Recruitment and differentiation of intramuscular preadipocytes in stromal-vascular cell cultures derived from neonatal pig semitendinosus muscles.

The present study examined the influence of dexamethasone (DEX) treatment on preadipocyte recruitment and expression of CCAAT/enhancing binding protein-alpha (C/EBPalpha) and peroxisome proliferator-activated receptor-gamma (PPARgamma) proteins in stromal-vascular (SV) cell cultures derived from neonatal subcutaneous adipose tissue and semitendinosus muscles. One adipose tissue SV cell culture and one semitendinosus muscle SV cell culture were established from each of six young pigs (5 to 7 d of age). Conventional SV cell-culture procedures were used to digest adipose and muscle tissue and to harvest and culture adipose and muscle SV cells. Muscles were digested after the removal of all visible connective tissue from the excised muscle. One hour after seeding, muscle SV cell cultures were rinsed and refed new media to remove debris and insoluble muscle protein. The SV cell cultures were double-stained for lipid and the AD-3 antibody, a preadipocyte marker, at 1, 3, and 6 d and were double-stained for lipid and C/EBPalpha or PPARgamma at d 6. Preadipocytes were randomly distributed and not clustered after 1 d in muscle and adipose SV cultures. Regardless of treatment, relative and absolute fat cell numbers were lower (P < 0.05) in muscle than in adipose-SV cell cultures. The DEX treatments produced similar magnitudes of increase in relative and absolute preadipocytes and adipocytes in muscle- and adipose-SV cultures. Several extracellular matrix substrata had no influence on adipogenesis in muscle-SV cell cultures. These studies indicate that muscle-SV cultures are characterized by a low number of adipocytes under basal conditions and a low number of glucocorticoid-responsive preadipocytes.