Replicating Katcher's 67% Rejuvenation: Inside the Open Brazilian Rat Study
A non-profit institute in Brazil is openly replicating Harold Katcher's landmark study, in which particles isolated from young pig plasma reportedly reversed 67% of epigenetic age in old rats. The team publishes every method, material and result so other labs can reproduce it, and adds a young-rat group plus a follow-on lifespan arm the original study did not have.
Overview
Nicolas describes the Rejuvenation Science Institute's plan to reproduce the experiment Harold Katcher published in 2023, in which extracellular particles from six-month-old pig plasma were injected into 25-month-old rats. Katcher's paper reported a 67% epigenetic age reversal alongside recovery of memory, grip strength and blood markers — a magnitude no other mammalian study has approached. The Brazilian replication starts two months earlier than planned, at 23 months of age, because rats in the older cohort had already begun dying.
The protocol collects plasma from young pigs, separates platelets by centrifugation, precipitates with polyethylene glycol, filters the nanoparticles through a chromatographic column and concentrates them by dialysis before four alternate-day injections, repeated after three months. Over five months the team measures grip strength from day 10, memory in months one, two, four and five, ten blood markers, and epigenetic age using Steve Horvath's updated clocks.
Three design changes distinguish it from the original: ten rats per group instead of six, an added group of treated young rats to test whether youth can be preserved, and no culling — the animals live on into a longevity arm. The work is done with Dr Marcelo Mori at UNICAMP and funded by roughly $75,000 in crowdfunding, with everything published and no intellectual property claimed. Nicolas frames the stakes beyond the data: if the result holds, it supports Katcher's hypothesis that ageing is driven by signalling in the blood rather than by time alone.
Key quotes
5There is no other scientific study that reaches something near 67% of epigenetic rejuvenation in a mammal.
This is a fight for life. This is not a business or a career.
It's not just inventing rejuvenation, it's understanding what ageing is.
People say they know what ageing is, but if they really knew, rejuvenation would already exist.
We don't usually think as much as we should about how our life is determined by the biology of our chronological age.
Key ideas
9Not exosomes — extracellular particles
The preparation isolated from young pig plasma contains exosomes, but the rejuvenating effect may not come from exosomes alone. The team therefore calls the material extracellular particles, or PEPs: pig plasma extracellular particles from young animals.
The 67% benchmark
Katcher's 2023 paper reported a 67% reversal of epigenetic age in old rats, with memory, grip strength and blood markers returning toward young levels. No other mammalian study has come close to that magnitude.
The isolation protocol
Plasma from six-month-old pigs is separated from red cells and platelets by centrifugation, precipitated overnight with polyethylene glycol, filtered through a chromatographic column that captures nanoparticles, then concentrated by dialysis membrane.
Dosing and timeline
Four doses are given on alternate days, then repeated three months later, with a two-month observation window before the full assessment. In practice the injection phase runs from April to late November because of staggered cohorts.
Three departures from the original
Ten rats per group instead of six, an added group of treated young rats to see whether youth can be maintained, and no culling — the animals continue into a lifespan study rather than being sacrificed for analysis.
Open science, no IP
The institute is a non-profit that publishes every method, material and result, invites outside observers to visit the farm and lab, and deliberately claims no intellectual property so that other laboratories can reproduce the work immediately.
Updated epigenetic clocks
Steve Horvath's foundation will run the epigenetic analysis using clocks refined since 2020. The same experiment read as 54% rejuvenation with the older clock and 67% with the improved version, showing how much the measurement instrument matters.
Why pigs and plasma matter
Most exosome research uses stem cells, amniotic fluid or placenta, which are costly and available only in small quantities. Katcher's distinguishing feature is an extraordinarily high dose, which is only affordable if the source is animal plasma.
Ageing as signalling
Katcher's hypothesis holds that ageing reflects the balance between damage accumulation and repair, modulated by signals carried in the blood. Cells already contain repair machinery — as shown by partial reprogramming and by embryos resetting epigenetic age — the question is how to switch it on deliberately.
Practical takeaways
7- 1
Watch the early physical markers 5:40
Grip strength is measured from day 10 and day 20, so the first signal of whether the replication is tracking Katcher's curve arrives within weeks, not months.
- 2
Interim results are published as they come 20:30
Partial data will appear in the institute's newsletter, with the caveat that averages from staggered sub-groups cannot be read like a finished dataset.
- 3
Reproducibility beats novelty here 27:00
A dramatic single result that no one has repeated stays a curiosity. Independent replication with published methods is what turns it into knowledge the rest of the field can build on.
- 4
Read the clock before the number 31:00
The same samples produced 54% and 67% depending on which version of the epigenetic clock was used — when comparing rejuvenation claims, check which clock generated them.
- 5
Dose is the variable most often overlooked 40:30
Many exosome studies inject a tiny fraction of what this protocol uses. Comparing outcomes across studies without comparing dose is what makes the literature look contradictory.
- 6
Basic science needs patient funding 48:00
Large capital enters only once a principle is proven, which is why small recurring donations rather than investors carry work at this stage — the whole replication costs around $75,000.
- 7
Follow it directly at the source 56:00
The institute's newsletter, website and social channels carry the raw updates, and they explicitly invite questions and in-person visits to the farm and laboratory.
Topics & chapters
15The institute and its single aim
Nicolas introduces the Rejuvenation Science Institute in Brazil and its founding goal: reproduce Katcher's rat experiment openly.
Why it isn't only exosomes
The preparation contains exosomes but also other extracellular particles, and the active fraction is not yet known.
What Katcher reported
67% epigenetic reversal plus recovery of memory, grip strength and blood markers in old rats.
Starting two months early
Rats in the original cohort began dying, so the study begins at 23 months rather than 25.
From pig blood to particles
Centrifugation, polyethylene glycol precipitation, chromatographic filtration and dialysis concentration, step by step.
Injection schedule
Four alternate-day doses, repeated at three months, with assessment at five months.
The measurement battery
Epigenetic testing before and after, ten blood markers, grip strength and memory tests throughout.
What was changed and why
Larger groups, an added young-rat arm, and animals kept alive for a longevity study.
UNICAMP and the crowdfunding
Collaboration with Dr Marcelo Mori and roughly $75,000 raised from about 44 donors.
Lifespan of the strain
Sprague Dawley rats rarely pass 36 months, which sets the natural window for the control group.
Which clocks will be used
Horvath's updated clocks, and why the same experiment read 54% in 2020 and 67% in 2023.
Storage, scale and cost
Particles can be frozen and batched, and plasma from pigs or cattle is the only source available at the required dose.
The theory being tested
Ageing by signalling, partial reprogramming, and the embryo that resets its own epigenetic age.
Why basic science needs small donors
Investors want a proven principle first; historic breakthroughs came from small labs, not large budgets.
Where to follow the experiment
Newsletter, multilingual website, social channels, and an open invitation to visit the lab.