Does old-to-young kidney transplantation rejuvenate old donor kidneys?

The number of older organ donors is increasing due to the aging population. Aged kidneys often face problems such as delayed graft function but previous murine experiments suggested the possibilities of rejuvenation, for example, in a parabiosis setting between old and young mice. To investigate kidney-graft rejuvenation, we compared an old-to-young (O-Y) patient transplantation group and a transplantation group with donors/recipients of approx. the same age (SA) with the renal senescence marker p16 in kidney biopsy samples at baseline and one year post-transplantation. We retrospectively analyzed our hospital's 32 cases of living-donor ABO-compatible transplants performed between 2013-2020. Both the baseline and one-year biopsy (n=9) or only the baseline biopsy (n=32) were analyzed. We divided the nine cases into an O-Y group (donors' median age 68 yrs, recipients 41, difference -27) and an SA group (donors' median age 53 yrs, recipients 51.5, difference -3.5). p16 was stained with the clones JC8 and E6H4 to determine the precise p16-positive rate. The 32 baseline biopsies' p16-positive rate was weakly related to donor age, suggesting that the p16-positive rate can help evaluate kidney senescence. The (n=5) O-Y group's p16-positive rates were at baseline 0.08 and one year 0.12; the (n=4) SA group's rate was 0.03 at both baseline and one year. No kidney rejuvenation was observed, even when old donor kidneys went to young recipients.