Influence of growth factors on growth and differentiation of 3T3-L1 preadipocytes in serum-free conditions.

The role of platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) in the adipose differentiation of 3T3-L1 preadipocytes was investigated in a chemically defined culture system. To eliminate the influence of unidentified adipogenic compounds present in serum or serum-derived medium additives, cells from a stock culture were grown to confluence under serum-free conditions in the presence of recombinant PDGF and insulin. To trigger differentiation of these cells, the usual stimuli for adipogenesis such as corticosterone and insulin at supraphysiological concentrations together with 3-isobutyl-1-methylxanthine were required but not sufficient for maximal stimulation. Either PDGF or EGF had to be added with insulin at a supraphysiological concentration or insulin-like growth factor-1 for four days in order to obtain complete differentiation. These results indicate that differentiation of 3T3-L1 preadipocytes is possible by replacing unknown serum factors by a combination of defined growth factors.