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

 描述(申请人提供)：尽管基于干细胞的疗法可能被用于治疗多种流行疾病，但其成功的临床翻译需要克服免疫排斥的主要障碍。此外，在自身免疫性疾病中，如1型糖尿病(T1D)，免疫耐受性的崩溃导致免疫介导的胰腺胰岛素产生细胞的破坏，潜在的自身免疫需要改变，以便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进治疗人类自身免疫性疾病的方法至关重要。在免疫系统中，胸腺通过教育发育中的T细胞，在建立中枢免疫耐受中起着关键作用。胸腺通过删除识别自身抗原的T细胞和产生能够抑制免疫反应的强大的调节性T细胞(Tregs)来加强耐受性。鉴于自我认同是由胸腺上皮细胞(TECs)编码的，在干细胞疗法的背景下操纵免疫耐受的一个有吸引力的方法是通过生成干细胞来源的TECs来重新编程免疫系统。最近，我们团队开发了一种新的方法，将人多能干细胞(HPSCs)分化为胸腺上皮祖细胞(TEPs)，移植到免疫缺陷小鼠体内后，TEPs成熟为有功能的胸腺组织。重要的是，这些hPSC来源的TEP具有成熟TEC的特征，允许产生能够安装同种异体免疫反应的功能性T细胞，以及通过关键抑制自身反应性T细胞来维持免疫耐受的Tregs的形成。这一独特且高度创新的工具现在将被用于建立新的人源化小鼠模型，更接近于体内人类的免疫反应。移植了hPSC来源的TEP的人源化小鼠将被用来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的自身反应性T细胞来开发T1D自身免疫的模型。事实上，通过改变胰岛素等抗原在hPSC来源的TEP中的表达，我们将有机会修改免疫系统，并潜在地影响胰岛特异性Tregs的发育。这将使我们能够利用人类免疫细胞和靶点在动物模型中检查T1D的早期阶段。最后，这些人源化的小鼠模型将被用来研究胸腺功能的操纵和Treg给药的影响，这些操作可能改变干细胞来源的移植物的同种异体反应和自身免疫反应。综上所述，我们建议的研究将提供独特的工具，以改进干细胞衍生品移植的研究和对T1D等自身免疫性疾病的建模。此外，我们的工作将为在自身免疫的背景下操纵胸腺免疫耐受以改善干细胞衍生品的植入奠定基础。

 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.