A new longevity stem cell therapy in monkeys showed an estimated...
Bryan Johnson@bryan_johnson
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Oct 04, 2025
~2 min read
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A new longevity stem cell therapy in monkeys showed an estimated 3–5 yrs of biological age reversal, across 54% of tissues. Scaled cautiously to humans, could correspond to ~9–15 years of rejuvenation.
If this replicates, it's a big deal. 🧵
If this replicates, it's a big deal. 🧵
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What researchers did: engineered human embryonic stem cells (hESCs) with a modified FOXO3 gene (FOXO3SA2/SA2) to resist degradation.
These hESCs were then differentiated into senescence-resistant mesenchymal progenitor cells (SRCs). When injected into cynomolgus monkeys (2 million cells/kg) across various age groups, SRCs demonstrated significant rejuvenation, reversing brain atrophy, blood senescence, inflammation, and oxidative stress.
Transcriptomic and epigenetic analyses confirmed biological age reversal in organs like skin, aorta, lungs, and the digestive system.
FOXO3-enhanced senescence resistant MPCs (SRCs) consistently outperformed wild-type MPCs, producing systemic rejuvenation across brain, blood, and organs.
On average, this corresponded to estimated 3–5 years of biological age reversal, across 54% of tissues (vs 31% with WTCs). Scaled cautiously to humans, this may approximate ~9–15 years of rejuvenation.
These hESCs were then differentiated into senescence-resistant mesenchymal progenitor cells (SRCs). When injected into cynomolgus monkeys (2 million cells/kg) across various age groups, SRCs demonstrated significant rejuvenation, reversing brain atrophy, blood senescence, inflammation, and oxidative stress.
Transcriptomic and epigenetic analyses confirmed biological age reversal in organs like skin, aorta, lungs, and the digestive system.
FOXO3-enhanced senescence resistant MPCs (SRCs) consistently outperformed wild-type MPCs, producing systemic rejuvenation across brain, blood, and organs.
On average, this corresponded to estimated 3–5 years of biological age reversal, across 54% of tissues (vs 31% with WTCs). Scaled cautiously to humans, this may approximate ~9–15 years of rejuvenation.
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Here are some of the effects in more detail.
SRCs = are special stem cells engineered with a FOXO3 tweak that makes them resistant to aging
WTCs = are the normal “wild-type” cells without that upgrade
Brain
+ Cortical thickness and volume restored toward youthful levels: SRC up to ~50–70% vs WTC ~10–20% (inferred from imaging and figure analysis; not direct author statistics).
+ Hippocampus sn-transcriptAge: SRC −2.5 years (WTC not reported).
+ Cognition: significant improvement with SRC; modest effect with WTC.
Blood / Immune
+ Age-related gene programs reversed: SRC 39% (upregulated) / 30% (downregulated); WTC reversed fewer (Fig. 2C–D, no exact percentages reported).
+ Equivalent immune rejuvenation: SRC 3 years vs WTC 1.5 years (observational estimate, not author statistic).
Organs (transcriptomic & epigenomic)
+ Average transcriptomic rejuvenation: SRC −3.34 years (54% of tissues) vs WTC −2.80 years (31% of tissues).
+ Standout tissues:
• Skin: SRC −5.6 years vs WTC −4.4 years
• Lung: SRC −4.1 years vs WTC −3.3 years
• Skeletal muscle: SRC −4.9 / −3.5 years vs WTC −3.2 / −2.4 years
• Spleen: SRC −2.6 years vs WTC −1.9 years
• Hippocampus: SRC −2.0 years vs WTC −1.5 years
+ Reproductive system: Ovaries SRC −4.5 years vs WTC −3.1 years; granulosa cells showed >6 years reversal with SRC.
+ DNAmAge: Brain −5 years, skeletal muscle −4 years, spleen −2 years with SRC; WTC changes negligible.
Safety
+ Dose: 2 million cells/kg IV biweekly for 44 weeks.
+ No fevers, immune rejection, or metabolic issues in either group.
+ No tumors at the primate dose of 2 million cells/kg, or even at 10× higher dose (20 million cells/kg) in nude mice.
SRCs = are special stem cells engineered with a FOXO3 tweak that makes them resistant to aging
WTCs = are the normal “wild-type” cells without that upgrade
Brain
+ Cortical thickness and volume restored toward youthful levels: SRC up to ~50–70% vs WTC ~10–20% (inferred from imaging and figure analysis; not direct author statistics).
+ Hippocampus sn-transcriptAge: SRC −2.5 years (WTC not reported).
+ Cognition: significant improvement with SRC; modest effect with WTC.
Blood / Immune
+ Age-related gene programs reversed: SRC 39% (upregulated) / 30% (downregulated); WTC reversed fewer (Fig. 2C–D, no exact percentages reported).
+ Equivalent immune rejuvenation: SRC 3 years vs WTC 1.5 years (observational estimate, not author statistic).
Organs (transcriptomic & epigenomic)
+ Average transcriptomic rejuvenation: SRC −3.34 years (54% of tissues) vs WTC −2.80 years (31% of tissues).
+ Standout tissues:
• Skin: SRC −5.6 years vs WTC −4.4 years
• Lung: SRC −4.1 years vs WTC −3.3 years
• Skeletal muscle: SRC −4.9 / −3.5 years vs WTC −3.2 / −2.4 years
• Spleen: SRC −2.6 years vs WTC −1.9 years
• Hippocampus: SRC −2.0 years vs WTC −1.5 years
+ Reproductive system: Ovaries SRC −4.5 years vs WTC −3.1 years; granulosa cells showed >6 years reversal with SRC.
+ DNAmAge: Brain −5 years, skeletal muscle −4 years, spleen −2 years with SRC; WTC changes negligible.
Safety
+ Dose: 2 million cells/kg IV biweekly for 44 weeks.
+ No fevers, immune rejection, or metabolic issues in either group.
+ No tumors at the primate dose of 2 million cells/kg, or even at 10× higher dose (20 million cells/kg) in nude mice.
