Using human stem cell-derived thymic epithelium to remodel T1D immune tolerance

 描述（由申请人提供）：尽管基于干细胞的疗法可能用于治疗许多流行疾病，但其成功的临床转化需要克服免疫排斥的主要障碍。此外，在自身免疫性疾病如1型糖尿病（T1D）中，免疫耐受性的破坏导致胰腺胰岛素产生细胞的免疫介导的破坏，需要改变潜在的自身免疫性以允许在没有免疫抑制的情况下成功植入。因此，开发在自身免疫背景下操纵免疫耐受的方法对于改善治愈和治疗人类自身免疫性疾病的方法至关重要。在免疫系统中，胸腺通过发育中的T细胞的教育在建立中枢免疫耐受中起关键作用。胸腺通过删除识别自身抗原的T细胞和产生可以抑制免疫反应的强效调节性T细胞（Tcells）来增强耐受性。鉴于自我身份是由胸腺上皮细胞（TEC）编码的，在干细胞治疗的背景下操纵免疫耐受的一种有吸引力的方法是通过产生干细胞衍生的TEC来重新编程免疫系统。 最近，我们的小组已经开发了一种新的方法，使人多能干细胞（hPSC）分化为胸腺上皮祖细胞（TEPs），移植到免疫缺陷小鼠后成熟为功能性胸腺组织。重要的是，这些hPSC衍生的TEP获得了成熟TEC的特征，其允许产生能够产生同种异体免疫应答的功能性T细胞以及形成通过对自身反应性T细胞的关键抑制来维持免疫耐受性的T细胞。这种独特的和高度创新的工具现在将用于建立新的人源化小鼠模型，更接近地模拟体内人类免疫反应。移植有hPSC衍生的TEP的人源化小鼠将用于研究另一种干细胞衍生物（胰腺β细胞）的植入。此外，将通过在胸腺内产生胰岛特异性自身反应性T细胞来开发T1D自身免疫模型。事实上，通过改变hPSC衍生的TEP中抗原如胰岛素的表达，我们将有机会修饰免疫库以及潜在地影响对胰岛特异性的THE3的发育。这将使我们能够使用人类免疫细胞和靶标在动物模型中检查T1D的早期阶段。最后，这些人源化小鼠模型将用于研究胸腺功能和Treg给药的操作的影响，这些操作有可能改变对干细胞衍生移植物的同种异体和自身免疫反应。 总之，我们提出的研究将提供独特的工具，使改进的干细胞衍生物移植和自身免疫性疾病，如T1D建模的研究。此外，我们的工作将奠定基础的潜力，胸腺免疫耐受可以被操纵，以改善移植的干细胞衍生物的背景下，自身免疫。

 DESCRIPTION (provided by applicant): Although stem cell-based therapies can potentially be used to treat numerous prevalent diseases, their successful clinical translation requires overcoming the major roadblock of immune rejection. In addition, in autoimmune diseases such as Type 1 diabetes (T1D), where a breakdown in immune tolerance leads to the immune-mediated destruction of pancreatic insulin-producing cells, the underlying autoimmunity needs to be altered to allow successful engraftment without immunosuppression. Developing approaches to manipulate immune tolerance in the context of autoimmunity is thus essential for improving methods to cure and treat human autoimmune diseases. Within the immune system, the thymus plays a critical role in establishing central immune tolerance through the education of developing T cells. The thymus enforces tolerance through the deletion of T cells that recognize self-antigens and the production of potent regulatory T cells (Tregs) that can suppress immune responses. Given that self-identity is encoded by thymic epithelial cells (TECs), an appealing approach to manipulating immune tolerance in the context of stem cell therapies would be to reprogram the immune system through the generation of stem cell-derived TECs. Recently, our group has developed a novel method to differentiate human pluripotent stem cells (hPSCs) into thymic epithelial progenitors (TEPs) that mature into functional thymic tissue upon transplantation into immunodeficient mice. Importantly, these hPSC-derived TEPs acquire characteristics of mature TECs that allow generation of functional T cells capable of mounting allogeneic immune responses as well as formation of Tregs that maintain immune tolerance through crucial inhibition of self-reactive T cells. This unique and highly innovative tool will now be used to establish novel humanized murine models that more closely mimic in vivo human immune responses. Humanized mice transplanted with hPSC-derived TEPs will be used to study engraftment of another stem cell derivative (pancreatic beta cells). Additionally, a model of T1D autoimmunity will be developed through the generation of islet-specific autoreactive T cells within the thymus. Indeed, by altering expression of antigens such as insulin in hPSC-derived TEPs, we will have an opportunity to modify the immune repertoire as well as potentially impact the development of Tregs specific to islets. This will allw us to examine the early stages of T1D in an animal model using human immune cells and targets. Finally, these humanized mouse models will be used to study the impact of manipulation of thymic function and Treg administration that have the potential to alter allogeneic and autoimmune responses to stem cell-derived grafts. Taken together, our proposed studies will provide unique tools to enable improved studies of stem cell derivatives transplantation and modeling of autoimmune disorders such as T1D. Furthermore, our work will lay the foundation for the potential that thymic immune tolerance can be manipulated to improve engraftment of stem cell derivatives in the context of autoimmunity.