REDUCED CONNEXIN43 EXPRESSION INHIBITS BALLOON-INDUCED INTIMAL HYPERPLASIA IN HYPERCHOLESTEROLEMIC MICE.

CE Chadjichristos (1), CM Matter (2), I Roth (1), E Sutter (1), G Pelli (1), TF Luscher (2) and BR Kwak (1)..

(1) Division of Cardiology, University Hospital Geneva, Geneva, Switzerland and (2) Cardiovascular Research, Institute of Physiology, University of Zurich and Cardiovascular Center, University Hospital, Zurich, Switzerland.

An increase in the gap junction protein connexin43 (Cx43) has been observed during neointimal development in atherosclerosis and restenosis. To determine whether Cx43 expression is causally related to neointima formation, we subjected Cx43 +/- LDLR -/- mice, and Cx43 +/+ LDLR -/- littermates to carotid balloon distension injury (BDI). Ten males per group were fed an atherogenic diet for 7 weeks. Carotid arteries were harvested 1 hour as well as 1, 4, 7 and 14 days after injury following pressure fixation. A progressive increase in Cx43 and a SM-actin has been observed in carotids 4, 7 and 14 days after injury. Interestingly, the remaining lumen of the carotids at the later time point was larger in Cx43 +/- LDLR -/- mice (87.6±1.1 m m 2 , mean±SEM) than in Cx43 +/+ LDLR -/- mice (62.9±0.7 m m 2 , p<0.05). Similarly, total counts of neointimal nuclei were lower in Cx43 +/- LDLR -/- (102±17) than in control mice (163±24; p<0.05). Reduced macrophage infiltration was observed in the Cx43 +/- LDLR -/- mice 7 days following the injury. In addition, in vitro chemotaxis assays showed reduced migration of Cx43 +/- LDLR -/- peritoneal macrophages (n=5, p<0.001). Reduced neointimal SMC infiltration was observed in mice expressing half of Cx43. Moreover, in vitro migration assays showed decreased migration of the Cx43 +/- LDLR -/- arterial SMC (n=5, p<0.01). Bromodeoxyuridine labeling showed a decreased proliferation in medial SMC at 7 and 14 days after injury in Cx43 +/- LDLR -/- mice (2.2-fold and 1.6-fold respectively, p<0.05). At 14 days, Cx43 +/- LDLR -/- mice revealed decreased proliferation in neointimal SMC (2.2-fold, p<0.05). At this time point, complete endothelial repair was found in Cx43 +/- LDLR -/- carotids with minimal restenosis. In conclusion, we demonstrate for the first time that reducing Cx43 expression in vivo decreases intimal hyperplasia after BDI in hypercholesterolemic mice. This reduction may result from a combination of a reduced inflammatory response and restricted SMC migration and proliferation which leads to an accelerated endothelial repair. Our findings might open novel therapeutic strategies for reducing restenosis after balloon angioplasty by targeting Cx43.