Endothelial alterations and senile calcific aortic stenosis: an electron microscopic observation.

Calcific degeneration of aortic valves were investigated in 10 patients with senile calcific aortic stenosis by means of high resolution scanning electron microscopy (HR-SEM) and transmission electron microscopy (TEM). All the specimens obtained during aortic valve surgery HR-SEM and TEM examinations consistently showed various degrees of pathological alterations and calcification involving surface endothelium, underlying basement membranes and deeper layers of interweaving networks of collagen fiber bundles in the pars fibrosa of the valve tissues. Calcific deposits in the valve tissues always occurred in the vicinity of the endothelial defects and in the subendothelial structures just beneath the defective endothelium. The amount of calcific deposits in the valve tissues increased in proportion to the severity of endothelial damage and gradually decreased from the defective endothelial surface to the deeper layer of collagen tissue. In addition, apoptotic cell death, particularly of the fibrocytes in the valve tissue, was closely related to the severity of endothelial injury. Cellular fragments derived from the apoptotic cells were always associated with calcium deposits. Based on the above findings, our results provide evidence that the alteration of endothelial integrity plays a contributory role in calcific degeneration in the aortic valve leading to the development of senile calcific aortic stenosis.