mUCMSCs inhibit the expression of the aging-related genes p53 and P16 by promoting the expression of autophagy- and anti-oxidative stress-related genes, such as LC3b, becline1, P62, SOD1, Sirt1 and Sirt3, thereby increasing the level of autophagy in the thymus tissue, inhibiting apoptosis and exerting therapeutic effects on thymus atrophy. Here, SIRT3 is linked to thymus atrophy.