Effect of centrifugal force on cellular activity of osteoblastic MC3T3-E1 cells in vitro

The effects of centrifugal force on growth and differentiation of osteoblas tic cells cultured in a-MEM containing 1% fetal bovine serum were investiga ted by assays of DNA synthesis, alkaline phosphatase activity and osteocalc in-production in osteoblastic MC3T3-E1 cells. Centrifugation of the cells in low concentrations (1%) of fetal bovine seru m caused a 1.9-fold increase of [H-3]thymidine incorporation on day 3 from the start of centrifugation, and gradually decreased with culture up to day 9. Alkaline phosphatase activity was not affected by centrifugal force unt il day 5, and increased rapidly after day 7. Stimulation of DNA synthesis b y centrifugation was abolished in the presence of H-7, an inhibitor of prot ein kinase C. These results suggest that centrifugal force stimulates the p roliferation of osteoblastic cells through an autocrine secretion of some d iffusable growth-promoting activity. Additional centrifugation of the cells also slightly stimulated alkaline phosphatase activity, although this did not directly influence the cell's osteocalcin-production activity.