Immunosuppression-free islet transplantation via localized immunomodulatory exosome tethering

项目总结/摘要 临床胰岛移植是治疗胰岛素依赖型糖尿病的一种有前途的方法， 通过恢复天然胰岛素信号传导消除长期继发性并发症的潜力。虽然临床 成功证明了通过胰岛替代实现胰岛素非依赖性的可行性 然而，长期免疫抑制方案的必要性限制了这种疗法的广泛适用性。 由于与慢性免疫抑制相关的实质性风险超过糖尿病风险， 相关疾病因此，人们对开发微囊化装置以 从受体免疫系统中分离移植细胞，目的是通过以下方式消除免疫识别： 直接抗原提呈途径。虽然这种策略可以降低对移植物的免疫反应， 包封不能阻止脱落抗原的扩散，脱落抗原通过间接抗原激活免疫细胞， 这些细胞通过递呈途径最终靶向并破坏移植细胞。因此，采取协同办法， 需要大囊化以完全改善对胰岛移植物的免疫应答。 胎盘微环境是一个独特的生物学例子， 耐受性，由胎儿-母体界面的滋养层通过两种机制维持：（1）产生屏障 防止同种异体组织和宿主之间的接触，和（2）局部呈递和分泌 免疫调节因子以诱导致耐受性先天性和适应性免疫细胞。一种有效的方法， 滋养层通过分泌的外泌体递送免疫调节有效载荷。我们的目标是模仿这两个 免疫隔离水凝胶包裹胰岛的滋养层细胞介导的耐受机制 装置并将免疫调节性滋养层来源的外来体系到装置表面。 我们假设，免疫调节性滋养层细胞来源的外来体的局部呈递在滋养层细胞中， 合成水凝胶宏包封装置表面将与免疫隔离协同作用， 对移植物的局部免疫耐受我们预计，局部化的外来体呈递将导致局部化的细胞凋亡。 通过在移植部位诱导致耐受性先天性和适应性免疫细胞来增强对移植物的耐受性。 水凝胶装置内的包封将防止直接抗原呈递，并且表面结合的外泌体将被释放。 将诱导致耐受性抗原呈递细胞，通过间接抗原识别防止免疫破坏。 这些假设将在以下具体目标的实验中得到解决：（1）工程师和 免疫调节外泌体呈递合成的基于水凝胶的宏包封装置;和（2）评估 免疫调节巨囊化装置对局部移植物免疫环境的影响。我们 预期本研究将证明致耐受性滋养层外来体的免疫抑制能力， 以及它们与胰岛包封协同作用的潜力。

PROJECT SUMMARY/ABSTRACT Clinical islet transplantation is a promising treatment for insulin-dependent diabetic patients, with the potential to eliminate long-term secondary complications by restoring native insulin signaling. While clinical successes have demonstrated the feasibility of achieving insulin independence through islet replacement therapy, the necessity of a long-term immunosuppressive regimen limits the widespread applicability of this procedure, as the substantial risk associated with chronic immunosuppression outweighs the risk of diabetes associated morbidities. As a result, there is great interest in the development of macroencapsulation devices to isolate transplanted cells from the recipient immune system, with the intent to eliminate immune recognition via the direct antigen presentation pathway. While this strategy can reduce immune response to the graft, encapsulation cannot prevent the diffusion of shed antigens, which activate immune cells via the indirect antigen presentation pathway to ultimately target and destroy the transplanted cells. As such, a synergistic approach to macroencapsulation is required to fully ameliorate the immune response to islet grafts. The placental microenvironment is a unique biological example of localized, normal physiological tolerance, maintained by trophoblasts at the fetal-maternal interface via two mechanisms: (1) creating a barrier to prevent contact between allogeneic tissue and host, and (2) localized presentation and secretion of immunomodulatory factors to induce tolerogenic innate and adaptive immune cells. One potent method by which trophoblasts deliver immunomodulatory payloads is via secreted exosomes. We aim to mimic these two mechanisms of trophoblast-mediated tolerance through encapsulating islets in an immunoisolating hydrogel device and tethering immunomodulatory trophoblast-derived exosomes to the device surface. We hypothesize that localized presentation of immunomodulatory trophoblast-derived exosomes at the surface of a synthetic hydrogel macroencapsulation device will synergize with immunoisolation to produce localized immune tolerance to the graft. We anticipate that localized exosome presentation will result in local tolerance to the graft by inducing tolerogenic innate and adaptive immune cells at the site of transplantation. Encapsulation within the hydrogel device will prevent direct antigen presentation, and surface-bound exosomes will induce tolerogenic antigen presenting cells, preventing immune destruction via indirect antigen recognition. These hypotheses will be addressed in the experiments of the following Specific Aims: (1) Engineer an immunomodulating exosome-presenting synthetic hydrogel-based macroencapsulation device; and (2) Evaluate immunomodulatory macroencapsulation device impact on the localized graft immune environment. We anticipate that this study will demonstrate the immunosuppressive capacity of tolerogenic trophoblast exosomes, and their potential for synergy with islet encapsulation.