Yamanaka factors, the transcription factors OCT4, SOX2, KLF4, and c-MYC (collectively OSKM), enable adult cells to revert toward a pluripotent state, reversing epigenetic aging markers such as DNA methylation patterns in controlled settings. Partial reprogramming, using transient or cyclic expression of OSKM or the subset OSK (excluding c-MYC), resets cellular age clocks without full dedifferentiation in cell cultures and mice. In human cells, short-term exposure has reduced epigenetic age by up to 30 years while preserving cell identity. Mouse studies show extended median remaining lifespan by 109 percent in aged animals via AAV-delivered OSK. No approved human rejuvenation therapy exists as of February 2026. The first Phase 1 trial for partial reprogramming targets optic neuropathies, not systemic aging reversal. Full-body youthful state restoration remains unachieved and carries risks including potential tumorigenesis.

State of the science: Yamanaka factors reverse aging markers in cells and extend lifespan in mice by up to 109%. But no human rejuvenation therapy has been approved. The first human trial targets eye diseases, not whole-body aging.

What Are Yamanaka Factors

The Yamanaka factors consist of four transcription-factor proteins discovered in 2006. OCT4 (also Pou5f1) maintains pluripotency. SOX2 supports stem cell self-renewal. KLF4 regulates cell proliferation and differentiation. c-MYC promotes cell growth but carries oncogenic potential. These factors, abbreviated OSKM, reprogram somatic cells into induced pluripotent stem cells (iPSCs) by activating pluripotency networks and erasing lineage-specific epigenetic marks.

Subsets like OSK (excluding c-MYC) reduce cancer risks in partial applications while retaining rejuvenation effects, making them the preferred configuration for in vivo animal studies and the upcoming human trial.

How Yamanaka Factors Reverse Cellular Aging Markers

Transient OSKM expression loosens age-locked epigenetic states without full pluripotency. In human fibroblasts, short-term induction reduces epigenetic age at rates up to 3.8 years per day through day 20, with multi-omic rejuvenation including transcriptomic and lipidomic profiles. Cells maintain identity when exposure stops before the “point of no return,” avoiding dedifferentiation.

This window of safe exposure is critical. Too little expression produces no measurable rejuvenation. Too much causes cells to lose their specialized identity entirely, reverting to a stem-cell-like state that can form teratomas in living organisms.

Rejuvenation Effects Shown in Cell and Mouse Studies

Most data derive from in vitro and in vivo animal models. At the cell level, effects include reversal of senescence markers such as p21 downregulation and improved proteasome activity, enhanced mitochondrial function and proliferation (KI67 increase), and restoration of youthful gene-expression patterns.

In vivo mouse outcomes from partial reprogramming are equally striking. Cyclic OSKM in progeroid mice extended median lifespan by 33 percent. AAV9-delivered OSK in 124-week-old wild-type mice increased median remaining lifespan by 109 percent with healthspan gains. Tissue-specific improvements include restored vision via retinal ganglion cell rejuvenation, cognitive recovery in Alzheimer's models via engram cell reprogramming, and reduced fibrosis and steatosis in liver. Single-cycle early-life OSKM prevented musculoskeletal decline and increased healthy lifespan by 15 percent with organ-specific DNA methylation changes.

109% lifespan extension: AAV9-delivered OSK in aged wild-type mice increased median remaining lifespan by 109%, with no gross teratomas detected in monitored studies.

Safety Risks and Limitations in Animal Models

Full sustained OSKM induces teratomas and dysplasia in multiple organs including liver, intestine, and kidney. Partial protocols mitigate but do not eliminate risks. c-MYC inclusion heightens tumorigenicity. Cyclic OSK shows no gross teratomas in monitored studies, but genomic instability and oncogene activation remain concerns. Different tissues require optimized dosing to avoid off-target effects, and the therapeutic window varies by cell type and age of the organism.

Current Status in Humans

No systemic human rejuvenation using Yamanaka factors exists. In vitro human cell studies confirm epigenetic reversal without identity loss. The first human trial (Phase 1) for partial reprogramming (ER-100, AAV-delivered OSK) received FDA clearance in 2026 for optic neuropathies (glaucoma, NAION), focusing on safety in localized eye delivery. No trials target whole-body youthful reversal, and broader applications require large-animal safety data that has not yet been completed.

When mouse lifespans double from a gene cocktail but human trials start with eye drops, the distance from petri dish to fountain of youth measures more in regulatory years than mouse months.

What Are Yamanaka Factors

How Yamanaka Factors Reverse Cellular Aging Markers

Rejuvenation Effects Shown in Cell and Mouse Studies

Safety Risks and Limitations in Animal Models

Current Status in Humans

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