Assessment of cardiomyocyte dna synthesis in the normal and injured
adult mouse heart.
Soonpaa, Mark H., and Loren J. Field.
Krannert Institute of Cardiology, Indiana University School of
Medicine, 1111 West 10th Street, Indianapolis, IN 46202-4800
APStracts 3:0291H, 1996.
Cardiomyocyte DNA synthesis was examined in normal and injured adult
mouse hearts. In preliminary studies DNA synthesis was monitored by
tritiated thymidine incorporation, fol lowed by autoradiographic
analysis of dispersed cell preparations. No synthetic cells were
identified when 20,000 ventricular cardiomyocytes from normal adult
hearts were examined. A high throughput assay was developed to
establish the actual labeling index for the adult mouse heart. The
assay utilized tritiated thymidine incorporation in transgenic mice
which expressed a nuclear-localized [beta]-galactosidase ([beta]GAL)
reporter gene exclusively in cardiac myocytes. Cardiomyocyte DNA
synthesis was evidenced by co-localization of [beta]GAL activity and
silver grains in autoradiograms of histologic sections. Examination
of 180,000 ventricular cardiomyocyte nuclei from normal adult
transgenic mice identified a single synthetic nucleus, suggesting a
maximum labeling index of 0.0005%. Cardiomyocyte DNA synthesis was
next examined in hearts injured by focal cauterization of the left
ventricular free wall. Only three synthetic nuclei were identified
when 36,000 cardiomyocyte nuclei in the peri-necrotic zone of the
injured heart were examined. No additional synthetic nuclei were
identified when 180,000 nuclei in regions distal to the necrotic zone
were examined. These data confirm that cardio myocyte DNA synthesis
in the adult mouse heart is extremely rare, and provide base line
data for analyses in genetically modified animals.
Received 13 March 1996; accepted in final form 8 July 1996.
APS Manuscript Number H242-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 July 1996