Smooth Muscle–Targeted Knockout of Connexin43 Enhances Neointimal Formation in Response to Vascular Injury

OBJECTIVE—Vascular disease alters and reduces connexin expression and a reduction in connexin 43 (Cx43) expression diminishes the extent of atherosclerosis observed in a high-cholesterol diet murine model. We hypothesized that connexins might play a role in the smooth muscle cell response to vascular injury. METHODS AND RESULTS—We therefore studied a line of smooth muscle cell-specific, Cx43 gene knockout mice (SM Cx43 KO) in which the carotid arteries were injured, either by vascular occlusion or by a wire injury. In the SM Cx43 KO mice both types of injury manifested accelerated growth of the neointima and of the adventitia. Isolated vascular smooth muscle cells from the SM Cx43 KO mice grew at a slightly faster rate in culture, and to marginally higher saturation densities than those of control mice, but these changes were not adequate to explain the large changes in the injured vessels. CONCLUSIONS—These observations provide direct evidence that smooth muscle Cx43 gap junctions play a multi-faceted role in modulating the in vivo growth response of vascular smooth muscle cells to vascular injury.