Supplemental Digital Content is available in the text.

Cumulatively, we provide the first evidence that DKK3 is a potent SMC differentiation factor, which might have a therapeutic effect in reducing intraplaque hemorrhage related to atherosclerotic plaque phenotype.

The process of vascular remodeling is associated with increased hypoxia. However, the contribution of hypoxia-inducible factor 1α (HIF1α), the key transcription factor mediating cellular hypoxic responses, to vascular remodeling is established, but not completely understood. In the angiotensin II (Ang II)-induced vascular remodeling model, HIF1α was increased and activated in vascular smooth muscle cells (VSMCs). Selective genetic disruption of Hif1a in VSMCs markedly ameliorated Ang II-induced vascular remodeling, as revealed by decreased blood pressure, aortic thickness, collagen deposition, inflammation, and aortic stiffness. VSMC Hif1a deficiency also specifically suppressed Ang II-induced infiltration of CD45 + CD11b + F4/80 + CD206 − M1 macrophages into the vessel. Mechanistically, HIF1α deficiency in VSMCs dramatically suppressed the expression of CCL7, a chemokine critical for macrophage recruitment. Bioinformatic analysis and chromatin immunoprecipitation assays revealed three functional hypoxia-response elements in the Ccl7 promoter, indicating that Ccl7 is a direct HIF1α target gene. Blocking CCL7 with antibody in vivo alleviated Ang II-induced hypertension and vascular remodeling, coincident with decreased macrophage infiltration. This study provides direct evidence that HIF1α activation in VSMCs exacerbates Ang II-induced macrophage infiltration and resultant vascular remodeling via its target gene Ccl7 , and thus may serve as a potential therapeutic target for remodeling-related vascular disease.

Recent studies have shown that Sca‐1+ (stem cell antigen‐1) stem/progenitor cells within blood vessel walls may contribute to neointima formation, but the mechanism behind their recruitment has not been explored. In this work Sca‐1+ progenitor cells were cultivated from mouse vein graft tissue and found to exhibit increased migration when cocultured with smooth muscle cells (SMCs) or when treated with SMC‐derived conditioned medium. This migration was associated with elevated levels of chemokines, CCL2 (chemokine (C‐C motif) ligand 2) and CXCL1 (chemokine (C‐X‐C motif) ligand 1), and their corresponding receptors on Sca‐1+ progenitors, CCR2 (chemokine (C‐C motif) receptor 2) and CXCR2 (chemokine (C‐X‐C motif) receptor 2), which were also upregulated following SMC conditioned medium treatment. Knockdown of either receptor in Sca‐1+ progenitors significantly inhibited cell migration. The GTPases Cdc42 and Rac1 were activated by both CCL2 and CXCL1 stimulation and p38 phosphorylation was increased. However, only Rac1 inhibition significantly reduced migration and p38 phosphorylation. After Sca‐1+ progenitors labeled with green fluorescent protein (GFP) were applied to the adventitial side of wire‐injured mouse femoral arteries, a large proportion of GFP‐Sca‐1+‐cells were observed in neointimal lesions, and a marked increase in neointimal lesion formation was seen 1 week post‐operation. Interestingly, Sca‐1+ progenitor migration from the adventitia to the neointima was abrogated and neointima formation diminished in a wire injury model using CCL2−/− mice. These findings suggest vascular stem/progenitor cell migration from the adventitia to the neointima can be induced by SMC release of chemokines which act via CCR2/Rac1/p38 and CXCR2/Rac1/p38 signaling pathways. Stem Cells 2016;34:2368–2380