Abstract 248: Homeobox C8 Suppresses Adipogenesis of Human Adipose Tissue-Derived Stem Cells
Background: Adipose tissue remodels consistently responding to dietary condition that causes the proliferation and maturation of preadipocytes. Although understanding the controlling machinery of adipogenesis would be beneficial for the treatment of obesity-related diseases, the precise molecular mechanism is not fully elucidated. A number of developmental genes, including Homeotic (Hox) genes are expressed unproportionally highly in adipose tissue, but their significance is not understood. Among them, we focused on Homeobox C8 (Hoxc8), which is expressed more strongly in white or visceral, rather than in brown or subcutaneous adipose tissue.
Methods and Results: We accustomed that Hoxc8 is more strongly expressed in human primary adipose tissue-derived stem cells (ADSCs) than in other cells we examined. Western blot analysis revealed that Hoxc8 was downregulated along adipogenesis and immunocytochemistry showed that the expression of Hoxc8 was almost lost in matured adipocytes in vitro. Forced expression of Hoxc8 by retroviral vector strongly inhibited adipogenesis and suppressed the expression of adipocyte differentiation marker genes such as PPARγ, aP2 and C/EBPα. To the contrary, Hoxc8 overexpression showed no effect on osteoblast or chondroblast differentiation. Interestingly, we found that the amount of Hoxc8 mRNA did not change significantly along differentiation, implying that the expression of Hoxc8 might be regulated post-transcriptionally. Accumulating evidences showed that several Hox genes are regulated by microRNA that targets the Hox gene mRNA 3′UTR. We found that miR-196a, which targets Hoxc8, was upregulated along adipogenesis in ADSCs by real time PCR. Antisense oligonucleotide that specifically antagonizes the function of miR-196a partially suppressed adipogenesis. Finally, lentiviral vector-mediated transfer of miR-196a and Hoxc8 shRNA suppressed the expression of Hoxc8, and promoted adipogenesis in ADSCs accompanied by enhanced expression of PPARγ, aP2 and C/EBPα.
Conclusion: Our results suggest that Hoxc8, which is strongly expressed in white and visceral adipose tissue, acts as a suppressor of adipogenesis in ADSCs and that the expression might be fine-tuned by miR-196a.