Fig. 6. Repletion of NAD⁺ via NAM restores mitochondrial function and preserves stem cell function in long-term cultured human mesenchymal stem cells (hMSCs).

Senescent hMSCs at late passages were treated with NAM for 96 h. a NAD level was increased and NADH level was decreased. b NAD⁺/NADH ratio was increased. c Sirt-1 and Sirt-3 expressions were both increased. d SA-β-gal activity was decreased. e Colony-forming ability (CFU-F) and f glycolytic ATP ratio were also increased. g Basal autophagy was restored in senescent hMSCs after NAM treatment. MFI mean fluorescence intensity. Mitochondrial fitness was restored. h Mitochondrial mass was decreased. i Mitochondrial transmembrane potential (MMP) and j electron transport chain complex I (ETC-I) activity was increased. k Mitophagy ability was restored. FCCP mitochondrial uncoupler carbonilcyanide p-triflouromethoxyphenylhydrazone. l Total reactive oxygen species (ROS) level was reduced as determined by flow cytometry. Biological replicates (n): n = 3. *p < 0.05; **p < 0.01.