Abstract 16746: Novel Role of Endothelial CD45 in Regulating Endothelial-to-Mesenchymal Transition (EndMT) in Atherosclerosis

Abstract

Introduction: Atherosclerosis is the leading cause of mortality in the United States and most other developed countries. Endothelial cell (EC) activation is a hallmark of the initiation and progression of atherosclerosis; identification of molecular markers of dysfunctional endothelium represents a biological challenge to developing new therapeutic targets. CD45 is a marker of hematopoietic cells, which is rarely expressed in ECs. However, recent studies indicated that CD45 is indispensable in driving the endothelial-to-mesenchymal transition (EndMT) following myocardial infarction. EndMT has also been implicated in the pathogenesis of atheroma progression. Thus, we aim to investigate whether endothelial CD45 contributes to the progression of atherosclerosis by facilitating the EndMT. Methods and results: In vitro , we used CRISPR/inactive Cas9 transcriptional activation system to express CD45 in human endothelial colony-forming cells (ECFCs). Using FACS analyses, we found that CD45+ECFCs upregulate transforming growth factors (TGFβ 1-3 ) that implicate EndMT but downregulate FGFR1 expression, which exacerbates EndMT. qRT-PCR and WB showed that CD45+ECFCs downregulate transcription factors KLFs. In vivo , we generated a tamoxifen-inducible EC-specific CD45 deficient mouse strain (EC-CD45iKO) in ApoE-deficient (ApoE-/-) background and fed with a Western diet (C57BL/6) for atherosclerosis and molecular analyses. We found that ApoE-/- / EC-iCD45KO mice reduced plaque macrophages, foam cells, expression of adhesion molecule, and lesion development compared to ApoE-/- controls. Interestingly, ApoE-/- / EC-iCD45KO mice showed the reduction of α-smooth muscle actin, which is typical of EndMT, in the aortic plaque. Single-cell RNA-seq analyses have been performed to characterize that endothelial CD45 regulates the expression of pro-inflammatory, EndMT, and endothelial cell markers genes on the aortic ECs. Conclusion: These findings demonstrate that endothelial CD45 potentiates atherosclerosis by inducing TGF signaling and mesenchymal phenotype, causing FGFR1 downregulation and attenuating KLFs expression to drive EndMT, highlighting endothelial CD45 may be a new drug target for the treatment of atherosclerosis.