Background: The decreased elastin concentration found in abdominal aortic aneurysms (AAAs) may result from a differential synthetic response wherein elastin gene expression fails to increase in parallel with type I procollagen (COL I) gene expression. The purpose of this study is to determine tissue mRNA levels for elastin and COL I in AAAs compared with levels in normal, age-matched aorta and to determine the relationship between aging and COL I gene expression.
Methods: Total RNA exacted from normal infrarenal aortic tissue (n = 7) and AAA (n = 10) tissue was subjected to Northern analysis. Mean values for COL I, elastin, and alpha-tubulin mRNA levels were compared by use of the Student t test. Age and COL I mRNA levels were analyzed by regression analysis.
Results: COL I mRNA was increased significantly in AAAs (1.18 +/- 0.13) compared with normal aortas (0.14 +/- 0.05). A commensurate increase in elastin mRNA (AAAs, 0.11 +/- 0.02, vs normal aortas, 0.39 +/- 0.2) was absent. There was no correlation between age and COL gene expression.
Conclusions: The decreased elastin concentration relative to collagen in AAAs may be explained, in part, by the changes in message level of elastin and collagen. The enhanced COL I gene expression in AAAs is unrelated to age.