ObjectiveTo explore the effect of timosaponin BⅡ （TBⅡ） combined with icariin （ICA） on osteoclast （OC）-osteoblast （OB） coupling and decipher the mechanism from the cellular level. MethodsThe cell counting kit-8 （CCK-8） was used to assess the effects of different concentrations of TBⅡ and different concentrations of TBⅡ+ICA on the growth of RAW264.7 cells. Soluble receptor activator of nuclear factor-κB ligand （sRANKL） was used to induce the differentiation of RAW264.7 pre-osteoclasts into osteoclasts. The cells were allocated into sRANKL， TBⅡ （1， 5， 10 μmol·L^-1）， and TBⅡ+ICA groups. Tartrate-resistant acid phosphatase staining was performed to assess the effects of TBⅡ and TBⅡ+ICA on osteoclast differentiation. Real-time quantitative polymerase chain reaction （Real-time PCR） was conducted to examine the effects of TBⅡ+ICA on the expression of key genes involved in osteoclast differentiation and osteoclast-derived coupling factors. The osteogenic differentiation conditioned medium mixed with osteoclast supernatant was used to induce osteogenic differentiation of MC3T3-E1 cells. Alkaline phosphatase staining and alizarin red S staining were employed to determine the effect of TBⅡ+ICA on osteogenic differentiation. Real-time PCR was employed to evaluate the effects of conditioned medium on key genes involved in osteogenic differentiation. ResultsTBⅡ at 1， 5， 10 μmol·L^-1 had no significant effect on the cell survival rate. Compared with the sRANKL group， TBⅡ inhibited osteoclast differentiation in a dose-dependent manner and achieved the best effect at 10 μmol·L^-1 （P<0.01）. Compared with the sRANKL group， different concentrations of TBⅡ down-regulated the mRNA levels of osteoclast differentiation-related genes c-Fos， RANK， and RANKL （P<0.05）. None of 10 μmol·L^-1 TBⅡ， 10 μmol·L^-1 TBⅡ+10^-4 μmol·L^-1 ICA， or 10 μmol·L^-1 TBⅡ+10^-3 μmol·L^-1 ICA affected the viability of RAW264.7 cells. TBⅡ and/or ICA inhibited osteoclast differentiation （P<0.01）， and TBⅡ + ICA had the best effect （P<0.01）. Compared with the sRANKL group， TBⅡ and/or ICA down-regulated the mRNA levels of c-Fos， RANK， and RANKL （P<0.05）. The single application of TBⅡ and ICA had no significant effect on the mRNA levels of Wnt10b， Cthrc1， and C3a， while TBⅡ+ICA exerted up-regulating effects （P<0.05）. Compared with those in the blank group， the bone differentiation and mineralization abilities of the normal osteogenic induction group and each osteogenic induction + osteoclast supernatant group were improved （P<0.01）. Compared with the blank group， the normal osteogenic induction group and the osteogenic induction + osteoclast supernatant group showed up-regulated mRNA levels of Runx2 and OCN （P<0.01）. ConclusionTBⅡ+ICA can inhibit osteoclast differentiation， maintain the normal osteoclast-osteoblast coupling， and promote osteogenic differentiation.