Figure 3: Cell proliferation activity in MC3T3-E1 cells after culture (2, 4, and 6 days) with a collagen membrane (CM) with/without platelet-derived growth factor (PDGF). The percentage of cell proliferation was calculated by comparing the appropriate luminescent signal to the signal obtained with the control cells. Each value represents the mean ± standard deviation from quadruplicates (white bars, CM; and black bars, CM with PDGF). As a control, non-treated cells were used. * p < 0.05.