The effect of sodium salicylate on the osteoclast-like cell formation and bone resorption in a mouse bone marrow culture

Salicylates are reported to have an inhibitory effect on bone resorption in vivo and in vitro. The present study examined the effect of sodium salicylate on the formation of osteoclast-like cells in vitro. When mouse bone marrow cells were cultured for 8 days with 10^-8 M 1α,25-dihydroxyvitamin D₃ (1α,25(OH)₂D₃), numerous clusters of mononuclear and multinucleated cells (MNCs) formed, which stained positive for tartrate-resistant acid phosphatase (TRAP-positive). In similar cultures using sodium salicylate, the number of both TRAP-positive mononuclear and TRAP-positive MNCs were found to diminish in proportion to the concentration of sodium salicylate. A time-course experimental model showed that the number of TRAP-positive MNCs decreased slightly when sodium salicylate was given early in the culture period, and decreased markedly when the drugs were given later in the culture period. Pit formation and bone-resorption area on the bone slices were also inhibited by adding sodium salicylate continuously with 1α,25(OH)₂D₃. The sodium salicylate showed no cytotoxic effect because the total number of adherent cells, including both TRAP-positive and TRAP-negative cells, was independent of the presence of sodium salicylate. These results suggest that sodium salicylate has an inhibitory effect on the recruitment of osteoclast-like MNCs and that this inhibition is greater during the later stage of mouse bone marrow culture.