CHANGES IN BIOMECHANICAL PROPERTIES, COMPOSITION OF COLLAGEN AND ELASTIN, AND ADVANCED GLYCATION ENDPRODUCTS OF THE RAT AORTA IN RELATION TO AGE

During ageing and senescence the aorta becomes stiffer and its elastic ity is reduced. The mechanism causing this increased stiffness of the aortic wall was studied using a rat model. Ring-shaped samples were pr epared from the thoracic aorta of three groups of rats aged 4.5, 14 an d 27 months, representing young, adult and old animals. Analysis of th e static biomechanical properties showed increased diameter (2.20 +/- 0.03 mm) and increased stiffness (4.0 +/- 0.2 mN) of aortic samples fr om old rats compared with adult rats (1.82 +/- 0.02 mm and 3.0 +/- 0.1 mN, respectively). The total hydroxyproline and elastin content per s ample was not changed. However, the hydroxyproline content/mm(2) of th e aortic wall was reduced by 20% and the elastin content/mm(2) of the aortic wall was reduced by 19% comparing the old with the adult rats. No differences were found in the pyridinoline concentrations between o ld and adult rats. The collagen- and elastin-associated fluorescence w as determined as a marker of advanced glycation endproducts (AGE). Bot h parameters were increased in the old rats compared with the adult ra ts, by 42% and 17%, respectively, and positively correlated with stiff ness at physiological loads. A positive correlation between collagen-a ssociated fluorescence and maximum stiffness was found as well. In con clusion, the age-related increase in stiffness of the aorta was associ ated with increased diameter, reduced collagen and elastin contents/mm (2) of the aortic wall, increased fenestration of elastic laminae and accumulation of fluorescent material in collagen and elastin.