Targeting blood stem cell activity and extramedullary monocytopoiesis to treat atherosclerosis

在动脉粥样硬化的早期阶段，单核细胞黏附并渗入血管床。一旦它们进入血管壁，它们就分化成巨噬细胞，众所周知，巨噬细胞可以放大血管炎症。虽然巨噬细胞的许多促炎功能已为人所知(例如，炎性小体的作用，泡泡减少，Netrin-1依赖的迁移功能受损)，但令人惊讶的是，人们对这些细胞的供应知之甚少。尤其是在炎症条件下，造血干细胞和祖细胞从骨髓中释放出来，并在脾中播种，在那里它们产生髓系祖细胞(GMP和MDP)，然后再产生促炎单核细胞。有趣的是，心肌梗死诱导骨髓中的造血干/祖细胞释放，髓外单核细胞生成持续增加，进而进一步加重血管炎症。虽然骨髓生态位在过去几年中得到了深入的研究，但所谓的脾造血生态位仍然知之甚少。然而，尤其是脾造血是许多慢性炎症过程的标志，并导致单核细胞的产生。自己的初步工作表明，特别是脾内皮细胞在髓外单核细胞生成的调节中起着关键作用。在动脉粥样硬化动物模型中，抑制内皮黏附分子(E-选择素)可降低脾中造血干/祖细胞的增殖率，并伴随着深刻的动脉粥样硬化保护作用(ApoE-/-)。下一步将破译脾内皮细胞与造血干、祖细胞之间的相互作用；具体地说，我们将研究髓系祖细胞的分化和增殖以及脾内皮细胞增殖性细胞因子的变化是否可能与观察到的效果有关。此外，我们将成像脾中的造血干细胞和造血祖细胞，并分析其在慢性炎症基线条件下的解剖定位。为此，我们将使用不同的转基因小鼠模型(例如内皮细胞特异性敲除小鼠)、小鼠脾移植模型以及各种其他细胞和分子技术，包括成像方法，如FMT/CT。脾内皮细胞将进行FAC分选。这项应用的总体目标是阐明特征不佳的脾造血利基，以便开发一种治疗策略来对抗血管炎症。

Monocytes adhere and infiltrate the vascular bed in the early stages of atherosclerosis. Once they have entered the vascular wall they differentiate into macrophages, which are known to amplify vascular inflammation. While many pro-inflammatory features of macrophages are already known (e.g. the role of the inflammasome, diminished efferocytosis, impaired netrin-1 dependent emigration), surprisingly little is known about the supply of these cells. Particularly under inflammatory conditions, hematopoietic stem and progenitor cells are released from the bone marrow and seed the spleen, where they give rise to myeloid progenitor cells (GMP and MDP), which then give rise to pro-inflammatory monocytes. Interestingly, myocardial infarction induces the release of hematopoietic stem and progenitor cells from the bone marrow with consecutively increased extramedullary monocytopoiesis, which in turn further aggravates vascular inflammation. While the bone marrow niche has been intensively studied in the last few years, the so-called splenic hematopoietic niche remains poorly understood. However, especially splenic hematopoiesis is a hallmark for many chronic inflammatory processes and leads to the generation of monocytes. Own preliminary work indicates that particularly splenic endothelial cells are crucially involved in the regulation of extramedullary monocytopoiesis. Inhibition of an endothelial adhesion molecule (e-selectin) reduces proliferation rates of hematopoietic stem and progenitor cells in the spleen and is accompanied by profound athero-protective effects in an animal model of atherosclerosis (ApoE-/-). The next step will be to decipher the interaction between splenic endothelial cells and hematopoietic stem and progenitor cells; specifically, we will investigate whether differentiation and proliferation of myeloid progenitor cells as well as an altered release of proliferative cytokines from splenic endothelial cells may be responsible for the observed effects. Further, we will image hematopoietic stem and progenitor cells in the spleen and analyze their anatomical localization in the context of chronic inflammatory base line conditions. To this end, we will use different transgenic mouse models (e.g. endothelial specific knockout mice), transplantation model of murine spleens, and various other cellular and molecular technologies, including imaging methods, such as FMT/CT. Splenic endothelial cells will be FAC-sorted. The overall aim of this application is to shed light on the poorly characterized, splenic hematopoietic niche in order to develop a treatment strategy to combat vascular inflammation.