Age-Dependent Loss Of Induced Regulatory T Cell Function Exacerbates Liver Ischemia-Reperfusion Injury

Background:Previous studies demonstrate that the number of regulatory T cells(Treg)increases in aged mice.However,these studies do not characterize iTreg across different ages or how these immune modulators contribute to the dysregulation of immunity in murine liver ischemia-reperfusion injury.Objective:This study aimed to examine the relationship between age and Treg function using a mouse model of hepatic ischemia-reperfusion injury(IRI)Methods:Liver ischemia-reperfusion model was established in 8-weeks and40-weeks mice.Liver injury was detected by serum alanine aminotransferase(ALT),aspartate aminotransferase(AST)and HE staining.Suzuki ~1 scores for liver biopsies from the treatment groups were evaluated to assess the severity of liver injury.The populations of cytokine-positive CD4~+T cells were evaluated by FACS.The percentages of T cell subsets harvested from spleens in normal mice were evaluated by FACS.The percentages of nTregs and the ratio of Teff/nTreg in aged-mice and young-mice were analyzed by FACS.Young-iTreg and aged-iTreg were induced in vitro to study the effect of aging on iTreg differentiation.CFSE co-culture method was used to study the effect of aging on the inhibitory function of iTreg in vitro.Flow cytometry was used to detect the expression of CLTA-4 and CD127.Liver ischemia-reperfusion model was established in which yong-Treg or aged-Treg were adoptive transferred to 40-weeks mice or not.The liver injury was detected by AST,ALT and HE staining.The proportion of iTreg activation in vivo was detected by flow cytometry.Results:In this model,aged-mice suffered more serious injury than yong-mice,with higher serum levels of ALT and AST and higher histological scores from liver biopsies.iTreg isolated from young-mice exhibited stronger immunosuppressive ability in vitro and had a greater response during IRI in vivo.Compared with untreated mice,injected with both aged-iTreg and young-iTreg groups had reduced ALT and AST levels.In addition,aged-mice that were pretreated with iTreg generated in young-mice had alleviated injury compared with mice pretreated with iTreg from aged-mice or no treatment group.Adoptive transfer of iTreg ameliorated liver IRI and promoted liver recovery.Conclusions:As the age increases,the tolerance of mice to hepatic ischemia reperfusion injury decreases.The exacerbated IRI observed in aged-mice is a result of decreased iTreg function.Therefore,improving iTreg function is important for disease treatment in elder patients.