激动核受体FXR促进移植间充质干细胞治疗缺血性心衰的作用及机制研究

Mesenchymal stem cells (MSCs) transplantation is a potential therapeutic approach for post-MI heart failure. However, the poor survival and weak repairing capability of transplanted MSCs in the ischemic environment limit their therapeutic efficacy. Our preliminary study demonstrated that activation of nuclear receptor FXR ameliorates post-MI cardiac dysfunction and remodeling by stimulating adiponectin secretion (Cardiovas Res, 2018). Previous studies found that nuclear receptor RARs regulate the proliferation and differentiation of neural and hematopoietic stem cells. However, whether FXR regulates the regenerative capability of MSCs for ischemic heart diseases has never been reported. Here we found that FXR activation by GW4064 significantly reduced H2O2-induced apoptosis of MSCs. Furthermore, the conditioned medium collected from GW4064 treated MSCs exerted stronger anti-apoptotic effect on cardiomyocytes. RNA-seq and real-time PCR analysis showed that GW4064 activates Nrf2/HO-1 signaling and increases apelin, which may respectively mediate the anti-apoptotic effect of GW4064 upon MSCs and its paracrine anti-apoptotic effect on cardiomyocytes. Here we hypothesize that FXR activation enhances MSCs-mediated cardioprotection by promoting MSCs survival via Nrf2/HO-1 signaling and enhancing the paracrine anti-apoptosis of MSCs via apelin secretion. The project aims to elucidate the new role of FXR and the underlying mechanisms, which may help to find a new small-molecular drug (GW4064) to improve MSCs-based therapy for ischemic heart failure.

移植间充质干细胞（MSCs）是防治心梗（MI）后心衰的重要方向，但移植MSCs难以存活、修复能力弱等难题尚待解决。申请人发现，激动核受体家族法尼酯X受体（FXR）通过促进脂肪因子分泌发挥心脏保护作用（Cardiovas Res, 2018）。而既往研究证实核受体RARs可调控神经及造血干细胞的增殖及分化。然而，FXR能否调节MSCs心肌修复能力尚无报道。预实验发现，FXR激动剂预处理可显著减少H2O2诱导的MSCs的细胞凋亡且预处理后培养上清可发挥心肌细胞保护作用，RNA-seq结果提示，上述效应可能与Nrf2/HO-1信号及心肌保护因子Apelin相关。据此我们假设：激动FXR一方面通过Nrf2/HO-1增强MSCs存活，另一方面促进Apelin释放增强其旁分泌心肌保护而发挥双重作用。本项目可望首次阐明FXR促进MSCs治疗缺血性心衰的作用及机制，探索药物提高MSCs疗效的临床新策略。

背景：胆汁酸-FXR信号激活在缺血心肌损伤中发挥重要作用。然而胆汁酸-FXR信号能否调节间充质干细胞（MSC）的心肌修复能力尚无报道。.方法：将脂肪来源MSC（ADSC）分别转染对照腺病毒（ADSC-con）或过表达FXR的腺病毒（ADSC-FXR）。应用左冠状动脉结扎术建立小鼠心梗（MI）模型，立即对各小鼠心梗周边区3个固定部位注射CM-DiI或tdTomato标记的ADSC。采用靶向代谢组学检测心肌梗死后心肌中胆汁酸变化。结合转录组测序、液相色谱/质谱及功能缺失实验寻找下游分子机制。离体研究采用ADSC、大鼠冠状动脉内皮细胞、乳鼠心肌细胞和FXR配体奥贝胆酸（OCA）。.结果：在体水平证实，FXR过表达显著增加MI后3天和7天时心肌内注射ADSC的存活，且ADSC-FXR显著改善MI小鼠的存活率，提高左心室射血分数（LVEF）、降低左心室舒张末内径（LVIDd）和收缩期内径（LVIDs），降低心肌纤维化面积，增加梗死周边血管密度、减少心肌细胞凋亡。离体水平证实，FXR过表达通过促进Angptl4的表达和分泌增强ADSC的促血管新生能力。而与在体实验结果不同，FXR过表达不能改善体外培养ADSC的生存率。结合靶向代谢组学结果证实，心肌微环境中存在胆汁酸池，ADSC-FXR需响应内源性胆汁酸信号，FXR被激活后通过促进Nqo-1的表达增强抗凋亡能力。最终证实被激活后的FXR需与RXRα形成二聚体，进一步能在转录水平直接调控Angptl4和Nqo-1表达。.结论及科学意义：心肌微环境中存在胆汁酸池，过表达FXR可促进移植ADSC对内源性胆汁酸信号的响应。胆汁酸-FXR信号激活后，一方面通过促进Angptl4的表达和分泌，增强了ADSC的旁分泌促血管新生能力；另一方面通过促进Nqo-1的表达，增强ADSC的生存能力，从“质”和“量”两个方面增强了ADSC的心肌保护能力。本项目揭示了胆汁酸-FXR信号对于ADSC的心肌修复作用至关重要，靶向这一信号是治疗MI的潜在策略。

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