Figure 2.

Cell density, serum, and growth factor regulation of C2C12 proliferation. A and B, The indicated number of cells were plated in DMEM/10% FBS, in 96-well plates and cultured for 24 hours. Cells were then cultured in serum-free (SF) DMEM/0.1% BSA with recombinant human myostatin (rhMSTN) (15) alone or in combination with 2.7 nM IGF-I. C, Cells were also cultured with or without 2% FBS and similarly treated with different concentrations of rhMSTN (M) or TGFβ1 (T). In each experiment, cells were treated for 48 hours before measuring cell number (optical density units [ODUs]). Significant differences are indicated by asterisks (panel A; compared with 0 controls) or by different letters whereas the same letters signify no difference (P ≤ .05).