MYOCARDIAL DNA STRAND BREAKS ARE DETECTED IN BIOPSY TISSUES FROM PATIENTS WITH DILATED CARDIOMYOPATHY

Background. Progressive damage of cardiomyocytes with interstitial and replacement fibrosis accompanied by less inflammatory cell infiltrati on is observed in patients with dilated cardiomyopathy (DCM), suggesti ng some other mechanisms rather than necrotic cell death. Hypothesis: The aim of this study was to assess the possible involvement of apopto tic process in the pathogenesis of DCM and myocarditis. Methods: Endom yocardial biopsy was performed in patients with DCM (n = 9), myocardit is (n = 4), or atypical chest pain syndrome (as controls; n = 5). The TUNEL method was used for in situ detection of oligonucleosomal DNA st rand breaks. Results: The TUNEL-positive cells were observed in three of nine patients with DCM and in all four with myocarditis, but in non e of the controls. The TUNEL-positive nuclei were observed exclusively in cardiomyocytes in DCM, whereas in myocarditis they were detected m ainly in interstitial cells and in a few myocytes. In DCM, interstitia l fibrosis was greater in the TUNEL-positive than in TUNEL-negative pa tients (p<0.05), In either DCM or myocarditis, electron microscopic ex amination could not reveal morphologic features of apoptosis of cardio myocytes. Conclusion: The DNA strand breaks were detected in cardiomyo cytes in patients with DCM and mainly in interstitial cells in myocard itis. It is possible that the DNA strand breaks can be involved in mec hanisms of progressive loss of functional cardiac units in these myoca rdial diseases.