Anatomy and Embryology

, Volume 205, Issue 3, pp 235–244 | Cite as

Cell cycle reentry of ventricular and atrial cardiomyocytes and cells within the epicardium following amputation of the ventricular apex in the axolotl, Amblystoma mexicanum: confocal microscopic immunofluorescent image analysis of bromodeoxyuridine-labeled nuclei

  • Irwin L. Flink
Original Article


To understand how to reinitiate cell division in adult human myocardium, a heart regeneration model was examined in the amphibian axolotl salamander, Amblystoma mexicanum. The ventricular apex was surgically amputated and resected for 3 weeks. At 14 days of recovery, the thymidine analog 5-bromo-2′-deoxyuridine (BrdU) was injected intraperitoneally to identify cell types undergoing S-phase by indirect immunofluorescence using primary anti-BrdU antibodies. This is the first report showing a concentrated area of cell division in the ventricle and cells throughout the atrial epicardium by confocal microscopic image analysis in response to wounding of the ventricle. Tissues coimmunostained with anti-BrdU and sarcomeric myosin-specific MF20 antibodies showed 12.8 ± 4.10% of myocytes contained BrdU+ nuclei in a 75 µm to 750 µm zone in the ventricular myocardium subjacent to the amputation plane. BrdU+ nuclei also were present in newly formed ventricular epicardium that surround dividing myocytes, and in epicardial mesothelium (74.3 ± 6.36 %) and connective tissue (44.9 ± 13.31%) cells distal to the wound. Unexpectedly, immunofluorescent BrdU+ nuclei were observed in isolated atrial myocytes (13.9 ± 1.45%) and in uninjured atrial epicardial mesothelium (64.3 ± 1.55%) and connective tissue (29.4 ± 5.50%). No BrdU+ nuclei were present in cardiomyocytes or epicardium from sham-operated and BrdU-treated controls. These results suggest that renewed cell division is a specific response to wounding of the ventricle. Additionally, release of a growth factor may be responsible for the specific localized mitotic ventricular cardiomyocyte response adjacent to the wound, and the more generalized atrial proliferative response distal to the amputation.

Bromodeoxyuridine Cardiomyocyte proliferation Fluorescent antibody immunostaining Epicardium Myocardium Regeneration Sarcomeric myosin 


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Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  • Irwin L. Flink
    • 1
  1. 1.University of Arizona Health Sciences Center, Department of Medicine and Sarver Heart Center, Room 6133, 1501 N. Campbell Avenue, PO Box 245046, Tucson, AZ 85724-5046, USA

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