IDO在PRF微环境调控BMSCs抑制异体皮肤移植排斥反应中的作用及机制

Allogenous skin transplantation is expected to solve the problem of autologous skin deficiency in severely burned patients, while allotransplantation rejection is currently one of the major difficulties. Previous studies by our group showed that BMSCs that express high levels of indoleamine 2,3- dioxygenase (IDO) could promote the differentiation of naive T-cells into Treg-cells, leading to alleviated allogenic skin rejection. In recent studies, the expression of IDO in BMSCs has been found to be regulated by several inflammatory factors in the microenvironment, such as TGF-β, IFN-γ and TNF-α; also, the platelet-rich fibrin (PRF) has been confirmed to sustainably release a variety of inflammatory cytokines and growth factors. However, whether PRF could provide the microenvironment that enables BMSCs to express IDO and thus plays its immune regulation function remains unclear. This project aims to investigate the effect of PRF microenvironment on the expression and activation of the receptors and downstream molecules of certain inflammatory cytokines, such as TGFR, in BMSCs via protein chip technique, also to examine the effect of IDO’s expression and activation on BMSCs’ immune regulation ability. In the meantime, this study proposes to observe the effect of BMSC-rich PRF on skin allograft rejection and skin survival in an established mouse model. Hopefully, this study would further reveal the molecular mechanism of BMSCs in immune regulation, and thus provide a novel strategy for reducing skin allograft rejection.

异体皮肤移植有望解决大面积烧伤自体皮源不足的难题，移植排斥反应是目前面临的主要难点。课题组前期研究发现，高表达吲哚胺2,3-双加氧酶（IDO）的BMSCs可促使初始T细胞向Treg细胞分化，减轻异体皮肤排斥反应。最新研究证实， BMSCs是否表达IDO受局部微环境中TGF-β、IFN-γ、TNF-α等多种炎性因子调控，而富血小板纤维蛋白（PRF）被证实可持续释放多种炎性因子及生长因子，PRF是否可为BMSCs表达IDO发挥免疫调节能力提供微环境尚不清楚。本项目拟通过蛋白芯片技术研究PRF微环境对BMSCs中TGFR等多种炎性因子受体及下游分子表达及活化的影响，检测IDO表达活化及其对BMSCs发挥免疫调节能力的影响；同时在小鼠异体皮肤移植模型上观察富载BMSCs的PRF对排斥反应及皮肤存活的影响。本研究有望进一步揭示BMSCs发挥免疫调控的分子机制，为减轻异体皮肤移植排斥提供新策略。

烧伤是平时和战时的常见损伤，自体皮源不足是大面积烧伤治疗的主要难题，也是导致患者死亡的重要原因。异体皮肤移植有望从根本上解决该问题，然而，严重的免疫排斥反应导致异体皮肤移植后存活时间十分有限，同时大面积烧伤所面临的严重感染也限制了免疫抑制剂的使用，这些因素严重阻碍了异体皮肤移植的临床应用。因此，异体皮肤移植后的免疫排斥及耐受形成机制一直是烧伤外科领域亟需解决的重大难题。本课题通过研究富血小板纤维蛋白（PRF）微环境对骨髓间充质干细胞（BMSCs）发挥免疫调节能力及异体皮肤移植排斥的影响，发现PRF可提高BMSCs的免疫调节能力，吲哚胺2,3-双加氧酶在其中发挥关键作用。同时将富含BMSCs的PRF应用创面后在进行异体皮肤移植，可显著延长异体皮肤的存活时间。同时发现IFN-γ干预后可显著提高移植后皮片IDO的表达，并延长皮片存活时间，具有潜在的临床应用价值。本研究后续计划构建富含PRF的人工皮肤支架材料，并负载BMSCs及异体皮肤种子细胞，期待实现对创面的永久修复。该目标如能实现，可为大面积皮肤缺损救治提供一种更加有效的技术手段。