BM-MSCs旁分泌调控小肠上皮干细胞修复小肠黏膜损伤的机制研究

Recent studies have shown that paracrine factors of bone marrow mesenchymal stem cells(BM-MSCs) can serve multiple positive functions in tissue regeneration instesd of MSCs transplantation. However, the key therapeutic paracrine factors and main pathways triggered by MSCs-derived molecules in reversion of injuried intestinal stem cells (IESC) were not defined. In previous work, We provided the first clear evidence that the paracrine action of MSCs leads to an intestinal cytoprotective effect by inhibiting epithelial cellular death and stimulating regeneration in vivo and vitro. Moreover, we identified 10 molecules up-regulated during intestinal regeneration, which may play key roles in the recovery of irradiated intestine. Base on this fingding, we now further study the mechanism of MSCs-derived molecules in injuried IESC in order to indentify the key therapeutic paracrine factors and main pathways triggered by MSCs-derived molecules in reversion of injuried IESC. This work would be great valuable in the field of injuried intestinal recovery.

近年研究发现，移植骨髓间充质干细胞(BM-MSCs)来源的旁分泌因子能够替代传统的干细胞移植修复多种组织损伤，但其修复小肠黏膜损伤的具体机制不明。本课题组在前期发现BM-MSCs旁分泌因子抑制小肠上皮细胞凋亡、促进其增殖、以及对其关键因子进行蛋白芯片筛选的工作基础上，进一步研究BM-MSCs旁分泌对肠黏膜核心细胞小肠上皮干细胞(IESC)的增殖、分化作用，寻找其调节IESC增殖、分化的关键细胞因子和主要信号通路。提出小肠黏膜损伤后，BM-MSCs分泌的修复因子增多，其中的关键因子通过相关信号通路调节受损IESC的增殖、分化，加速受损肠黏膜修复这一新的理论模式。本课题在肠道修复领域具有重大的理论和应用价值。

1辐射炎症环境下激活的MSCs旁分泌因子（MSC-CMIR）能延长辐射损伤大鼠的生存率，促进损伤小肠结构和功能的恢复，而正常培养环境的MSCs旁分泌因子（MSC-CMNOR）未见明显的修复作用。.2 其修复机制包括促进小肠上皮细胞增殖，抑制细胞凋亡，促进小肠干细胞再生，抑制系统和局部炎症因子表达，上调Treg细胞比例。.3 与MSC-CMNOR相比，MSC-CMIR中多种重要的生长因子、趋化因子、基质修复相关因子显著升高，这些因子具有促进血管生成，抑制凋亡，增强细胞再生，促进干细胞归巢等一系列与小肠修复相关的生物学特性。.4 进一步的抗体中和实验发现，IGF-1可能是MSC-CMIR修复辐射小肠黏膜损伤的关键因子。.5 用于激活MSCs的辐射损伤小肠上皮IEC-6细胞分泌多种前炎因子，其中以肿瘤坏死因子-α（Tumor necrosis factor-α, TNF-α）、白介素-1β（Interleukin-1β, IL-1β）和一氧化氮（nitric oxide, NO）辐射后升高最为显著。.6 外源性添加TNF-α, IL-1β和NO供体能诱导MSCs分泌多种重要的生长因子，修复辐射损伤小肠，其旁分泌因子的变化以及修复效应与MSC-CMIR相似。而阻断上述三种因子的表达，能够显著抑制MSC-CMIR旁分泌改变以及对损伤小肠黏膜的修复作用，表明MSC-CMIR的优势修复作用主要通过TNF-α, IL-1β和NO诱导实现。.7 TNF-α, IL-1β和NO供体能诱导MSCs的血红素加氧酶-1（heme oxygenase-1, HO-1）表达升高，而敲除HO-1的表达可使MSCs的多种重要旁分泌因子分泌显著减少，部分因子恢复激活前水平。输注敲除HO-1的MSCs旁分泌因子，与未敲除前比较，辐射损伤大鼠生存率、损伤小肠增殖、凋亡以及炎症情况均明显恶化，表明MSC-CMIR的优势修复作用可能部分通过TNF-α, IL-1β和NO上调MSCs血红素加氧酶-1表达实现。