Effect Of Rapamycin On Osteogenesis Of Bone Marrow Mesenchymal Stem Cells Induced By Titanium Particles

Objective To investigate the effect of rapamycin activated autophagy on osteogenic potential of bone marrow mesenchymal stem cells(BMSCs)induced by titanium particles.Methods BMSCs cells of C57 mice were cultured with rapamycin at concentrations of 0,1,5,10,20,50 and 100 nM for 48 hours respectively.Cell viability was determined by CCK8 method at different time points after rapamycin treatment with different concentrations.Setting up control group,Western blot was used to detect the expression levels of autophagy-related proteins Atg5 and LC-3 I/II 24 hours after the treatment of bone marrow mesenchymal stem cells with the optimal concentration of rapamycin(10nM)to determine the autophagy of bone marrow mesenchymal stem cells.Then the experiment was divided into four groups: group A: osteogenic induction and differentiation medium,group B: osteogenic induction and differentiation medium + titanium particles,group C: osteogenic induction and differentiation medium + rapamycin,group D: osteogenic induction and differentiation medium + titanium particles + rapamycin.Osteogenic differentiation and culture of cells in each group for 21 days.ALP content in culture medium was detected on 7th,14 th and 21 th day,calcium deposition was detected by alizarin red staining,and expression levels of osteogenic differentiation-related proteins Runx2 and OCN were detected by Western blot.Results BMSCs of C57 mice were treated with 10 nM rapamycin for 24 hours,and the cell viability was the best.After treated with 10 nM rapamycin for 24 hours,the expression levels of Atg5 and LC3-I/II were significantly higher than those of control group.Theexpression levels of ALP activity,calcium deposition,Runx2 and OCN in group B were significantly lower than those in group A(P < 0.05),while the expression levels of ALP activity,calcium deposition,Runx2 and OCN in group C were significantly higher than those in other groups(P < 0.05).The ALP activity,calcium deposition,Runx2 and OCN expression in group D were lower than those in group C(P < 0.05).Conclusion Titanium particles inhibited the osteogenic ability of bone marrow mesenchymal stem cells,and rapamycin can effectively reduce the osteogenic ability of bone marrow mesenchymal stem cells inhibited by titanium particles,which may be related to the enhancement of autophagy level of bone marrow mesenchymal stem cells.