title: Immunocytochemical analysis of the regeneration of myofibrils in long-term cultures of adult cardiomyocytes of the rat.
abstract: Dissociated adult rat ventricular cardiomyocytes obtained from hearts by retrograde perfusion with collagenase were investigated in long-term cultures. Myofibril regeneration, isoprotein transition of alpha- and beta-myosin heavy chain (MHC), and M-band localization of M-creatine kinase in the reconstituting heart cells were studied. Myofibril formation was demonstrated by the use of antibodies against either cardiac C-protein or myomesin as early differentiation markers. Four days after plating, small myofibrils could be identified in attached cells in a perinuclear fashion; later in culture the cells displayed various shapes and myofibril distribution. Frequently a patchy distribution of myofibrils within the extending peripheral processes could be observed. Colocalization of sarcomeres and phalloidin-stained F-actin filament bundles was demonstrated by double fluorescence staining and by the use of high intensifying video microscopy and computerized image processing. The immunofluorescence distribution of alpha- and beta-MHC isoproteins in newly isolated and cultured cardiomyocytes changed from 100% alpha-MHC and 70% beta-MHC in rod-shaped cells to about 100% beta-MHC and 70% alpha-MHC in spread out cultured cells. This shift was corroborated by a relative gradual decline in alpha-MHC at the expense of increasing amounts of beta-MHC with time in culture as assessed by sodium dodecyl sulfate gel electrophoresis of total cell homogenates. In addition, whereas rod-shaped newly isolated cardiomyocytes showed a clear M-band association of M-creatine kinase as found in adult heart tissue, adult cultivated spread out cells did not show a cross-striated pattern after incubation with antibody. Taken together, these observations suggest that adult cardiomyocytes not only undergo extensive morphological transitions in long-term cultures, but also generate new myofibrillar structures lacking M-creatine kinase and containing the beta-MHC, thus fitting the characteristics of fetal myofibrils. These results indicate a change from the adult terminally differentiated to a less differentiated state of the cardiac cells in culture.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002352:Carrier Proteins / Q000502:physiology; D002478:Cells, Cultured; D064211:Connectin; D003402:Creatine Kinase / Q000502:physiology; D005455:Fluorescent Antibody Technique; D006321:Heart / Q000502:physiology; D009124:Muscle Proteins / Q000502:physiology; D009206:Myocardium / Q000166:cytology*; D009218:Myosins / Q000145:classification / Q000502:physiology; D051381:Rats; D012038:Regeneration
chemical_list: D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D064211:Connectin; D009124:Muscle Proteins; C020723:citrate-binding transport protein; D003402:Creatine Kinase; D009218:Myosins