Culture of the terminally differentiated adult cardiac muscle cell: A light and scanning electron microscope study

Abstract

Cardiac muscle cells were isolated from adult rat heart by retrograde perfusion via the aorta with medium containing 1 mg/ml of collagenase; following perfusion the cells were completely dissociated by mincing the ventricular muscle and incubating the fragments in medium containing collagenase. Isolated myocytes when placed in culture were observed to undergo a process which can be analogized to a metamorphosis. Freshly isolated cells are striated and cylinder-shaped, typical of intact ventricular cardiac muscle. These cells then shorten, round up, and lose their cross striations. They then attach to the surface of the culture flask and extend pseudopod-like processes. With increased time in culture the cells spread out and become entirely flattened and organized bands of myofibrils reappear. These cells are somewhat similar morphologically to cardiac muscle cells isolated from neonatal rats and grown in culture, however, they are much larger and also contain multiple nuclei. Most myocytes continue to contract spontaneously during most stages of this “metamorphosis” and nearly all of the flattened, spread-out cells are contracting. Some of these cells appear to be in the process of dividing and on rare occasions some are associated with what appear to be neurons. These studies show that adult ventricular cardiac muscle cells when placed in culture dedifferentiate and lose their highly organized morphology and then redifferentiate into spontaneously contracting myocytes with reorganized myofibrils.