Absolute proliferation of MC3T3-E1 cells maintained in six types of tissue culture medium in duplicates over three two-week periods and assayed in duplicates (). Two types of media were used, one with osteogenic factors (BM+) and one without (BM−). At day 5, the MC3T3-E1 cell counts in the wells containing vitamin D metabolites ± osteogenic factor were statistically lower than the negative control (BM−). At day 10, the OPC1 cell counts in the wells containing vitamin D metabolites ± osteogenic factors (BM+) were also statistically lower () then than the negative control (BM−) and remained at around 50% of the BM− cellular confluency. MC3T3-E1 cells treated with BM+ and vitamin D₃ were indistinguishable from 1,25OH₂D₃ in that both experienced the largest statistically () antiproliferative effect. Means ± SEM are shown with linear trendlines in the same color scheme for each experimental group.