BIOACTIVE LIPIDS IN STEM CELL HOMING AND MOBILIZATION

描述（由申请人提供）：提出了拔河概念，以解释骨髓（BM）和外周血（PB）之间的趋化性基质衍生因子-1（SDF-1）梯度如何决定细胞是从BM释放和动员到PB中，还是从PB返回BM微环境。然而，这一概念需要重新评估，因为血浆SDF-1水平与造血干/祖细胞（HSPC）的动员并不一致。与此同时，越来越清楚的是，SDF-1在HSPC归巢到BM中并不起唯一作用，这意味着存在其他因素。来自我们实验室的新数据以及其他研究人员最近的观察结果支持，确定了生物活性鞘脂鞘氨醇-1磷酸（S1 P）和神经酰胺-1磷酸（C1 P）在HSPC运输中的潜在重要作用。S1 P和C1 P是i）HSPC的强化学引诱剂，ii）对蛋白水解酶具有抗性，和iii）在动员期间在PB中和在用于移植的清髓性预处理后在BM中表现出显著增加的水平。基于这些数据，我们提出了三个相互关联的目标，重新评估SDF-1在干细胞运输中的作用，并解决我们的中心假设，即生物活性脂质S1 P和C1 P在HSPCs的归巢和动员中发挥重要且目前未被重视的作用。除了临床研究外，我们的方法还将在小鼠模型中利用基于小分子和遗传学的策略。具体目标1。生物活性脂质S1 P和C1 P作为HSPC动员的执行者。我们最近发表的数据支持S1 P-S1 P受体1型（S1 P1）轴在HSPC从BM进入PB的过程中起关键作用。我们将研究动员对血室之间S1 P分布的影响，并确定PB中S1 P水平是否与患者的动员疗效相关。与此同时，我们将探讨C1 P的作用，并研究是否一种或两种生物活性脂质（储存在循环红细胞中）负责动员溶血综合征患者的HSPC。最后，我们将机械地定义哪些动员步骤是由S1 P和C1 P促进的。具体目标2。生物活性脂质作为HSPCs的新型归巢因子。用于移植的清髓性预处理诱导BM中的蛋白水解微环境，导致具有化学活性的SDF-1减少。我们已经发现，BM中S1 P和C1 P的水平在预处理过程中增加，并且S1 P1的拮抗作用损害HSPC的植入。由于这些脂质是HSPC的强HSPC化学引诱剂，我们将集中在他们的潜在作用，归巢的HSPC和阐明这种现象的分子和细胞基础。具体目标3。制定策略，通过调节S1 P和C1 P信号来改善造血干细胞的动员和归巢。根据我们的初步数据，我们建议开发新的策略，将提高动员和归巢的HSPCs。这些策略将首先在小鼠中进行测试，随后在嵌合人HSPC/免疫缺陷小鼠异种移植模型中进行验证。

DESCRIPTION (provided by applicant): A tug-of-war concept has been proposed to explain how a chemotactic stromal derived factor-1 (SDF-1) gradient between bone marrow (BM) and peripheral blood (PB) determines whether cells will be released and mobilized from BM into PB or home back from PB to the BM microenvironment. This concept, however, needs reappraisal because plasma SDF-1 levels do not consistently correlate with mobilization of hematopoietic stem/progenitor cells (HSPCs). At the same time, it is becoming clear that SDF-1 does not play an exclusive role in the homing of HSPCs into BM, implying the existence of additional factors. New data from our laboratory and supported by recent observations from other researchers, identify a potentially important role for the bioactive sphingolipids sphingosine-1 phosphate (S1P) and ceramide-1 phosphate (C1P) in trafficking of HSPCs. S1P and C1P are i) strong chemoattractants for HSPCs, ii) resistant to proteolytic enzymes, and iii) exhibit markedly increased levels in PB during mobilization and in BM after myeloablative conditioning for transplantation. Based on these data, we propose three interrelated aims to reappraise the role of SDF-1 in stem cell trafficking and address our central hypothesis that the bioactive lipids S1P and C1P play an important and presently unappreciated role in homing and mobilization of HSPCs. In addition to clinical studies, our approach will exploit small molecule- and genetics-based strategies in mouse models. Specific Aim 1. Bioactive lipids S1P and C1P as executors of HSPC mobilization. Our recently published data support a pivotal role for the S1P- S1P receptor type 1 (S1P1) axis in egress of HSPCs from BM into PB. We will investigate the impact of mobilization on the distribution of S1P between blood compartments and determine whether the level of S1P in PB correlates with mobilization efficacy in patients. In parallel, we will address the role of C1P and investigate whether one or both bioactive lipids (which are stored in circulating red blood cells) are responsible for mobilization of HSPCs in patients with hemolytic syndromes. Finally, we will mechanistically define which mobilization steps are promoted by S1P and C1P. Specific Aim 2. Bioactive lipids as a novel homing factors for HSPCs. Myeloablative conditioning for transplantation induces a proteolytic microenvironment in BM leading to a decrease in chemotactically active SDF-1. We have found that BM levels of S1P and C1P are increased during conditioning and that antagonism of S1P1 impairs engraftment of HSPCs. Since these lipids are strong HSPC chemoattractants for HSPCs, we will focus on their potential role in homing of HSPCs and elucidate the molecular and cellular basis for this phenomenon. Specific Aim 3. Develop strategies to improve mobilization and homing of hematopoietic stem cells by modulating S1P and C1P signaling. Based on our preliminary data we propose to develop new strategies that will improve both mobilization and homing of HSPCs. These strategies will be tested first in mice and subsequently validated in chimeric human HSPCs/immunodeficient mouse xenotransplant models.