Endothelial CD45 Mediates Endothelial-to-Mesenchymal Transition (EndMT) in Atheroma Progression

Abstract ID 87958 Poster Board 264 CD45 is a marker of hematopoietic cells, which is rarely expressed in endothelial cells (EC). However, recent studies indicated that CD45 is indispensable in driving the endothelial-to-mesenchymal transition (EndMT) following sheep myocardial infarction. EC activation is a hallmark of the initiation and atheroma progression; EndMT has also been implicated in the pathogenesis of atherosclerosis. Here, we aim to investigate whether endothelial CD45 contributes to the progression of atherosclerosis by facilitating the EndMT. In vitro, we utilized CRISPR/inactive Cas9 transcriptional activation system to express CD45 in human endothelial colony-forming cells (ECFCs). We showed that CD45+ECFCs upregulated transforming growth factors (TGFβ) that implicate EndMT but downregulate FGFR1 and transcription factors KLF4 expression, which exacerbates EndMT. In vivo, we generated a tamoxifen-inducible EC-specific CD45 deficient mouse strain (EC-CD45iKO) in an ApoE-deficient (ApoE−/−) background and fed with a Western diet (C57BL/6) for atherosclerosis and molecular analyses. Flow cytometry data indicated that the progression of atherosclerosis coincides with increased endothelial CD45 and decreased FGFR1, suggesting CD45-driven EndMT in ApoE-deficient mice. In addition, we found that ApoE−/−/ EC-iCD45KO mice reduced plaque macrophages, foam cells, expression of adhesion molecule ICAM1, and lesion development compared to ApoE−/− controls. Importantly, 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 performed on the aortic EndMT cells indicated an upregulation of EC maker genes while a downregulation of SMC and EndMT marker genes. These findings demonstrate that endothelial CD45 drives EndMT by inducing EndMT marker expression and mesenchymal phenotype, causing FGFR1 downregulation to potentiate atheroma progression, highlighting endothelial CD45 may be a new drug target for the treatment of atherosclerosis. AHA 23POST1021226 (Q. Peng) 5 R01 HL141853 (PI: Chen, Wang)