Induction of allogeneic tolerance with bioengineered thymus organoids

 描述：同种异体移植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物排斥反应，但其疗效有限，而且往往伴随着严重的副作用。潜在的问题是，胸腺不断产生对同种异体抗原有反应的新T细胞。虽然已经做出了许多努力来调节胸腺功能以诱导供者特异性免疫耐受，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 胸腺上皮细胞(TECs)的生存和功能，胸腺基质细胞是胸腺基质细胞的主要群体，对于T细胞的发展和定义个人的“免疫自我”(在体内区分自我和非自我分子并做出相应反应的能力)是必不可少的。在这里，我们提出了一种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去细胞技术，它允许我们用分离的TEC重建具有功能的胸腺器官。植入生物工程胸腺的裸鼠能够对模型抗原卵清蛋白产生强烈的体液反应，并迅速排斥同种异体皮肤移植。相反，通过移植共表达供体和受体主要组织相容性复合体(MHC)分子的胸腺器官类化合物，可以实现对同种异体皮肤移植的耐受。基于这些观察，我们假设生物工程胸腺有机化合物可以在体内重现胸腺的功能，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翻译实验重点是1型糖尿病(T1D)，在T1D中，由于丧失自我耐受性，胰腺中分泌胰岛素的β细胞成为自身免疫破坏的目标，我们将重点研究生物工程胸腺有机化合物能否重建对β细胞的免疫耐受。此外，我们还将研究能否利用胸腺生物工程技术同时诱导供者对同种异体胰岛移植的免疫耐受。目标1中的实验将优化从脱细胞胸腺支架体外构建胸腺有机类化合物。我们在目标2中的重点是优化生物工程胸腺有机化合物在体内的长期存活和功能。目的3旨在证明用表达胰岛素的同种异体TECs构建的生物工程胸腺可以有效地调节适应性免疫系统，逆转胰岛素自身免疫，这是T1D进展的主要驱动力之一，并建立同种异体胰岛移植物的免疫耐受。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.