PHYSIOLOGICAL LEVELS OF HYDROSTATIC-PRESSURE ALTER MORPHOLOGY AND ORGANIZATION OF CYTOSKELETAL AND ADHESION PROTEINS IN MG-63 OSTEOSARCOMA CELLS

The response of human MG-63 osteosarcoma cells to physiological levels of hydrostatic pressure was studied. Cell cultures were subjected to a 20-min, 4-MPa hydrostatic pressure pulse. Adhesion was measured at 20 min and 2 h post-hydrostatic pressure. Morphometric measurements of cell shape and immunofluorescent assays of cytoskeletal and adhesion proteins were done pre- and post-hydrostatic pressure. Pressure-treated cells showed increased adhesion (resistance to deadhesion by trypsinization) with increased recovery time. Indirect immunofluorescence demonstrated increased heterotypic adhesion receptor at cell-cell interfaces and increased alpha3,beta1-integrin at cell-substrate interfaces. Indirect immunofluorescence demonstrated depolymerization of alpha-tubulin, vimentin, and actin during the pressure pulse. Actin reorganization was slower than that of alpha-tubulin and vimentin, with stress filaments not well organized even after 1 h postpressure. The depolymerization of alpha-tubulin, vimentin, and actin observed at relatively low levels of hydrostatic pressure suggests disintegration of the integrin-cytoskeletal attachment complex. The increased resistance of the cells to trypsinization and the increase in both heterotypic adhesion receptor and the alpha3,beta1-integrin at cell interfaces suggest that cells compensate for loss of cytoskeletal integrity by increasing attachment to both adjacent cells and the extracellular matrix.