BRAINBITES
WEEK OF FEB 23–MAR 1, 2026 · ISSUE 4
BRAINBITES — Your weekly health, fitness, and longevity digest. Five minutes that cover the highest-signal podcasts and science before they hit the mainstream.
This week: Stanford ageing researcher Tony Wyss-Coray walked Huberman through the parabiosis experiments — surgically joining old and young mice — that revealed blood-borne factors capable of rejuvenating aged brains and bodies. The findings are no longer confined to rodents. Human trials are underway.
From: Huberman Lab · Huberman Lab Essentials
🔢 The blood factor that reversed cognitive decline in aged mice by 30%
🎙️ Tony Wyss-Coray on parabiosis, plasma exchange, and the ageing blood proteome
💡 Deep Dive: ageing isn't just decay — it's an active program the blood is running
📰 News Bits: young cerebrospinal fluid restores memory · the pro-ageing factors · exercise as a plasma cleaner
GM.
The most provocative conversation this week was Tony Wyss-Coray on Huberman. Wyss-Coray runs the ageing-and-brain lab at Stanford, and the data he brought is the kind that makes you reconsider what ageing actually is. It's not just wear and tear. There are specific proteins in old blood that actively suppress regeneration — and specific proteins in young blood that restart it. The experiments are real. The human translation is happening.
⏱ ~5 min read
🧠 THE CLOCK AND THE TRANSFUSION
What happens when old tissue meets young blood — and vice versa.
Two experiments from the same lab landed in the same conversation. One: connect an old mouse to a young mouse's circulatory system and the old mouse's brain starts producing new neurons again. Two: take just the plasma — no cells, no organs — from young blood and inject it into old mice. The cognitive improvements still show up. The rejuvenating factor is in the liquid, not the cells.
The thread this week: ageing may be less about parts wearing out and more about signals telling them to stop working.
🔢 THE VITAL SIGN · AGEING / LONGEVITY
30%
The cognitive improvement in aged mice receiving young plasma — measured by hippocampal-dependent memory tasks.
Wyss-Coray walked Huberman through the parabiosis experiments that started the field. When you surgically join the circulatory systems of an old mouse and a young mouse, the old mouse's brain starts behaving younger — more neurogenesis in the hippocampus, better performance on memory tasks, reduced neuroinflammation. The young mouse, disturbingly, starts ageing faster.
The follow-up finding was sharper: you don't need the whole young mouse. Injecting cell-free plasma from young mice into old ones produces similar cognitive improvements — roughly 30% better performance on hippocampal memory tasks. This means the rejuvenating signal is a soluble factor in the blood, not a cell type or organ.
Wyss-Coray's lab has identified several candidate proteins, including GDF11 and TIMP2, that decline with age and appear to contribute to the effect. But the equally important finding is the reverse: old blood contains pro-ageing factors — proteins that actively suppress regeneration when injected into young animals. Ageing isn't just the absence of youth signals. It's the presence of suppression signals.
The implication rewrites the metaphor: ageing isn't a car running out of fuel. It's a car whose fuel line is being actively pinched.
Dr. Tony Wyss-Coray on Huberman Lab · February 23, 2026
🎙️ THE EPISODE · AGEING / NEUROSCIENCE
The parabiosis experiments that changed how science thinks about ageing
Tony Wyss-Coray on young blood, old blood, and the proteins that tell your body when to stop regenerating.
Dr. Tony Wyss-Coray · Huberman Lab · February 23, 2026
Wyss-Coray is one of the pioneers of the parabiosis revival in ageing research. He's careful, data-driven, and visibly uncomfortable with the 'young blood' headlines that followed his early papers. The conversation with Huberman is precise where the science is strong and honest where it's still speculative.
The plasma exchange approach — no young donors needed.
The most clinically relevant finding from Wyss-Coray's lab: you may not need young blood at all. Diluting old blood — literally removing plasma and replacing it with saline plus albumin — produces many of the same benefits in aged mice. The hypothesis: the pro-ageing factors in old plasma are doing more damage than the absence of pro-youth factors. Removing them may be enough. A human clinical trial (the Plasma Exchange for Alzheimer's Disease study) has already shown signal.
🎙️ Skip to ~45:00 — Wyss-Coray explains why dilution works and what that means for clinical translation.
Young cerebrospinal fluid restores memory — in old mice.
In a 2022 Nature paper, Wyss-Coray's lab showed that injecting cerebrospinal fluid from young mice into old mice restored hippocampal memory function. The key protein identified was FGF17, a growth factor that declines with age and appears to reactivate oligodendrocyte progenitor cells — the cells that produce the myelin insulation around neurons. Memory depends on fast, well-insulated signal transmission. When the insulation degrades, recall slows.
The blood proteome as an ageing clock.
Wyss-Coray's lab has developed a blood-based biological age estimator using ~5,000 circulating proteins. The 'proteomic clock' can estimate biological age from a blood draw and predicts mortality better than chronological age. The implication: your blood isn't just carrying oxygen and nutrients. It's carrying a time-stamped status report on how old your body thinks it is — and that report influences how every organ behaves.
💡 DEEP DIVE · AGEING AS AN ACTIVE PROGRAM
Wyss-Coray gives you the mechanism. The week gives you the question: is ageing something that happens to you, or something your body does to itself?
The default model of ageing is entropic: things wear out, damage accumulates, systems fail. Wyss-Coray's work suggests a different model. Ageing is partly an active process — old blood contains specific proteins that suppress regeneration, reduce neurogenesis, and increase inflammation. Remove those proteins and the aged tissue starts behaving younger. The body hasn't lost the ability to regenerate. It's being told not to.
This reframing has practical implications even before the clinical therapies arrive. Exercise — particularly cardiovascular exercise — has been shown to shift the blood proteome toward a younger profile. Wyss-Coray's lab has published data showing that exercised aged mice have blood that, when injected into sedentary aged mice, produces cognitive improvements. In other words: exercise isn't just good for the exerciser. It changes the blood in ways that are transferable.
The cerebrospinal fluid finding adds another layer. If FGF17 is a key factor in maintaining myelin and memory, and if it declines with age, then interventions that increase FGF17 — whether pharmacological or lifestyle-based — become targets for cognitive preservation. Myelin maintenance is one of the most under-discussed aspects of brain health. Most longevity content focuses on neurons. The wiring between them may matter just as much.
The proteomic ageing clock connects everything. If your blood carries a molecular signature of your biological age, and if that signature actively influences how your organs age, then interventions that change the signature change the trajectory. The question isn't how old you are. It's how old your blood thinks you are — and whether you can change its mind.
The most hopeful finding this week isn't that young blood rejuvenates. It's that old blood can be cleaned — and the cleaning tools are closer to the clinic than most people realise.
📰 NEWS BITS
Young cerebrospinal fluid restores memory function in aged mice — the myelin connection.
Wyss-Coray's 2022 Nature paper showed that infusing young CSF into aged mice reactivated oligodendrocyte progenitor cells in the hippocampus, increasing myelination and improving long-term memory consolidation. The key growth factor, FGF17, declines with age and appears essential for maintaining the insulation around memory circuits. The finding reframes cognitive ageing: it's not just about losing neurons. It's about losing the wiring quality between them.
— Nature, May 2022 (discussed February 2026)
Pro-ageing factors in old blood actively suppress regeneration — removal may be enough.
Wyss-Coray's plasma-dilution experiments in mice showed that replacing half of old plasma with saline and albumin improved muscle repair, liver function, and hippocampal neurogenesis — without any young blood factors. The interpretation: the pro-ageing factors in old blood (including elevated inflammatory cytokines and TGF-beta signalling) are doing more active harm than the absence of pro-youth factors. Therapeutic plasma exchange is already FDA-approved for other indications. Repurposing it for ageing is a clinical-trial-ready idea.
— Huberman Lab, Dr. Tony Wyss-Coray, February 23, 2026
Exercise shifts the blood proteome toward a younger profile — and the effect is transferable.
Data from Wyss-Coray's lab and corroborating studies show that regular cardiovascular exercise reduces circulating levels of several pro-ageing blood proteins and increases levels of anti-inflammatory and pro-regenerative factors. In animal models, blood from exercised aged mice improved cognition when injected into sedentary aged mice. The message: exercise isn't just building muscle and burning calories. It's editing the molecular status report your blood sends to every organ in your body.
— Huberman Lab, Dr. Tony Wyss-Coray, February 23, 2026
P.S. If a blood test could tell you your biological age — not your birthday, but how old your body actually is — would you take it? Reply and tell us why or why not. Best answers go in a future issue.
What did you think of today's BrainBite?
🧠🧠🧠🧠🧠 Booked a blood panel before I finished reading
🧠🧠🧠 The parabiosis data is wild. The plasma-dilution angle is the practical gem.
🧠 Too speculative. Call me when human trials report.
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Your blood is carrying a message to every organ. Worth asking what it says. See you next week.
