胚胎干细胞来源的胸腺上皮祖细胞表达MOG治疗多发性硬化症的实验研究

Multiple sclerosis（MS） is a devastating autoimmunity disease. Myelin antigen is attacked by self-reactive T cells in MS. The most logical way for preventing MS would be to induce self-antigen-specific tolerance and delete or suppress functionally self-reactive T cells, which is followed by the same mechanism that the immune system uses to maintain self-tolerance throughout life. However, it is well known that the thymus profoundly undergoes age-dependent involution, and its functions are seriously compromised in the elderly. Thymic epithelial cells (TECs) are the major component of the thymic microenvironment for T cell development. Our preliminary results show that embryonic stem cells (ESCs) can be induced in vitro to generate thymic epithelial progenitors(TEPs) that further develop into functional TECs in vivo. We will investigate whether transplantation of mESC-TEPs expressing disease-causative self-antigen myelin oligodendrocyte glycoprotein (MOG) in mice results in enhanced T cell regeneration, long-term expression of MOG in the thymus, prevention of MS development, and remission of established MS in mice. We will also investigate the underlying mechanisms and determine whether the treatment is related to central (self-reactive T cells deleted) or/and peripheral(inhibitory effect of regulatory T cell ) tolerance and whether or not the tolerance is mediated by TECs directly. Our findings may suggest that transplantation of ESC-TEPs expressing disease-causative self-antigen(s) may provide an effective approach for the prevention and treatment of autoimmune disease.

多发性硬化症（MS）是由自身反应性T细胞介导对髓鞘抗原免疫耐受破坏所致的自身免疫病。诱导长期抗原特异性耐受，清除或抑制自身反应性T细胞，可有效防止MS发生。但胸腺功能随年龄依赖逐渐退化和其内自身抗原的不稳定表达限制了治疗效果。我们前期实验证实，胚胎干细胞来源的胸腺上皮祖细胞（ESC-TEPs）移植到体内，可分化为胸腺上皮细胞（TECs），重建胸腺结构，促进T细胞发育。本课题拟在此基础上建立MS动物模型，将引起MS的关键致病性抗原（髓鞘少突胶质细胞糖蛋白，MOG）表达在mESC-TEPs内，胸腺内移植，研究其能否在分化为TECs改善微环境的同时，实现胸腺内MOG长期表达，诱导耐受，实现自身反应性T细胞清除或抑制,达到治疗MS的目的；并探讨该治疗机制是与中枢耐受或/和外周耐受有关，及TECs是否直接提呈抗原，介导自身耐受发生。这对通过诱导自身免疫耐受，去治疗MS类的自身免疫病具有重要意义。

研究表明多发性硬化症(MS)是由自身反应性T细胞介导对髓鞘抗原免疫耐受破坏所致的自身免疫病，其研究最常用的动物模型为实验性自身免疫性脑脊髓炎（EAE）。诱导长期抗原特异性耐受，清除或抑制自身反应性T细胞，可有效防止MS发生。但胸腺功能随年龄依赖逐渐退化和其内自身抗原的不稳定表达限制了治疗效果。我们前期实验证实，胚胎干细胞来源的胸腺上皮祖细胞(ESC-TEPs)移植到体内，可分化为胸腺上皮细胞(TECs)，重建胸腺结构，促进T细胞发育。本课题在此基础上，1、建立了MS的常用动物模型EAE，将致病性抗原(髓鞘少突胶质细胞糖蛋白，MOG)表达在mESC-TEPs内，胸腺内移植，研究MOG/mESC-TEPs胸腺内移植对MS（EAE）的作用及其相关机制，我们发现，MOG/mESC-TEPs胸腺内移植，可有效改善该小鼠EAE的发病情况，临床评分及组织病理学改变，对MOG诱导的EAE模型有明显的预防和治疗的作用；可降低MOG刺激的T细胞增殖反应，并减少Th1/Th17细胞因子产物的分泌；促进胸腺和脾脏中Tregs的产生。 2、运用2D2TCR转基因小鼠EAE模型，进一步证实了胸腺内MOG/mESC-TEPs移植诱导了针对自身抗原MOG的抗原特异性耐受，胸腺内MOG抗原特异性自身反应性T细胞删除，外周MOG抗原特异性Treg s增加，抑制了抗原特异性自身反应性T细胞反应，从中枢耐受和外周耐受两个机制达到防治EAE的目的。3、利用本研究建立的成熟技术和方法基础上，将ESC-TEPs胸腺内移植用于慢性移植物抗宿主病（cGVHD）和1型糖尿病（T1D）两种自身免疫性疾病研究，取得疗效，与本研究的结果一致，进一步证实了本研究的相关发现，说明本研究中运用ESC来源的TEPs胸腺内移植可有效改善胸腺结构，促进T细胞发育，诱导自身反应性T细胞删除和Tregs的增加，通过中枢耐受和外周耐受机制，对自身免疫病（如EAE、cGVHD和T1D等）实现有效地防治作用。这对通过诱导自身免疫耐受，去治疗MS类的自身免疫病具有重要意义。