The human osteoblast-like cell line MG63 (Chinese Academy of Medical Sciences, 3111C0001CCC000080) and mouse embryonic fibroblast cell line MC3T3-E1 (Chinese Academy of Medical Sciences, 3111C0001CCC000012) were maintained in Dulbecco's minimum essential medium (DMEM), supplemented with 10% fetal bovine serum (FBS). Subsequently, the cells were cultured in an incubator at 37°C with 5%CO 2. The cells were sub-cultured using 0.25% trypsin-EDTA when they were 85-90% confluent. All experiments were performed within 2-3 passages after cell revival from cryopreservation. Cells were harvested and adjusted to a concentration of 1.5×10 6 /mL.
Porphyromonas gingivalis (ATCC 33277) was purchased from American Type Culture Collection (ATCC). Cells were maintained on enriched trypticase soy agar plates containing 3% sheep blood and grown in brain heart infusion (BHI) broth (BD Diagnostics). Bacteria were cultured anaerobically (85% N 2, 10% H2 and 5% CO2) and grown aerobically at 37°C until logphase growth. Subsequently, bacterial concentrations were adjusted to 0.5 McFarland turbidity standards (equivalent to 1.5×10 8 colony forming units/mL) to perform the experiments described below. The cultivation of Porphyromonas gingival has been described in detail elsewhere 35, 36) .
Porphyromonas gingivalis (ATCC 33277) was purchased from American Type Culture Collection (ATCC). Cells were maintained on enriched trypticase soy agar plates containing 3% sheep blood and grown in brain heart infusion (BHI) broth (BD Diagnostics). Bacteria were cultured anaerobically (85% N 2, 10% H2 and 5% CO2) and grown aerobically at 37°C until logphase growth. Subsequently, bacterial concentrations were adjusted to 0.5 McFarland turbidity standards (equivalent to 1.5×10 8 colony forming units/mL) to perform the experiments described below. The cultivation of Porphyromonas gingival has been described in detail elsewhere 35, 36) .