Temporal expression of growth factor genes of primary porcine satellite cells during myogenesis

Abstract

ABSTRACTThe present experiment was undertaken to study the transcription of members of the insulin‐like growth factor (IGF) system and myostatin in porcine satellite cells through myogenesis and to study the effects of 1 µmol/L insulin on stimulating fusion. Cultured cells were harvested at 50 and 80% confluence and at days 1, 2, 3 and 4 following induction of fusion and differentiation. Increased levels of myogenin transcription and creatine kinase from 50% confluence until day 2 indicated that fusion and differentiation were induced. The mRNA abundance of IGF‐I (P < 0.001), IGF‐II (P < 0.001), IGF binding protein (BP) 5 (P < 0.01), type I IGF receptor (P < 0.001) and myostatin (P < 0.01) increased from proliferation to differentiation. Insulin stimulated differentiation as indicated by elevated creatine kinase activity (P < 0.001) but did not affect myogenin mRNA abundance (P = 0.98). Insulin downregulated transcription of IGF‐I (P < 0.01) and during the first 2 days after switching to differentiation medium insulin downregulated IGF receptor transcription (P < 0.001), whereas insulin did not affect transcription of IGF‐II (P = 0.06), IGFBP5 (P = 0.76) or myostatin (P = 0.50). In conclusion, transcriptions of IGF‐I, IGF‐II, type I IGF receptor, IGFBP5 and myostatin were changed during myogenesis, suggesting autocrine/paracrine roles in regulating the transition from proliferation to differentiation of porcine satellite cells.