LL-37-EGF通路在肠成纤维细胞调节肠粘膜屏障功能中的机制研究

The crosstalk between the intestinal fibroblasts and intestinal epithelial cells (IEC) plays an important role in the regulation of intestinal epithelial barrier. However, the mechanism is still unclear. Intestinal fibroblasts derived EGF can stimulate proliferation and differentiation of IEC, meanwhile maintain the intestinal barrier. We hypothesize that endogenous antimicrobial peptide LL-37，which derived from IEC, may activate the receptor P2X7 to stimulate EGF expression derived from intestinal fibroblasts. Fibroblast-IEC co-cultured model and mouse mucosal injury model will be established, RNA interference will be used to investigate if LL-37 via P2X7 activation to stimulate the expression of EGF in intestinal fibroblasts. furthermore to investigate the role of LL-37-EGF pathway in the maintenance of intestinal epithelial barrier function under physiological and pathological conditions, then provide a theoretical basis to clarify the important role of the intestinal fibroblast cells in the maintenance of the intestinal mucosal barrier function and provide new ideas for the research of prevention and treatment about intestinal mucosal barrier dysfunction.

肠成纤维细胞与肠上皮细胞（IEC）间的对话可能在肠粘膜屏障功能调节中起重要作用，但对其调控机制尚缺乏深入了解。肠成纤维细胞来源的EGF可明显促进IEC的增殖、分化，促进肠粘膜屏障功能，我们推测IEC来源的内源性抗菌肽LL-37则可能通过其受体P2X7途径调节肠成纤维细胞表达EGF。因此，本研究拟通过体外肠成纤维细胞-IEC共培养模型及肠粘膜功能损伤动物模型，利用RNA干扰等技术，观察LL-37是否是通过激活P2X7促进肠成纤维细胞中EGF的表达，验证LL-37-EGF通路的存在，并进一步评价LL-37-EGF通路在生理及病理条件下对维持肠粘膜屏障功能的重要意义，为阐明肠成纤维细胞在维持肠粘膜屏障功能中的重要作用提供理论依据，为肠粘膜屏障功能障碍防治研究提供新思路。

肠黏膜屏障是机体防御的重要屏障，肠黏膜缺氧可能是多种急慢性病理条件诱发肠屏障功能(IBF)损伤的关键机制。我们前期研究发现，缺氧诱导因子（HIF-1α）在维护肠粘膜屏障中起着关键性作用，其转录活性受控于多个信号通路， 其中骨肉瘤蛋白（OS-9）能够明显抑制HIF-1α的活性。由此我们推测，OS-9可以通过调节HIF-1α来调控肠黏膜屏障功能。本项目通过化学合成特异性siRNA干扰和慢病毒转染过表达，观察到OS-9在缺氧条件下能上调紧密连接蛋白claudin-1和occludin的表达，从而起到对肠黏膜屏障的保护作用。在机制部分，我们发现OS-9 调控肠上皮屏障是并不依赖HIF-1α的，而是通过p38信号途径，当阻断p38信号通路后，可显著抑制OS-9对肠上皮屏障的保护功能。此外，肠上皮下成纤维细胞在维护肠黏膜屏障功能中也发挥了重要作用。在炎症模型下，其通过与肠上皮细胞之间的crosstalk，促使上皮细胞分泌内源性抗菌肽LL-37，从而参与肠上皮的增殖、分化以及免疫调节。通过本项目，不但能够完善肠黏膜屏障功能调控的分子机制，也将为临床炎症性肠病的治疗提供理论依据。且在该项目的资助下，共发表带基金标注的SCI论文3篇，其中1篇已接收，2篇已见刊。