ROLE OF TLR2 IN REGULATING NORMAL AND PREMALIGNANT HEMATOPOIETIC STEM CELLS

项目总结 这个项目的目标是了解炎症信号如何通过Toll样受体2(TLR2) 调节正常和癌前造血干细胞(HSCs)。TLR2是TLR家族的成员 在先天免疫反应中起核心作用的模式识别受体。对TLRs的研究有 主要集中在成熟的免疫细胞群体，但TLR也表达在造血干细胞上，最近 研究表明，TLR信号可能从肝星状细胞水平影响免疫应答。 此外，解除TLR信号，特别是增加TLR2的表达和信号，是 与骨髓增生异常综合征(MDS)相关的一组HSC疾病的特征是无效 造血和转化为急性白血病的高风险。因此，异常的TLR2信号可能具有 对造血干细胞有显著的临床不良影响。 我们的初步数据表明，TLR2信号影响HSC的数量、动员和功能。 利用嵌合小鼠研究，我们确定TLR2信号对HSCs的这些影响是通过 细胞自主和细胞非自主机制。因此我们假设TLR2信号 多种细胞类型参与了对HSC的调节，TLR2诱导的HSC功能改变可能 参与MDS的发病机制。在本提案中，我们将使用CyTOF质量细胞术和条件性 基因敲除小鼠研究以确定MDS中TLR2信号增强的细胞类型并确定 不同造血细胞和基质细胞TLR2信号的条件性缺失对小鼠骨髓基质细胞增殖的影响 肝星状细胞的监管。此外，我们将使用MDS的小鼠模型，在该模型中，我们可以增加或减少 TLR2信号，以验证增强的TLR2信号有助于这种疾病的发病机制的假说 疾病。这些研究将进一步加深我们对TLR2如何调节HSC的理解，并测试它作为一种 MDS的治疗靶点。更广泛地说，我们希望更好地了解TLR信号是如何调节的 正常的和癌前的HSC，我们预计这些研究将不仅对 MDS的发病机制，但TLR信号异常(例如，慢性感染)可能对其他 骨髓衰竭和/或白血病5例。未来的研究将以这些结果为基础，并将重点放在 TLR2信号对造血干细胞影响的下游介体，目的是识别 参与HSC的循环、分化、动员和/或功能丧失，以响应TLR信号。

PROJECT SUMMARY The goal of this project is to understand how inflammatory signaling through toll like receptor 2 (TLR2) regulates both normal and premalignant hematopoietic stem cells (HSCs). TLR2 is a member of the TLR family of pattern-recognition receptors that play a central role in the innate immune response. Studies of TLRs have largely focused on mature immune cell populations, however TLRs are also expressed on HSCs, and recent reports demonstrate that TLR signaling may influence the immune response from the level of the HSC. Furthermore, deregulated TLR signaling, and in particular increased TLR2 expression and signaling, is associated with myelodysplastic syndromes (MDS), a group of HSC disorders characterized by ineffective hematopoiesis and a high risk of transformation to acute leukemia. Thus, aberrant TLR2 signaling may have clinically significant detrimental effects on HSCs. Our preliminary data suggest that TLR2 signals influence HSC numbers, mobilization and function. Using chimeric mouse studies, we determined that these effects of TLR2 signaling on HSCs are mediated by both cell autonomous and cell non-autonomous mechanisms. We therefore hypothesize that TLR2 signaling from multiple cell types contributes to the regulation of HSCs, and TLR2-induced changes in HSC function may contribute to the pathogenesis of MDS. In this proposal we will use CyTOF mass cytometry and conditional knockout mouse studies to identify the cell types in which TLR2 signaling is enhanced in MDS and determine the effects of conditional loss of TLR2 signaling from different hematopoietic and stromal cells types to the regulation of HSCs. In addition, we will use a mouse model of MDS in which we either augment or reduce TLR2 signaling to test the hypothesis that enhanced TLR2 signaling contributes to the pathogenesis of this disease. These studies will further our understanding of how TLR2 regulates HSCs and test it's utility as a therapeutic target in MDS. More broadly, we hope to gain a better understanding of how TLR signals regulate both normal and premalignant HSCs, and we anticipate that these studies will have implications not only for the pathogenesis of MDS, but for how aberrant TLR signaling (e.g., chronic infection) may contribute to other cases of bone marrow failure and/or leukemogenesis. Future studies will build upon these results and focus on the downstream mediators of the effects of TLR2 signaling on HSCs, with the goal of identifying genes that contribute to HSC cycling, differentiation, mobilization and/or loss of function in response to TLR signals.