Spontaneous arterial lesions: their possible role in arteriosclerosis

Spontaneous lesions of the arterial wall involving the internal elastic lamellae and variable amounts of the intima are described in the spontaneously hypertensive rat caudal, renal, and mesenteric arteries. A simple model for producing similar circumferential lesions in rat and rabbit carotid arteries has been developed and the subsequent repair of these lesions is described. Two types of circumferential lesion can be produced by the application of 50-160 g of longitudinally applied tension. Small lesions can be up to 400 micron in length and are characterized by the loss of a small area of endothelium and rupture of the internal elastic lamellae. No demonstrable damage to the media is detected in these lesions. Larger lesions can be up to 1 mm in length and are characterized by the loss of endothelium and rupture of the internal as well as a variable number of medial elastic lamellae. Little, if any, damage to the medial smooth muscle cells is observed although the extracellular matrix is often disrupted. Small lesions are completely reendothelialized within 24 hr and larger lesions within 7-10 days. Both large and small lesions repair without the formation of an intimal thickening of smooth muscle cells, despite quite marked damage to the media of the larger lesions.