Proliferating cells in adult cardiomyopathic hamster ventricles.

Myocardium of hereditary hypertrophic cardiomyopathic hamsters UM.X7.1 between 60 and 90 days of life shows large clusters of densely packed, actively proliferating cells with a rhabdoid appearance. Immunohistochemical studies showed that most of proliferating cells express, although with variable patterns, muscular markers such as desmin, alpha-sarcomeric actin, myoglobin and alpha/gamma-smooth muscle actin. The simultaneous occurrence of a poorly differentiated appearance, intense proliferating activity and expression of muscular markers seems to indicate that cluster cells may be muscular in origin and that their proliferation can be a fundamental pathophysiological step in the onset of cardiomyopathy. The possibility that myocardial proliferating cells originated from de-differentiated adult cardiomyocytes, which undergo a short cellular proliferation program, or from not fully matured (fetal) cardiomyocytes scattered throughout the myocardium is discussed.