Regulation of monocyte lineage development in systemic and vascular inflammation and the influence of Notch signaling

单核吞噬系统和血管不断相互作用以维持稳态。内皮细胞（EC）提供特异性信号并引导经典（Ly 6Chi）单核细胞分化为巡逻（Ly 6Clo）单核细胞、MHC-II+单核细胞或巨噬细胞（MF）和树突状细胞（DC）。另一方面，成熟的吞噬细胞参与炎症反应和血管或组织监测。这种多功能的EC与单核细胞的串扰受到慢性环境应激的损害，其诱导低度炎症并使单核细胞发育程序失调。这导致炎性细胞的扩张和活化、血管的浸润和随后的损伤以及心血管疾病的发展。当失调的吞噬细胞暴露于额外的微生物应激物时，炎症和血管病理学进一步增强。Ly 6Chi单核细胞对一系列吞噬细胞具有发育可塑性，因为它们分化成表型和功能不同的成熟细胞，包括Ly 6Clo、MHC-II+单核细胞、MF和DC。单细胞生成的这一晚期步骤由EC至骨髓Notch信号传导严格控制。然而，很少有人知道的单核细胞，单核细胞祖细胞和分化途径，定义单核细胞的异质性，发育可塑性和influencinginflammation.We的早期步骤已经假设，并显示在初步的结果，单核细胞是来自至少两个独立的祖细胞谱系，即MDP 2和cMoP依赖的途径，这一过程是由Notch控制。我们开发了一种新的小鼠模型，其中Notch 2在早期MDP 2依赖性单细胞生成中特异性缺失，而替代的cMoP依赖性单细胞生成保持完整。Notch 2缺失导致稳定状态下Ly 6Clo-的减少和MHC-II+单核细胞和DC的扩增。当受到炎性刺激时，这些小鼠发生严重的炎症，血液中MF样细胞和MHC-II+单核细胞异常扩增，以及主要血管的MF浸润。在体外Notch配体DLL 1诱导Ly 6Clo单核细胞的特异性扩增，而DLL 4支持MHC-II+单核细胞发育。在体内，在血管炎症过程中，血管中Dll 1的下调和Dll 4的上调与MHC-II+单核细胞、DC和MF的同时扩增证实了单核细胞命运的配体特异性调节。因此，Notch调控单核细胞的异质性、分化、功能和炎症反应，我们希望通过研究单核细胞的单细胞生成途径，阐明单核细胞异质性的机制。我们打算定义信号机制控制单核细胞，单核细胞的功能和炎症的影响。这些知识对于理解炎症和血管损伤的病理生理学可能是至关重要的，并显着有助于设计有效的治疗策略和预防措施。

Mononuclear-phagocytic system and blood vessels constantly interact with each other to maintain homeostasis. Endothelial cells (EC) provide specific signals and guide classical (Ly6Chi) monocyte differentiation into patrolling (Ly6Clo) monocytes, MHC-II+ monocytes, or macrophages (MF) and dendritic cells (DC). On the other hand, mature phagocytes are implicated in inflammatory reactions and vascular or tissue monitoring. Such versatile EC-to-monocyte cross-talk is impaired by chronic environmental stress, which induces low-grade inflammation and dysregulates monocyte developmental program. This leads to expansion and activation of inflammatory cells, infiltration and subsequent damage of blood vessels and development of cardiovascular disease. Inflammation and vascular pathology is further enhanced when dysregulated phagocytes are exposed to the additional microbial stressors.Ly6Chi monocytes have developmental plasticity for a spectrum of phagocytes as they differentiate into phenotypically and functionally distinct mature cells including Ly6Clo, MHC-II+ monocytes, MF and DCs. This late step of monopoiesis is tightly controlled by EC-to-myeloid Notch signaling. Yet little is known about early steps of monopoiesis, monocyte progenitors and differentiation pathways which define monocyte heterogeneity, developmental plasticity and influence inflammation.We have hypothesized and show in preliminary results that monocytes are derived from at least two independent progenitor lineages, i.e. MDP2- and cMoP-dependent pathways, and this process is controlled by Notch. We developed a new mouse model where Notch2 is specifically deleted in early MDP2-dependent monopoiesis, while the alternative, cMoP-dependent monopoiesis remains intact. Notch2 deletion causes reduction of Ly6Clo- and expansion of MHC-II+ monocytes and DCs in steady state. When subjected to inflammatory stimuli, these mice develop severe inflammation with aberrant expansion of MF-like cells and MHC-II+ monocytes in the blood and MF infiltration of major blood vessels. In vitro Notch ligand DLL1 induced specific expansion of Ly6Clo monocytes, while DLL4 supported MHC-II+ monocyte development. In vivo, downregulation of Dll1 and upregulation of Dll4 in blood vessels with simultaneous expansion of MHC-II+ monocytes, DC and MF during vascular inflammation confirmed ligand-specific regulation of monocyte cell fate. Thus, Notch controls monocyte heterogeneity, differentiation, function and influences inflammation.Here we propose to study pathways of monopoiesis and address the mechanisms of monocyte heterogeneity. We intend to define signaling mechanisms controlling monopoiesis, the function of monocytes and implication for inflammation. This knowledge might be crucial for understanding of the pathophysiology of inflammation and vascular damage and significantly contribute to the design of efficient treatment strategies and preventive measures.