Novel stemness markers in murine adipose-derived stem cells

抄録

Obesity is associated with proliferation and differentiation of adipose-derived stem cells (ADSCs) into mature adipocytes. Nutritional stimuli induce ADSCs proliferation and differentiation and this process is well established because master regulators of adipogenic differentiation, C/EBPalpha and PPARgamma were identified. However, under normal condition, molecular mechanisms to maintain ADSCs in a quiescent and undifferentiated state are largely unknown.

To identify genes essential for the maintenance, microarray analysis was performed for comparison of gene expression between freshly isolated murine ADSCs and 4-day cultured ADSCs (preadipocytes). Among the 223 up-regulated transcriptional factor genes in ADSCs, we focused on nuclear receptor 4a (Nr4a) family, which play diverse roles including metabolic processes. ADSCs selective expressions of Nr4a were confirmed by RT-qPCR analysis. To evaluate roles of Nr4a in adipogenic differentiation, we retrovirally overexpressed Nr4a into preadipocytes. Nr4a-overexpressed preadipocytes showed reduced accumulation of lipid droplet and decreased expressions of C/EBPalpha and PPARgamma. ChIP analysis confirmed that Nr4a directly bound to C/EBPalpha and PPARgamma promotor. Nr4a family is induced by multiple signals such as cyclic AMP and MAP kinases in a cell type-specific manner. We next tested the effects of the cAMP signal in ADSCs. Application of a cAMP analogue to ADSCs induced Nr4a expressions and decreased expressions of PPARgamma. These data suggested that Nr4a inhibited ADSCs differentiation in a cAMP-dependent manner.