Overexpression of transforming growth factor β1 in smooth muscle cells of human abdominal aortic aneurysm

Objective: to examine the expression of transforming growth factor beta1 (TGF-beta1) and the cell kinetics of smooth muscle cells (SMCs) at the neck of abdominal aortic aneurysms (AAAs). Materials and Methods: expression of alpha-smooth muscle actin and TGF-beta1 was evaluated by immunostaining, and cell kinetics were estimated by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay and Ki-67 immunostaining in 11 AAAs (at both the dilated region and the neck) and eight occlusive aortas. Results: the TUNEL-positive SMC ratio in the neck and dilated region was significantly higher than in the occlusive aorta (p < 0.01). The percentage of Ki-67-positive SMCs in the neck was significantly higher than in the dilated region (p < 0.01) and the occlusive aorta (p = 0.032). When compared with the occlusive aorta, the aneurysmal neck had increased TGF-beta1 expression (p = 0.01) and reduced SMC density, and the aneurysmal dilated aorta had much more increased TGF-beta1 expression (p < 0.01) and much more reduced SMC density (p < 0.01). Conclusions: these results suggest that overexpression of TGF-beta1 might be associated with the reduction of SMC density through SMC apoptosis and reduced proliferative ability of SMCs, leading to dilatation in AAAs.