Growth and differentiation of cultured satellite cells from callipyge and normal lambs

Abstract

We tested whether the muscle enlargement found in callipyge sheep is linked to increased proliferation, differentiation, and protein accrual of cultured satellite cells. Satellite cells were isolated from the longissimus muscle of three callipyge and three normal lambs. The satellite cells were grown using serum from horse, normal lambs, and callipyge lambs and cultured under conditions that promoted differentiation into myotubes and accumulation of myofibrillar protein. There was no difference in the population doubling times (PDT) or fusion percentages for callipyge and normal satellite cells, but PDT was longer (P < 0.05) for satellite cells grown in callipyge serum (pooled mean PDT = 22 h) than for cells grown in normal sheep serum (PDT = 20 h) or horse serum (PDT = 18 h). The protein:DNA ratios of the cultures increased during 96 h in differentiation media (P < 0.01), but there was no difference in protein:DNA ratios between cells from callipyge and normal lambs. These results suggest that muscle hypertrophy of callipyge sheep is not linked to the inherent capacity of their cultured satellite cells to proliferate, fuse or accrue protein, but hypertrophy may be linked to the influence of serum-born factors on satellite cell proliferation.