Influence of short-term hydrostatic pressure on organization of stress fibers in cultured chondrocytes.

The present study describes changes in the organization of stress fibers that occur in articular cartilage chondrocytes subjected to hydrostatic pressure. Primary cultures of chondrocytes from bovine articular cartilage, grown on coverslips, were subjected to 5, 15, or 30 MPa hydrostatic pressure at 37 degrees C. The pressure was applied continuously or cyclically at two frequencies: 0.125 Hz (4 seconds of pressure and 4 seconds of no pressure) or 0.05 Hz (1 second of pressure and 19 seconds of no pressure) for a period of 2 hours. Control chondrocytes showed a polygonal form with prominent stress fibers extending across the cells. The exposure of cells to 30 MPa pressure caused a nearly total disappearance of stress fibers and retraction of the cells from each other. With pressure at 15 MPa or cyclic pressure, the number of cells with stress fibers was decreased. In cells subjected to 5 MPa pressure, the stress fibers resembled those in control chondrocytes. The pressure effects were reversible after 2 hours. Pressure had no effect on the staining pattern of vinculin, which suggests that microfilaments are more vulnerable to pressure than vinculin. The results indicate that cytoskeletal changes may be an integral part of the response of chondrocytes to hydrostatic pressure.