Histological evaluation of autophagic cell death in calcified aortic valve stenosis.
BACKGROUND AND AIM OF THE STUDY: Calcification in aortic valves is the most common valvular lesion in western populations. This event is correlated with cellular degeneration in the valvular cusps, although there is no exact evidence how these cells die: this requires further exploration. METHODS: Twelve human severely calcified aortic valves obtained during cardiac surgery were studied by semi-quantitative analysis, and results compared with data from 12 human control aortic valves obtained during autopsy. Tissue analysis was by hematoxylin and eosin and Alcian blue staining. Detection of neurons was by immunohistochemical staining of PGP9.5 and neurofilament. In order to detect autophagy, an immunohistochemical staining for ubiquitin was used. The TUNEL technique was used to detect apoptosis. Co-localization of Alizarin red with ubiquitin labeling was performed on non-decalcified aortic valves. RESULTS: Hematoxylin and eosin staining showed moderate to severe mineralization in 10 of 12 patients in the surgical group, but in only one of 12 in the autopsy group. No significant observations were made with regard to PGP9.5 and neurofilament staining. Moderate to severe ubiquitin labeling was found initially in the majority of the surgical resection group (9/12) compared to a minority in the autopsy group (1/12). TUNEL-positive labeling was very rare and found mostly at the endothelial layer of the valvular cusps. CONCLUSION: Immunohistochemical methods showed the main cell death mechanism involved in the calcification of aortic leaflets to be autophagy rather than apoptosis. These findings suggest that autophagic cell death might play a role in the release of matrix vesicles in early degenerative aortic valves, thereby attracting inflammatory cells, and this could eventually lead to mineralization.