INFLUENCE OF SHORT-TERM HYDROSTATIC-PRESSURE ON ORGANIZATION OF STRESS FIBERS IN CULTURED CHONDROCYTES

The present study describes changes in the organization of stress fibe rs that occur in articular cartilage chondrocytes subjected to hydrost atic pressure. Primary cultures of chondrocytes from bovine articular cartilage, grown on coverslips, were subjected to 5, 15, or 30 MPa hyd rostatic pressure at 37 degrees C. The pressure was applied continuous ly or cyclically at two frequencies: 0.125 Hz (4 seconds of pressure a nd 4 seconds of no pressure) or 0.05 Hz (1 second of pressure and 19 s econds of no pressure) for a period of 2 hours. Control chondrocytes s howed a polygonal form with prominent stress fibers extending across t he cells. The exposure of cells to 30 MPa pressure caused a nearly tot al disappearance of stress fibers and retraction of the cells from eac h other. With pressure at 15 MPa or cyclic pressure, the number of cel ls with stress fibers was decreased. In cells subjected to 5 MPa press ure, the stress fibers resembled those in control chondrocytes. The pr essure effects were reversible after 2 hours. Pressure had no effect o n the staining pattern of vinculin, which suggests that microfilaments are more vulnerable to pressure than vinculin. The results indicate t hat cytoskeletal changes may be an integral part of the response of ch ondrocytes to hydrostatic pressure.