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A novel strategy for isolation of mice bone marrow endothelial cells (BMECs).

ABSTRACT:

Background

In the bone marrow microenvironment (BM), endothelial cells are individual cells that form part of the sinusoidal blood vessels called the "bone marrow endothelial-vascular niche." They account for less than 2% of the bone marrow cells. They play essential functions by generating growth and inhibitory factors that promote the hematopoietic stem cells (HSCs) regulation. In response to inflammatory stimuli, the BMECs increase in proliferation to maintain the blood vessels' integrity within the BM. The inflammatory response releases cytokines such as tumor necrosis factor-alpha (TNF-α) that promote vascular endothelial cells' expansion and upregulation of adhesion molecules (ICAM-1 and VCAM-1, respectively) in the BM. However, the evaluation of mouse BMECs in the bone marrow microenvironment is scared by a lack of mouse bone marrow endothelial cell primary culture METHODS: Two steps approach for isolation of bone marrow endothelial cells (BMECs) from mice. In brief, the bone marrow cells extracted from the mice long bones were cultured overnight with Dulbecco's modified Eagle's medium (DMEM) supplemented with 20% fetal bovine serum (FBS) and antibiotics to separate between marrow-derived adherent and non-adherent cells. The floating cells were discarded, and the adhered section detached with accutase and BMECs selected using CD31 microbeads. The isolated BMECs were cultured in a dish pre-coated with rat-tail collagen type 1 with endothelial cells medium supplement with growth factors. The cells were verified by confocal microscopy for morphology and tube formation by matrigel assay. We validate the cells' purity by flow cytometry, RT-qPCR, immunofluorescence staining, and immunoblotting by established BMEC markers, PECAM-1, VE-cadherin, vascular endothelial cell growth factor receptor-2 (VEGFR2), CD45, E-selectin, and endothelial selectin adhesion molecule (ESAM). Lastly, we characterize BMEC activation with recombinant TNF-α.

Results

Our method clearly defined the cells isolated have the characteristics of BMECs with the expression of CD31, VE-cadherin, E-selectin, VEGFR-2, and ESAM. The cells' response to TNF-α indicates its inflammatory function by increasing proliferation and upregulation of adhesion molecules.

Conclusions

This study outline a simple new technique of isolating mouse BMEC primary culture and a suitable method to evaluate the function and dysregulation of BMEC in in vitro studies using mouse models.

SUBMITTER: Smith AO

PROVIDER: S-EPMC8091666 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundDiabetes mellitus is a prevalent public health problem that affects about one-third of the US population and leads to serious vascular complications with increased risk for coronary artery disease. How bone marrow hematopoiesis contributes to diabetes mellitus complications is incompletely understood. We investigated the role of bone marrow endothelial cells in diabetic regulation of inflammatory myeloid cell production.MethodsIn 3 types of mouse diabetes mellitus, including streptozotocin, high-fat diet, and genetic induction using leptin-receptor-deficient db/db mice, we assayed leukocytes, hematopoietic stem and progenitor cells (HSPC). In addition, we investigated bone marrow endothelial cells with flow cytometry and expression profiling.ResultsIn diabetes mellitus, we observed enhanced proliferation of 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 mellitus. To explore whether endothelial Egfr plays a functional role in myelopoiesis, we generated mice with endothelial-specific deletion of Egfr (Cdh5Cre Egfrfl/fl). We found enhanced HSPC proliferation and increased myeloid cell production in Cdh5Cre Egfrfl/fl mice compared with wild-type mice with diabetes mellitus. 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 mellitus. Inflammatory myeloid cells accumulated more in skin wounds of diabetic Cdh5Cre Egfrfl/fl mice, significantly delaying wound closure. Atherosclerosis was accelerated in Cdh5Cre Egfrfl/fl mice, leading to larger and more inflamed atherosclerotic lesions in the aorta.ConclusionsIn diabetes mellitus, bone marrow endothelial cells participate in the dysregulation of bone marrow hematopoiesis. Diabetes mellitus reduces endothelial production of Cxcl12, a quiescence-promoting niche factor that reduces stem cell proliferation. We describe a previously unknown counterregulatory pathway, in which protective endothelial Egfr signaling curbs HSPC proliferation and myeloid cell production.