BIOACTIVE LIPIDS IN STEM CELL HOMING AND MOBILIZATION

描述(申请人提供)：已经提出了一个拉锯赛概念来解释骨髓(BM)和外周血(PB)之间的趋化基质衍生因子-1(SDF-1)梯度如何决定细胞是从BM释放和动员到PB还是从PB回到BM微环境。然而，这一概念需要重新评估，因为血浆SDF-1水平与造血干细胞/祖细胞(HSPC)的动员并不一致。与此同时，越来越明显的是，SDF-1在HSPC归巢到BM的过程中并不是唯一的角色，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支持，确定了生物活性鞘氨醇-1-磷酸(S1P)和神经酰胺-1-磷酸(C1P)在HSPC运输中的潜在重要作用。S1P和C1P对HSPC有很强的趋化作用，对蛋白水解酶具有抗性，动员过程中外周血和骨髓中S1P和C1P的水平显著升高。基于这些数据，我们提出了三个相互关联的目标，以重新评估SDF-1在干细胞运输中的作用，并解决我们的核心假设，即生物活性脂类S1P和C1P在HSPC的归巢和动员中发挥重要而目前未被认识的作用。除了临床研究，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。具体目的1.生物活性脂类S1P和C1P作为HSPC动员的执行者。我们最近发表的数据支持S1P-S1P受体1型(S1P1)轴在HSPC从BM到PB的出口中起着关键作用。我们将研究动员对S1P在血室间分布的影响，并确定外周血中S1P水平是否与患者的动员效果相关。同时，我们将讨论C1P的作用，并调查是否有一种或两种生物活性脂类(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S1P和C1P推动哪些动员步骤。特定目的2.生物活性脂类作为HSPC新的归巢因子。用于移植的清髓性条件诱导骨髓中的蛋白分解微环境，导致化学活性SDF-1的减少。我们发现，在条件化过程中，骨髓中S1P和C1P的水平升高，S1P1的拮抗作用损害了HSPC的植入。由于这些脂类对HSPC具有很强的趋化作用，我们将重点研究它们在HSPC归巢中的潜在作用，并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S1P和C1P信号来改善造血干细胞的动员和归巢。基于我们的初步数据，我们建议开发新的战略，以改善HSPC的动员和归位。这些策略将首先在小鼠身上进行测试，然后在嵌合的人类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.