Figure 1

Insulin-like growth factor (IGF)-1 and ALK inhibition counteracts interleukin (IL)-1α- and tumor necrosis factor (TNF)-α-induced inhibition of human skeletal muscle cell (HuSKMC) differentiation. (A) HuSKMC myotubes differentiated for 5 days in the absence (Con) and presence of IL-1α (0.1 ng/ml) and TNF-α (0.1 ng/ml), alone and in combination with IGF-1 (100 nmol/l) or SB431542 (1 μmol/l), were stained with anti-myosin heavy chain (MyHC) and DAPI. Shown are representative pictures and analysis of fusion index which was determined as the percentage of nuclei occurring in myotubes stained with MyHC on four pictures. Data are means ± SEM from three to six independent experiments. Differences from untreated HuSKMCs (control; first column),*P < 0.05; differences from IL-1α- and TNF-α-treated HuSKMCs (control; second and third column), #P < 0.05. (B) Analysis of creatine kinase (CK) activity in HuSKMC myotubes differentiated for 4 days and treated with either IL-1α (0.01-0.1 ng/ml) and TNF-α, alone (0.01 to 0.1 ng/ml) or in combination with IGF-1 (100 nmol/l) or SB431542 (1 μmol/l). Data are expressed as percentage of control untreated HuSKMCs. Data are means ± SEM from four to nine independent experiments. Differences from untreated HuSKMCs (control; first column),*P < 0.05; differences from IL-1α- and TNF-α-treated HuSKMCs (control; second to fourth columns), #P < 0.05.