Abstract
BackgroundIn vitro studies using the myogenic cell line C2C12 demonstrate that bone morphogenetic protein-2 (BMP-2) converts the developmental pathway of C2C12 from a myogenic cell lineage to an osteoblastic cell lineage. Further, in vivo studies using null mutation mice demonstrate that BMPs inhibit the specification of the developmental fate of myogenic progenitor cells. However, the roles of BMPs in the phases of differentiation and maturation in skeletal muscles have yet to be determined. The present study attempts to define the function of BMP-2 in the final stage of differentiation of mouse tongue myoblast.ResultsRecombinant BMP-2 inhibited the expressions of markers for the differentiation of skeletal muscle cells, such as myogenin, muscle creatine kinase (MCK), and fast myosin heavy chain (fMyHC), whereas BMP-2 siRNA stimulated such markers. Neither the recombinant BMP-2 nor BMP-2 siRNA altered the expressions of markers for the formation of cartilage and bone, such as osteocalcin, alkaline phosphatase (ALP), collagen II, and collagen X. Further, no formation of cartilage and bone was observed in the recombinant BMP-2-treated tongues based on Alizarin red and Alcian blue stainings. Neither recombinant BMP-2 nor BMP-2 siRNA affected the expression of inhibitor of DNA binding/differentiation 1 (Id1). The ratios of chondrogenic and osteogenic markers relative to glyceraldehyde-3-phosphate dehydrogenase (GAPDH, a house keeping gene) were approximately 1000-fold lower than those of myogenic markers in the cultured tongue.ConclusionsBMP-2 functions as a negative regulator for the final differentiation of tongue myoblasts, but not as an inducer for the formation of cartilage and bone in cultured tongue, probably because the genes related to myogenesis are in an activation mode, while the genes related to chondrogenesis and osteogenesis are in a silencing mode.
Highlights
In vitro studies using the myogenic cell line C2C12 demonstrate that bone morphogenetic protein-2 (BMP-2) converts the developmental pathway of C2C12 from a myogenic cell lineage to an osteoblastic cell lineage
In vitro studies using the myogenic cell line C2C12 demonstrate that Bone morphogenetic proteins (BMPs)-2 converts the developmental pathway of C2C12 from a myogenic lineage to an osteoblastic lineage by reducing the activity of the myoD family, such as that of myoD and myogenin, and by up-regulating inhibitor of DNA binding/differentiation 1 (Id1) and runt-related gene 2 (Runx2) [7,8,9,10,11]
No marked difference was found between the expression level of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA stimulated by the vehicle and that stimulated by recombinant BMP-2, suggesting that the recombinant BMP-2 had no inhibitory effect on the cultured tongues
Summary
In vitro studies using the myogenic cell line C2C12 demonstrate that bone morphogenetic protein-2 (BMP-2) converts the developmental pathway of C2C12 from a myogenic cell lineage to an osteoblastic cell lineage. In vitro studies using the myogenic cell line C2C12 demonstrate that BMP-2 converts the developmental pathway of C2C12 from a myogenic lineage to an osteoblastic lineage by reducing the activity of the myoD family, such as that of myoD and myogenin, and by up-regulating inhibitor of DNA binding/differentiation 1 (Id1) and runt-related gene 2 (Runx2) [7,8,9,10,11]. This conversion of the developmental pathway of C2C12 seems to inhibit myogenic differentiation, including myotube formation. We recently reported that BMPs and their receptors are expressed in the myoblasts and myotubes of mouse embryonic tongues which are actively differentiating and maturating, implying that BMPs play a role in myoblast differentiation [21]
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