REMODELING OF CARDIOMYOCYTE CYTOARCHITECTURE VISUALIZED BY 3-DIMENSIONAL (3D) CONFOCAL MICROSCOPY

The break-down and reassembly of myofibrils in long-term cultures of a dult rat cardiomyocytes was investigated by a novel combination of con focal laser scanning microscopy and three-dimensional image reconstruc tion, referred to as FTCS, to visualize the morphological changes thes e cells undergo in culture. FTCS is discussed as an alternative imagin g mode to low-magnification scanning electron microscopy. The three-di mensional shape of the cells are correlated with the assembly state of myofibrils in different stages. Based on immunofluorescence and confo cal laser scanning microscopy it was shown that myofibrils are degrade d within a few days after plating and that newly assembled myofibrils are predominantly confined to the continuous area in the perinuclear r egion close to the membrane in contact with the substratum. The locali zation of myofibrils along the cell's vertical axis has been investiga ted both by optical sectioning using confocal light microscopy and by physical sectioning followed by transmission electron microscopy. Base d on the distribution of myofibrillar proteins we propose a model of m yofibrillar growth locating the putative assembly sites to a region co ncentric around the nuclei. We provide evidence that the cell shape is dominated by the myofibrillar apparatus.