Aging clocks put machine-perfused donor livers about 30% younger than iced ones

The second reading in this work comes from an abdomen that is still open. Alban Longchamp, one of the transplant surgeons involved, described taking a biopsy about an hour after the graft's blood supply was restored ^[12]. "Then you just do a quick biopsy before you close," he said ^[13]. Those paired samples are what supports the claim that the effect lasts. Every liver's clock age rose once it went into a recipient, probably from the stress of implantation, and the perfused ones were still younger ^[17].

The evidence is two runs. An epigenetic clock read 37 samples from 19 donated livers ^[9]. A second set of clocks, which measure how genes are working, read 208 samples from 103 livers stored up to around six hours either on ice or on the pump ^[11]. That comes to 245 samples from 122 organs, roughly two per liver ^[23]. Heidi Yeh, who led the work, said the machine-perfused livers came out with a lower biological age than livers that were chronologically younger and had not been perfused, even when the pumped organs were older or carried other disadvantageous characteristics ^[10].

The case for perfusion so far has been hours and triage. The machines pump nutrients and remove waste for around six to 12 hours, doctors use that window to assess the organ, and some recent studies suggest perfused organs do better once transplanted ^[2][3]. This adds a biological reason why. Jesse Poganik, who studies aging at Brigham and Women's Hospital in Boston and coauthored the study, said that once chronological age is adjusted out, "the difference between the two is on the order of 30%," and that "It's logical to say that perfusion drives this effect" ^[16]. Longchamp put it more bluntly: "Pumping them at 34 degrees with oxygen and nutrients actually reversed the biological age," he said ^[15]. The account, given to MIT Technology Review, describes results also shared with colleagues at an industry conference, and does not name a journal ^[4][5].

Nathanael Raschzok, a transplant surgeon at Charite Universitatsmedizin Berlin who was not involved, called the work impressive and said it is not yet clear what the changes mean for the recipients of these organs ^[18]. The donors in the study were people in their 30s, 40s and 50s ^[19]. "Every so often, we use organs from 70-, 80-, 85-year-old donors," he said ^[20].

For anyone signing off on a perfusion program, the case splits in two. One half is a preservation and assessment device, and its outcome evidence remains the suggestive transplant literature that predates these clocks ^[3]. The other half is a measurement: the clocks were developed to score age and risk of death, and the team hopes to turn them into tests of organ health and into tools to repair organs that would otherwise be discarded ^[14][21]. The first half you can budget for now. For the second, the question to ask each time a vendor mentions organ scoring is which donor ages the clock has actually been read on, because so far the answer stops in the fifties ^[19].