| Macrophage migration inhibitory factor was originally described as an important regulator of inflammation that inhibits the random migration of macrophages. Increasing studies show that MIF can also regulate adipogenesis and may promote macrophage recruitment to adipose tissue during obesity, which subsequently leads to inflammation and insulin resistance. Recent investigations reveal that the number of macrophages in skeletal muscle is also increasing during obesity, but the underlying causes and its biological effects remain elusive. Considering its close relationship with energy metabolism, we assumed that MIF may play a role in the proliferation and differentiation of myoblasts, and get involved in the interaction network of macrophages,adipocytes and skeletal muscle cells.Using C2C12myogenic cells as a model, we investigated the effects of MIF on proliferation and differentiation of myoblasts, and exploited the molecular mechanisms using various techniques including cell transfection, RNAi, MTT, FACS, Real time PCR and Western Blotting. The major results of this study are as follows:1. The level of Mif mRNA was down-regulated during onset of C2C12cell differentiation, suggesting MIF may play a role in the early phase of myogenesis.2. Immunofluoresence microscopy found that overexpression of Mif in C2C12cells inhibits myogenesis and impairs myotube formation.3. Knockdown of Mif in C2C12cells by siRNA retarded cell cyle at G1, partially due to the down-regulation of CyclinDl and CDK4.4. Overexpressing Mif in C2C12cells reduced the mRNA level of MyoD, whereas Mif knockdown up-regulated its level and inhibited the expression of Myf5, and increased p21expression. Besides, ISO-1(MIF inhibitor) treatment led to a dose-dependent increase in expression of MyoD, p21and MyoG.In conclusion, our results indicate that MIF can retard cell cycle exit during proliferation of myoblasts, and thus inhibit subsequent differentiation. |
PDF Full Text Request