Background. Abdominal aortic aneurysms (AAA) are characterized by both increases in proteolysis and changes in the biosynthesis of the extracellular matrix (ECM) proteins. Proteoglycans are important components of the ECM, particularly the small proteoglycans, biglycan and decorin. Biglycan and decorin regulate cell proliferation and collagen assembly. Therefore, the purpose of this study is to quantify the levels of mRNA for biglycan and decorin in normal aorta (NA) and AAA. Materials and methods. Northern blot hybridization and competitive polymerase chain reaction using gene-specific external standards were used to quantify mRNA levels of biglycan and decorin in RNA derived from AAA and NA. Results are expressed as a percentage of glyceraldehyde-3-phosphate dehydrogenase or normalized to ribosomal RNA content and compared using the unpaired t test. Results. A statistically significant 15-fold decrease in biglycan mRNA expression was observed in AAA compared to NA (176.9% vs 11.8%, P < 0.001). In contrast to biglycan, the decorin mRNA expression is unchanged in AAA compared to NA. Conclusions. The marked decrease in biglycan mRNA levels is unique to aneurysmal disease of the aorta. In atherosclerosis and restenosis, biglycan expression is increased in comparison with normal artery. This decrease in biglycan expression may reflect important regulatory changes specific for the AAA. Furthermore, a decrease in biglycan gene expression and biosynthesis could have a broad impact on the physiology and matrix architecture of the aorta.
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