The effect of adipocyte differentiation on the capacity of 3T3-L1 cells to undergo apoptosis in response to growth factor deprivation

Abstract

Objective: Little is known about the regulation of apoptosis in the adipocyte. Using the 3T3-L1 cell model of adipogenesis, we investigated whether induction of apoptosis by serum-starvation is differentiation-specific.

Methods: Apoptosis was assessed by phase-contrast microscopy, Hoechst staining and DNA fragmentation. Protein expression levels were evaluated by immunoblot analysis.

Results: Following serum deprivation, Hoechst staining revealed chromatin condensation and formation of apoptotic bodies in 3T3-L1 preadipocytes, but not in differentiated adipocytes. Similarly, although cell cultures of serum-starved 3T3-L1 preadipocytes displayed extensive apoptotic DNA fragmentation, this was barely detectable for cell cultures subjected to differentiation medium, in which 70-90% of the cells had assumed the mature phenotype. Consistent with the ability of the adipocytes to resist apoptosis, immunoblot analysis revealed that differentiated cell cultures expressed Bcl-2 and the endonuclease DNase I at higher and lower levels, respectively.

Conclusion: Expression of cell survival genes is modulated during 3T3-L1 adipocyte differentiation, potentially contributing to the state of resistance to apoptosis observed for mature 3T3-L1 adipocytes upon growth factor deprivation.