Abstract
Objective Endothelial cells (ECs) can undergo an endothelial-mesenchymal transition (EndMT) during tissue fibrosis. Wnt- and Msx2-regulated signals participate in arteriosclerotic calcification and fibrosis. We studied the impact of Wnt7, Msx2, and Dkk1 (Wnt7 antagonist) on EndMT in primary aortic endothelial cells (AoECs). Methods and Results Transduction of AoECs with vectors expressing Dkk1 suppressed EC differentiation and induced a mineralizing myofibroblast phenotype. Dkk1 suppressed claudin 5, PECAM, cadherin 5 (Cdh5), Tie1 and Tie2. Dkk1 converted the cuboidal cell monolayer into a spindle-shaped multilayer and inhibited EC cord formation. Myofibrogenic and osteogenic markers - e.g., SM22, type I collagen, Osx, Runx2, alkaline phosphatase – were upregulated by Dkk1 via activin-like kinase / Smad pathways. Dkk1 increased fibrosis and mineralization of AoECs cultured under osteogenic conditions - the opposite of mesenchymal cell responses. Msx2 and Wnt7b maintained the “cobblestone” morphology of differentiated ECs and promoted EC marker expression. Deleting EC Wnt7b with the Cdh5-Cre transgene in Wnt7b(fl/fl);LDLR-/- mice upregulated aortic osteogenic genes (Osx, Sox9, Runx2, Msx2) and nuclear pSmad1/5, and increased collagen accumulation. Conclusions Dkk1 enhances EndMT in AoECs, while Msx2-Wnt7 signals stabilize EC phenotype. EC responses to Dkk1, Wnt7b, and Msx2 are the opposite of mesenchymal cell responses, coupling EC phenotypic stability with osteofibrogenic predilection during arteriosclerosis.
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