Rat carotid arteriotomy: c-myc is involved in negative remodelling and apoptosis

OBJECTIVE: c-myc is the main proto-oncogene responsible for restenosis in cardiovascular surgery. The aim of our study was to evaluate the effects of c-myc antisense (AS) phosphorothioate oligodeoxynucleotides (ODNs) in the remodelling process induced by surgical carotid arteriotomy on an experimental rat model. METHODS: Fifty-five rats with carotid stenosis and apoptosis induced by arteriotomy were submitted to gene expression analysis 4 h after surgery, to TUNEL assay 48 h after surgery and to histological analysis 30 days later. RESULTS: AS ODNs induced a 60% decrease in target c-myc mRNA in injured carotid arteries compared to control sense and scrambled ODN-treated carotid arteries (P < 0.05). Histological evaluation revealed that stenosis stimulated by arteriotomy was mainly due to adventitial constrictive remodelling rather than to neointimal hyperplasia, observed only in a limited number of samples. Morphometric analysis showed that lumen area in c-myc AS ODN-treated carotid arteries was 35% greater than in control arteries (P < 0.05), whereas the media/lumen area ratio showed a 63% reduction in AS ODN-treated carotid arteries in comparison to control arteries (P < 0.05). Surgical injury affected the expression of apoptosis-related genes Bcl-2, Bax, Bcl-xL and Bcl-xS, inducing a mean 3.5-fold decrease in the Bcl-2/ Bax ratio and a 9-fold decrease in the Bcl-xL/S ratio 4 h after injury as compared with uninjured carotid arteries. TUNEL assay experiments revealed increased apoptosis in AS ODN-treated carotid arteries in comparison to control carotid arteries. CONCLUSIONS: c-myc AS ODNs reduce the negative remodelling induced by arteriotomy. The imbalance between proliferative stimulus represented by surgery and the c-myc mRNA decrease induced greater apoptosis in AS ODN-treated carotid arteries without further affecting mRNA levels of Bcl-2, Bax, Bcl-xL and Bcl-xS genes.