Variation in response to growth factor stimuli in satellite cell populations

Variation in response to growth factor stimuli in myogenic satellite cell populations was investigated using a clonal-derived satellite cell culture system. Satellite cell clones were established from one muscle from one individual animal. One clone ("Early") which reached confluence on day 19 and one clone ("Late"), which reached confluence on day 29, were chosen for further examination. In previous studies, these two clones were found to differ in their growth rates in serum-containing medium. In the present study, the influence of growth factors on the proliferation of the two clones was compared in serum-free defined medium. Although basic fibroblast growth factor (bFGF), insulin-like growth factor-I (IGF-I), insulin, and platelet-derived growth factor-BB (PDGF-BB) stimulated proliferation of both clones, the Early clone was more responsive to all growth factors tested than the Late clone (P < or = 0.05). The Early clone was also more responsive to the proliferative and differentiative depressing effects of administered transforming growth factor-beta (P < or = 0.05). Examination of properties of the PDGF, FGF, and IGF-I receptors on these two clones revealed no differences in either dissociation constants or receptor numbers (P > or = 0.05). The results suggest that there is heterogeneity in satellite cell response to growth factors.