C型凝集素受体Clec12b通过调控肠道疣微菌群介导溃疡性结肠炎黏膜愈合的机制研究

溃疡性结肠炎（UC）发病机制不明，疗效欠佳。促进患者肠黏膜愈合可明显改善UC的预后。我们之前发现C型凝集素受体Clec7a通过抑制肠道乳酸杆菌的增殖而参与小鼠结肠炎的发病。Clec12b是与Clec7a处于同一基因簇的另一C型受体，但其功能未见报道。我们前期在成功构建Clec12b基因敲除（KO）小鼠的基础上发现：在结肠炎模型中KO小鼠较野生型小鼠的黏膜损伤明显加重；KO小鼠的粪便菌群移植到无菌小鼠后此菌群可明显加重结肠黏膜炎症；正常小鼠菌群植入无菌KO小鼠后肠道疣微菌群的比例显著降低甚至消失。据此我们假设：Clec12b可通过促进疣微菌的肠道内定植来抑制肠道炎症和促进黏膜愈合。本课题拟应用微小肠类器官培养、多聚糖微阵列分析和免疫微生物学的研究手段，探索Clec12b调控特定肠道菌群及该菌群调节黏膜稳态的分子机制，最终揭示Clec12b介导肠黏膜愈合的免疫学功能，为UC的治疗提供新的靶标。

With the unclarified pathogenic mechanism, Ulcerative colitis (UC), is still one of the most refractory gastroenterological disease in the world. We previously reported that by controlling the colonization of intestinal commensal Lactobacillus, one C-type lectin member Dectin-1 (Clec7a) promotes the development of mouse colitis, suggesting that members of this receptor family have some potential roles in the regulation of intestinal immunity. Clec12b, another C-type lectin receptor which gene locates in the nearby locus with Clec7a inside the Dectin-1 gene cluster, has the ITIM motif in the C-terminal. Although belonging to the same family with Clec7a, the function of Clec12b in the intestinal immune system is rarely studied. By using the chemical induced colitis model, we found that Clec12b-deficient (Clec12b–/–) mice exhibit significantly exacerbate colitis compared with wild-type (WT) mice. By transferring the fecal commensal bacteria isolated from Clec12b–/– mice into germ-free (GF) WT mice, we found these Clec12b–/– mouse microbiota-received hosts exhibited significantly aggravating symptom of colitis compared with the GF host receiving WT mouse microbiota. Interestingly, when transferring the whole normal commensal microbiota into GF Clec12b–/– mice, the proportion of Verrucomicrobia in these hosts was gradually decreased until totally disappeared. These preliminary founding supports the hypothesis that by controlling the growth or colonization of commensal Verrucomicrobia, Clec12b plays a protective role against mouse intestinal inflammation. In the present study, by using the intestinal organoid model, glycan array and other immunological and microbiological analysis, we will firstly identify the Clec12b-expressing cells in mouse intestines, then clarify the major commensal bacteria species specifically controlled by Clec12b signaling, examine the potential function of this bacteria species on the regulation of mouse colitis, and finally discover the mechanism by which Clec12b control this commensal microbiota-mediated intestinal inflammation and mucosal healing consequently. We will also try to identify the unknow ligand(s) of Clec12b to provide the new evidence for developing the UC-therapeutic strategy.