Endothelial cells regulate immune reconstitution after hematopoietic stem cell transplantation

摘要 胸腺的再生是一个关键的过程，允许免疫能力的更新 在感染、休克、细胞减少性化疗或放射治疗和其他原因的胸腺损伤之后。这是 特别是与异基因造血细胞移植（allo-HCT）的接受者相关， 细胞减少性预处理和移植物抗宿主病引起的移植后T细胞缺乏延长 （GVHD），导致感染和恶性复发的发病率和死亡率增加。之一 该项目的主要目标是确定内源性胸腺再生的新途径， 用于临床相关的免疫再生策略。 我们发现了胸腺内皮细胞在胸腺再生中的新作用 在侮辱之后。我们发现，胸腺损伤后，抗辐射EC增加了BMP 4的产生， 作用于胸腺上皮细胞（TEC），增加其Foxn 1的表达，Foxn 1是一种关键的转录因子， 参与TEC的开发、维护和再生。这些作用促进TEC再生， 损伤后胸腺整体重建。因此，通过药理学或药理学方法消除BMP 4作用是可能的。 遗传抑制损害胸腺修复。重要的是，我们证明了体外过继转移 扩增的胸腺EC（exECThy）代表了在胸腺中递送BMP 4的可行方法，并增强了BMP 4的表达。 免疫损伤后的胸腺再生。此外，我们还发现，氧化应激的副产物，如 损伤后，脂质过氧化产物在胸腺中积累，并向EC发出促存活信号 通过激活损伤感应受体TRPA 1。我们证明了TRPA 1激动剂可以 通过激活内皮细胞增强胸腺再生。 基于这些发现，我们假设：（a）内皮细胞在T细胞再生中起重要作用 胸腺损伤后，（B）促进EC存活和功能的途径可用于 增强胸腺再生，和（c）可以施用exEC、BMP 4和/或TRPA 1激动剂， 用作增强移植后免疫重建的治疗策略。我们在目标1中提出 为了研究给予HCT受者exECThy和BMP 4对胸腺再生、外周T细胞增殖、胸腺细胞分化和胸腺细胞增殖的影响， 细胞重建、GVHD和移植物抗肿瘤活性。在目标2中，我们将研究 胸腺内皮细胞的抗损伤能力，重点是a）脂质过氧化产物和TRPA 1，和B）抗- 氧化剂途径如Nrf 2。 这些机制和临床前研究有可能确定重要的新途径， 胸腺再生，这可能导致临床方法，以增强T细胞免疫，不仅为 allo-HCT的接受者，但也适用于由于衰老而具有T细胞缺陷的个体（淋巴萎缩）， 自身免疫性疾病、传染病、休克、放射或化学疗法和辐射损伤。

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.