Induction of allogeneic tolerance with bioengineered thymus organoids

 同种异体移植物的慢性排斥反应仍然是器官移植和再生医学的主要障碍。虽然免疫抑制药物可以在一定程度上预防移植排斥反应，但其疗效有限，并且通常伴有严重的副作用。根本的问题是，新的T细胞反应同种异体抗原不断产生的胸腺。虽然已经做出了许多努力来调节胸腺功能以诱导供体特异性免疫耐受，但操纵胸腺被证明是困难的。一个主要的挑战是复制其独特的细胞外基质微环境，这对肿瘤的生长至关重要。 胸腺上皮细胞（TEC）的存活和功能，所述TEC是胸腺基质细胞的主要群体，其对于T细胞的发育和定义个体的“免疫自我”（区分体内自我与非自我分子并相应地响应的能力）是必需的。在这里，我们提出了一个创新的生物工程方法来调节胸腺功能。我们最近开发了一种胸腺脱细胞技术，使我们能够重建一个功能性胸腺类器官从头与孤立的TEC。移植了生物工程胸腺的无胸腺小鼠能够对模型抗原卵清蛋白产生强烈的体液反应，并迅速排斥皮肤移植物。相反，对同种异体皮肤移植物的耐受性可以通过移植共表达供体和受体的主要组织相容性复合物（MHC）分子的胸腺类器官来实现。基于这些观察结果，我们假设生物工程胸腺类器官可以重现体内胸腺的功能，并能够重新定义适应性免疫系统的“免疫自我”。鉴于我们小组的主要转化实验重点是1型糖尿病（T1D），其中胰腺的胰岛素分泌β细胞由于自身耐受性的丧失而成为自身免疫破坏的目标，我们将重点研究生物工程胸腺类器官是否可以重建对β细胞的免疫耐受性。此外，我们还将探讨胸腺生物工程技术能否同时诱导供者对同种异体胰岛移植物的特异性免疫耐受。目的1中的实验将优化体外从脱细胞胸腺支架构建胸腺类器官。我们在目标2中的重点是优化生物工程胸腺类器官在体内的长期存活和功能。目的3中的实验是证明用表达胰岛素的同种异体TEC构建的生物工程胸腺可以有效地调节适应性免疫系统以逆转胰岛素自身免疫（T1D进展的主要驱动力之一），并建立胰岛同种异体移植物的免疫耐受。该研究项目的长期目标是将胸腺生物工程技术转化为临床应用。

 DESCRIPTION: Chronic rejection of allografts remains a major hurdle in organ transplantation and regenerative medicine. While immunosuppressive drugs can prevent graft rejection to a certain degree, their efficacies are limited and often associate with severe side effects. The underlying problem is that new T-cells reactive to alloantigens are continuously generated from the thymus. While numerous efforts have been made to modulate thymic function to induce donor-specific immune tolerance, manipulating the thymus proves to be difficult. One major challenge is to reproduce its unique extracellular matrix microenvironment that is critical for the survival and function of thymic epithelial cells (TECs), the predominant population of thymic stromal cells that are essential for the development of T-cells and for defining the "immunological self" of an individual (the capability to distinguish self from non-self molecules i the body and respond accordingly). Here, we propose an innovative bioengineering approach to modulate the thymus function. We have recently developed a thymus decellularization technique, which allows us to reconstruct a functional thymus organoid de novo with isolated TECs. Athymic mice engrafted with the bioengineered thymus are able to develop strong humoral responses against model antigen ovalbumin and promptly reject skin allografts. Conversely, tolerance to allogeneic skin grafts can be achieved by transplanting thymus organoids co-expressing both donor and recipient's major histocompatibility complex (MHC) molecules. Based on these observations, we hypothesize that the bioengineered thymus organoid can recapitulate the function of a thymus in vivo, and are able to redefine the "immunological self" of the adaptive immune system. Given that the major translational experimental focus in our group is on Type 1 diabetes (T1D), in which the insulin-secreting beta cells of the pancreas becomes targets of autoimmune destruction due to loss of self-tolerance, we will focus our investigation on whether the bioengineered thymus organoids can re-establish immune tolerance to beta-cells. Furthermore, we will investigate whether we can simultaneously induce donor-specific immune tolerance to islet allografts with the thymus bioengineering technology. Experiments in Aim 1 will optimize the construction of the thymus organoids from decellularized thymic scaffolds in vitro. Our focus in Aim 2 is to optimize the long-term survival and function of the bioengineered thymus organoids in vivo. Experiments in Aim 3 is to demonstrate that the bioengineered thymus constructed with insulin- expressing allogeneic TECs can effectively modulate the adaptive immune system to reverse insulin-autoimmunity, one of the primary driving forces for T1D progression, and to establish immune tolerance of islet allografts. The long-term goal of the research project is to translate the thymus bioengineering technique into clinical applications.