Role of resident mesenchymal stem cells in lung allograft rejection

描述（由申请人提供）：慢性排斥反应或闭塞性细支气管炎（BO）仍然是肺移植术后长期生存的主要障碍。BO是对反复或慢性损伤的移植物重塑反应，但移植物细胞而不是宿主来源的细胞在BO发病机制中的作用仍有待研究。我们最近在人肺同种异体移植的支气管肺泡灌洗液中发现了供体来源或肺常驻间充质干细胞（LR-MSCs）群体。我们现在表明，灌洗液中这些细胞的数量与同种异体移植物损伤的证据直接相关，并预测肺功能下降（闭塞性细支气管炎综合征（BOS））。我们的初步数据进一步证明，LR-MSCs既能抑制T细胞反应，又能向成纤维性肌成纤维细胞分化。lr - msc衍生的前列腺素（PGE2）作为T细胞活化的旁分泌抑制剂和其纤维化分化的自分泌抑制剂是重要的。我们假设LR-MSCs参与了肺同种异体移植反应，并且它们的数量和功能可以作为预测BO发展的生物标志物。我们进一步提出，在促纤维化环境下，前列腺素合成和反应中获得缺陷，触发了LR-MSC表型从免疫调节性到促纤维化的“开关”。本应用程序的目的是利用我们直接从肺同种异体移植中研究LR-MSCs的独特能力，了解调节LR-MSCs纤维化分化的机制。该应用将(1)利用来自正常肺同种异体移植物的LR-MSCs确定LR-MSCs（一种因损伤而积累的移植物衍生细胞）与局部细胞因子环境之间的相互作用，重点关注PGE2在这种相互作用中的作用；(2)通过一项匹配的病例对照研究，确定从BOS患者中分离的LR-MSCs是否表现出表型改变，其特征是分泌和响应PGE2的能力下降，导致纤维化分化倾向增加；(3)通过前瞻性队列研究，在人肺同种异体移植物中，前瞻性地确定BAL中LR-MSCs的数量及其纤维增生性表型是否能预测BOS的发生和进展。这项应用代表了研究这种新型移植物衍生的多能间充质祖细胞的首次尝试，并将为它们在肺同种异体移植物损伤的适应性和非适应性反应中的作用提供重要的机制见解。公共卫生相关性：我们提出的研究将首次研究肺常驻间充质干细胞作为肺移植慢性排斥反应的生物标志物，并提供关于人肺移植慢性同种异体移植排斥反应的细胞和生化调节剂的新机制信息。

DESCRIPTION (provided by applicant): Chronic rejection or bronchiolitis obliterans (BO) continues to be the major impediment to long-term survival after lung transplantation. BO is a graft remodeling response to repeated or chronic injury, but the role of graft- as opposed to host-derived cells in the pathogenesis of BO remains to be investigated. We have recently identified in bronchoalveolar lavage from human lung allografts a population of donor-derived or lung resident mesenchymal stem cells (LR-MSCs). We now show that the number of these cells in lavage fluid correlates directly with evidence of allograft injury and predict decline in lung functions (bronchiolitis obliterans syndrome (BOS)). Our preliminary data further demonstrate that LR-MSCs are capable of both inhibiting T cell responses and undergoing differentiation to fibrogenic myofibroblasts. LR-MSC-derived prostaglandin (PGE2) is important as both a paracrine inhibitor of T cell activation and as an autocrine inhibitor of their fibrogenic differentiation. We hypothesize that LR-MSCs participate in lung allograft responses and that their numbers and functions serve as biomarkers which predict the development of BO. We further propose that acquisition of a defect in prostaglandin synthesis and response, a phenomenon promoted by pro-fibrotic milieu, triggers a "switch" in LR-MSC phenotype from immunoregulatory to pro-fibrotic. The aim of this application is to understand the mechanisms that regulate the fibrotic differentiation of LR-MSCs utilizing our unique ability to study LR-MSCs directly from lung allografts. This application will (1) Utilizing LR-MSCs from normal lung allografts determine the interaction between LR-MSCs (a graft-derived cell which accumulates in response to injury) and local cytokine milieu focusing on the role of PGE2 in this interaction; (2) Using a matched case control study determine whether LR-MSCs isolated from patients with BOS demonstrate an altered phenotype marked by a decreased capacity to secrete and respond to PGE2 leading to an increased propensity towards fibrotic differentiation and; (3) Using a prospective cohort study prospectively determine in human pulmonary allografts whether number of LR-MSCs in BAL and their fibroproliferative phenotypes predict onset and progression of BOS. This application represents the first attempt to study this novel population of graft derived multipotent mesenchymal progenitor cells and will provide important mechanistic insights into their role in adaptive and maladaptive responses to lung allograft injury. PUBLIC HEALTH RELEVANCE: Our proposed studies will be the first to investigate lung resident mesenchymal stem cells as biomarkers of chronic rejection in lung transplantation and provide novel mechanistic information regarding cellular and biochemical modulators of chronic allograft rejection in human lung transplantation.