Abstract 16403: Occurrence of Autophagy and Bridging of the Autophagic Process to Apoptotic and Necrotic Cell Death in the Human Heart With End-Stage Heart Failure
Objectives: Although originally described as a survival mechanism against stressful events, such as starvation, whether and to what extent autophagy is implicated in the terminal stages of heart failure is unknown. Hence, we studied magnitude and evolution of autophagy in patients with intractable heart failure.
Methods: Myocardial samples were obtained from 19 patients with ischemic cardiomyopathy (n=11) and idiopathic dilated cardiomyopathy (n=8), who underwent cardiac transplantation. Hearts from 11 subjects deceased from noncardiac causes were used as controls. Autophagy was evaluated by immunostaining with a monoclonal LC3 antibody, while its relationship with apoptosis and necrosis was assessed by double staining with TUNEL assay and complement 9 (C9) immunological staining, respectively.
Results: Heart failure hearts showed levels of myocyte autophagy over 7 fold greater than control hearts. Myocyte autophagy, revealed by staining with a monoclonal LC3 antibody, was detected in 8.7±1.6% of the entire myocyte population from heart failure heart and in 1.2±0.3% of cardiac myocytes from control hearts. LC3 positive vacuoles formation was observed to start at one nuclear pole, before becoming bipolar and involving the cytosol. Subsequently, the autophagic process extended also to the nuclei, which, in the final stages, underwent a progressive vacuolization and disintegration, assuming a peculiar “strawberry like aspect”. Interestingly, cardiac cells in which the autophagic vacuoles covered less than 50% of their surface, nuclear disintegration was not observed. Consensually, this cell population never showed colocalization of LC3 and C9 staining (to demonstrate colocalization of autophagy and necrosis) or TUNEL reagents (to demonstrate colocalization of autophagy and apoptosis). On the contrary, myocytes in which the autophagic vacuoles covered more than 50% of the cellular body, exhibited nuclear degeneration, which was associated with TUNEL and C9 positive staining.
Conclusions: Autophagy was extensively detected in end-stage heart failure and progression of the process, causing broad cytosolic destruction and nuclear disintegration, finally resulted in cell death by apoptosis and necrosis.
- © 2010 by American Heart Association, Inc.