Hematopoietic stem and progenitor cell regulation of the niche through extracellular vesicles

摘要 过继移植造血干祖细胞(HSPC)可为非霍奇金淋巴瘤提供有效治疗。 异基因造血干细胞移植(HSCT)或作为平台的恶性疾病 进行自体基因治疗。骨髓(BM)利基是由操作定义的核心单元，用于维持 造血功能，来自非造血支持细胞的信号使HSPC输出适应生物体 需求。然而，在BM中使用HSPC是一个竞争的过程，HSCT患者通常需要 条件反射，消除内源性造血，“创造空间”，从而促进归巢和 在高度血管化的壁龛中植入。分泌活动是HSPC的基本属性，但其影响 从HSPC产生的信号以及它们在利基中的细胞目标还没有被很好地理解。中国的差距 关于HSPC和血管壁龛内皮细胞之间的串扰的知识可能持有 重要的生物学洞察力和机会，以提高竞争性HSPC生态位适应能力，并具有潜在的 抵消造血干细胞移植调节治疗的毒性和长期副作用的新策略。这个 运输蛋白和RNA货物的纳米级细胞外小泡(EVS)的分泌是构成成分 细胞功能。有趣的是，动员的CD34+HSPC-在移植后提供了已知的优势 HSCT-已经被证明可以释放EV(EVCD34)，这种EV在microRNA-126中高度丰富，是一种“血管转录因子”。 这调节Akt/mTOR信号，而Akt/mTOR信号又是EC造血支持的核心。其他人则表明， 过继转导富含miR-126的EVCD34可促进EC的增殖和功能。我们的委托人 假设miR-126的EVHSPC运输积极地塑造了血管BM生态位中的EC功能 以提高入住率和改善再人口状况。三个目标将检验我们的假设。在目标1中，我们将 确定细胞自主分泌EVHSPC对自我更新和再繁殖能力的影响 动态平衡和压力的状态。目标2将测试内皮细胞作为主要细胞的作用 电动汽车在BM利基市场的目标。目标3将剖析miR-126在调节BM中的具体作用 内皮细胞命运及其涉及的信号通路。作为原则性研究的证明，这项建议将 对EVHSPC的实验和机制关注，但对HSPC分泌组的生物学作用的洞察 BM的利基市场将是广阔的。翻译过来，我们的长期目标是开发新的、无毒的 改善异基因造血干细胞移植和自体基因治疗后预后的方法。

ABSTRACT Adoptive transfer of hematopoietic stem and progenitor cells (HSPC) can provide effective treatment for non- malignant disorders in the form of allogeneic hematopoietic stem cell transplantation (HSCT) or as a platform for autologous gene therapy. Bone marrow (BM) niches are the operationally-defined core units that sustain hematopoietic function, where signals from non-hematopoietic support cells adapt HSPC output to organismal demand. HSPC occupancy in the BM, however, is a competitive process, and HSCT patients typically require conditioning to eliminate endogenous hematopoiesis and “create space”, thereby promoting homing and engraftment in highly vascularized niches. Secretory activity is a fundamental HSPC property, but the impact of signals that emerge from HSPC, and their cellular targets in the niche are not well understood. The gap in knowledge regarding the crosstalk between HSPC and vascular niche endothelial cells specifically, may hold important biological insight and opportunities to improve competitive HSPC niche fitness, and a potentially novel strategy to offset the toxicity and long-term side effects from HSCT conditioning treatments. The secretion of nanometer sized extracellular vesicles (EVs) that traffic protein and RNA cargo is a constitutive cellular function. Intriguingly, mobilized CD34+ HSPC -which provide known advantages to engraftment after HSCT- have been shown to release EVs (EVCD34) that are highly abundant in microRNA-126, an “angiomiR” that regulates Akt/mTOR signaling, which in turn is central to EC hematopoiesis support. Others showed that adoptively transferred EVCD34, rich in miR-126, enhance EC proliferation and function. Our principal hypothesis is that EVHSPC trafficking of miR-126 actively shapes EC function in the vascular BM niche to enhance occupancy and improve repopulation. Three aims will test our hypothesis. In Aim 1 we will determine the cell-autonomous impact of EVHSPC secretion on self-renewal and repopulation potency under conditions of homeostasis and stress. Aim 2 will test the role of endothelial cells as predominant cellular targets for EV trafficking in the BM niche. Aim 3 will dissect the specific role of miR-126 and in regulating BM endothelial cell fates and the involved signaling pathways. As a proof of principle study, this proposal places an experimental and mechanistic focus on EVHSPC, but insight into the biologic role of the HSPC secretome in the BM niche will be broad. Translationally, our long-term goal is the development of new, non-toxic approaches to improve outcomes after allogeneic HSCT and autologous gene therapy.