IDO基因修饰BMSCs干预Th17/Treg细胞分化在异体移植免疫耐受形成中的作用及机制

Prolongation of skin allografts survival time by suppressing or avoiding the immune rejection is very important for the patients with extensive burns. Bone marrow-derived mesenchymal stem cells(BMSCs) have the low immunogenicity and immunoregulatory capacity. However, the immunoregulatory capacity of BMSCs couldn't inhibit graft rejection totally. It has been verified that indoleamine 2, 3-dioxygenase(IDO) could promote apoptosis and inhibit proliferation on effector T cell. The expression of IDO by BMSCs is affected by a variety of extracellular factors, which often decrease or abolish the immunoregulatory capacity of BMSCs on T cell. It has great significance for further research the effect of stable high expression of IDO by gene transfection in BMSCs on its immunomodulatory ability. Therefore, IDO gene transfected BMSCs(IDO-BMSCs) will be built in this research. The effect and mechanism of IDO-BMSCs on naive T cells differentiation to Th17/Treg cells will been researched in vitro. Furthermore, the recipient mouse will accepted both IDO-BMSCs an allo-skin transplantation, in order to verifying the effect of IDO-BMSCs on immune rejection. This research will provide new molecule targets and therapies. Meanwhile, explore application of BMSCs as trager in the field of transplant rejection.

通过降低甚至避免移植排斥反应延长异体皮肤存活时间对自体皮源不足的大面积烧伤救治尤为重要。BMSCs具有低免疫原性及免疫调节特性，但其免疫调节作用尚不足以完全抑制移植排斥反应。IDO被证实对效应T细胞具有促凋亡、抑增殖的作用，同时可诱导调节性T细胞产生。但BMSCs表达IDO受胞外微环境的影响，往往导致其对T细胞的调节能力降低甚至丧失。通过基因转染使BMSCs稳定高表达IDO能否增强其免疫调节能力值得深入研究。据此，本课题拟通过基因转染技术构建高表达IDO的BMSCs（IDO-BMSCs），在体外研究其对初始T细胞向Th17/Treg细胞分化的影响及机制，进一步将IDO-BMSCs输注小鼠体内，同时进行异体皮肤移植，观察IDO-BMSCs对移植排斥/耐受形成的影响。本研究有望为抑制甚至避免移植排斥反应寻求新的分子靶点及治疗方法，同时探索BMSCs作为细胞载体在移植排斥研究领域的应用。

BMSCs具有低免疫原性及免疫调节特性，但其免疫调节作用尚不足以完全抑制移植排斥反应。IDO被证实对效应T细胞具有促凋亡、抑增殖的作用，同时可诱导调节性T细胞产生。研究结果提示经过IDO（GFP）-Lenti基因感染修饰后的BMSCs，可稳定表达IDO，并发挥其酶学活性，加速色氨酸耗竭，犬尿氨酸蓄积，从而抑制T淋巴细胞增殖。在体外混合淋巴细胞实验中加入IDO-BMSCs培养上清液，反应性T细胞凋亡明显增多，同时Treg/Th17细胞比例显著提高。在小鼠异体皮肤移植模型中证实，IDO-BMSCs可有效降低异体皮肤移植后的淋巴细胞浸润，抑制异体移植排斥反应，显著延长异体皮肤存活时间。在大鼠异体肢体移植模型中得到了相同的研究结果。课题组还尝试将异体脂肪干细胞与脂肪组织混合移植，发现异体脂肪干细胞同样具有抑制免疫排斥的能力，病理结果提示炎性细胞浸润明显减少，显著提高移植后的成活率及成活时间。本研究有望为抑制甚至避免移植排斥反应寻求新的分子靶点及治疗方法，同时探索BMSCs作为细胞载体在移植排斥研究领域的应用。相关研究结果发表SCI论文3篇。