Figure 4: mRNA levels of differentiation maker genes, runt-related transcription factor 2 (RUNX2) (A), bone sialoprotein (BSP) (B), osteopontin (OPN) (C), and
osteocalcin (OCN) (D) in MC3T3-E1 cells measured by real-time PCR after cell culture with a collagen membrane (CM) with/without platelet-derived growth factor
(PDGF). Data represent relative expression to the level of the cell control, set at 1, and mean value ± standard deviation from quadruplicates (white bars, cell control;
gray bars, CM; and black bars, CM with PDGF). * p < 0.05, ** p < 0.01, and *** p < 0.001.