Deficiency of Endothelial Cxcr4 Reduces Reendothelialization and Enhances Neointimal Hyperplasia After Vascular Injury in Atherosclerosis-Prone Mice

Abstract

Objective— The Cxcl12/Cxcr4 chemokine ligand/receptor axis mediates the mobilization of smooth muscle cell progenitors, driving injury-induced neointimal hyperplasia. This study aimed to investigate the role of endothelial Cxcr4 in neointima formation. Approach and Results— β-Galactosidase staining using bone marrow x kinase ( Bmx ) -CreER T2 reporter mice and double immunofluorescence revealed an efficient and endothelial-specific deletion of Cxcr4 in Bmx-CreER T2+ compared with Bmx-CreER T2− Cxcr4-floxed apolipoprotein E–deficient ( Apoe −/− ) mice (referred to as Cxcr4 EC-KO ApoE −/− and Cxcr4 EC-WT ApoE −/− , respectively). Endothelial Cxcr4 deficiency significantly increased wire injury–induced neointima formation in carotid arteries from Cxcr4 EC-KO ApoE −/− mice. The lesions displayed a higher number of macrophages, whereas the smooth muscle cell and collagen content were reduced. This was associated with a significant reduction in reendothelialization and endothelial cell proliferation in injured Cxcr4 EC-KO ApoE −/− carotids compared with Cxcr4 EC-WT ApoE −/− controls. Furthermore, stimulation of human aortic endothelial cells with chemokine (C-X-C motif) ligand 12 (CXCL12) significantly enhanced their wound-healing capacity in an in vitro scratch assay, an effect that could be reversed with the CXCR4 antagonist AMD3100. Also, flow cytometric analysis showed a reduced mobilization of Sca1 + Flk1 + Cd31 + and of Lin − Sca1 + progenitors in Cxcr4 EC-KO ApoE −/− mice after vascular injury, although Cxcr4 surface expression was unaltered. No differences could be detected in plasma concentrations of Cxcl12, vascular endothelial growth factor, sphingosine 1-phosphate, or Flt3 (fms-related tyrosine kinase 3) ligand, all cytokines with an established role in progenitor cell mobilization. Nonetheless, double immunofluorescence revealed a significant reduction in local endothelial Cxcl12 staining in injured carotids from Cxcr4 EC-KO ApoE −/− mice. Conclusions— Endothelial Cxcr4 is crucial for efficient reendothelialization after vascular injury through endothelial wound healing and proliferation, and through the mobilization of Sca1 + Flk1 + Cd31 + cells, often referred to as circulating endothelial progenitor cells.

Endothelial Bmx tyrosine kinase activity is essential for myocardial hypertrophy and remodeling

“…In our experiments, Bmx silencing completely abrogated STAT3 activation by Ang II in endothelial cells and also significantly attenuated phosphorylation in vivo. Although we cannot fully exclude the possibility that Bmx functions also in cardiomyocytes, our results and those of others strongly suggest that Bmx mainly acts in endothelial cells (24). Thus, the present results highlight the importance of endothelial cell-to-cardiomyocyte signaling in cardiac remodeling (see the schematic summary in Fig.…”

Stromal Cell–Derived Factor-1α/C-X-C Chemokine Receptor Type 4 Axis Promotes Endothelial Cell Barrier Integrity via Phosphoinositide 3-Kinase and Rac1 Activation

“…CXCR4 is classified as a Gi-coupled G protein-coupled receptor and is expressed on the surface of endothelial cells (ECs). 2 Although there are several reports showing that SDF-1α/CXCR4 signal activation promotes EC migration, proliferation, and nitric oxide (NO) production, [3][4][5] additional roles for SDF-1α on ECs remain unknown.…”

Chemokines

“…However, the cell type-specific effects remained to be addressed. Noels et al 28 investigated the specific effects of endothelial CXCR4 on injury-induced neointima formation. This study showed that endothelial CXCR4 deficiency significantly increased neointima formation and that formed lesions in these mice contained a higher number of macrophages, but reduced number of SMCs and collagen content.…”