Connexin 43 Deficiency Is Associated with Reduced Myocardial Scar Size and Attenuated TGFβ1 Signaling after Transient Coronary Occlusion in Conditional Knock-Out Mice.

Laura Valls-Lacalle,Javier Inserte,Ignasi Barba,Ignacio Ferreira-González,Marisol Ruiz-Meana,Antonio Rodríguez-Sinovas,Marta Consegal,Begoña Benito

doi:10.3390/biom10040651

Abstract

Previous studies demonstrated a reduction in myocardial scar size in heterozygous Cx43+/- mice subjected to permanent coronary occlusion. However, patients presenting with ST segment elevation myocardial infarction often undergo rapid coronary revascularization leading to prompt restoration of coronary flow. Therefore, we aimed to assess changes in scar size and left ventricular remodeling following transient myocardial ischemia (45 min) followed by 14 days of reperfusion using Cx43fl/fl (controls) and Cx43Cre-ER(T)/fl inducible knock-out (Cx43 content: 50%) mice treated with vehicle or 4-hydroxytamoxifen (4-OHT) to induce a Cre-ER(T)-mediated global deletion of the Cx43 floxed allele. The scar area (picrosirius red), measured 14 days after transient coronary occlusion, was similarly reduced in both vehicle and 4-OHT-treated Cx43Cre-ER(T)/fl mice, compared to Cx43fl/fl animals, having normal Cx43 levels (15.78% ± 3.42% and 16.54% ± 2.31% vs. 25.40% ± 3.14% and 22.43% ± 3.88% in vehicle and 4-OHT-treated mice, respectively, p = 0.027). Left ventricular dilatation was significantly attenuated in both Cx43-deficient groups (p = 0.037 for left ventricular end-diastolic diameter). These protective effects were correlated with an attenuated enhancement in pro-transforming growth factor beta 1 (TGFβ1) expression after reperfusion. In conclusion, our data demonstrate that Cx43 deficiency induces a protective effect on scar formation after transient coronary occlusion in mice, an effect associated with reduced left ventricular remodeling and attenuated enhancement in pro-TGFβ1 expression.

Highlights

Connexins are a family of proteins that constitute integral components of plasma membranes
The scar area, determined by picrosirius red staining 14 days after transient coronary occlusion, was reduced in both oil (50% Connexin 43 (Cx43) expression) and 4-OHT (
Two-way analysis of variance (ANOVA) analysis demonstrated a significant effect of genotype, whereas no significant effects of treatment or interactions between treatment and genotype were detected (Figure 1B)

Summary

Introduction

Connexins are a family of proteins that constitute integral components of plasma membranes. In addition to electrical coupling, gap junctions allow chemical communication between neighboring cells, and are involved in spreading of cell death during acute myocardial ischemia–reperfusion injury [4] In this sense, previous studies have demonstrated that gap junctions may facilitate propagation of hypercontracture and cardiomyocyte death during reperfusion, by a mechanism involving Na+ passage between adjacent cells and subsequent Ca2+ influx secondary to Na+/Ca2+ exchange [5]. The protective effect of heptanol was extended to other gap junction uncouplers [7], and to other situations as hypoxia/reoxygenation [8] These findings were further strengthened by data obtained in our group demonstrating that isolated hearts from transgenic mice lacking Cx43, either by replacement with Cx32, or by inducible knock-out, had smaller acute infarctions after one hour of reperfusion following transient global ischemia [9,10]

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