Abstract: Object To investigate the effects of preconditioning with low-concentration hydrogen peroxide （H2O2）on oxidative stress-induced bone marrow mesenchymal stem cells (BMSCs) apoptosis and its mechanism．Methods Mouse bone marrow mesenchymal stem cells (BMSCs) were isolated and purified by differential centrifugation, and were treated with 0，200，250，300， 500 μmol/L H2O2 after being preincubated with 50 μmol/L H2O2 or control medium. Apoptosis of these cells was measured by flow cytometry, and the expression of phosphorylated PI3K, Akt and mTOR was analyzed by Western blot; BMSCs were also primed with PI3K inhibitor LY294002 for 30 min, then preincubated with 50 μmol/L H2O2 or control medium for 12 h before treatment with 300 μmol/LH2O2. Expression of apoptosis proteins Bcl-2, Bax, caspaase-3, cleaved-caspase-3 and the key proteins of the PI3K/Akt/mTOR pathway were detected by Western blot. Results As demonstrated by flow cytometry results, H2O2 induced BMSCs apoptosis in a dose-dependent manner，and pretreatment of BMSCs with low concentration of H2O2 significantly decreased H2O2-induced apoptosis of the BMSCs. Western blot results revealed that preconditioning with low-concentration H2O2 remarkably reversed the decrease in Bcl-2, total and phosphorylated PI3K, Akt and mTOR levels, and the increase in Bax, cleaved-caspase-3 expression after high-dose H2O2 treatment. Such effects were abolished by PI3K inhibitor LY294002. Conclusions Preincubation with low-concentration H2O2 may grant resistance of BMSC to oxidative stress, and such effect may involve inhibition of pro-apoptotic proteins and activation of the PI3K/Akt/mTOR pathway.

Key words: bone marrow mesenchymal stem cells, oxidative stress injury, apoptosis, hydrogen peroxide, preincubation