Morphological dedifferentiation of adult cardiac myocytes in coculture with hepatocytes.

When adult heart cells are plated on a dish covered with a monolayer of hepatocytes gradual morphological changes are observed. While during the first day the myofibrils are still organized in rod-like shape, later the cells become flat and spread on top of underlying hepatocytes. After two days most cells have a flat, polygonal appearance with spread myofibrillar bundles. At this stage they start spontaneous rhythmic contractions which are characteristic for embryonic myocytes, but not for isolated adult ventricular cells. In this culture myocytes form specific contact structures to adjacent myocytes as well as to hepatocytes. These results demonstrate the phenotypical plasticity of adult heart muscle cells which are believed to be terminally differentiated.