Human umbilical cord mesenchymal stem cells improve testicular function in aging mice by upregulating Nrf2 signaling
Objective To investigate the effect and mechanism of human umbilical cord mesenchymal stem cells(hUCMSCs)transplantation on testicular function in aging mice with oxidative damage.Methods Totally 18 SPF grade C57BL/C male mice aged 6-8 weeks were randomly divided into 3 groups using a complete randomization method.In control group,mice were injected with an equal amount of physiological saline;in model group,mice were subcutaneous injected D-galactose into the neck and back for 9 consecutive weeks,on the 4th weekend of modeling,the mice were injected with physiological saline via the tail vein;in hUCMSCs group:mice were subcutaneous injected D-galactose into the neck and back for 9 consecutive weeks,on the 4th weekend of modeling,the mice were injected with hUCMSCs via the tail vein of each mouse.After 9 weeks,body weight and testicular weight of the three groups mice were measured and testicular index was calculated.The contents of testosterone,malondialdehyde(MDA)and superoxide dismutase(SOD)in serum and testicular tissue were detected by enzyme-linked immunosorbent assay(ELISA)method.Visual observation of testicular appearance,the histopathological changes of testis were observed by hematoxylin-eosin(HE)staining,and the expression of NF-E2-related factor 2(Nrf2)signal transduction-related genes and proteins were detected by RT-PCR and Western blotting,respectively.Results Compared with control group[(0.81±0.13)％],the testicular index of mice in model group[(0.64±0.05)％,P=0.006]was decreased.In model group,the volume of testis was reduced,the integrity of spermatogenic tubules was damaged,spermatogenic cells and sperm were reduced,and the interstitium was sparse.In model group,serum testosterone[(4.10±0.67)μg/L]and SOD[(48.87±6.40)U/mg Prot]were decreased compared with control group[(5.71±0.81)μg/L,P=0.002;(78.53±9.70)U/mg Prot,P=0.001],MDA[(1.11±0.19)nmol/mg Prot]was increased compared with control group[(0.77±0.07)nmol/mg Prot,P=0.001],Keap1 mRNA and protein expression were increased(P=0.006,P=0.043).The expression levels of Nrf2,SOD and NQO1 mRNA were significantly lower than those in control group(P=0.002,P＜0.001,P=0.001),and the expression levels of Nrf2 and HO-1 protein were significantly lower than those in control group(P=0.011,P=0.021).Compared with the model group,the testicular index[(0.79±0.03)％,P=0.010]increased in hUCMSCs group,and the tissue structure of testis was clear and complete,spermatogenic cells at all levels of spermatogenic tubules,spermatogenic cells and stromal cells were abundant.Compared with the model group,the content of dihydrotestosterone[(5.24±0.21)μg/L,P=0.028]in serum and SOD[(79.47±14.32)U/mg Prot,P=0.001]in testicular tissue increased in hUCMSCs group,while the content of MDA[(0.77±0.08)nmol/mg Prot,P=0.001]decreased,Nrf2,SOD and NQO1 mRNA expression levels increased(P=0.024,P=0.037,P=0.005),Keap1 mRNA expression decreased(P=0.044),Nrf2 and HO-1 proteins expression increased(P=0.009,P=0.012),while Keap1 protein expression decreased(P=0.035).There were no statistically significant differences in testicular index,serum testosterone,SOD and MDA between hUCMSCs group and control group(all P＞0.05).Conclusion hUCMSCs significantly improve testicular structure and function damage caused by oxidative damage in aging mice,and the mechanism of action is related to upregulating Nrf2 signaling and downstream antioxidant activity SOD and HO-1 protein expression,reducing Keap1 mediated Nrf2 degradation.
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