Molecular insights into hypertrophic cardiomyopathy

Apoptosis in dilated cardiomyopathy

OBJECTIVE

Cardiomyopathy, a popular diagnosis that always obscures more than it reveals, nevertheless has several characteristic histological features. These prominently include widespread focal myocardial fibrosis and associated hypertrophy of surviving cardiac myocyte. In fact, focal noninflammatory degeneration (not necrosis) has been demonstrated as a feature of many forms of cardiac hypertrophy. We hypothesized that this loss of myocardial cells in dilated cardiomyopathy (DCMP) may result from cell death by apoptosis.

METHODS

Endomyocardial biopsy specimens from the right ventricles of six patients who suffered from DCMP were studied, and myocardial specimens from two persons who died in motor vehicle accidents were used as negative controls. For identification of apoptosis, immunohistochemistry with terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end-labeling was performed. In addition, apoptosis was confirmed morphologically by confocal laser scanning microscopy with propidium iodide.

RESULTS

Apoptosis, that was represented by an apoptotic index ranging from 19.8 to 25.4%, could be extensively seen in myocytes and also rarely in non-myocytes of interstitium and vascular endothelium. Morphologically, there were a lot of nuclei with clumps of condensed chromatin, suggestive of apoptosis.

CONCLUSION

The present study demonstrated that myocyte loss in DCMP might be mainly due to the apoptosis of myocytes and interstitial cells, rather than inflammation or cell necrosis.

Hypertrophic cardiomyopathy and pregnancy

The case of a young primiparous woman with defibrillator-assisted familial hypertrophic cardiomyopathy (HCM) has led us to review the literature on this pathology, which is exceptional because of its scarcity and the originality of the problems encountered. To our knowledge, this is the first observation ever reported of defibrillator-assisted activation during pregnancy in a woman with HCM. Several questions raised from this particular case, e.g. what are the risks caused by pregnancy in these patients, what is the impact of therapeutics, does the activation of an internal defibrillator involve particular risks, what is the best disposition for delivery and what are the risks for fetuses? We have tried to ask all of these questions, using as exhaustive a literature review as possible.

Normal and abnormal consequences of apoptosis in the human heart. From postnatal morphogenesis to paroxysmal arrhythmias

Apoptosis and necrosis are two distinctly different forms of cell death, and both occur in the human heart. In contrast to necrosis, apoptosis is not associated with inflammation for two reasons. First, the apoptotic cell does not swell or rupture before it is engulfed by either a macrophage or even a neighboring like cell. Second, the phagocytosis occurs with unusual rapidity. Apoptosis, also thought of as cell suicide, is a tidy way of removing cells no longer useful, in essence a form of selective deletion. These features make apoptosis a valuable component of morphogenesis, mediation of hormonal and immunologic responses, and the homeostatic balance between hypertrophy and atrophy or involution. In the human heart apoptosis has been found in the sinus node of patients with the long QT syndrome. It most likely participates in the important postnatal morphogenesis of the sinus node, AV node, and His bundle. Apoptosis may also participate in the genesis and pathophysiology of cardiomyopathy, paroxysmal arrhythmias, or conduction disturbances (some of which may be responsible for sudden death), focal fibromuscular dysplasia of small coronary arteries, hereditary medial degeneration of the tunica media of coronary arteries, and arrhythmogenic right ventricular dysplasia. The possible role apoptosis in numerous other changes in the human heart, among them the pathogenesis of atherosclerosis and mechanisms of aging in the myocardium, merits future investigation.

Discussion points to consider in research related to the human genome

The advances in DNA technology and molecular genetics, spurred by the Human Genome Project, have created new challenges for human subjects research and the system of institutional review board (IRB) review. The populations to be studied are vulnerable because of genetic diseases or risk for them; until now, IRB review has concentrated on overt physical and medical hazards. Attention to the interests of individuals and families participating in, or affected by, research on the human genome frames the agenda for IRB deliberations and suggests the information to be conveyed to prospective participants. By a series of questions, this article explores how human genome research involves a distinct paradigm in human subjects research with its own imperatives for researchers and IRBs.