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

小鼠和人造血干细胞(HSC)的表型组成和功能 对其进行了详尽的研究，使其成为哺乳动物中最具特征的细胞组之一 生物学。尽管如此，之前还没有一个单一的功能标记被鉴定出来，这对小鼠和 人的HSC同时也表达在至少三种重要的造血细胞成分上 NICE(HN)，即成骨细胞(OB)、内皮细胞(EC)和间充质干细胞(MSC)。我们的重点是 CD166始于我们第一次确定CD166识别参与促进造血的OB时 活动。我们还发表了CD166在正常小鼠和人的HSC上的表达，并在 确定他们的职能能力和HN的能力。我们最近证实CD166是 在EC和Nestin+MSC的子集上表达。由于CD166能够介导异性恋者和同性恋者 细胞之间的相互作用，我们认为CD166既是HSC相互作用的配体，也是HSC与HSC相互作用的受体 小生境中的细胞成分，是HN和茎的能力的重要调节因素 细胞功能。CD166-/-小鼠的HSC在致死剂量照射的宿主体内植入效果不佳。另一方面CD166-/- 小鼠不支持LT-HSC的植入，提示CD166的丢失会取消 HN。野生型(WT)供者的骨髓来源的LSK细胞更接近宿主小鼠的骨内膜 来自基因敲除(KO)动物的相似细胞表明，植入受到缺乏 HSC-OB同源CD166-相互作用7.WT和CD166-/-CD150+CD48-LSK的单细胞RNAseq分析 与固定化CD166蛋白孵育的细胞显示CD166与这些细胞的结合被激活 细胞因子信号、表观遗传途径、干细胞多能基因和线粒体相关信号 小路。基于这些发现，我们推测CD166是HSC所必需的功能标记物。 支持造血生态位能力的生态位相互作用。我们还认为， 生态位中优先的CD166同源相互作用有助于HSC的调节和维持 干细胞的造血潜能。我们将通过调查两个目标来验证这些假设：1)测试 假设CD166在造血龛的OB、EC和MSC上的表达是 造血生态位的能力和2)检验造血干细胞缺乏的假说 CD166与OB、EC和MSC在小生境中的同源相互作用不能正常发展并获得 植入物缺陷。这项提议的意义在于，它将审查一个新的和独特的 人和小鼠HSC的功能标志，并将研究CD166调节对干细胞的影响 功能。这项提议的新颖性源于它有可能将CD166牵连到HN的监管中 和HSC，它们驻留在这个微环境中富含CD166的细胞元件中，并与之相互作用。这些研究 有可能定义CD166的同嗜性相互作用如何促进HSC自我更新。

The phenotypic makeup and functional capacity of murine and human hematopoietic stem cells (HSC) has been exhaustively investigated making HSC one of the most-characterized groups of cells in mammalian biology. Still, not a single functional marker has been previously identified that is common to both murine and human HSC while being also expressed on at least three important cellular components of the hematopoietic niche (HN), namely osteoblasts (OB), endothelia cells (EC), and mesenchymal stem cells (MSC). Our focus on CD166 began when we first established that CD166 identifies OB that mediate a hematopoiesis enhancing activity. We also published that CD166 is expressed on normal murine and human HSC and plays a key role in determining their functional capacity and the competence of the HN. We recently confirmed that CD166 is expressed on a subset of EC and nestin+ MSC. Since CD166 is capable of mediating hetero- and homophilic cell-cell interactions, we propose that CD166 serves as both ligand and receptor of HSC interactions with cellular elements of the niche and is an important regulator of the competence of the HN and of stem cell function. HSC from CD166-/- mice engraft poorly in lethally irradiated hosts. On the other hand CD166-/- mice do not support the engraftment of LT-HSC suggesting that loss of CD166 abrogates the competence of the HN. Marrow-homed LSK cells from wildtype (WT) donors lodged closer to the endosteum of host mice than similar cells from knockout (KO) animals suggesting that engraftment is adversely impacted by the lack of HSC-OB homophilic CD166-interactions7. Single-cell RNAseq analysis of WT and CD166-/- CD150+CD48- LSK cells incubated with immobilized CD166 protein revealed that engagement of CD166 on these cells activated cytokine signaling, epigenetic pathways, stem cell pluripotency genes, and mitochondria-related signaling pathways. Based on these findings, we hypothesize that CD166 is a functional marker required for HSC- niche interactions that support the competence of the hematopoietic niche. We also believe that preferential CD166 homophilic interactions in the niche contribute to HSC regulation and maintenance of the hematopoietic potential of stem cells. We will test these hypotheses by investigating 2 aims: 1) Test the hypothesis that CD166 expression on OB, EC, and MSC in the hematopoietic niche is required for the competence of the hematopoietic niche and 2) Test the hypothesis that hematopoietic stem cells lacking CD166 homophilic interactions with OB, EC, and MSC in the niche fail to develop normally and acquire an engraftment defect. 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 novelty of this proposal stems from its potential to implicate CD166 in the regulation of the HN and HSC that reside in and interact with CD166-rich cellular elements of this microenvironment. These studies have the potential to define how homophilic CD166 interactions promote HSC self-renewal.