Effects of aging and blood pressure on the structure of the thoracic aortain SAM mice: a model of age-associated degenerative vascular changes

The effects of aging and blood pressure on the structural alterations of th e thoracic aorta were examined using male, accelerated senescence-prone, sh ort-lived SAMP11 mice or accelerated senescence-resistant, long-lived SAMR1 mice. The aortic wall thickness increased significantly by 34% in SAMR1 an d by 62% in SAMP11 with advanced age. We observed branching, breakage and d isorganization of the elastic lamellae, an increase in thin collagen fibril s between the medial smooth muscle cells and hypertrophy but a significant decrease in the number of medial smooth muscle cells with aging in both str ains. These alterations observed in SAMP11 occurred earlier and were more e xaggerated with advanced age than in SAMR1. The aortic lumen dilated gradua lly in SAMR1, but narrowed significantly in SAMP11 with aging. The systolic blood pressure did not differ significantly among SAMP11s aged 3-9 months, or among all ages of SAMR1. However, it was elevated in SAMP11 at the term inal stage of their life. Our results suggest that the aorta in SAMR1 might reflect the physiological process of aging, whereas SAMP11 showed earlier changes due to the senescence acceleration of the vascular cells, which wer e exaggerated by the elevated blood pressure. (C) 2001 Elsevier Science Inc . All rights reserved.