Psilocybin treatment extends cellular lifespan and improves survival of aged mice

Psilocybin, a naturally occurring psychedelic produced by certain mushrooms, has attracted substantial clinical interest because single-dose and short-course treatments produce durable improvements in psychiatric and some neurodegenerative conditions. Despite a growing clinical literature (>150 studies completed or ongoing), the molecular and systemic mechanisms that might underpin these prolonged benefits remain poorly understood. Previous work has largely emphasised neural and behavioural outcomes; comparatively few studies have investigated peripheral or cellular ageing pathways such as telomere dynamics, oxidative stress, or canonical senescence markers. Kato and colleagues set out to test the ‘‘psilocybin‑telomere hypothesis’’ by experimentally evaluating whether psilocybin (via its active metabolite psilocin) directly affects cellular ageing and organismal longevity. The study used in vitro replicative senescence models (human fetal lung and adult skin fibroblasts) treated with psilocin, and an in vivo longevity experiment in aged (19‑month) female mice treated monthly with oral psilocybin. The investigators aimed to measure effects on cellular lifespan, senescence markers, oxidative stress, telomere length, and survival in aged animals to assess whether psilocybin/psilocin exerts geroprotective effects.

The study combined cell culture experiments with an aged‑mouse survival study. For in vitro work, human fetal lung fibroblasts (IMR‑90) and adult human skin fibroblasts were purchased at passage 7–8, expanded 2–3 passages, then serially passaged until replicative senescence. Psilocin was used for all cell experiments (50 mM DMSO stock); doses reported in the text were 10 μM and 100 μM. Cells were plated at a fixed density (1 × 10^6), counted every 3–4 days, and re‑plated; cumulative population doublings (PD) and Area Under the Growth Curve (AUC) were used to quantify proliferative potential. Senescence was assessed by β‑galactosidase assays, and biochemical analyses included western immunoblotting for markers such as p21, p16, PCNA, RB/pRB, SIRT1, GADD45a, Nox4, Nrf2 and others. Reactive oxygen species (H2O2) were measured using the Amplex Red assay. Telomere length was measured by qPCR on genomic DNA using a commercial human telomere kit with a single copy reference on chromosome 17 for normalisation. For the in vivo component, 19‑month‑old female C57BL/6J mice were obtained and acclimated for one month before random allocation to control or psilocybin treatment groups; the extracted text does not clearly report group sizes. Dosing followed a pragmatic rationale: an initial acclimation dose of 5 mg/kg psilocybin given orally, followed by monthly high doses of 15 mg/kg by oral gavage for a total of 10 treatments. Doses were administered between ~09:00 and 12:00, mice were weighed on treatment days, and gavage volumes ranged 100–200 μl. Mice were monitored for body weight and morbidity; the study end point was triggered when one group reached 50% mortality (the first group to reach median survival), at which point all remaining mice were euthanised. Investigators report they were not blinded to group allocation. Reagents, antibodies and kits are listed in the Methods; all animal procedures had IACUC approval at Emory University. Statistical analysis used GraphPad Prism. For cell data, technical replicates (4 replicates per passage for PD counts; 3–5 technical replicates for other assays) were used to produce means ± SD. Comparisons used two‑tailed unpaired t‑tests with unequal variance or two‑way ANOVA where appropriate. Survival analyses used the log‑rank (Mantel‑Cox) test. The extracted text states complete details of n and exact tests are provided in figure legends, but those specific numbers are not clearly reported in the provided extraction.

In vitro replicative senescence experiments showed dose‑dependent extension of cellular lifespan with psilocin. In IMR‑90 fetal lung fibroblasts, 10 μM psilocin produced a 29% extension of cellular lifespan (delayed exhaustion of proliferative potential, increased cumulative PDs and decreased population doubling time) relative to vehicle. A higher concentration (100 μM) produced a larger effect (reported as a 57% extension). Parallel experiments in adult human skin fibroblasts found that 100 μM psilocin increased cellular lifespan by 51%. In all cases both vehicle and psilocin groups ultimately reached replicative senescence, and the investigators report no evidence of oncogenic transformation in treated cells. Markers consistent with reduced senescence and enhanced proliferation accompanied the lifespan extension. Psilocin‑treated cells showed decreased β‑galactosidase activity, dose‑dependent reductions in cell‑cycle arrest markers p21 and p16, and increased markers of proliferation and DNA replication (PCNA and phosphorylated RB). Psilocin also elevated SIRT1 levels and reduced GADD45a, suggesting altered DNA‑damage response signalling. Oxidative stress measurements (H2O2 by Amplex Red) were reduced in a dose‑dependent manner, with corresponding decreases in NADPH oxidase‑4 (Nox4) and increases in the antioxidant regulator Nrf2. Telomere qPCR indicated that senescent vehicle‑treated cells exhibited shortened telomeres relative to young controls, whereas telomere length was preserved in age‑matched psilocin‑treated cells. In the in vivo study, monthly psilocybin treatment of aged female mice was associated with improved survival. At the study end point (when the first group reached median survival), survival was 80% in the psilocybin group versus 50% in vehicle controls; this difference was analysed with a log‑rank test (exact p‑value not reported in the extracted text). Treated mice displayed an acute head‑twitch response within 30 minutes of dosing (a behavioural marker of serotonergic hallucinogenic activity). Body‑weight trajectories showed some loss in both groups but no significant difference between psilocybin and vehicle. The authors also note qualitative improvements in fur quality (hair growth and reduced white hair) in treated animals, but these observations were not quantified in the provided text. The extracted material does not clearly state the number of mice per group or provide detailed adverse‑event tables; other assay‑specific replicate numbers are mentioned for cell work (3–5 technical replicates) but not definitively for animals.

Kato and colleagues interpret their findings as the first experimental evidence that psilocin/psilocybin can modulate cellular ageing pathways and improve survival when administered late in life in a mouse model. They propose that psilocin’s effects on SIRT1, reductions in oxidative stress, preservation of telomere length, and decreased expression of senescence markers together constitute impacts on multiple hallmarks of ageing that could underlie the observed lifespan benefits. The authors highlight serotonergic signalling, particularly 5‑HT2A receptor activation, as a plausible upstream mechanism because this receptor is widely expressed in peripheral tissues and prior work links 5‑HT2A stimulation to SIRT1‑dependent antioxidant gene expression. The investigators acknowledge several limitations and uncertainties. The study used a single‑sex (female) design to reduce biological variability, so sex‑specific effects remain untested and merit future study. Researchers were not blinded to group allocation, and the extracted text does not clearly report animal group sizes, which constrains assessment of power and reproducibility. Although in vitro data did not indicate oncogenic transformation, delayed senescence could theoretically influence cancer risk, and long‑term in vivo cancer incidence was not evaluated; the authors call for rigorous assessment of malignancy risk in future work. Mechanistically, it remains unclear whether effects are strictly 5‑HT‑dependent or involve additional pathways such as epigenomic remodelling; the authors suggest epigenetic modulation is a plausible contributor given prior literature on long‑lasting psychedelic effects. Finally, the discussion situates the findings within translational and regulatory contexts. The authors note that human psilocybin trials report durable symptom benefit and an acceptable safety profile, and that the FDA has granted psilocybin breakthrough therapy designation for certain indications, supporting feasibility in older adults. Nevertheless, they emphasise regulatory barriers (Schedule I status) and limited federal funding as constraints on mechanistic research. Key open questions enumerated include optimal age and frequency of intervention, dosing regimens, potential sex differences, effects on maximal lifespan, and safety with prolonged or repeated treatments.