Preconditioning of Mesenchymal Stem Cells with Non-ToxicConcentration of Hydrogen Peroxide Against Oxidative StressInduced Cell Death: The Role of Hypoxia-Inducible Factor-1

To investigate the protective effect of preconditioning with non-toxic dose of hydrogen peroxide (H2O2) as a possible cell signaling molecule, against cell death induced by toxic concentration of H2O2 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 H2O2, cells preconditioning was performed by H2O2 (20 μM) for 12 h and cell tolerance against serum deprivation or toxic levels of H2O2 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 H2O2 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 H2O2 compared to control group. Moreover after exposure to 100 μM H2O2, western blotting analysis showed that cell pretreatment with 20 μM H2O2, decremented Bax/Bcl2 ratio and up-regulated HIF-1α and pAkt-1 compared to the control group. Increased tolerance of H2O2-pretreated cells led to the suggestion that transplantation of H2O2 preconditioned MSCs may improve therapeutic potential of stem cells in cell therapy procedures.