INFLUENCE OF AN INTERMITTENT COMPRESSIVE FORCE ON MATRIX PROTEIN EXPRESSION BY ROS 17/2.8 CELLS, WITH SELECTIVE STIMULATION OF OSTEOPONTIN

The purpose of this study was to determine the response of bone cells to physical stress. Intermittent compressive force (ICF) was applied to 13 kPa to subconfluent ROS 17/2.8 cells at 18 cycles/min. After 48 h of this application, the cells were labelled with [S-35]-methionine or [(PO4)-P-32]. Application of ICF over this time did not alter the synthesis of type I collagen, fibronectin or bone SPARC (osteonectin) compared to that of control cells. However, the activity of alkaline phosphatase was increased 1.5-fold, and the synthesis of a (PO4)-P-32-labelled, 75-kDa phosphoprotein, recognized as osteopontin by immunoprecipitation with specific antibodies, was increased 1.4-fold. Also, an increase in osteopontin mRNA starting within 12 h of ICF application was observed. The selective increase in osteopontin expression associated with ICF may be important in the remodelling of bone tissues during growth and development and in response to functional forces.