A transplanted heart adopts the biological age of the recipient, not the donor. Aging theorist Yuri Deigin sees confirmation that aging is reversible; MIT Technology Review editor Antonio Regalado sees a blow to the idea of extending life through organ replacement

A transplanted heart adopts the biological age of the recipient, not the donor. Aging theorist Yuri Deigin sees confirmation that aging is reversible; MIT Technology Review editor Antonio Regalado sees a blow to the idea of extending life through organ replacement

This comes from a new preprint by Vadim Gladyshev's lab: a transplanted heart rapidly "forgets" the donor's age and takes on the age of the new body. On September 25, Deigin and Regalado responded to the paper independently, each reading a different lesson from the same finding, neither citing the other.

Vadim Gladyshev and Steve Horvath's team transplanted hearts between mice of different ages and measured the graft's age using epigenetic clocks, a method that estimates tissue age from chemical marks on DNA. A young heart in an old body aged rapidly; an old heart in a young body grew younger. The recipient's own heart, liver, and blood remained unchanged. The same pattern held in archival biopsies and clinical data from hundreds of patients: the graft's age was predicted by the recipient, not the donor.

Yuri Deigin read this as confirmation of the "Strong Epigenetic Theory of Aging," the idea that mammalian aging is not random tissue wear but a regulated, reversible process in which DNA marks function as a rewritable program that the body adjusts to match its age. Previously he could point only to static associations, such as the loss of marks on silenced genes that accumulates with age. This was a rare instance of the same tissue shifting its trajectory in both directions in response to a change in the surrounding body.

"This is exactly what one would expect if aging is a regulated systemic state in which the epigenome acts as a rewritable control layer that tissues continuously adjust to the organism's age," Deigin wrote.

Antonio Regalado, biomedicine editor at MIT Technology Review since 2011, saw a practical problem: "Bad news for longevity via continuous 'replacement' of young organs. The transplanted organ adopts the recipient's age, not the other way around." The word "replacement" is deliberate: that is how the field refers to this strategy, including a roadmap published in Aging Cell co-authored by Gladyshev himself. If an old body ages every new organ it receives, indefinite parts replacement ceases to be a viable standalone path to rejuvenation.

Both conclusions go further than the authors themselves are prepared to claim. In the preprint's discussion, they describe their hypothesis (that the graft and the body exchange accumulated damage) as no more than a starting point for future work. Independent expert João Pedro de Magalhães of the University of Birmingham noted that the cause remains unclear and proposed an additional explanation involving the immune system. First author Jesse Poganik added: "Some aspects of biological age are probably reversible; others probably are not."

Regalado's conclusion was no surprise to the lab. At the ARDD conference in 2025, Gladyshev had already shown that "age assimilation" is visible in heart, ovarian, and adipose tissue and that a single organ does not rejuvenate the organism because surgical trauma and the immune response interfere. The same dataset confirmed Deigin's model, recalled the limits of organ replacement, and left the core question open: whether to control the rate of aging through systemic signals or to repair it by replacing parts.