Differentiation of skeletal muscle Mesenchymal progenitor cells to myofibroblasts is reversible.

Accumulation of intramuscular adipose tissue (IMAT) and development of fibrous tissues due to accumulation of collagen both affect meat quality such as tenderness, texture, and flavor. Thus, it is important for the production of high-quality meat to regulate the amount of adipose and fibrous tissues in skeletal muscle. IMAT is comprised of adipocytes, while collagens included in fibrous tissues are mainly produced by activated fibroblasts. Both adipocytes and fibroblasts are differentiated from their common ancestors, called mesenchymal progenitor cells (MPC). We previously established rat MPC clone, 2G11 cells. As several reports implicated the plasticity of fibroblast differentiation, in the present study, using 2G11 cells, we asked whether myofibroblasts differentiated from MPC are capable of re-gaining adipogenic potential in vitro. By treating with bFGF, their αSMA expression was reduced and adipogenic potential was restored partially. Furthermore, by lowering cell density together with bFGF treatment, 2G11 cell-derived myofibroblasts lost αSMA expression and showed the highest adipogenic potential, and this was along with their morphological change from flattened- to spindle-like shape, which is typically observed with MPC. These results indicated that MPC-derived myofibroblasts could re-acquire adipogenic potential, possibly mediated through returning to an undifferentiated MPC-like state.