Circulating monocyte adhesion repairs endothelium-denuded injury through downstream of kinase 3-mediated endothelialization

The integrity of the endothelial monolayer is critical for preventing life-threatening hemorrhaging and thrombosis. However, how severe endothelium-denuded injury is rapidly repaired remains unknown. Given the common biological properties between endothelial cells and circulating monocytes, we aimed to examine whether blood monocytes are involved in endothelium wound healing. The in vivo common carotid artery endothelium-denuded (CCAED) model was established through a wire-induced injury. Monocyte adhesion was assessed using immunofluorescence and a parallel plate flow chamber. We initially observed that the circulating monocyte-mediated endothelialization was better downstream of kinase 3 deficient mice (DOK3^-/-) than that of wild-type (WT) mice following induction of the CCAED model. Rapid endothelialization increased endothelial integrity, prevented coagulation, and decreased thrombosis. Mechanistically, following endothelium-denuded injury, monocyte chemoattractant protein 1 (MCP1) disassociated from DOK3 and C-C chemokine receptor type 2B (CCR2B), increased the intracellular Ca²⁺ concentration, and promoted adhesion in circulating monocytes. However, this process was inhibited by the CCR2B inhibitor INCB3344. Moreover, the adhesive functions of circulating monocytes isolated from DOK3^-/- mice were stronger than those from WT mice. Furthermore, adhered monocytes expressed endothelial-specific markers and compensated for endothelium-dependent vasorelaxation in WT mice. Similarly, these effects were enhanced in DOK3^-/- mice. Bindarit, a selective MCP1 inhibitor, suppressed endothelialization following CCAED surgery in WT mice but not in DOK3^-/- mice. In conclusion, endothelialization mediated by circulating monocytes repairs endothelium-denuded injury to compensate for endothelial functions through MCP1/DOK3/CCR2B/Ca²⁺ signaling. Our findings indicate that circulating monocyte adhesion is an important endothelial wound healing mechanism.