Cardiac myocytes divide after myocardial infarction

The scarring of the heart tissue after a myocardial infarction suggests that the myocytes are unable to divide. In June 7 New England Journal of Medicine Antonio Beltrami and colleagues from the New York Medical College, Valhalla, challenge the current dogma and demonstrate the existence of a significant degree of mitosis among myocytes after myocardial infarction in humans.

Beltrami et al sampled infarcted and non-infarcted areas of the myocardium from 13 patients who had died 4 to 12 days after infarction and ten control normal hearts. They measured cell division by labelling of the nuclear antigen Ki-67 and found that Ki-67 expression was present in 4% of myocyte nuclei in the infarcted regions and 1% in the distal regions. The myocytes exhibited many of the classical characteristics associated with cell division — the formation of the mitotic spindles, contractile rings, karyokinesis and cytokinesis (NEJM 2001, 344:1750-1757).

These...