CD166 Regulates Human and Murine Hematopoietic Stem Cell Function and the Hematopoietic Niche

 描述（由申请人提供）：造血干细胞（HSC）、成骨细胞（OB）、间充质干细胞（MSC）和内皮细胞（EC）之间的生态位相互作用对于HSC自我更新和维持干细胞库至关重要。然而，介导这些相互作用的分子并没有很好地定义。我们发表的数据确定，CD 166，免疫球蛋白超家族的成员，表达在正常小鼠HSC和巢OB。最近，我们确定了CD 166也表达在推定的MSC和骨髓（BM）来源的EC上。由于其嗜同性的细胞-细胞相互作用，CD 166可能是HSC与造血生态位的所有这些元件相互作用的配体和受体。我们发表了CD 166鉴定了一小部分高度富集HSC功能的鼠BM细胞（LSK CD 48-CD 166 + CD 150+）。超过90%的人脐带血衍生细胞的长期体内再增殖潜力限于共表达CD 166的CD 34 + CD 38-谱系细胞。来自CD 166-/-小鼠的HSC在致死剂量照射的宿主中的植入是有缺陷的，并且CD 166-/-小生境不能支持重建HSC的长期植入。STAT 3-/-LSKCD 48-CD 150+细胞上的CD 166表达显著降低，并且STAT 3的抑制伴随着CD 166表达降低。STAT 3-/- HSC的植入在10和20受体中被显著抑制，并且STAT 3结合至CD 166启动子，这表明CD 166和STAT 3两者在功能上偶联并且参与HSC能力。我们假设CD 166是支持移植和HSC自我更新的HSC-小生境相互作用所需的通用功能标志物，并且CD 166介导的HSC自我更新的控制可以通过受STAT 3影响的信号传导途径来操纵，以增强HSC的临床疗效。我们的两个具体目标是：1）检验造血小生境的HSC和OB、MSC和EC上的CD 166表达是维持干细胞功能所需的假设，以及HSC或造血小生境的任何这些细胞元件上的CD 166表达的丧失对HSC功能是有害的假设，和2）检验gp 130激活的STAT 3调节CD 166表达和HSC的植入的假设，并且CD 166表达的治疗靶向可以被转化为在脐带血移植的情况下增强人HSC植入。该提案的意义在于，它将研究人类和小鼠HSC的新的和独特的功能标记物的作用，并将研究CD 166调节对干细胞功能的影响。保守的鼠和人CD 166同源性促进了旨在增强HSC植入和临床实用性的有效翻译研究。该提议的新奇源于其建立存在于鼠和人HSC两者上以及存在于HN的至少3种细胞类型上的标志物的功能能力的潜力。这项研究具有创新性，因为它涉及STAT 3在CD 166表达的调控中，并将探索一种新的分子机制，通过这种机制，涉及CD 166和STAT 3控制HSC功能，自我更新和植入。

 DESCRIPTION (provided by applicant): Interactions in the niche between hematopoietic stem cells (HSC), osteoblasts (OB), mesenchymal stem cells (MSC), and endothelial cells (EC) are critical for HSC self-renewal and maintenance of the stem cell pool. However, molecules mediating these interactions are not well defined. Our published data determined that CD166, a member of the immunoglobulin superfamily, is expressed on normal murine HSC and niche OB. More recently, we determined that CD166 is also expressed on putative MSC and bone marrow (BM)-derived EC. With its homophilic cell-cell interactions, CD166 may be both ligand and receptor of HSC in their interactions with all these elements of the hematopoietic niche. We published that CD166 identifies a very small group of murine BM cells (LSKCD48-CD166+CD150+) highly enriched for HSC function. More than 90% of long-term in vivo repopulating potential of human cord blood-derived cells is restricted to CD34+CD38- Lineage- cells that coexpress CD166. Engraftment of HSC from CD166-/- mice in lethally irradiated hosts is defective and the CD166-/- niche cannot support the long-term engraftment of repopulating HSC. CD166 expression on STAT3-/- LSKCD48-CD150+ cells is significantly reduced and inhibition of STAT3 concomitantly reduces CD166 expression. Engraftment of STAT3-/- HSC is significantly suppressed in 1o and 2o recipients and STAT3 binds to the CD166 promoter suggesting that both CD166 and STAT3 are functionally coupled and involved in HSC competence. We hypothesize that CD166 is a universal functional marker required for HSC-niche interactions that support engraftment and HSC self-renewal and that CD166-mediated control of HSC self-renewal can be manipulated via signaling pathways impacted by STAT3 to enhance HSC clinical efficacy. Our two specific aims will: 1) Test the hypothesis that CD166 expression on HSC and on OB, MSC, and EC of the hematopoietic niche is required for the maintenance of stem cell function and that loss of CD166 expression on HSC or any of these cellular elements of the hematopoietic niche is detrimental to HSC function and 2) Test the hypothesis that gp130-activated STAT3 regulates CD166 expression and the engraftment of HSC, and that therapeutic targeting of CD166 expression can be translated to enhance human HSC engraftment in the setting of cord blood transplantation. The significance of this proposal is that it will examine the role of a new and unique functional marker of human and murine HSC and will investigate the impact of CD166 modulation on stem cell function. The conserved murine and human CD166 homology facilitates efficient translational investigations aimed at enhancing HSC engraftment and clinical utility. The novelty of this proposal stems from its potential to establish the functional capacity of a marker present on both murine and human HSC and on at least 3 cell types of the HN. The proposed research is innovative because it implicates STAT3 in the regulation of CD166 expression and will explore the molecular mechanism through which a new pathway involving CD166 and STAT3 controls HSC function, self-renewal, and engraftment.