Transplanted organs take on host age

A preprint from a Harvard‑led team and mouse experiments suggest that an organ’s biological (epigenetic) age shifts to match the recipient after transplantation — older hearts become 'younger' in younger hosts and young hearts age in older hosts. The result challenges simple interpretations of rejuvenation from parabiosis and implies older donor organs might be clinically usable if host environment can reprogram organ age. — If robust, this finding could increase the usable donor pool, change transplant triage and consent practices, and force a rethinking of circulating‑factor rejuvenation claims in aging research.