Notch与Lgr5/Wnt信号通路在溃疡性结肠炎粘膜损伤与再生修复中作用的机制研究

The characteristic pathologic changes of ulcerative colitis (UC) are the lack of mucosal mucus layer and decrease of goblet cells. The Lgr5 positive cells in the basal layer of crypts possess the potential of self regeneration and proliferative differentiation of intestinal stem cells（ISCs）, maintaining the balance of regeneration and repair of intestinal epithelium. During mucosal inflammation, the normal process of these cells will be in disorder. The Wnt signaling pathway plays an important role in the regenerative proliferation of ISCs. Our previous studies illuminated that Lgr5 positive cells were low expressed in normal colon membranes, but significantly up regulated in Wnt activated ISCs, possessing both regenerative and proliferative capacity in UC. The Notch signaling regulates the differentiation of ISCs to mature goblet cells. It was estimated that the regulation of the proliferation and differentiation of Lgr5+ ISCs was highly related to the mucous epithelial inflammation, regeneration and repair in UC. Now the synergism mechanism of the two signaling pathways was not clear. We propose to confirm the alteration of the self regeneration, proliferation and differentiation of Lgr5 positive ISCs and find the key factors in the balance of mucosal injury, regeneration and repair in intestinal epithelium, by constructing UC models by transgenetic mouse of Lgr5-EGFPCreERT2 and regulating Wnt and Notch signaling pathway both in vivo and in vitro. The study aims to discuss the mechanism of Wnt and Notch regulation in the mucosal injury, regeneration and repair in UC and investigate for novel treatment strategy.

溃疡性结肠炎(UC)特征病理改变为粘液层缺失和杯状细胞减少。位于隐窝基底层的Lgr5阳性细胞具有结肠干细胞(ISCs)的自我再生和增殖分化潜能，维持粘膜上皮再生修复平衡，炎性病变时其有序过程发生异常。Wnt通路在ISCs增殖中起主导因素。前期研究，Lgr5阳性细胞在正常结肠粘膜低表达，而UC中Wnt信号被激活同时ISCs细胞明显增多。Notch信号则调控ISCs向杯状细胞的分化。课题组推测：调控Lgr5阳性ISCs增殖与分化，与UC粘膜炎性改变和再生修复密切相关。而两种信号途径共调控机制尚不清楚。拟通过转基因小鼠Lgr5-EGFPCreERT2构建UC模型，结合体外和体内实验特异性调控Wnt和Notch信号，检测Lgr5阳性ISCs自我更新、增殖及分化功能改变，寻找粘膜再生修复平衡的关键因素。旨在探讨Wnt和Notch信号共调控UC粘膜损伤和再生修复的内在机制，为探索新的治疗策略奠定基础。

人体内隐窝干细胞调控并增殖分化成熟的杯状细胞，UC病变粘膜特征性存在着粘膜黏液层缺失和杯状细胞减少。既往研究表明位于隐窝基底层的Lgr5阳性细胞具有结肠干细胞(ISCs)的自我再生和增殖分化潜能，维持粘膜上皮再生修复平衡，炎性病变时其有序过程发生异常。而Wnt通路在ISCs增殖中起主导因素。我们前期研究发现，Lgr5阳性细胞在正常结肠粘膜低表达，而UC中Wnt信号被激活同时ISCs细胞明显增多。Notch信号则调控ISCs向杯状细胞的分化。在本课题的资助下，我们通过转基因小鼠Lgr5-EGFPCreERT2构建了UC模型，结合体外和体内实验特异性调控Wnt和Notch信号，发现炎性损伤的结肠粘膜中Wnt通路的激活以及Notch通路的抑制可促进原本处于静息低表达的Lgr5阳性ISCs活化增殖，经典Wnt和Notch通路协同调控ISCs的增殖与分化。这一发现为溃疡性结肠炎发病机制和再生修复机制提供了新的生物学认识，为探索新的治疗策略奠定基础。