The role of PDGF-dependent suppression of apoptosis in differentiating 3T3-L1 preadipocytes.

In a chemically defined serum-free culture system, platelet-derived growth factor (PDGF) as the only externally applied growth factor, in concert with corticosterone, 3-isobutyl-1-methylxanthine (IBMX) and low insulin (1nM), stimulates adipose conversion of 3T3-L1 preadipocytes. Omission of PDGF during the induction period results in loss of differentiation competence and apoptotic cell death. Induction of apoptosis is shown to be clearly mediated by PDGF withdrawal, since neither corticosterone nor IBMX affect the apoptotic behaviour of 3T3-L1 cells. Cell viability in the absence of the survival factor PDGF could be achieved by application of high insulin (1 microM) or ectopical expression of the anti-apoptotic proto-oncogene Bcl-2. However, PDGF-independent suppression of cell death does not trigger adipose conversion in the presence of corticosterone and IBMX. Therefore, we conclude that suppression of apoptosis per se is not permissive for differentiation of 3T3-L1 preadipocytes and PDGF might exert some additional differentiation-promoting effect(s).