OBJECTIVETo investigate the effects of sonicated extracts of Porphyromonas gingivalis (Pg) on osteogenic differentiation of mouse osteoblast cell line MC3T3-E1.

METHODSPgW83 was cultured under standard anaerobic conditions and extracted by sonication. Mouse osteoblast cell line MC3T3-E1 was cultured with various concentrations of the extraction (0, 10, 100, 1000 mg/L). Western blotting was applied to investigate the expression of osteocalcin (OC), bone sialoprotein (BSP), osteopontin (OPN) and osteonectin (ON). The activity of alkaline phosphatase (ALP) was detected by microplate reader after 14 days. Mineralization nodule formation was measured by alizarin red staining after 21 days.

RESULTSCompared with the control group, the extracts of Pg decreased OC and ON expression in a dose-dependent manner (OC relative expression:1.000 ± 0.000,0.852 ± 0.110,0.625 ± 0.451,0.213 ± 0.053), (ON relative expression: 1.000 ± 0.000, 1.035 ± 0.133,0.141 ± 0.023,0.020 ± 0.003) (P < 0.05). The expression of OPN was down-regulated significantly in MC3T3-E1 treated with 1000 mg/L extraction (0.572 ± 0.162) compared with control group, 10 and 100 mg/L (1.000 ± 0.000, 1.029 ± 0.135, 1.199 ± 0.337) (P < 0.05). The expression of BSP remained unchanged when the cells were cultured with or without extraction (BSP relative expression:1.000 ± 0.000,0.831 ± 0.182,0.897 ± 0.115,0.778 ± 0.235) (P > 0.05). Meanwhile, the extracts of Pg decreased ALP activity [control group:(0.0275 ± 0.0014) U/gprot, 10 mg/L: (0.0140 ± 0.0011) U/gprot, 100 mg/L: (0.0057 ± 0.0013) U/gprot, 1000 mg/L: (0.0020 ± 0.0008) U/gprot] (P < 0.05) and reduced mineralization nodule formation.

CONCLUSIONSThe results suggest that Pg may inhibit osteoblasts'osteogenic function by down-regulation of osteogenic differentiation related proteins.