嗜热链球菌促进IDO表达抑制异体皮肤移植免疫排斥的机制研究

Allogenous skin transplantation is a promising solution for severely burned patients due to deficiency of autologous skin , where allotransplantation rejection appears to be a bottleneck. Our previous studies showed that Bone Mesenchymal Stem Cells (BMSCs) with high expression of IDO could promote the differentiation of naive T-cells into Treg-cells, leading the alleviation of allogenic skin rejection. Additionally, we proved that Streptococcus thermophilus could up-regulate the expression of IDO in small intestine and prolong the survival time of allografts. However, the mechanism connection between the strain and rejection remains unclear. Although recent studies suggested that gut microbiota and organ transplantation were closely related, but whether gut microbiota changed after allogenous skin transplantation still needs investigation. Our further studies alluded that S. thermophilus can deduct the disturbance of gut microbiota result from inflammation and reduce the symptom, but whether S. thermophilus prolong the survival time of allografts through improving the gut microbiota should also be clarified. Hence, the aim of this project was to study the relationship between gut microbiota and allogenous skin transplantation using Miseq method, to identify the microorganism species related to Treg/Th17 differentiation through Pearson correlation analysis, to illuminate the specific mechanism of how S. thermophilus prolonged the survival time of allografts by protein microarray. Overall, this study would offer novel research ideas and therapeutic approaches to suppress the immune rejection induced by organ transplantation.

异体皮肤移植有望解决大面积烧伤自体皮源不足的难题，而排斥反应是其面临的主要难点。课题组前期研究结果显示：灌胃嗜热链球菌可延长皮片存活时间；高表达IDO的骨髓间充质干细胞可促使初始T细胞向Treg细胞分化，减轻异体皮肤排斥反应；而嗜热链球菌可提高小肠等组织IDO表达，但其促进IDO表达的具体分子机制尚不清楚。近期文献证实，肠道菌群和器官移植密切相关，但异体皮肤移植后肠道菌群状态是否改变尚不清楚。我们进一步研究结果显示：嗜热链球菌可改善炎症导致的肠道菌群紊乱进而减轻炎症反应，但嗜热链球菌是否通过改善肠道菌群进而延长皮片存活时间尚不清楚。本项目拟通过微生物测序研究肠道菌群和异体皮肤移植的关系，通过皮尔逊相关性分析明确哪些肠道菌群改变和Treg/Th17分化相关；通过蛋白质芯片手段阐明嗜热链球菌促进IDO表达延长皮片存活时间的具体机制，为抑制免疫排斥反应或诱导免疫耐受寻找新的研究思路和治疗途径。

异体皮肤移植有望解决大面积烧伤自体皮源不足的难题，而排斥反应是其面临的主要难点。目前器官移植也以抑制免疫排斥反应为主要研究方向，但目前常用药物均存在一些不良反应和并发症，而益生菌在抑制免疫排斥方应方面的研究给延长异体皮肤移植移植物存活时间提供了一个新的选择。嗜热链球菌是酸奶里的益生菌成分之一，本课题组拟在前期研究基础上通过体外体内实验，深入研究嗜热链球菌延长异体皮肤移植移植物存活时间的作用及其机制，自2019年以来在国家自然科学基金青年项目的资助下主要完成了以下研究：嗜热链球菌对巨噬细胞RAW264.7细胞系的细胞活力检测；异体皮肤移植后，小鼠肠道菌群发生显著性改变；嗜热链球菌通过改变异体皮肤移植后小鼠肠道菌群的组成从而延长移植物存活时间；嗜热链球菌能减少脾脏中 Th17 细胞比例，增加 Treg 细胞比例，使 Th17/Treg 平衡向免疫耐受方向改变；嗜热链球菌能诱导肠道组织和皮肤组织IDO表达。通过上述研究，完善了异体皮肤移植和肠道微生物之间的关系，完善了嗜热链球菌延长异体皮肤移植移植物存活时间的理论基础，为益生菌改善免疫排斥反应相关研究提供了参考依据。研究期间获得发明专利授权1项，发表SCI论文2篇，培养博士研究生2名，硕士研究生1名。