Yamanaka Factors and Partial Reprogramming: The Science of Cellular Age Reversal
In 2006, Shinya Yamanaka's lab showed that four transcription factors could turn mouse fibroblasts back into pluripotent stem cells.1 Expressing some of these factors briefly, known as partial reprogramming, has restored youthful gene activity and function in mouse tissues,3 and in 2026 the first partial-reprogramming therapy entered a human safety trial.6 Here is the science, honestly assessed.
- The four Yamanaka factors, Oct3/4, Sox2, c-Myc and Klf4, turned mouse embryonic and adult fibroblasts into induced pluripotent stem (iPS) cells, which formed tumours containing tissues from all three germ layers when transplanted.1
- Partial reprogramming restores youthful gene expression in some cell types but can temporarily suppress the genes that give a cell its identity, and different factor combinations vary in both effects.5
- In mice, expressing three of the factors (OSK) in retinal nerve cells restored youthful DNA methylation patterns and reversed vision loss in a glaucoma model and in aged animals.3
- The main safety concern is tumours: briefly switching on all four factors throughout the body of mice produced teratomas in multiple organs.4
- In June 2026, Life Biosciences dosed the first participant in a phase 1 trial of ER-100, an OSK therapy for optic nerve diseases, not for ageing itself.6
The 2012 Nobel Prize in Physiology or Medicine was shared by John Gurdon and Shinya Yamanaka for showing that mature cells can be reprogrammed to pluripotency. Yamanaka's 2006 paper showed that introducing four factors, Oct3/4, Sox2, c-Myc and Klf4, could turn mouse embryonic or adult fibroblasts into induced pluripotent stem cells that behaved like embryonic stem cells and contributed to mouse development.1
Applying this to ageing asks a narrower question: can expressing the factors briefly, at lower levels or in subsets turn back markers of cellular age without erasing a cell's identity? Mouse and cell studies suggest it partly can, but with trade-offs.5
The Epigenetic Information Theory of Aging
The idea behind it is the information theory of ageing, championed by David Sinclair: that ageing is driven largely by a loss of epigenetic information rather than by DNA mutations. In a 2023 study, his lab induced DNA breaks that changed the epigenome without causing mutations, saw ageing-like changes in mice and tried to reverse some of them by resetting the epigenome; commentators called the causal claim provocative and in need of further study.2
A key prediction is that restoring youthful epigenetic patterns should restore youthful function. The 2020 retina study supports this in one tissue: the benefits of OSK for nerve regeneration and vision required the DNA demethylases TET1 and TET2.3
The Key Preclinical Evidence
In that 2020 study, expressing OSK in mouse retinal ganglion cells restored youthful DNA methylation patterns and gene activity, promoted regeneration of nerve fibres after injury, and reversed vision loss both in a glaucoma model and in aged mice.3
Whole-body evidence is more limited. In 2016, short repeated bursts of all four factors improved signs of ageing and extended lifespan in a mouse model of premature ageing, and improved recovery from metabolic disease and muscle injury in older normal mice.7
The Safety Challenges
The main safety concerns are loss of cell identity and tumours. Briefly switching on all four factors in mice produced teratomas, tumours containing multiple tissue types, in several organs, showing that full reprogramming can happen inside the body.4 Partial reprogramming can also temporarily suppress the genes that define a cell's identity, to a degree that depends on the factors used.5
Results in the mouse eye do not show what would happen if every cell in a body were partly reset. That would need extensive safety data before any responsible human use.
Where the Science Stands in 2026
Partial reprogramming has now reached its first human test. In June 2026, Life Biosciences reported dosing the first participant in a phase 1 trial of ER-100, an OSK therapy for optic nerve diseases including open-angle glaucoma and non-arteritic anterior ischemic optic neuropathy (NAION).6 The trial is evaluating safety and tolerability, with additional measures of visual function, so it will not show whether reprogramming slows ageing; whole-body use in people remains a distant prospect.
References
- 1Takahashi K, Yamanaka S. "Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors." Cell. 2006;126(4):663-76. PubMed · DOI
- 2Schaffer ED, et al. "Frontiers in aging special issue: DNA repair and interventions in aging perspective on "loss of epigenetic information as a cause of mammalian aging"." Front Aging. 2023;4:1199596. PubMed · DOI
- 3Lu Y, et al. "Reprogramming to recover youthful epigenetic information and restore vision." Nature. 2020;588(7836):124-129. PubMed · DOI
- 4Abad M, et al. "Reprogramming in vivo produces teratomas and iPS cells with totipotency features." Nature. 2013;502(7471):340-5. PubMed · DOI
- 5Roux AE, et al. "Diverse partial reprogramming strategies restore youthful gene expression and transiently suppress cell identity." Cell Syst. 2022;13(7):574-587.e11. PubMed · DOI
- 6Life Biosciences. "Life Biosciences Announces First Patient Dosed in Phase 1 Trial of ER-100 for Optic Neuropathies." Press release, June 9, 2026. lifebiosciences.com (checked 2026-10-01).
- 7Ocampo A, et al. "In Vivo Amelioration of Age-Associated Hallmarks by Partial Reprogramming." Cell. 2016;167(7):1719-1733.e12. PubMed · DOI
