BMP-7 opposes TGF-beta1-mediated collagen induction in mouse pulmonary myofibroblasts through Id2

Mesenchymal cells, primarily fibroblasts and myofibroblasts, are the principal matrix-producing cells during pulmonary fibrogenesis. Transforming growth factor (TGF)-beta signaling plays an important role in stimulating the expression of type I collagen of these cells. Bone morphogenetic protein (BMP)-7, a member of the TGF-beta superfamily, has been reported to oppose the fibrogenic activity of TGF-beta1. Here, we have addressed the effects of BMP-7 on the fibrogenic activity of pulmonary myofibroblasts. We first established cell lines from the lungs of transgenic mice harboring the COL1A2 upstream sequence fused to luciferase. They displayed a spindle shape and expressed vimentin and alpha-smooth muscle actin, but not E-cadherin. COL1A2 promoter activity was dose dependently induced by TGF-beta1, which was further augmented by adenoviral overexpression of Smad3, but was downregulated by Smad7. Under the identical condition, adenoviral overexpression of BMP-7 attenuated the TGF-beta1-dependent COL1A2 promoter activity. By immunocytochemistry, the ectopic expression of BMP-7 led to the nuclear localization of phospho-Smad1/5/8 and suppressed that of Smad3. BMP-7 suppressed the expression of mRNAs for COL1A2 and tissue inhibitor of metalloproteinase-2 while increasing those of inhibitors of differentiation (Id) 2 and 3. Ectopic expression of Id2 and Id3 was found to decrease the COL1A2 promoter activity. Finally, BMP-7 and Id2 decreased TGF-beta1-dependent collagen protein secretion. In conclusion, these data demonstrate that BMP-7 antagonizes the TGF-beta1-dependent fibrogenic activity of mouse pulmonary myofibroblastic cells by inducing Id2 and Id3.     

Osteogenesis versus chondrogenesis by BMP-2 and BMP-7 in adipose stem cells

Bone morphogenetic proteins (BMPs) initiate, promote, and maintain chondrogenesis and osteogenesis. We hypothesize that BMP-2 induces an osteogenic, and BMP-7 a chondrogenic phenotype in adipose tissue-derived mesenchymal stem cells (AT-MSCs). We compared the effects of a short 15min BMP-2 or BMP-7 (10ng/ml) treatment on osteogenic and chondrogenic differentiation of AT-MSCs. Gene expression was studied 4 and 14 days after BMP-treatment. At day 4 BMP-2, but not BMP-7, stimulated runx-2 and osteopontin gene expression, and at day 14 BMP-7 down-regulated expression of these genes. At day 4 BMP-2 and BMP-7 stimulated biglycan gene expression, which was down-regulated by BMP-7 at day 14. BMP-7 stimulated aggrecan gene expression at day 14. Our data indicate that BMP-2 treatment for 15min induces osteogenic differentiation, whereas BMP-7 stimulates a chondrogenic phenotype of AT-MSCs. Therefore, AT-MSCs triggered for only 15min with BMP-2 or BMP-7 provide a feasible tool for bone and cartilage tissue engineering.     

Wnt signaling during BMP-2 stimulation of mesenchymal chondrogenesis

Members of both the Wnt and bone morphogenetic protein (BMP) families of signaling molecules have been implicated in the regulation of cartilage development. A key component of the Wnt signaling pathway is the cytosolic protein, beta-catenin. We have recently shown that the chondrogenic activity of BMP-2 in vitro involves the action of the cell-cell adhesion protein, N-cadherin, which functionally complexes with beta-catenin. The aim of this study is to test the hypothesis that Wnts may be involved in BMP-2 induced chondrogenesis, using an in vitro model of high-density micromass cultures of the murine multipotent mesenchymal cell line, C3H10T1/2. Expression of a number of Wnt members was detected in these cultures, including Wnt-3A and Wnt-7A, whose levels were up- and downregulated, respectively, by BMP-2. To assess the functional involvement of Wnt signaling in BMP-2 induced chondrogenesis, cultures were treated with lithium chloride, a Wnt-7A mimetic that acts by inhibiting the serine/threonine phosphorylation activity of glycogen synthase kinase-3beta (GSK-3beta). Lithium treatment significantly inhibited BMP-2 stimulation of chondrogenesis as well as GSK-3beta enzymatic activity, and decreased the levels of N-cadherin protein and mRNA. Furthermore, lithium decreased BMP-2 upregulation of total and nuclear levels of LEF-1 and beta-catenin as well as their interaction during later chondrogenesis; similarly, the interaction of beta-catenin with N-cadherin was also decreased. Interestingly, lithium treatment did not affect the ability of BMP-2 to decrease ubiquitination of beta-catenin, although it did reduce the interaction of beta-catenin with GSK-3beta during late chondrogenesis (days 9-13). We suggest that the chondro-inhibitory effect of lithium on BMP-2 induced chondrogenesis indicates antagonism between lithium-like Wnts and BMP-2 during mesenchymal condensation.     

Differential regulation of osteoadherin (OSAD) by TGF-beta1 and BMP-2

Osteoadherin (OSAD) is a member of the small leucine rich-repeat proteoglycan (SLRP) family. SLRPs are normally found in extracellular matrices, but OSAD is the only member restricted to mineralized tissues. We investigated the promoter region of OSAD by in silico analysis and found that the proximal promoter region contains sites for Smad-3, Smad-4, and AP-1. All are effectors of TGF-beta family signalling. We tested sensitivity of the promoter to the two TGF-beta family members TGF-beta1 and BMP-2. We found TGF-beta1 to down regulate OSAD, while BMP-2 up regulates OSAD. As a consequence of how OSAD is regulated by TGF-beta1 and BMP-2 and its temporal expression pattern in osteoblasts and bone development, we can conclude OSAD as an early marker for terminally differentiated matrix producing osteoblasts.     

Differential effects of TGF-beta1 and BMP-4 on the hypoxic induction of cyclooxygenase-2 in human pulmonary artery smooth muscle cells

Chronic hypoxia-induced pulmonary hypertension results partly from proliferation of smooth muscle cells in small peripheral pulmonary arteries. Previously, we demonstrated that hypoxia modulates the proliferation of human peripheral pulmonary artery smooth muscle cells (PASMCs) by induction of cyclooxygenase-2 (COX-2) and production of antiproliferative prostaglandins. The transforming growth factor (TGF)-beta superfamily plays a critical role in the regulation of pulmonary vascular remodeling, although to date an interaction with hypoxia has not been examined. We therefore investigated the pathways involved in the hypoxic induction of COX-2 in peripheral PASMCs and the contribution of TGF-beta1 and bone morphogenetic protein (BMP)-4 in this response. In the present study, we demonstrate that hypoxia induces activation of p38MAPK, ERK1/2, and Akt in PASMCs and that these pathways are involved in the hypoxic regulation of COX-2. Whereas inhibition of p38(MAPK) or ERK1/2 activity suppressed hypoxic induction of COX-2, inhibition of the phosphoinositide 3-kinase pathway enhanced hypoxic induction of COX-2. Furthermore, exogenous TGF-beta1 induced COX-2 mRNA and protein expression, and our findings demonstrate that release of TGF-beta1 by PASMCs during hypoxia contributes to the hypoxic induction of COX-2 via the p38MAPK pathway. In contrast, BMP-4 inhibited the hypoxic induction of COX-2 by an MAPK-independent pathway. Together, these findings suggest that the TGF-beta superfamily is part of an autocrine/paracrine system involved in the regulation of COX-2 expression in the distal pulmonary circulation, and this modulates hypoxia-induced pulmonary vascular cell proliferation.     

TGF-beta 1 modulation of IGF-I signaling pathway in rat thyroid epithelial cells

Transforming growth factor beta 1 (TGF-beta 1) and insulin-like growth factor I (IGF-I) have contrasting effects on cell cycle regulation in thyroid cells and TGF-beta 1 induces a dramatic decrease in IGF-I-induced cell proliferation. The aim of the present study was to investigate the molecular mechanism of cross-talk between TGF-beta 1 and IGF-I in FRTL-5 cells. TGF-beta 1 affected IGF-I-stimulated insulin receptor substrate 1 (IRS-1) tyrosine phosphorylation and its association with Grb2 protein. Moreover, TGF-beta 1 decreased the IGF-I-induced tyrosine phosphorylation of the adaptor protein CrkII and its association with the IGF-I receptor. These results were accompanied by TGF-beta 1 inhibition of IGF-I-stimulated mitogen-activated protein kinase phosphorylation and activation. Conversely, TGF-beta 1 did not alter IGF-I-stimulated IRS-1-associated phosphatidylinositol 3-kinase activity, IGF-I-induced tyrosine phosphorylation of Shc, and its binding to Grb2. Taken together, these findings provide a molecular basis for the growth-inhibitory action of TGF-beta 1 on the IGF-I-induced mitogenic effect.     

T-cell cytokine induction of BMP-2 regulates human mesenchymal stromal cell differentiation and mineralization

How T-cells, attracted to local sites of inflammation in arthritides, affect heterotopic ossification is presently unknown. Here, we tested the hypothesis that T-cell cytokines play a role in the differentiation of human mesenchymal stromal cells (HMSC) into the osteoblast phenotype by inducing autologous BMP-2, providing a possible mechanism for heterotopic ossification. HMSC from multiple donor bones were treated with either activated T-cell conditioned medium (ACTTCM) or physiological concentrations of the major inflammatory cytokines, TNF-alpha, TGF-beta, IFN-gamma, and IL-17 (TTII), individually or in combinations. ACTTCM induced BMP-2 protein in a time-dependent manner over a 48 h period and alkaline phosphatase (AlkP) within 7 days. In combination, TTII, like ACTTCM, induced AlkP and synergistically induced BMP-2 protein. Either individually, or in combinations of up to three, the T-cell cytokines failed to induce BMP-2 above control levels while a combination of all four cytokines synergistically induced BMP-2 10-fold as assessed by ELISA. TTII induced mineralized matrix as effectively as dexamethasone. Inhibition of p38 MAPK completely inhibited TTII-induced BMP-2 production and matrix mineralization. Real time RT-PCR analysis demonstrated a striking early (within 4 h) increase in BMP-2 gene expression by TTII, which was suppressed by p38 MAP kinase inhibition. In localized chronic inflammatory diseases, T-cell cytokines released at localized sites of inflammation may be the driving force for differentiation of local mesenchymal stromal cells into the osteoblast phenotype thereby playing a significant role in the heterotopic ossification observed in these diseases.     

Stimulation of chondrogenesis in limb bud mesoderm cells by recombinant human bone morphogenetic protein 2B (BMP-2B) and modulation by transforming growth factor beta 1 and beta 2

Bone morphogenetic protein 2B (BMP-2B) also called BMP-4 is one of a family of cartilage and bone-inductive proteins derived from bone matrix and belongs to the transforming growth factor beta (TGF-beta) superfamily. These bone-inductive proteins isolated from adult bone may be involved in bone repair. However, they may also play a role in cartilage and bone formation during embryonic development. To test whether BMP-2B influences cartilage formation by embryonic cells, recombinant human BMP-2B was applied to cultured limb bud mesoderm plated at three different densities. BMP-2B stimulated cartilage formation as assessed by Alcian blue staining and incorporation of radioactive sulfate into sulfated proteoglycans. Cells cultured at all three densities in the presence of 10 ng/ml BMP-2B formed a nearly continuous sheet of cartilage with abundant extracellular matrix and type II collagen. In addition, when cells were cultured in 0.5% serum in the presence of 10 ng/ml of BMP-2B for 5 days there was an increase in alkaline phosphatase as detected by histochemical and biochemical methods. Transforming growth factor beta isoforms (TGF-beta 1 and TGF-beta 2) inhibited sulfate incorporation into proteoglycans in a dose-dependent manner. This inhibition by TGF beta was overcome by recombinant BMP-2B. This study demonstrates that recombinant BMP-2B stimulates cartilage formation by chick limb bud mesoderm in vitro and is further modulated by TGF-beta isoforms.     

BMP-7 counteracts TGF-beta1-induced epithelial-to-mesenchymal transition and reverses chronic renal injury

Bone morphogenic protein (BMP)-7 is a 35-kDa homodimeric protein and a member of the transforming growth factor (TGF)-beta superfamily. BMP-7 expression is highest in the kidney, and its genetic deletion in mice leads to severe impairment of eye, skeletal and kidney development. Here we report that BMP-7 reverses TGF-beta1-induced epithelial-to-mesenchymal transition (EMT) by reinduction of E-cadherin, a key epithelial cell adhesion molecule. Additionally, we provide molecular evidence for Smad-dependent reversal of TGF-beta1-induced EMT by BMP-7 in renal tubular epithelial cells and mammary ductal epithelial cells. In the kidney, EMT-induced accumulation of myofibroblasts and subsequent tubular atrophy are considered key determinants of renal fibrosis during chronic renal injury. We therefore tested the potential of BMP-7 to reverse TGF-beta1-induced de novo EMT in a mouse model of chronic renal injury. Our results show that systemic administration of recombinant human BMP-7 leads to repair of severely damaged renal tubular epithelial cells, in association with reversal of chronic renal injury. Collectively, these results provide evidence of cross talk between BMP-7 and TGF-beta1 in the regulation of EMT in health and disease.     

BMP-2-enhanced chondrogenesis involves p38 MAPK-mediated down-regulation of Wnt-7a pathway

The bone morphogenetic protein (BMP) family has been implicated in control of cartilage development. Here, we demonstrate that BMP-2 promotes chondrogenesis by activating p38 mitogen-activated protein kinase (MAPK), which in turn downregulates Wnt-7a/b-catenin signaling responsible for proteasomal degradation of Sox9. Exposure of mesenchymal cells to BMP-2 resulted in upregulation of Sox9 protein and a concomitant decrease in the level of b-catenin protein and Wnt-7a signaling. In agreement with this, the interaction of Sox9 with b-catenin was inhibited in the presence of BMP-2. Inhibition of the p38 MAPK pathway using a dominant negative mutant led to sustained Wnt-7a signaling and decreased Sox9 expression, with consequent inhibition of precartilage condensation and chondrogenic differentiation. Moreover, overexpression of b-catenin caused degradation of Sox9 via the ubiquitin/26S proteasome pathway. Our results collectively indicate that the increase in Sox9 protein resulting from downregulation of b-catenin/Wnt-7a signaling is mediated by p38 MAPK during BMP-2 induced chondrogenesis in chick wing bud mesenchymal cells.     

Effect of TGF-beta 1, TGF-beta 2, and bFGF on chick cartilage and muscle cell differentiation

In insulin containing defined medium TGF-beta 1, TGF-beta 2, and bFGF all stimulate chondrogenic differentiation in high-density micromass cultures of distal limb bud mesenchyme cells of chick embryos. In addition bFGF inhibits myogenic differentiation, while TGF-beta 1 and TGF-beta 2 appear to have no effect. TGF-beta 1 and bFGF together act additively to enhance chondrogenesis, while TGF-beta blocks the bFGF inhibitory action on myoblasts, thus allowing them to differentiate. In the absence of insulin, the inhibitory effect of bFGF on muscle cell differentiation is reduced; cartilage differentiation in the presence of the above growth factors is also slightly reduced.     

Transcriptional induction of Smurf2 ubiquitin ligase by TGF-beta

Smad ubiquitination regulatory factor 2 (Smurf2), a ubiquitin ligase for Smads, plays critical roles in the regulation of transforming growth factor-beta (TGF-beta)-Smad signaling via ubiquitin-dependent degradation of Smad2 and Smad7. We found that TGF-beta stimulates Smurf2 expression. TGF-beta activated the Smurf2 promoter in a TGF-beta responsive cell lines, whereas IL-1alpha, PDGF and epidermal growth factor did not. TGF-beta-mediated Smurf2 promoter activation was inhibited by Smad7 or an activin receptor-like kinase 5 inhibitor but not by dominant negative Smad or disruption of Smad-binding elements in the promoter. Moreover, inhibition of the phosphatidil inositol 3 kinase (PI3K)/Akt pathway suppressed TGF-beta-mediated Smurf2 induction. These results suggest that TGF-beta stimulates Smurf2 expression by Smad-independent pathway such as PI3K/Akt pathway via TGF-beta receptor.     

Tissue-engineered intervertebral disc and chondrogenesis using human nucleus pulposus regulated through TGF-beta1 in platelet-rich plasma

Human intervertebral disc (IVD) degeneration often initiated from the human nucleus pulposus (hNP) with aging leading to IVD destruction and extracellular matrix (ECM) depletion. Previously, we have successfully employed transforming growth factor-beta1 (TGF-beta1) to promote chondrogenesis of mesenchymal progenitor cells (MPCs) and immortalized human mesenchymal stem cells. In this study, we examine the role of TGF-beta1 in platelet-rich plasma (PRP) on disc regeneration, including proliferation, redifferentiation, and the reconstitution of tissue-engineered NP. hNP cells were isolated from volunteers with different ages and cultured in the presence of PRP. We found that the most effective concentration for hNP proliferation was 1 ng/ml TGF-beta1 in PRP, which was further applied in the following experiments. hNP cell proliferation in all age groups were increased time-dependently by PRP and cell morphologies showed aggregation. The mRNA of Sox9, type II collagen, and aggrecan were all significantly upregulated by PRP through RT-PCR. Glycosaminoglycan (GAG) accumulation reached the highest value at day 7 and continued to day 9 culture. PRP promoted NP regeneration via the Smad pathway was also determined and highly activated p-Smad2/3 at 30 min and continuously sustained to 120 min. Immunostaining of type II collagen indicates that PRP participates in chondrogenesis of tissue-engineered NP with collagen scaffolds. We concluded that growth factors in PRP can effectively react as a growth factor cocktail to induce hNP proliferation and differentiation, and also promote tissue-engineered NP formation. These findings are the first to demonstrate that PRP might be a therapeutic candidate for prevention of disc degeneration.     

Induction of chondrogenesis and expression of superficial zone protein (SZP)/lubricin by mesenchymal progenitors in the infrapatellar fat pad of the knee joint treated with TGF-beta1 and BMP-7

Superficial zone protein (SZP) is a key mediator of boundary lubrication of articular cartilage in joints. In this investigation, we made the unexpected discovery that SZP was expressed in infrapatellar fat pad (IFP) from bovine knee. Quantitative analysis of secreted proteins in the medium of the IFP stromal cells demonstrated a significant stimulation by TGF-β1 and BMP-7. Real-time PCR analysis revealed the SZP expression was up-regulated by TGF-β1 and BMP-7. Chondrogenically differentiated IFP progenitor cells were stimulated by TGF-β1 and BMP-7 to synthesize and secrete SZP. SZP mRNA was significantly up-regulated by chondrogenic induction for 21 days. These findings indicate that the stimulation of SZP expression by TGF-β and BMP-7 may lead to functional improvement of damaged intraarticular tissues and that IFP progenitor cells may be a potential useful source for inducing superficial zone of articular cartilage by tissue engineering for regeneration of damaged articular cartilage due to osteoarthritis     

Regulation of human Cripto-1 gene expression by TGF-beta1 and BMP-4 in embryonal and colon cancer cells

Human Cripto-1 (CR-1) is a cell membrane protein that is overexpressed in several different types of human carcinomas. In the present study we investigated the mechanisms that regulate the expression of CR-1 gene in cancer cells. We cloned a 2,481 bp 5'-flanking region of the human CR-1 gene into a luciferase reporter vector and transfected NTERA-2 human embryonal carcinoma cells and LS174-T colon cancer cells to test for promoter activity. Activity of CR-1 promoter in both cell lines was modulated by two TGF-beta family members, TGF-beta1 and BMP-4. In particular, TGF-beta1 significantly up-regulated CR-1 promoter activity, whereas a dramatic reduction in CR-1 promoter activity was observed with BMP-4 in NTERA-2 and LS174-T cells. Changes in the CR-1 promoter activity following TGF-beta1 and BMP-4 treatments correlated with changes in CR-1 mRNA and protein expression in NTERA-2 and LS174-T cells. We also identified three Smad binding elements (SBEs) within the CR-1 promoter and point mutation of SBE1 (-2,197/-2,189) significantly reduced response of the CR-1 promoter to both TGF-beta1 and BMP-4 in NTERA-2 and LS174-T cells. Chromatin immunoprecipitation assay also demonstrated binding of Smad-4 to a CR-1 promoter DNA sequence containing SBE1 in LS174-T cells. Finally, BMP-4 inhibited migration of LS174-T cells and F9 mouse embryonal carcinoma cells by downregulation of CR-1 protein. In conclusion, these results suggest a differential modulation of CR-1 gene expression in embryonal and colon cancer cells by two different members of the TGF-beta family.     

Endoglin modulation of TGF-beta1-induced collagen synthesis is dependent on ERK1/2 MAPK activation.

BACKGROUND/AIMS: Transforming growth factor-beta1 (TGF-beta1) plays a pivotal role in the extracellular matrix accumulation observed in fibrotic diseases. Endoglin is an important component of the TGF-beta receptor complex highly expressed in tissues undergoing fibrotic processes. Endoglin expression regulates the effect of TGF-beta on extracellular matrix synthesis. The purpose of our study has been to understand the molecular mechanism by which endoglin exerts its effects on fibrosis and the possible role of MAP kinases in these effects. METHODS: We have assessed in mock and in endoglin-transfected L6E9 myoblasts the effect of TGF-beta1 on collagen mRNA by Northern blot and effect of TGF-beta1 on collagen content in the cultured medium by [(3)H]-Proline incorporation into collagen proteins. Total and activated MAPK and their role on collagen synthesis were assessed by Western blot. RESULTS: TGF-beta1 induced an increase on alpha(2) (I) collagen mRNA expression and collagen accumulation in mock-transfected myoblasts, whereas the response was much lower in endoglintransfected cells. TGF-beta1 activated the ERK1/2 and p38 MAPK pathways but not the JNK pathway in L6E9 myoblasts. TGF-beta1-induced alpha(2) (I) collagen mRNA expression and collagen accumulation were completely inhibited by SB203580, in either mock or endoglintransfected myoblasts. PD98059 increased TGF-beta1 induced-collagen synthesis and accumulation in endoglin-transfected myoblasts but not in mock cells. CONCLUSION: Our studies demonstrate that TGF-beta1- induced collagen synthesis is mediated by p38 MAPK activation in L6E9 myoblasts. Furthermore, endoglin expression reduces basal and TGF-beta1 induced collagen synthesis when ERK1/2 pathway is operating.