Qian Shu-Wen, Li Xi, Zhang You-You, Huang Hai-Yan, Liu Yuan, Sun Xia, Tang Qi-Qun
Institute of Stem Cell Research and Regenerative Medicine, Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, PR China.
BMC Dev Biol. 2010 May 7;10:47. doi: 10.1186/1471-213X-10-47.
Adipocyte hyperplasia is associated with obesity and arises due to adipogenic differentiation of resident multipotent stem cells in the vascular stroma of adipose tissue and remote stem cells of other organs. The mechanistic characterization of adipocyte differentiation has been researched in murine pre-adipocyte models (i.e. 3T3-L1 and 3T3-F442A), revealing that growth-arrest pre-adipocytes undergo mitotic clonal expansion and that regulation of the differentiation process relies on the sequential expression of three key transcription factors (C/EBPbeta, C/EBPalpha and PPARgamma). However, the mechanisms underlying adipocyte differentiation from multipotent stem cells, particularly human mesenchymal stem cells (hBMSCs), remain poorly understood. This study investigated cell cycle regulation and the roles of C/EBPbeta, C/EBPalpha and PPARgamma during adipocyte differentiation from hBMSCs.
Utilising a BrdU incorporation assay and manual cell counting it was demonstrated that induction of adipocyte differentiation in culture resulted in 3T3-L1 pre-adipocytes but not hBMSCs undergoing mitotic clonal expansion. Knock-down and over-expression assays revealed that C/EBPbeta, C/EBPalpha and PPARgamma were required for adipocyte differentiation from hBMSCs. C/EBPbeta and C/EBPalpha individually induced adipocyte differentiation in the presence of inducers; PPARgamma alone initiated adipocyte differentiation but the cells failed to differentiate fully. Therefore, the roles of these transcription factors during human adipocyte differentiation are different from their respective roles in mouse.
The characteristics of hBMSCs during adipogenic differentiation are different from those of murine cells. These findings could be important in elucidating the mechanisms underlying human obesity further.
脂肪细胞增生与肥胖相关，是由于脂肪组织血管基质中的常驻多能干细胞及其他器官的远程干细胞发生脂肪生成分化所致。在小鼠前脂肪细胞模型（即3T3-L1和3T3-F442A）中对脂肪细胞分化的机制特性进行了研究，结果表明生长停滞的前脂肪细胞会经历有丝分裂克隆扩增，且分化过程的调控依赖于三种关键转录因子（C/EBPβ、C/EBPα和PPARγ）的顺序表达。然而，多能干细胞，尤其是人间充质干细胞（hBMSC）向脂肪细胞分化的潜在机制仍知之甚少。本研究调查了hBMSC向脂肪细胞分化过程中的细胞周期调控以及C/EBPβ、C/EBPα和PPARγ的作用。
利用BrdU掺入试验和人工细胞计数表明，在培养中诱导脂肪细胞分化会导致3T3-L1前脂肪细胞而非hBMSC经历有丝分裂克隆扩增。敲低和过表达试验表明，hBMSC向脂肪细胞分化需要C/EBPβ、C/EBPα和PPARγ。在诱导剂存在的情况下，C/EBPβ和C/EBPα分别诱导脂肪细胞分化；单独的PPARγ启动脂肪细胞分化，但细胞未能完全分化。因此，这些转录因子在人类脂肪细胞分化过程中的作用与其在小鼠中的各自作用不同。
hBMSC在脂肪生成分化过程中的特征与鼠细胞不同。这些发现可能对进一步阐明人类肥胖的潜在机制具有重要意义。
