Epigenetic reprogramming and ageing clocks: what the research shows

Prepared by: Research Desk. Sources are linked for verification.

Few lines of research have shaped how scientists think about aging clocks as much as epigenetic reprogramming. When adult cells are pushed back toward a pluripotent, embryo-like state, their DNA methylation age resets as well. That raises a core measurement question. If a clock reading can be moved, what exactly was the clock measuring, and what does a lower reading mean? This explainer covers the main cell and mouse findings, the idea of partial reprogramming, the teratoma problem, and the limits of using clocks as the readout.

What "epigenetic reprogramming" means

Reprogramming here means converting a specialised adult cell into a less specialised state by switching on a set of transcription factors. These are known as the Yamanaka factors, often abbreviated OSKM. Reviews of the field describe two broad versions:

• Full reprogramming: the cell becomes an induced pluripotent stem cell (iPSC).

• Partial reprogramming: the cell is exposed to the factors only briefly. This is also called interrupted reprogramming. The aim is to shift age-related features without erasing what kind of cell it is [2][6].

Both versions are studied mainly in cultured cells and in mice. Galkin and colleagues note that reprogramming can be carried out both in vitro (in a dish) and in vivo (inside a living animal). Both settings are framed as research models of cellular rejuvenation [3].

Full reprogramming: the clock goes back toward the start

The reference observation comes from iPSCs. Puri and colleagues' 2023 review states that generating iPSCs resets age-associated molecular features. These include:

• elongation of telomeres

• resetting of epigenetic clocks

• age-associated changes in gene expression

• escape from replicative senescence [2]

The clock evidence is older than the rejuvenation debate. Horvath's 2013 paper built a multi-tissue DNA methylation age estimator. It reported that DNA methylation age is close to zero for embryonic stem cells and induced pluripotent stem cells [1]. For background on how that estimator was trained, see the Horvath clock explainer and how epigenetic clocks work.

Galkin and colleagues describe iPSCs as cells representing the early stages of life. That points to a possibility of resetting the age of cells inside an organism [3]. They pair this with a caution. Organisms contain fully differentiated, irreplaceable cells and structures, such as neurons and the skeleton, and deterioration of these may not be undone by a cell-level reset [3].

Partial reprogramming: resetting age while keeping identity

Full reprogramming has an obvious problem for any whole-organism use. It removes cell identity entirely. Puri and colleagues summarise recent studies indicating that limited exposure to reprogramming factors can reset epigenetic ageing clocks while cells keep their identity [2].

The same review is frank about the gaps:

• There is no commonly accepted definition of partial reprogramming.

• It is unclear how the process can be controlled.

• It is unclear whether partial reprogramming represents a stable intermediate state.

• A central open question is whether the rejuvenation program can be uncoupled from the pluripotency program [2].

An and colleagues' 2025 review places partial OSKM reprogramming within a wider set of experimental strategies, including CRISPR-dCas9 epigenome editing. It evaluates these by their reported effects on epigenetic age [6]. Noroozi and colleagues trace how DNA methylation clocks moved from estimating chronological age to indicating lifespan and healthspan. They discuss reprogramming strategies as research methods for resetting those clocks [5].

A mouse example: the ERCC1 progeroid model

Paine and colleagues (2023) built a reprogrammable mouse model of accelerated aging carrying an ERCC1 mutation, which impairs DNA repair [4]. The design combined small molecules with the Yamanaka factors, which the authors call enhanced partial reprogramming. They reported:

• a marked reduction in DNA damage

• significant upregulation of multiple DNA damage repair processes

• restoration of the epigenetic clock [4]

They also presented evidence on pharmacological inhibition of ALK5 and ALK2 receptors in the TGF-beta pathway [4]. Their introduction summarises earlier work reporting that in vivo partial reprogramming extended lifespan and restored aging phenotypes in mouse models [4].

Three points matter when reading this result:

1. The model is a mouse. It is a genetically engineered model of premature aging, not natural aging.

2. The scale is not stated. The abstract does not report group sizes.

3. The readout is specific. "Restoration of the epigenetic clock" describes a change in a methylation-based estimate, which is a specific measurement and not a whole-body outcome.

Why the choice of clock matters

Clocks are trained against different targets:

• Horvath's estimator was built to predict chronological age across many tissues [1].

• GrimAge was trained using mortality-related information and predicts lifespan and healthspan [8].

• DunedinPACE estimates the pace of aging rather than an age in years [9].

A reset in a first-generation clock in cultured cells does not automatically imply the same shift in a mortality-trained clock or a pace-of-aging measure. The guide to clock generations covers these design differences.

An and colleagues propose integrating single-cell multiomics with second-generation clocks to track rejuvenation strategies more precisely [6]. That is a recognition that a single bulk-tissue number can hide cell-type differences. For the same reason, epigenetic age acceleration is always interpreted relative to the model and tissue it came from.

Risks and open questions

Teratoma formation. Reprogramming to iPSCs carries a risk of teratoma formation, a type of tumour. It also causes complete loss of cellular identity. Puri and colleagues flag both as central concerns for any whole-organism application [2].

What cannot be reset. Bartoszewicz and colleagues (2026) propose a "polycentric" framework drawing on somatic cell nuclear transfer (SCNT) experiments. They argue that selected epigenetic and developmental states can be extensively reconfigured. Other features show only context-dependent reset or recurrence:

• telomere dynamics

• mitochondrial state

• proteostasis

• stem-cell capacity

• senescence

Nuclear DNA sequence and structural damage remain least resettable [7]. The framework proposes epigenetic regulation as a dominant, but not exclusive, lifespan-limiting center in human aging [7]. That framing is a hypothesis-organising review, not a trial result.

Measurement versus mechanism. A clock moving does not show which underlying process changed. This is why the ERCC1 study paired the clock readout with direct DNA damage measures [4].

How this connects to consumer biological-age tests

The reprogramming findings summarised here come from cells and mice. Consumer epigenetic tests use related clock families, but a consumer result says nothing about reprogramming. It is one estimate from one sample, with measurement noise. For how these tests are built and how far a single number can be read, see the biological age test guide and biological age test accuracy. Most consumer clock tests are laboratory-developed tests. How biological age tests are regulated explains what that status does and does not cover. Our about page describes how sources are chosen for pages like this one.

Further reading

Books are a practical way to build background in stem cell and ageing biology before reading primary papers. Useful comparison criteria include:

• Publication date. The field moves fast, and older titles predate partial-reprogramming work.

• Citations. Whether claims cite peer-reviewed studies.

• Evidence separation. Whether cell, mouse and human evidence are kept clearly apart.

• Measurement coverage. Whether the book explains how aging is measured, not only theorised.

• Author background. Whether the author works in the research area.

• Format. Textbook depth suits researchers; narrative science writing suits general readers.

Books that discuss rejuvenation without separating dish, animal and human data are harder to check against the literature. Titles with full reference lists make cross-checking against PubMed straightforward.

Frequently asked questions

What are Yamanaka factors?

They are a set of transcription factors, abbreviated OSKM, that can convert adult cells into induced pluripotent stem cells [6]. Full conversion resets several age-associated features, including epigenetic clock readings [2].

Does partial reprogramming reset epigenetic age in mice?

In an ERCC1 premature-aging mouse model, Paine and colleagues reported restoration of the epigenetic clock alongside reduced DNA damage [4]. Reviews summarise similar findings while noting there is no agreed definition of partial reprogramming [2].

Why is teratoma risk discussed so often?

Full reprogramming produces pluripotent cells, which carry a risk of teratoma formation and lose their original identity [2]. Controlling exposure to avoid this is one of the field's main unsolved problems [2].

Can a consumer biological age test detect reprogramming effects?

No. Reprogramming is measured in research settings with tissue-specific clocks and direct molecular assays [4][6]. A consumer result is a single estimate with its own error, explained in the biological age test guide.

Related on this site

• How old are you, biologically?

• Biological age tests: how epigenetic clocks work and what they mean

• Are biological age tests FDA approved? How aging tests are regulated

• The Horvath clock: the 2013 multi-tissue epigenetic age estimator

• Telomere length and epigenetic clocks: two different aging signals

• About BioAge Peptide: how this site works and disclosures

Last updated: 26 October 2026.

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