The Expression of Transforming Growth Factor-β1 and α-Smooth Muscle Actin is Increased in the Human Myxomatous Valve

Background : In vitro experimental studies have reported that transforming growth factor-beta 1 (TGF-beta 1) stimulates the production of alpha-smooth muscle actin (alpha-SMA) in porcine valves. However, the relation between TGF-beta 1 and alpha-SMA in myxomatous valves has not been elucidated. Methods : We classified 27 subjects into two groups: 1) myxomatous group (11:12, mean age=55 +/- 15 years) and 2) rheumatic group (M:F=3:1 mean age=41 +/- 17 years) according to preoperative echocardiographic and postoperative histologic findings. Twenty-seven valve specimens from the patients who underwent valve replacement were obtained. Tissue samples were analyzed by immunohistochemistry for TGF-beta 1 and alpha-SMA. The positively stained areas were measured using an image analysis program (image Pro-Plus 4.5), and then the TGF-beta 1 volume fraction (TGF-VF) and alpha-SMA volume fraction (alpha-Si were calculated. Results : TGF-VF in myxomatous valves was higher than in rheumatic valves (2,759 +/- 2,294 vs 864 +/- 276, p=0.04). alpha-SMA-VF in myxomatous valves was higher than in rheumatic valves (4,122 +/- 2,275 vs 2,421 +/- 844, p=0.002). There was a significant correlation between TGF-beta 1 and alpha-SMA in myxomatous valves (r=0.38, p=0.04). There was no significant correlation between TGF-beta 1 and alpha-SMA in rheumatic valves (r=0.50, p=0.67). Conclusions : TGF-beta 1 and alpha-SIMA may be related to the pathogenesis of myxomatous valves. The activation of TGF-beta 1 might increase the expression of alpha-SMA in human myxomatous valves.