However, the expression levels were significantly down-regulated in late times of differentiation concomitant with the up-regulation of myofibrillar genes, Myosin Heavy Chain, alpha Skeletal Actin, Troponin and Myogenin, suggesting that fibrogenic trans-differentiation of C2C12 cells was inhibited during terminal myogenic differentiation. In order to assess whether miR-29 is a critical factor in determining the fate of myoblast differentiation, miR-29 was overexpressed in C2C12. As anticipated, the myogenic differentiation was accelerated as assessed by increased expression levels of Myogenin, MyHC, Troponin and a-Actin. However, the expressions of Col 1A1, Col 1A2, and Col 3A1 were suppressed, suggesting that miR-29 inhibits fibrogenic differentiation likely through targeting collagens. Interestingly, a-SMA and VIM were also found to be down-regulated although they are not predicted to be direct targets of miR-29 by multiple computational algorithms, indicating that miR-29 may GSI-IX customer reviews control a-SMA and VIM expression indirectly. This regulation appeared specific to miR-29 binding since changes in luciferase activity were not impacted when transfections were repeated with an irrelevant miRNA, miR-212, or with the miR-29 site deleted from the collagen 39UTR. In addition to miR-29c, the other two members of miR-29 family, miR-29a and miR-29b could also target Collagen 39UTR. Collectively, our findings suggest that high level of miR-29 is important for driving myogenic differentiation and loss of miR-29 promotes transdifferentiation of myoblasts into myofibroblasts by targeting Collagens. Having gained insights into the role of miR-29 during the conversion of myoblasts to myofibroblasts, we now turned our attention to its upstream regulator by asking: what leads to the down-regulation of miR-29 in this process? TGF-b has been individuated as the major inducer of myogenic cell into fibrogenic cells but the underlying mechanism is still largely obscure. We thus speculated that the pro-fibrogenic action of TGF-b mediated through miR-29 represents a novel signaling event contributing to fibrogenic conversion of myoblasts. Subsequently, the effects of TGF-b in myogenic and fibrogenic differentiation of C2C12 cells were evaluated. In agreement with previous finding, TGF-b treatment of C2C12 cells led to significant delay of myogenic program whereas the expressions of a number of fibrotic genes were increased. Further IF staining revealed that TGF-b treatment induced a loss of MyoD whereas the a-SMA is increased. In addition, both cell proliferation rate and cell mobility were increased. These SAR131675 results indicated a conversion of C2C12 to myofibroblasts. As shown in Figure 3A, very low level of a-SMA was detected in untreated cells where MyoD is highly expressed.