Zhang Shaoheng, Zhao Lan, Wang Jiahong, Chen Nannan, Yan Jian, Pan Xin
Department of Cardiology, the Third Affiliated Hospital of Southern Medical University, 183 West Zhongshan Road, Tianhe District, Guangzhou 510630, China.
Department of Cardiology, Dahua Hospital, 901 Laohumin Rd, Xuhui District, Shanghai 200237, China.
Cell Death Dis. 2017 Jan 12;8(1):e2548. doi: 10.1038/cddis.2016.480.
Poor cell survival and limited functional benefits have restricted mesenchymal stem cell (MSC) efficacy for treating myocardial infarction (MI), suggesting that a better understanding of stem cell biology is needed. The transcription factor HIF-2α is an essential regulator of the transcriptional response to hypoxia, which can interact with embryonic stem cells (ESCs) transcription factor Oct4 and modulate its signaling. Here, we obtained very small embryonic-like mesenchymal stem cells (vselMSCs) from MI patients, which possessed the very small embryonic-like stem cells' (VSELs) morphology as well as ESCs' pluripotency. Using microarray analysis, we compared HIF-2α-regulated gene profiles in vselMSCs with ESC profiles and determined that HIF-2α coexpressed Oct4 in vselMSCs similarly to ESCs. However, this coexpression was absent in unpurified MSCs (uMSCs). Under hypoxic condition, vselMSCs exhibited stronger survival, proliferation and differentiation than uMSCs. Transplantation of vselMSCs caused greater improvement in cardiac function and heart remodeling in the infarcted rats. We further demonstrated that HIF-2α and Oct4 jointly regulate their relative downstream gene expressions, including Bcl2 and Survivin; the important pluripotent markers Nanog, Klf4, and Sox2; and Ang-1, bFGF, and VEGF, promoting angiogenesis and engraftment. Importantly, these effects were generally magnified by upregulation of HIF-2α and Oct4 induced by HIF-2α or Oct4 overexpression, and the greatest improvements were elicited after co-overexpressing HIF-2α and Oct4; overexpressing one transcription factor while silencing the other canceled this increase, and HIF-2α or Oct4 silencing abolished these effects. Together, these findings demonstrated that HIF-2α in vselMSCs cooperated with Oct4 in survival and function. The identification of the cooperation between HIF-2α and Oct4 will lead to deeper characterization of the downstream targets of this interaction in vselMSCs and will have novel pathophysiological implications for the repair of infarcted myocardium.
细胞存活率低和功能效益有限限制了间充质干细胞（MSC）治疗心肌梗死（MI）的疗效，这表明需要更好地理解干细胞生物学。转录因子HIF-2α是低氧转录反应的重要调节因子，它可与胚胎干细胞（ESC）转录因子Oct4相互作用并调节其信号传导。在此，我们从MI患者中获取了非常小的胚胎样间充质干细胞（vselMSC），其具有非常小的胚胎样干细胞（VSEL）的形态以及ESC的多能性。通过微阵列分析，我们比较了vselMSC中HIF-2α调节的基因谱与ESC谱，并确定HIF-2α在vselMSC中与Oct4共表达，这与ESC相似。然而，在未纯化的MSC（uMSC）中不存在这种共表达。在低氧条件下，vselMSC比uMSC表现出更强的存活、增殖和分化能力。vselMSC移植使梗死大鼠的心脏功能和心脏重塑有更大改善。我们进一步证明，HIF-2α和Oct4共同调节其相对下游基因表达，包括Bcl2和Survivin；重要的多能性标志物Nanog、Klf4和Sox2；以及Ang-1、bFGF和VEGF，促进血管生成和植入。重要的是，这些效应通常因HIF-2α或Oct4过表达诱导的HIF-2α和Oct4上调而放大，在HIF-2α和Oct4共过表达后产生最大改善；过表达一个转录因子同时沉默另一个转录因子会消除这种增加，而HIF-2α或Oct4沉默则消除这些效应。总之，这些发现表明vselMSC中的HIF-2α与Oct4在存活和功能方面相互协作。HIF-2α与Oct4之间协作关系的确定将导致对vselMSC中这种相互作用的下游靶点进行更深入的表征，并将对梗死心肌的修复产生新的病理生理学意义。
