Role of resident mesenchymal stem cells in lung allograft rejection

描述(申请人提供)：慢性排斥或毛细支气管炎闭塞症(BO)仍然是肺移植后长期存活的主要障碍。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。我们最近在人肺移植的支气管肺泡灌洗液中发现了一群供者来源的或驻留在肺内的间充质干细胞(LR-MSCs)。我们现在证明，灌洗液中这些细胞的数量与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表明，LR-MSCs既能抑制T细胞反应，又能向纤维性肌成纤维细胞分化。LR-MSC来源的前列腺素(PGE2)既是T细胞活化的旁分泌抑制因子，也是T细胞纤维化分化的自分泌抑制因子。我们假设LR-MSCs参与了同种异体肺移植的反应，它们的数量和功能可作为预测BO发生的生物标志物。我们进一步提出，前列腺素合成和反应缺陷的获得，这是一种由促纤维化环境促进的现象，触发了LR-MSC表型从免疫调节到促纤维化的“切换”。这一应用的目的是利用我们直接从肺移植中研究LR-MSCs的独特能力来了解调节LR-MSCs纤维化分化的机制。这项应用将(1)利用来自正常肺移植的LR-MSCs确定LR-MSCs(一种在损伤后聚集的移植物衍生细胞)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)使用配对病例对照研究确定从BOS患者分离的LR-MSCs是否表现出以分泌和反应PGE2的能力降低为特征的改变表型，从而增加纤维化分化的倾向；(3)采用前瞻性队列研究，前瞻性地确定BAL中的LR-MSCs数量及其纤维增殖表型是否可以预测BOS的发生和进展。这项应用是首次尝试研究移植物来源的多潜能间充质祖细胞这一新的群体，并将为了解它们在肺移植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。

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.