Preconditioning of Mesenchymal Stem Cells with Non-Toxic Concentration of Hydrogen Peroxide Against Oxidative Stress Induced Cell Death: The Role of Hypoxia-Inducible Factor-1.

To investigate the protective effect of preconditioning with non-toxic dose of hydrogen peroxide (HO) as a possible cell signaling molecule, against cell death induced by toxic concentration of HO or by serum deprivation in human Wharton's jelly-derived mesenchymal stem cells (HWJ-MSCs) and underlying mechanisms. HWJ-MSCs were isolated and identified using flow cytometry. After finding non-toxic concentration of HO, cells preconditioning was performed by HO (20 μM) for 12 h and cell tolerance against serum deprivation or toxic levels of HO was assayed by MTT test. Effect of preconditioning on mRNA and protein expression of Akt-1, Bcl-2 and Bax were examined using reverse transcription polymerase chain reaction (RT-PCR) and western blotting respectively. Role of hypoxia-inducible factor (HIF)-1α was explored in presence HIF-1α inhibitor. Preconditioning with 20 μM HO for 12 h was non-toxic and decreased cell death induced by oxidative stress and serum deprivation in MSC cultures. However, the increased tolerance reversed in the presence of inhibitor of HIF-1α. By regards to RT-PCR and western blotting data, although expression of Akt-1, Bcl-2 and Bax was not change considerably but phosphorylated Akt-1 (pAkt-1) was up regulated after treatment with 20 μM HO compared to control group. Moreover after exposure to 100 μM HO, western blotting analysis showed that cell pretreatment with 20 μM HO, decremented Bax/Bcl2 ratio and up-regulated HIF-1α and pAkt-1 compared to the control group. Increased tolerance of HO-pretreated cells led to the suggestion that transplantation of HO preconditioned MSCs may improve therapeutic potential of stem cells in cell therapy procedures.