MyD88介导Treg/Th17肠稳态失衡在坏死性小肠结肠炎中的作用机制研究

Necrotizing enterocolitis (NEC) is the leading cause of neonatal gastrointestinal mortality; effective diagnosis or effective intervention are lacking with limited understanding of the pathogenesis of NEC. The pathologic features of NEC include the accumulation of a rich inflammatory cell infiltrate into the intestinal mucosa of the premature host and the development of systemic sepsis, which together reflect a marked disruption of the intestinal barrier. The roles of immune cells in NEC are dynamic, and there is an imbalance of immune cells that favor a exaggerated pro-inflammatory state. This is remarkably demonstrated by the relationship between Tregs and Th17 cells. It has been demonstrated that MyD88 plays an important role in regulating Treg/Th17 imbalance. The results from our preliminary study showed: The development of NEC requires an influx of lymphocytes into the lamina propria of the newborn mouse especially CD4(+) T cells, and there was an increase in Th17 cell, decrease in Treg cells; MyD88-/- resulted in reduced inflammatory severity. Based on these results, we propose that MyD88 modulate immune response functions in the pathogenesis of NEC. This project will focus on MyD88-mediated Treg/Th17 imbalance in NEC, by using MyD88 gene knockout mice, co-culture system and intestine samples of NEC patients, to further explore the exact role of MyD88-mediated Treg/Th17 intestinal homeostasis imbalance in NEC. The results from this project will provide new insight for NEC pathogenesis, and provide research evidence for further transnational intervention or therapeutic strategy for NEC.

坏死性小肠结肠炎（NEC）是新生儿最常见的胃肠道致死性疾病之一，目前尚缺乏有效诊治措施。不成熟宿主肠道黏膜中大量免疫细胞浸润、肠道屏障破坏、败血症的发生是NEC主要临床病理特征。免疫细胞失衡导致免疫细胞趋向于呈放大的促炎状态，尤其是Treg/Th17。研究证实MyD88在多种疾病中参与Treg/Th17平衡的调节。团队前期研究发现：NEC中肠道固有层有大量免疫细胞浸润以CD4(+)T细胞为主，且Th17增加，Treg减少；MyD88敲除后，MyD88依赖性信号通路被阻断，NEC炎症程度明显降低。提示，NEC中存在MyD88介导的炎症免疫反应。本研究拟以MyD88介导Treg/Th17平衡为切入点，采用基因敲除小鼠、体外共培养体系，结合NEC患者标本，进一步探索MyD88介导Treg/Th17肠稳态失衡在NEC中的作用机制，为NEC发病机制提出新的认识，并为其治疗提供转化思路和实验依据。

【研究背景及目的】坏死性小肠结肠炎(NEC)是一种影响早产儿胃肠道的严重的炎症性疾病，并在这一人群中有显着的发病率和死亡率。尽管国内外存在大量NEC相关的研究报道，包括流行病学、细胞及动物实验以及临床研究，但其确切的病因及发病机制尚未明确阐明。前期研究已发现在NEC动物模型肠道组织中有大量的免疫细胞浸润；在NEC中，肠道固有层中有大量免疫细胞浸润是以CD4(+)T细胞为主，且Th17细胞增加，Treg细胞减少；MyD88敲除后，MyD88依赖性信号通路被阻断，使NEC炎症程度明显降低，肠上皮细胞凋亡减少，避免了炎症的进一步发生发展。目前MyD88调节Treg/Th17平衡在NEC中的作用尚未见报道。因此，本研究拟以MyD88介导Treg/Th17肠稳态失衡为切入点，进一步探索MyD88介导Treg/Th17肠稳态失衡对NEC发生发展的影响及可能机制，研究结果将对NEC发病机制提出新的认识，并为NEC治疗提供转化思路和实验依据。.【研究内容】1.NEC中肠道固有层免疫细胞浸润情况，T细胞组成成分以及促炎因子导致的黏膜损伤在NEC中的作用机制研究；2.MyD88缺失条件下，对NEC炎症及损伤的影响，以及其对肠道固有层中T细胞的组成成分调节的研究；3.MyD88介导Treg/Th17失衡的蛋白机制的研究。.【研究结果】在NEC发生发展中，肠道固有层有大量免疫细胞浸润，其中主要以CD4(+)T细胞为主，且肠道固有层中Th17细胞增加，Treg细胞减少。Th17细胞主要效应因子IL-17在NEC发生发展中起到重要作用，IL-17增加了NEC的炎症程度以及肠道粘膜的损伤。MyD88通路在NEC发生发展中起保护作用，通过调节Treg/Th17平衡，从而影响NEC的炎症程度。MyD88通路主要通过调节pSTAT3的表达介导Treg/Th17失衡，从而影响NEC的发生发展。.【结论】本研究提供的证据表明，NEC可以被认为是一种淋巴细胞介导的疾病，而有害的淋巴细胞的募集需要肠上皮细胞中的MyD88信号。恢复耐受淋巴细胞平衡的进一步策略可能为NEC的预防或治疗提供新的方法。