Preconditioning of bone marrow-derived mesenchymal stem cells with N-acetyl-L-cysteine enhances bone regeneration via reinforced resistance to oxidative stress

Oxidative stress on transplanted bone marrow-derived mesenchymal stem cells (BMSCs) during acute inflammation is a critical issue in cell therapies. N-acetyl-L cysteine (NAC) promotes the production of a cellular antioxidant molecule, glutathione (GSH). The aim of this study was to investigate the effects of pre-treatment with NAC on the apoptosis resistance and bone regeneration capability of BMSCs. Rat femur-derived BMSCs were treated in growth medium with or without 5 mM NAC for 6 h, followed by exposure to 100 μM H₂O₂ for 24 h to induce oxidative stress. Pre-treatment with NAC significantly increased intracellular GSH levels by up to two fold and prevented H₂O₂-induced intracellular redox imbalance, apoptosis and senescence. When critical-sized rat femur defects were filled with a collagen sponge containing fluorescent-labeled autologous BMSCs with or without NAC treatment, the number of apoptotic and surviving cells in the transplanted site after 3 days was significantly lower and higher in the NAC pre-treated group, respectively. By the 5th week, significantly enhanced new bone formation was observed in the NAC pre-treated group. These data suggest that pre-treatment of BMSCs with NAC before local transplantation enhances bone regeneration via reinforced resistance to oxidative stress-induced apoptosis at the transplanted site.