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

Abstract

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. (Arterioscler Thromb Vasc Biol.

Targeting Connexin 43 Prevents Platelet-Derived Growth Factor-BB–Induced Phenotypic Change in Porcine Coronary Artery Smooth Muscle Cells

“…25 We observed restricted IT formation after balloon injury in Cx43 ϩ/Ϫ LDLR Ϫ/Ϫ mice that was associated with decreased inflammatory response and reduced SMC proliferation and migration toward the injured site. Our findings are in sharp contrast to the work of Liao et al, 27 who studied the effects of carotid artery injury in a line of smooth muscle cell-specific Cx43 gene knockout mice (SM-Cx43 KO). Surprisingly, injury to carotid arteries in these mice produced markedly greater IT and adventitial growth than seen in control animals.…”

“…22 Similarly, balloon distension, as well as wire injury in animal models, results in increased Cx43 expression in the IT, [23][24][25][26] and reducing Cx43 expression changes the course of the restenotic process in mice. 25,27 These in vivo studies suggest that Cx43 could be associated to SMC phenotype, a concept also proposed after cytokine-or growth factor-induced dedifferentiation of SMCs. 20,28 -30 It is therefore of interest to study the effects of Cx43 modulation in 2 distinct medial SMC populations, of which 1 displays an IT-prone phenotype.…”

Regulation of Cellular Communication by Signaling Microdomains in the Blood Vessel Wall

“…Although gap junctional communication has been clearly identified between ECs in numerous vascular beds, the presence of gap junction between VSMCs and at the MEJ seems to differ according to the vascular beds and the species (Johnstone et al, 2009a;Billaud et al, 2011). Within the blood vessel wall, gap junctions play an integral role in key physiologic responses, including vascular resistance, vascular growth, and cell differentiation, and are highly adapted during diseases, implicating them as key members in modulating different aspects of disease responses (Kwak et al, 2002;Liao et al, 2007;Chadjichristos et al, 2008) (see Table 5). The formation of gap junctions and gap junction channel properties are highly regulated through intracellular environment but also through direct protein interactions in signaling microdomains.…”

“…Endothelium-derived hyperpolarizing factor Edwards et al, 1998;Hutcheson et al, 1999;Yamamoto et al, 1999;Beny and Schaad, 2000;Kansui et al, 2004;Mather et al, 2005;Rath et al, 2012;Howitt et al, 2013Vascular conducted responses Kruger et al, 2002Dora et al, 2003b;Simon and McWhorter, 2003;Wolfle et al, 2007;Duling, 2008 Feedback on vasoconstriction Dora et al, 1997;Straub et al, 2011 Smooth muscle cell proliferation Chadjichristos et al, 2006;Liao et al, 2007;Johnstone et al, 2010;Zhong et al, 2012 a Smooth muscle cell differentiation Kwak et al, 2003;Chadjichristos et al, 2008;Shen et al, 2010;Gairhe et al, 2011Gairhe et al, , 2012 Endothelial cell proliferation Larson et al, 1997;Kwak et al, 2001;Yeh et al, 2006;Nakano et al, 2008;Wang et al, 2008 c Endothelial cell dysfunction Xie and Hu, 1994;Makino et al, 2008;Chadjichristos et al, 2010;Wang et al, 2012;Ebong and Depaola, 2013 Endothelial cell migration Pepper and Meda, 1992;Pepper et al, 1989;Kwak et al, 2001 a Evidence that gap junction independent pathways are involved in this regulation . b Evidence that although connexin expression and/or gap junction communication levels correlated to disease they do not appear to be directly linked...…”

Control and Coordination of Vasomotor Tone in the Microcirculation

“…Damage of carotid artery by vascular occlusion or wire injury resulted in an increase in neointima and adventitia formation in smooth muscle cell Cx43 specific knockout mice as compared to wild type animals (Liao et al, 2007), suggesting an accelerated growth of smooth muscle cell with the Cx43 deletion, which was further confirmed using cultured cells. Nevertheless, in apparent opposition to these findings, Chadjichristos et al (Chadjichristos et al, 2006) show that in heterozygous Cx43 knockout mice the neointimal formation was reduced.…”