F-Actin Plaque Formation as a Transitional Membrane Microstructure Which Plays a Crucial Role in Cell-Cell Reconnections of Rat Hepatic Cells after Isolation

Cell-cell reconnection after isolation or during healing process after injury is a cell membrane function. It is assumed that each tissue has its own architecture and accordingly, cells in different tissues could have different adaptability to resume their tissue-specific architectures. How membranes adapt themselves to make cell-cell reconnections has not been elucidated. This study investigated how rat hepatic cell membranes adapt themselves after isolation to establish cell-cell reconnections, which is essential to liver tissue healing process. Hepatic cells were obtained from rat liver by collagenase perfusion. The cells were maintained in suspension using a gyratory-mediated cell spheroid culture method. F-actin, claudin-2 and connexin-32 on cell membranes were stained and observed by confocal microscopy. Cells and spheroids were also observed by Scanning Electron Microscopy. It was found that hepatic cells underwent adaptive change after enzymatic isolation by diminishing membrane F-actin residues and forming F-actin plaques. Once an F-actin plaque is formed (within 1-4 h), it is ready to make initial contact with other cells through plaque-plaque overlapping in a manner similar to 'Velcro-like' binding. A cell could form one or more F-actin plaques and establish plaque-plaque contacts with one or more other cells. When the cells had established plaque-plaque contacts, their contacts would further develop to make full cell-cell bindings. Claudin-2, a tight-junction molecule, and connexin-32, a gap-junction molecule, gradually diminished and lost their original distribution patterns within 4 h after isolation. They did not show involvement in establishing initial cell-cell connections. It is concluded that F-actin plaque formation is a characteristic change that precedes cell-cell reconnection. F-actin plaques are transitional microstructures that serve as a special device to facilitate cell-cell contacts in the early stage after cell isolation. F-actin can be used as a biomarker to study membrane adaptability and the healing process of hepatic cells.