The tree · Inflammation and the body's messaging
Young blood rejuvenates an old animal
In 2005 a Stanford group joined the circulations of a young and an old mouse, an old surgical trick called parabiosis, and found that the old mouse's muscle and liver stem cells woke up and repaired damage like a young animal's. The finding started a search for the factors in young blood that do it and the factors in old blood that stop it, and a cottage industry of selling young plasma to old people. Infusions of young plasma into people with Alzheimer's disease were reported safe in 2019 in a tiny trial built to test safety, not benefit (thinking did not change; caregivers rated daily function better, an unconfirmed result), and no controlled trial has found a benefit on an age-related function. A 2025 Stanford trial in 38 older people having a joint replacement found that four infusions of a young-donor plasma fraction changed their immune and inflammatory response to the surgery, which is not a benefit to an age-related function. The leaf is at the animal rung and the test asks for a person to measurably improve, not to receive the infusion.
What would count
An old living animal given blood or plasma from a young one afterwards has a measurably rejuvenated tissue function compared with untreated old controls, in a peer-reviewed report. The first-human rung needs a controlled trial in which older people given young plasma, or a defined factor from it, improve on an age-related measure more than placebo. For the clinic rung: a regulator approves such a treatment for an age-related condition.
Who settles it: Peer-reviewed reports; the regulator's approval record for the clinic rung.
Where it stands
Shown in animals. Reached 17 February 2005, on the record of Conboy and 5 others, 17 February 2005 (doi.org). Next rung more than 20 years away, if ever.
When it reaches the clinic: the project's estimate
This is the one thing on this page that is a judgment rather than a record. The project's estimate of the year it reaches the clinic is 2048, no earlier than 2035 and no later than not this century; the model draws from that range every run, with the likely year the most probable draw. Set 16 October 2026, a first pass awaiting an outside review.
| Rung | No earlier than | Most likely | No later than | |
|---|---|---|---|---|
| First human | 2029 | 2034 | 2060 | |
| In clinical use | 2035 | 2048 | not this century | feeds the year at the top |
Why. Twenty years after the mouse result there is no positive controlled human trial, and the defined-factor route (a single protein from young blood as a drug) is where the companies now are. The likely year assumes one such factor shows a controlled human benefit in the early 2030s and reaches an approval in the late 2040s; the earliest assumes a factor already in trials reads out positive soon; the latest allows for the whole effect being a mouse artefact of the joined circulation.
Changes to this record
- 17 October 2026, description: caregivers rated daily function better, an unconfirmed result), and no controlled trial has found a benefit. became caregivers rated daily function better, an unconfirmed result), and no controlled trial has found a benefit on an age-related function. A 2025 Stanford trial in 38 older people having a joint replacement found that four infusions of a young-donor plasma fraction changed their immune and inflammatory response to the surgery, which is not a benefit to an age-related function.. [reading 2026-10-17] The description's 'no controlled trial has found a benefit' was true but narrower than it looked; the nearest controlled human result is now named. The stage stays at shown in animals. Source: Gaudilliere and 12 others, 14 February 2025.
- 17 October 2026, notes: (nothing; text added at the end of the notes) became Added 2026-10-17, from the weekly reading of that date: the nearest controlled human result is gaudilliere-2025, a double-blind placebo-controlled phase 2a trial (NCT03981419) of a young-donor plasma fraction in 38 older patients having a hip or knee replacement, which the authors call a first proof of principle that such a fraction regulates immune and inflammatory responses in older people. Its measure is the response to surgical injury and not an age-related function, so the first-human test is not met on a plain reading. Whether such a measure could count is John's ruling. No stage or year was changed.. [reading 2026-10-17] Adds the nearest controlled human trial to the notes and leaves the question of whether it counts for John. Source: Gaudilliere and 12 others, 14 February 2025.
The last readings
- 17 October 2026 Left for the author
Nothing in the window: no controlled trial of young plasma or a defined factor from it in older people, and no new animal report, dated 2026-10-10 to 2026-10-17 was found, and nothing new on the plasma-fraction product GRF6019 or a TIMP2 drug. One older record the leaf does not mention bears on the first-human test: a double-blind, placebo-controlled trial published in the Journal of Translational Medicine in 2025-02 randomised 38 older patients having major joint replacement to four infusions of a young-donor plasma protein fraction or placebo, and reported a changed immune and inflammatory response to the surgery. Its measure is the response to tissue injury, not an age-related function, and it is described as a proof of principle, so it does not meet the test on a plain reading. Left for the author: The leaf's description says no controlled trial of young plasma in people has found a benefit. The 2025 trial above is a controlled trial in older people that found an effect on immune and inflammatory markers after surgery, without a clinical benefit, so the sentence still reads true but is now a narrower truth than it looks. I would add the trial to the notes as the nearest controlled human result and leave the stage and estimate alone. It is dated before the window, I could not open the paper to check its authors, registration or main measure, and whether a surgical inflammatory response is an age-related measure for the test is the author's ruling. To log in the publications log once its page has been read, as the reading's rule asks: Infusion of young donor plasma components in older patients modifies the immune and inflammatory response to surgical tissue injury: a randomized clinical trial (Journal of Translational Medicine (2025), 2025-02; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11829456/).source 1, source 2, source 3
What the story so far says about it
On the record
- 17 February 2005Rejuvenation of aged progenitor cells by exposure to a young systemic environment
- 14 February 2025Infusion of young donor plasma components in older patients modifies the immune and inflammatory response to surgical tissue injury: a randomized clinical trial
Notes
Later mouse work split the effect: diluting old plasma helps as much as adding young, which is the plasma-exchange leaf beside this one; and single factors (GDF11, oxytocin, TIMP2) each account for part of it. The branch's own line asks for a measured effect in people of exchanging or diluting plasma, and that is the companion leaf. Added 2026-10-17, from the weekly reading of that date: the nearest controlled human result is gaudilliere-2025, a double-blind placebo-controlled phase 2a trial (NCT03981419) of a young-donor plasma fraction in 38 older patients having a hip or knee replacement, which the authors call a first proof of principle that such a fraction regulates immune and inflammatory responses in older people. Its measure is the response to surgical injury and not an age-related function, so the first-human test is not met on a plain reading. Whether such a measure could count is John's ruling. No stage or year was changed.