Malondialdehyde(MDA)is a well known inducer of carbonyl stress in a variety of human cells,however,its effects on human bone marrow mesenchymal stem cells(hMSCs)have not been documented.In this study,the effects of MDA concentration on the growth rate and proliferation of hMSCs in vitro were assessed.Under high concentrations of MDA,the cell count was decreased and the population doubling time(PDT)was lengthened.Flow cytometry(FCM)demonstrated that MDA triggered cells to undergo apoptosis.in parallel with the findings in MTT[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide]assay which showed that it can also impair cellular viability.Surprisingly,FCM also determined that the percentage of hMSCs in G2/M- and S-phases also increased in a dose-dependent manner with respect to MDA concentration.These results strongly suggest that even though hMSCs were severely impaired by high concentrations of MDA,they were still able to send signals that resulted in accelerated cellular proliferation process.This study provided important insights on how carbonyl stress affects cell cycle and proliferation of hMSCs.