Endothelial cells regulate immune reconstitution after hematopoietic stem cell transplantation

摘要 胸腺的再生是允许更新免疫能力的关键过程。 感染、休克、细胞减少性化疗或放射治疗及其他导致胸腺损伤的原因。这是 尤其与异基因造血细胞移植(allo-hct)的接受者有关，他们经历了 细胞还原调节和移植物抗宿主病引起的移植后T细胞长期缺乏 (GVHD)，导致感染和恶性复发的发病率和死亡率增加。其中一个 该项目的主要目标是确定内源性胸腺再生的新途径，以便它们可能 被开发成临床上相关的免疫恢复策略。 我们发现了胸腺内皮细胞(ECs)在调节胸腺再生中的新作用。 在受到侮辱之后。我们发现，在胸腺受到侮辱后，辐射抵抗的内皮细胞增加了BMP4的产生， 作用于胸腺上皮细胞(TECs)以增加其关键转录因子Foxn1的表达 参与TEC的开发、维护和更新。这些作用促进了TEC的再生和 损伤后胸腺的整体重建。因此，通过药物或药物来消除BMP4的影响 基因抑制会损害胸腺修复。重要的是，我们证明了体外领养转移 扩增的胸腺内皮细胞(ExECThy)是一种在胸腺中传递BMP4的可行方法，并增强了 免疫损伤后的胸腺再生。此外，我们还发现，氧化应激的副产品，如 脂质过氧化产物，在损伤后积聚在胸腺，并向内皮细胞发出促进生存的信号 通过它们激活损伤感知受体TRPA1。我们证明了TRPA1激动剂可以 通过激活内皮细胞促进胸腺再生。 基于这些发现，我们假设：(A)内皮细胞在T细胞再生中发挥重要作用 在胸腺受损后，(B)促进EC存活和功能的通路可用于 增强胸腺再生和(C)给予EXECS、BMP4和/或TRPA1激动剂 用作促进移植后免疫重建的治疗策略。我们在目标1中建议 目的：研究骨髓移植受者切除联合BMP4对胸腺再生、外周血T细胞亚群的影响。 细胞重建、GVHD和移植物抗肿瘤活性。在目标2中，我们将研究涉及的机制 胸腺内皮细胞的抗损伤作用，主要集中在a)脂质过氧化产物和TRPA1，以及b)抗 氧化途径，如NRF2。 这些机制和临床前研究有可能定义重要的新途径在 胸腺再生，这可能导致临床方法来增强T细胞免疫，不仅是为了 Allo-HCT的接受者，但也适用于因年龄增长而患有T细胞缺陷(淋巴萎缩)的个人， 自身免疫性疾病、传染病、休克、放射或化疗和辐射损伤。

ABSTRACT Regeneration of the thymus is a critical process that allows for renewal of immune competence following infection, shock, cytoreductive chemo- or radiation therapy and other causes of thymic injury. This is particularly relevant for recipients of allogeneic hematopoietic cell transplantation (allo-HCT), who experience prolonged post-transplant T cell deficiency caused by cytoreductive conditioning and graft-versus-host disease (GVHD), which results in increased morbidity and mortality from infections and malignant relapse. One of the major goals of this project is to identify novel pathways of endogenous thymic regeneration so that they may be exploited into clinically relevant strategies for immune rejuvenation. We have uncovered a novel role for thymic endothelial cells (ECs) in mediating thymic regeneration after insults. We found that following thymic insults radioresistant ECs increase their production of BMP4, which acts on thymic epithelial cells (TECs) to increase their expression of Foxn1, a key transcription factor involved in TEC development, maintenance and regeneration. These effects promote TEC regeneration and overall thymic reconstitution after injury. Accordingly, abrogation of BMP4 effects by either pharmacologic or genetic inhibition impairs thymic repair. Importantly, we demonstrated that the adoptive transfer of ex vivo expanded thymic ECs (exECThy) represents a feasible approach to deliver BMP4 in the thymus and enhances thymic regeneration after immune damage. In addition, we also found that oxidative stress byproducts, such as lipid peroxidation products, accumulate in the thymus after injury and instruct pro-survival signals to the ECs through their activation of the damage sensing receptor TRPA1. We demonstrated that TRPA1 agonists can enhance thymic regeneration through activation of ECs. Based on these findings, we hypothesize that (a) ECs play an important role in T cell regeneration following thymic insult, (b) pathways that promote EC survival and function can be employed to enhance thymic regeneration and (c) administration of exECs, BMP4 and/or TRPA1 agonists can be used as therapeutic strategies to enhance post-transplant immune reconstitution. We propose in Aim 1 to study the effects of exECThy and BMP4 administration to HCT recipients on thymic regeneration, peripheral T cell reconstitution, GVHD and graft-versus-tumor activity. In Aim 2 we will study the mechanisms involved in the damage-resistance of thymic ECs with a focus on a) lipid peroxidation products and TRPA1, and b) anti- oxidant pathways such as Nrf2. These mechanistic and pre-clinical studies have the potential to define important novel pathways in thymic regeneration, which could result in clinical approaches to enhance T cell immunity, not only for recipients of allo-HCT, but also for individuals with T cell deficiencies due to aging (lymphoid atrophy), autoimmune diseases, infectious diseases, shock, radio- or chemo-therapy and radiation injury.