Correspondence

Apoptosis in the Heart

N Engl J Med 1997; 336:1025-1026April 3, 1997

Article

To the Editor:

Narula et al. (Oct. 17 issue)1 describe the existence of apoptosis in seven explanted human hearts. On the basis of our own data on 10 explanted hearts (5 ischemic and 5 nonischemic),2 we agree that cardiomyocyte apoptosis is present in terminally failing human hearts but wish to raise several points of criticism regarding the work of Narula et al.

We were surprised by the very high percentages (5.5 to 35.5 percent) of apoptotic cardiomyocytes in the hearts studied. Using essentially similar methods, we found an average of 0.08 percent apoptotic cardiomyocytes in the failing hearts, as compared with less than 0.01 percent in control samples. Our calculation of mean percentages involved an average of 3500 microscopical fields (×400) and 85,000 cells per patient. Narula et al. may have overestimated the apoptotic index by excluding areas with less than 2 percent positive cells from the calculations. Other possible reasons include the high variation between stainings,3 DNA degradation caused by autolysis (Narula et al. did not give the time from death to autopsy), and the presence of DNA degradation in overtly necrotic cells in the infarcted myocardium4 (which in our opinion cannot replace DNase I–treated myocardial sections as true positive controls for apoptosis). Moreover, the sensitivity of the assay is critically dependent on the kinetics of the staining procedure.

On the basis of the lack of extensive DNA fragmentation in two of the three hearts studied, Narula et al. conclude that cardiomyocyte apoptosis does not occur in ischemic cardiomyopathies. In contrast, our results showed that apoptosis occurred in five ischemic and five nonischemic cardiomyopathic hearts in similar quantities.2 Apoptosis occurs in a particularly patchy pattern during ischemia reperfusion.3,5 Thus, the use of different parts of the left ventricle for in situ end-labeling and DNA electrophoresis could have resulted in erroneously discrepant results in patients with ischemic cardiomyopathies.

Finally, the authors show large numbers of end-labeling–positive intact cardiomyocytes but do not discuss whether the morphologic features of late-phase apoptosis (apoptotic bodies with condensed chromatin) were observed. Thus, the important question — whether degradation of cells with fragmented DNA is described by necrotic or apoptotic morphology — remains unanswered.

Antti Saraste, M.B.
Liisa-Maria Voipio-Pulkki, M.D.
Martti Parvinen, M.D.
Kari Pulkki, M.D.
University of Turku, FIN-20520 Turku, Finland

5 References

1. 1

   Narula J, Haider N, Virmani R, et al. Apoptosis in myocytes in end-stage heart failure. N Engl J Med 1996;335:1182-1189
   Full Text | Web of Science | Medline

2. 2

   Saraste A, Pulkki K, Kallajoki M, et al. Apoptosis in explanted failing human hearts. Presented at the Scientific Conference on the Molecular Biology of the Normal, Hypertrophied, and Failing Heart, Salt Lake City, August 21–25, 1996. abstract.
   

3. 3

   Gottlieb RA, Burleson KO, Kloner RA, Babior BM, Engler RL. Reperfusion injury induces apoptosis in rabbit cardiomyocytes. J Clin Invest 1994;94:1621-1628
   CrossRef | Web of Science | Medline

4. 4

   Kajstura J, Cheng W, Reiss K, et al. Apoptotic and necrotic myocyte cell deaths are independent contributing variables of infarct size in rats. Lab Invest 1996;74:86-107
   Web of Science | Medline

5. 5

   Saraste A, Pulkki K, Kallajoki M, Henriksen K, Parvinen M, Voipio-Pulkki L-M. Apoptosis in human myocardial infarction. J Mol Cell Cardiol 1996;28:A106-A106 abstract.
   CrossRef | Web of Science

Author/Editor Response

The authors reply:

To the Editor: We, and various investigators working in the field of apoptosis, all agree that there is much to learn about apoptosis in the myocardium. We have indeed just begun to uncover evidence that various forms of injury to the myocardium can induce apoptosis in the heart. It has been the conventional wisdom that terminally differentiated cells do not undergo apoptosis. However, we, as well as others, have observed not only that apoptosis occurs in pathologic myocardium but also that its occurrence is not confined to single cells; apoptosis in the myocardium is observed in small clusters of cells of variable number. Furthermore, it would be simplistic to assume that the rate of apoptotic loss of cells in the (terminally differentiated) myocardial cells would be the same as that in other organs. Therefore, it is not certain whether the statistic presented by Saraste et al. in their letter regarding the rate of loss of myocytes is valid, especially since we have seen apoptotic nuclei in normal-looking myocytes. It may be possible that this is another exception to the conventional wisdom.

In our study, apoptosis was observed in all patients with dilated cardiomyopathy; however, it was detected in only one patient with ischemic cardiomyopathy.1 We did not conclude, as suggested by Saraste et al., that cardiomyocyte apoptosis does not occur in ischemic cardiomyopathies. Rather, this statement appeared in the accompanying editorial.2 Neither have we claimed that apoptosis can differentiate between the two cardiomyopathic states. It is not surprising that Saraste et al. found apoptosis in both ischemic and dilated cardiomyopathy, and their findings provide evidence supporting our report. The variability in the distribution of apoptotic cells, as indicated in our report, may be related to the use of myocardial samples from different regions of the myocardium.1 This may have resulted in the seemingly discrepant (not erroneous) observations of the extent of apoptosis. Furthermore, because of the possibility of variability in the sensitivity of the staining procedure, we also used an independent technique to demonstrate apoptosis by DNA laddering. Finally, we would like to point out that the Methods section clearly stated that the cardiomyopathic samples were obtained from patients undergoing transplantation and not autopsy, and that the samples were snap-frozen or placed in buffered formaldehyde fixative after explantation. It is unlikely that the variability seen in apoptosis resulted from tissue handling and autolysis.

Jagat Narula, M.D., Ph.D.
G. William Dec, M.D.
Massachusetts General Hospital, Boston, MA 02114

Renu Virmani, M.D.
Armed Forces Institute of Pathology, Washington, DC 20306-6000

Ban-An Khaw, Ph.D.
Northeastern University, Boston, MA 02115

2 References

1. 1

   Narula J, Haider N, Virmani R, et al. Apoptosis in myocytes in end-stage heart failure. N Engl J Med 1996;335:1182-1189
   Full Text | Web of Science | Medline

2. 2

   Colucci WS. Apoptosis in the heart. N Engl J Med 1996;335:1224-1226
   Full Text | Web of Science | Medline

Citing Articles (5)

Citing Articles

1. 1

   Song-Jung Kim, Alex Kuklov, George J. Crystal. (2011) In vivo gene delivery of XIAP protects against myocardial apoptosis and infarction following ischemia/reperfusion in conscious rabbits. Life Sciences 88:13-14, 572-577
   CrossRef

2. 2

   Kenji Fukushima, Mitsuru Momose, Chisato Kondo, Takahiro Higuchi, Kiyoko Kusakabe, Nobuhisa Hagiwara. (2010) Myocardial 99mTc-sestamibi extraction and washout in hypertensive heart failure using an isolated rat heart. Nuclear Medicine and Biology 37:8, 1005-1012
   CrossRef

3. 3

   Nam-Ho Kim, Peter M. Kang. (2010) Apoptosis in Cardiovascular Diseases: Mechanism and Clinical Implications. Korean Circulation Journal 40:7, 299
   CrossRef

4. 4

   Ilka Pinz, Stephen D. Wax, Paul Anderson, Joanne S. Ingwall. (2008) Low over-expression of TNFα in the mouse heart increases contractile performance via TNFR1. Journal of Cellular Biochemistry 105:1, 99-107
   CrossRef

5. 5

   Kari J. Pulkki. (1997) Cytokines and Cardiomyocyte Death. Annals of Medicine 29:4, 339-343
   CrossRef