Nuclear Lamin Expression in Chronic Hibernating Myocardium in Man

Cardiomyocytes of chronic hibernating myocardium are known to undergo structural changes, indicative of dedifferentiation. Amongst these are changes in nuclear shape and chromatin distribution. Nuclear A-type lamins are known to be expressed in a differentiation-related fashion and to contribute to nuclear integrity and chromatin organization. Lamin expression was investigated with immunocytochemical staining procedures in biopsies from patients with chronic hibernating myocardium. The expression of A-type (lamin A and C) were shown to be downregulated during hibernation, while lamin B2 remained present in hibernating cardiomyocytes in a way similar to embryonic muscle cells. All heart muscle cells were shown to be negative for lamin B1. The absence of A-type lamins in chronic hibernating cardiomyocytes could be taken as an additional argument for the dedifferentiation state of these cells. The absence of A-type lamins was accompanied by dispersion of the nuclear heterochromatin, in a way similar to nuclei of embryonic cardiomyocytes.