PPARγ/STAT5A pathway plays a key factor in adipogenesis of hBMSCs and 3T3‐L1 preadipocytes

Adipogenesis is a complex process involving proliferation of precursor cells, their commitment to the adipogenic lineage and terminal differentiation. STAT proteins are expressed and regulated by cytokine‐mediated phosphorylation and nuclear translocation during adipogenesis of human bone marrow derived stromal cells. However, the role of STAT5A and STAT5B in adipogenesis is not clearly understood. We observed that the STAT5A is regulated at transcriptional level by PPARγ and RXRα while STAT5B is regulated by C/EBPβ and C/EBPα. The PPRE regulatory element of STAT5A existed at promoter region ranging −346 to −101 and the C/EBP regulatory element was located on −196 to −118 region of STAT5B promoter. The C/EBPβ and C/EBPα binds to STAT5B promoter region while PPARγ binds to that of STAT5A in EMSA and ChIP assay. RNA interference with STAT5A completely blocked the differentiation, while inhibition of STAT5B only partially blocked the differentiation. We propose that C/EBPα, C/EBPβ and PPARγ controls adipogenesis by regulating STAT5B and STAT5A, respectively, and that the STAT5A is an absolute necessity while STAT5B is plays supplementary role during the adipogenesis.