Targeting blood stem cell activity and extramedullary monocytopoiesis to treat atherosclerosis

在动脉粥样硬化的早期阶段，单核细胞粘附并浸润血管床。一旦它们进入血管壁，它们就会分化成巨噬细胞，巨噬细胞会放大血管炎症。虽然巨噬细胞的许多促炎特征是已知的（例如炎性小体的作用、减少的细胞增多症、受损的netrin-1依赖性迁移），但令人惊讶的是，对这些细胞的供应知之甚少。特别是在炎症条件下，造血干细胞和祖细胞从骨髓释放并接种脾脏，在那里它们产生骨髓祖细胞（GMP和MDP），然后产生促炎单核细胞。有趣的是，心肌梗死诱导造血干细胞和祖细胞从骨髓中释放，髓外单核细胞生成持续增加，这反过来又进一步加剧了血管炎症。虽然骨髓生态位在过去几年中得到了深入研究，但所谓的脾造血生态位仍然知之甚少。然而，特别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，特别是脾内皮细胞是至关重要的参与调节髓外单核细胞生成。在动脉粥样硬化动物模型（ApoE-/-）中，内皮粘附分子（e-选择素）的抑制降低了脾脏中造血干细胞和祖细胞的增殖率，并伴随着显著的动脉粥样硬化保护作用。下一步将是破译脾内皮细胞和造血干细胞和祖细胞之间的相互作用，具体来说，我们将调查是否分化和骨髓祖细胞的增殖以及从脾内皮细胞增殖细胞因子的释放改变可能是负责观察到的效果。此外，我们还将对脾脏中的造血干细胞和祖细胞进行成像，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（例如内皮特异性敲除小鼠），小鼠脾脏移植模型，以及各种其他细胞和分子技术，包括成像方法，如FMT/CT。将对脾内皮细胞进行FAC-sorted。本申请的总体目的是阐明表征不佳的脾造血生态位，以开发对抗血管炎症的治疗策略。

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.