Time course of the effect of TSA on the formation of TRAP⁺ POCs.

Stroma-free rat bone marrow cells were cultured under the conditions necessary to form POCs for 4 days with (▪) or without (░) 10 nM TSA, following the indicated treatment schedule. Culture was fed every day with fresh medium, hormone, factors, and TSA. Before changing to new medium, the culture was washed 3 times by replacing 80% of the culture medium with fresh medium to eliminate the remaining factors. Factors and TSA were then added for the indicated periods. After 4 days of culture, the cells were fixed and stained for TRAP. The number of TRAP⁺ mononuclear cells was counted in each well. Each value represents the mean ± SEM of quadruplicate cultures. Data were analyzed by Student t test. *P < .001 compared with the culture without TSA.