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MLKL preserves the splenic microenvironment to repress hematopoiesis during atherosclerosis

ABSTRACT: Dysregulation of the hematopoietic niche during hyperlipidemia facilitates pathologic leukocyte production, driving atherogenesis. While definitive hematopoiesis primarily occurs in the bone marrow, during atherosclerosis this also occurs in the spleen. Cells of the bone marrow niche, in particular endothelial cells, have been studied in atherosclerosis, while little is known about how splenic endothelial cells respond to the atherogenic environment. Here we show unique dysregulated pathways in splenic compared to bone marrow endothelial cells during atherosclerosis, including perturbations of lipid metabolism and endocytic trafficking pathways. As part of this response, we identified MLKL as a repressor of splenic, but not bone marrow, myelopoiesis. Silencing MLKL in splenic endothelial cells results in inefficient endosomal trafficking and lipid accumulation, ultimately promoting the production of myeloid cells that participate in plaque development. These studies identify endocytic trafficking by MLKL as a key mechanism of splenic endothelial cell maintenance, splenic hematopoiesis, and subsequently atherosclerosis.

ORGANISM(S): Mus musculus

PROVIDER: GSE216341 | GEO | 2024/03/29

REPOSITORIES: GEO

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Project description:Background—Diabetes is a prevalent public health problem that affects about one third of the U.S. population and leads to serious vascular complications with increased risk for coronary artery disease. How bone marrow hematopoiesis contributes to diabetes complications is incompletely understood. We thus investigated the role of bone marrow endothelial cells in diabetic regulation of inflammatory myeloid cell production. Methods and Results—In three types of mouse diabetes, we observed enhanced proliferation of hematopoietic stem and progenitor cells (HSPC) leading to augmented circulating myeloid cell numbers. Analysis of bone marrow niche cells revealed that endothelial cells in diabetic mice expressed less Cxcl12, a retention factor promoting HSPC quiescence. Transcriptome-wide analysis of bone marrow endothelial cells demonstrated enrichment of genes involved in epithelial growth factor receptor (EGFR) signaling in mice with diet-induced diabetes. To explore whether endothelial EGFR plays a functional role in myelopoiesis, we generated mice with endothelial-specific deletion of EGFR (Cdh5Cre EGFRfl/fl). Unexpectedly, we found enhanced HSPC proliferation and increased myeloid cell production in Cdh5Cre EGFRfl/fl mice compared to wild type mice with diabetes. Disrupted EGFR signaling in endothelial cells decreased their expression of the HSPC retention factor angiopoietin-1. We tested the functional relevance of these findings for wound healing and atherosclerosis, both implicated in complications of diabetes. Inflammatory myeloid cells accumulated more in skin wounds of diabetic Cdh5Cre EGFRfl/fl mice, significantly delaying wound closure. Atherosclerosis accelerated in Cdh5Cre EGFRfl/fl mice, leading to larger and more inflamed atherosclerotic lesions in the aorta. Conclusions—In diabetes, bone marrow endothelial cells participate in the dysregulation of bone marrow hematopoiesis and promote cardiovascular complications via leukocyte overproduction. Specifically, diabetes reduces endothelial production of Cxcl12, a quiescence-promoting niche factor that reduces stem cell proliferation. We also describe a previously unknown counter-regulatory pathway, in which protective endothelial EGFR signaling curbs HSPC proliferation and myeloid cell production via angiopoietin-1.

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MLKL preserves the splenic microenvironment to repress hematopoiesis during atherosclerosis

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