Regulation of macrophage maturation in ischemia: Topography and composition of the ischemic vascular niche and regulation by Notch signaling.

缺血引起炎症反应，旨在恢复灌注和促进愈合，但往往加重损伤。巨噬细胞是功能性动脉在缺血反应中生长所必需的，但具有多种功能，从破坏性到营养或修复作用。在缺血过程中巨噬细胞的分化和功能是如何调节的，目前还不清楚。在小鼠后肢缺血模型中，我们最近发现血管通过Notch信号控制巨噬细胞从募集的单核细胞分化和成熟，从而促进动脉发生和缺血组织恢复。巨噬细胞的成熟由血管内皮细胞中表达的Notch配体Dll1控制，并需要巨噬细胞通过Rbpj规范Notch信号，同时抑制炎症性巨噬细胞的命运。此外，Notch激活的作用足以使单核细胞在体外产生成熟的巨噬细胞，即使在促炎刺激下也表现出稳定的抗炎表型。我们拟通过Notch信号研究缺血巨噬细胞生态位的地形和组成，以及调控缺血巨噬细胞分化的分子事件。我们将识别控制巨噬细胞成熟的血管结构域，并将特异性识别在缺血中介导巨噬细胞成熟的Notch受体。我们将进一步确定缺血巨噬细胞成熟所必需的生长因子背景。我们将在小鼠后肢缺血模型中采用遗传报告研究和条件删除策略，以及在特定条件下建立巨噬细胞培养的体外研究来解决这些问题。利用这些发现，我们将在一项转化研究中尝试在体外产生具有治疗潜力的人巨噬细胞。

Ischemia causes an inflammatory response that is intended to restore perfusion and promote healing but often aggravates damage. Macrophages are essential for growth of functional arteries in response to ischemia yet show diverse functions ranging from destructive to trophic or reparative actions. How macrophage differentiation and function is regulated during ischemia remains largely unknown. In a mouse model of hind limb ischemia we have recently shown that blood vessels control macrophage differentiation and maturation from recruited monocytes via Notch signaling, which in turn promotes arteriogenesis and ischemic tissue recovery. Macrophage maturation is controlled by Notch ligand Dll1 expressed in vascular endothelial cells and requires macrophage canonical Notch signaling via Rbpj, which simultaneously suppresses an inflammatory macrophage fate. Furthermore, the effects of Notch activation are sufficient to generate mature macrophages from monocytes ex vivo that display a stable anti-inflammatory phenotype, even when stimulated with pro-inflammatory stimuli. We here propose to study the topography and composition of the ischemic niche and the molecular events regulating ischemic macrophage differentiation by Notch signaling. We will identify the vascular domain controlling macrophage maturation and will specifically identify the Notch receptors mediating macrophage maturation in ischemia. We will further define the growth factor context essential for ischemic macrophage maturation. We will employ genetic reporter studies and conditional deletion strategies in mouse models of hind limb ischemia as well as in vitro studies with macrophage cultures established under defined conditions to address these questions. Using these findings we will try, in a translational study, to generate human macrophages ex vivo with therapeutic potential.