Histological assessment of apoptotic cell death in cardiomyopathies

Apoptosis in the myocardium is complex and often difficult to recognise. Myocyte apoptosis is scattered across the myocardial wall and is restricted to individual cells. In the present study, we describe the amount of apoptosis in 50 endomyocardial biopsies taken from 50 patients with dilated cardiomyopathy, in 14 hearts with hypertrophic cardiomyopathy and in five hearts with arrhythmogenic dysplasia of the right ventricle. As a control group, 15 endomyocardial biopsies from 15 transplanted hearts (of live patients) were used. Apoptosis was immunohistochemically determined in paraffin sections with the TUNEL method. In each specimen the TUNEL index was calculated as the percentage of TUNEL-positive nuclei among a total number of 200 counted nuclei. Cellular morphology was assessed in conjunction with TUNEL staining. The mean percentage of TUNEL-positive myocardial cells varied from 4% for dilated cardiomyopathy to 17.5% for arrhythmogenic right ventricle dysplasia and 18.5% for hypertrophic cardiomyopathy, whereas no signs of apoptotic myocardial cell death were found in normal subjects. The numbers of apoptotic cells in dilated cardiomyopathy specimens were significantly lower by comparison with both those of hypertrophic cardiomyopathy and those of arrhythmogenic right ventricular dysplasia specimens. It is evident that apoptosis constitutes a major biological phenomenon in the development of at least some heart diseases, but its role in their pathophysiology has yet to be delineated.