Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
Stem Cells Dev. 2012 Sep 20;21(14):2703-17. doi: 10.1089/scd.2011.0604. Epub 2012 May 17.
Bone marrow stem cells (BMSCs) have been shown to improve neurological function recovery in cerebral ischemia. Hypoxia-inducible factor-1 (HIF-1) α-AA is a more stable mutant form of HIF-1α, which is a crucial oxygen-sensitive regulator. To investigate the protective effects of HIF-1α-AA-modified BMSCs on neuron survival in cerebral ischemia models, we co-cultured HIF-1α-AA-modified BMSCs with neuron-like cells (PC12 cells) and observed a significant increase in the release of vascular endothelial growth factor (VEGF) from BMSCs, the decreased PC12 cell apoptosis, and the upregulation of Survivin expression reduced by hypoxia in PC12 cells compared to enhanced green fluorescent protein (EGFP) BMSCs. In addition, to explore whether VEGF secreted by HIF-1α-AA-modified BMSCs plays an important role in preventing hypoxia-induced apoptosis and the possible mechanism involved, exogenous VEGF were applied and the similar protective effects on PC12 cells were observed in vitro. Furthermore, hypoxia reduced the expression of phosphorylated Akt and phosphorylated FoxO1, whereas the administration of VEGF reversed these changes. Transfection of FoxO1 H215R, a DNA-binding mutant, abrogated the inhibitory ability on Survivin promoter activity, whereas FoxO1 AAA, the active form of FoxO1, presented further repression on Survivin promoter, indicating that FoxO1 directly binds on Survivin promoter as a transcriptional repressor and that phosphorylation status of FoxO1 affects its inhibition on the Survivin promoter. Transplantation of HIF-1α-AA-modified BMSCs after cerebral ischemia in vivo sufficiently reduced neurons apoptosis, decreased cerebral infarction volume, and induced a significant improvement on the modified neurological severity score compared to the EGFP BMSCs group. In conclusion, HIF-1α-AA-modified MSCs showed an obvious protective effect on neuron-like cells or neuron after ischemia in vitro and in vivo, at least in part, through the VEGF/PI3K/Akt/FoxO1 pathway.
骨髓间充质干细胞（BMSCs）已被证明可改善脑缺血后的神经功能恢复。缺氧诱导因子-1（HIF-1）α-AA 是 HIF-1α 的一种更稳定的突变形式，是一种关键的氧敏感调节因子。为了研究 HIF-1α-AA 修饰的 BMSCs 对脑缺血模型中神经元存活的保护作用，我们将 HIF-1α-AA 修饰的 BMSCs 与神经元样细胞（PC12 细胞）共培养，观察到 BMSCs 中血管内皮生长因子（VEGF）的释放显著增加，PC12 细胞凋亡减少，缺氧诱导的 Survivin 表达上调，与增强型绿色荧光蛋白（EGFP）BMSCs 相比。此外，为了探讨 HIF-1α-AA 修饰的 BMSCs 分泌的 VEGF 是否在预防缺氧诱导的细胞凋亡中发挥重要作用及可能涉及的机制，我们应用外源性 VEGF，并观察到其对 PC12 细胞的类似保护作用。此外，缺氧降低了磷酸化 Akt 和磷酸化 FoxO1 的表达，而 VEGF 的给药逆转了这些变化。FoxO1 H215R 的转染，一种 DNA 结合突变体，消除了对 Survivin 启动子活性的抑制能力，而 FoxO1 AAA，FoxO1 的活性形式，对 Survivin 启动子进一步抑制，表明 FoxO1 直接作为转录抑制剂结合 Survivin 启动子，FoxO1 的磷酸化状态影响其对 Survivin 启动子的抑制作用。体内脑缺血后移植 HIF-1α-AA 修饰的 BMSCs 可充分减少神经元凋亡，减少脑梗死体积，并显著改善改良神经严重程度评分，与 EGFP BMSCs 组相比。总之，HIF-1α-AA 修饰的 MSC 在体内和体外对缺血后的神经元样细胞或神经元均显示出明显的保护作用，至少部分通过 VEGF/PI3K/Akt/FoxO1 途径。
