Age-related modulation of vascular smooth muscle cells proliferation following arterial wall damage

The proliferative response of vascular smooth muscle cells (SMC) to an arterial wall injury has been investigated in young (3-6 months) and old (30-52 months) rabbits, employing two different experimental models. In the first model the lesion was produced by passing an inflated balloon catheter along the abdominal and descending thoracic aorta, while in the second, the endothelium was removed from a segment of the right carotid artery by air-drying. Both experimental models produced very heterogeneous lesions in which the de-endothelialization of the arteries was often accompanied by foci of cellular necrosis of variable extension throughout the vascular wall. The autoradiographic evaluation of the proliferative response of arterial SMCs following in vivo administration of 3H-thymidine revealed different patterns of labeling according to the type of lesion produced. A significant negative correlation (p less than 0.001) was found between the proliferative response and the cellular density of the vascular district. An age-related decrease in the proliferative response of SMCs was observed only in the thoracic aorta where the damage to the tunica media was less extensive as compared to the other vascular districts.