties of juvenile cartilage explants can be maintained in vitro through the addition of dexamethasone to culture media. Functional properties of mature cartilage can be preserved for at least 4 weeks in culture regardless of the presence of dexamethasone.

CLINICAL RELEVANCE

Biochemical and biomechanical properties of osteochondral allograft tissue may be enhanced by the addition of dexamethasone to culture media. These findings may translate to longer shelf life of preserved osteochondral allograft transplantation tissue and increased clinical availability of grafts.

Immortalization and characterization of mouse floxed Bmp2/4 osteoblasts

Generation of a floxed Bmp2/4 osteoblast cell line is a valuable tool for studying the modulatory effects of Bmp2 and Bmp4 on osteoblast differentiation as well as relevant molecular events. In this study, primary floxed Bmp2/4 mouse osteoblasts were cultured and transfected with simian virus 40 large T-antigen. Transfection was verified by polymerase chain reaction (PCR) and immunohistochemistry. To examine the characteristics of the transfected cells, morphology, proliferation and mineralization were analyzed, expression of cell-specific genes including Runx2, ATF4, Dlx3, Osx, dentin matrix protein 1, bone sialoprotein, osteopontin, osteocalcin, osteonectin and collagen type I was detected. These results show that transfected floxed Bmp2/4 osteoblasts bypassed senescence with a higher proliferation rate, but retain the genotypic and phenotypic characteristics similar to the primary cells. Thus, we for the first time demonstrate the establishment of an immortalized mouse floxed Bmp2/4 osteoblast cell line.

Treatment of rabbit femoral defect by firearm with BMP-4 gene combined with TGF-beta1

BACKGROUND

Firearm bone fractures are difficult to treat compared with general ones as both soft tissue and bone are injured more extensively and severely with contamination in the wound track. The bone morphogenetic protein (BMP) and transforming growth factor (TGF)-beta play an important role in bone fracture healing. Therefore, BMP-4 combined with TGF-beta1 was used to improve and accelerate the repair of rabbit femoral defect resulting from firearm.

METHODS

Femoral defect was made with 0.375 g steel ball fired at 350 m/s. At 6 hours after wounding, the debridement and irrigation were performed, followed by trimming the ends of defected bone at day 7. Plasmid-encoded BMP-4 gene identified in vitro and TGF-beta1 were injected into the tissue of upper and lower parts and the epicenter of the defected area at 2 weeks after wounding, again TGF-beta1 was given at 5 weeks. At 3, 7, 11, and 15 weeks after wounding, the expression of mRNA and protein of BMP-4 were detected by reverse transcription-polymerase chain reaction and Western blot. The activity of alkaline phosphatase and calcium content were measured for describing osteogenetic ability. The course and quality of osteogenesis were determined quantitatively by pathohistological and X-ray examinations.

RESULTS

In vivo BMP-4 mRNA and protein could be continually expressed for 8 weeks. The determination of alkaline phosphatase activity and calcium content showed osteogenetic ability was significantly enhanced by BMP-4 gene combined with TGF-beta1. The pathohistological and X-ray examinations revealed that osteogenetic speed was prominently accelerated, and the quality was improved after the treatment.

CONCLUSION

The repair of rabbit femoral defect resulting from firearm can be significantly improved and accelerated by BMP-4 gene combined with TGF-beta1.

Effect of recombinant human bone morphogenetic protein-7 (rhBMP-7) on the viability, proliferation and differentiation of osteoblast-like cells cultured on a chemically modified titanium surface

AIM

The aim of the present study was to assess the influence of the chemical characteristics and roughness of titanium surfaces on the viability, proliferation and differentiation of osteoblast-like cells cultured in a medium supplemented with recombinant human bone morphogenetic protein-7 (rhBMP-7).

MATERIAL AND METHODS

Osteo-1 cells were grown on titanium disks presenting with the following surfaces: (1) machined, (2) coarse grit-blasted and acid-attacked (SLA) and (3) chemically modified SLA (SLAmod) in the absence or presence of 20 ng/ml rhBMP-7 in culture medium. The viability and number of osteo-1 cells were evaluated after 24 h. Analyses of total protein content (TP) and alkaline phosphatase (AP) activity at 7, 14 and 21 days, collagen content at 7 and 21 days and mineralized matrix formation at 21 days were performed.

RESULTS

Cell viability (P=0.5516), cell number (P=0.3485), collagen content (P=0.1165) and mineralized matrix formation (P=0.5319) were not affected by the different surface configurations or by the addition of rhBMP-7 to the medium. Osteo-1 cells cultured on SLA surfaces showed a significant increase in TP at 21 days. The ALPase/TP ratio (P=0.00001) was affected by treatment and time.

CONCLUSION

The results suggest that the addition of rhBMP-7 to the culture medium did not exert any effect on the viability, proliferation or differentiation of osteoblast-like cells grown on the different surfaces tested. All titanium surfaces analyzed allowed the complete expression of the osteoblast phenotype such as matrix mineralization by osteo-1 cells.

Mechanical and biochemical characterization of cartilage explants in serum-free culture

Allografts of articular cartilage are both used clinically for tissue-transplantation procedures and experimentally as model systems to study the physiological behavior of chondrocytes in their native extracellular matrix. Long-term maintenance of allograft tissue is challenging. Chemical mediators in poorly defined culture media can stimulate cells to quickly degrade their surrounding extracellular matrix. This is particularly true of juvenile cartilage which is generally more responsive to chemical stimuli than mature tissue. By carefully modulating the culture media, however, it may be possible to preserve allograft tissue over the long-term while maintaining its original mechanical and biochemical properties. In this study juvenile bovine cartilage explants (both chondral and osteochondral) were cultured in both chemically defined medium and serum-supplemented medium for up to 6 weeks. The mechanical properties and biochemical content of explants cultured in chemically defined medium were enhanced after 2 weeks in culture and thereafter remained stable with no loss of cell viability. In contrast, the mechanical properties of explants in serum-supplemented medium were degraded by ( approximately 70%) along with a concurrent loss of biochemical content (30-40% GAG). These results suggest that long-term maintenance of allografts can be extended significantly by the use of a chemically defined medium.

Short-term effects of adhesion peptides on the responses of preosteoblasts to pBMP-9

Adhesion peptides are currently used to enhance the interactions of osteoblasts with biomaterials. However, little is known about the effects of adhesion peptides on cell responses to growth factors, especially the bone morphogenetic proteins (BMPs). We used adhesion peptides Ac-CGGNGERPRGDTYRAY-NH(2) (pRGD), derived from bone sialoprotein, and Ac-CGGDGEA-NH(2) (pDGEA), derived from collagen, which interact with alpha(v)beta(3) and alpha(2)beta(1) integrins, respectively. We analyzed the effects of pRGD- and pDGEA-coated polystyrene (PS) on the responses of murine MC3T3-E1 preosteoblasts to a peptide derived from human BMP-9 (pBMP-9) in serum-free medium. After 1h, pRGD favoured interactions with alpha(v) while pDGEA bound beta(1) integrin subunits. Adding pBMP-9 (400 ng/mL) increased the amount of alpha(v) integrin subunits in cell membranes on pRGD-coated PS, but had no effect on beta(1) integrin subunits. Only on this substratum, collagen type I mRNA was enhanced and the addition of pBMP-9 promoted the early cell differentiation, increasing their alkaline phosphatase (ALP) activity within 24 h. These cells also organized beta(1) integrin subunits at their focal adhesion points. Inhibiting alpha(2)beta(1) integrins by pDGEA pre-treatment decreased this ALP activity. It is therefore important to understand the impact of adhesion peptides on the early cell responses to growth factors in order to improve biomimetic materials.

Characterization of bone cells obtained from the calvaria of neonatal rats (osteo-1) after serial subculture

The objective of the present study was to characterize bone cells grown in two culture media, and to determine the effective concentration of OP-1 on the growth of osteo-1 cells. Subcultured rat bone cells (osteo-1) were grown in alpha-modified Eagle’s minimal essential medium (α-MEM) and Dulbecco’s modified Eagle’s medium (DMEM) and total protein content, alkaline phosphatase activity and the formation of mineralized nodules were evaluated after 7, 14 and 21 days. Cells were exposed to different concentrations of rhOP-1 for 1, 3, 5 and 7 days and compared with an untreated control. Osteo-1 cells presented a significant increase in alkaline phosphatase activity and calcium deposits were observed at 21 days. Cells treated with 10 and 20 ng/mL rhOP-1 for 24 h showed a significant increase in cell viability when compared to control. Osteo-1 cells cultured on DMEM demonstrated an osteoblastic phenotype as indicated by high alkaline phosphatase activity and the presence of calcified nodules. The results suggest that low concentrations of OP-1 may promote an osteogenic effect on osteo-1 cells.