Partial reprogramming

This is an experimental technology, not a treatment. Nothing called "reprogramming" is approved or proven safe for healthy people, and nothing sold under that name is what was tested in these studies.

What it is

Every cell in your body carries essentially the same DNA. What makes a liver cell a liver cell is a layer of chemical marks on top of the DNA, the epigenome, which switches genes on and off. That layer drifts with age, and the drift is one of the hallmarks of aging.

Four genes, called the Yamanaka factors, can push an adult cell all the way back to a stem-cell state, erasing its epigenetic marks. Partial reprogramming uses the same four factors, or three of them, but switches them on only briefly, or in on-off cycles. The goal is to reset the aged marks while the cell keeps its identity: a younger liver cell, not a stem cell.

What it has done in mice

The results so far are all in animals, and they are striking.

• Vision. Switching on the factors in nerve cells of the eye restored youthful gene-activity patterns and reversed age-related vision loss.^[1]
• Whole-body rejuvenation. Applied long-term and intermittently to normally aging mice, the factors rejuvenated skin and kidney, reversed the epigenetic clock, and damped genes for inflammation and cell ageing. The authors concluded that such regimens can be designed to be safe.^[2]
• Lifespan. In one company-run study, a gene therapy carrying three of the factors was given to male mice already near the end of a normal mouse lifespan (124 weeks old). It about doubled their remaining lifespan, from about 9 to about 18 weeks, and made them less frail.^[3]

The lifespan study needs repeating before anyone leans on it. It used only males, did not report its group sizes in the main text, and had no comparison group given an empty virus.

The catch: the same genes cause cancer

The factors that rejuvenate a cell can, if switched on too long or too strongly, push it all the way back to a stem-cell-like state, or leave it stuck partway, and in mice both have led to tumours.

• Switching on all four factors in living mice produced tumours called teratomas in several organs.^[4]
• Even a short burst followed by switching off left behind cancer-like growths, including kidney tumours.^[5]
• Keeping the factors on continuously killed the animals within days.^[6]

Making the reset brief and tightly controlled is the central safety challenge.

Chemical cocktails instead of genes

One line of work tries to replace the genetic factors with drug-like chemical cocktails, which would not require changing a cell's genes. A screen found six combinations that made aged cells in a dish look younger by their gene-activity patterns within a week. The study was in cells only, and the authors say the cocktails must be tested for safety in animals before any human use.^[7]

The first human trial

The first test in people has only just begun. In 2026 a small early-stage safety trial started giving a reprogramming gene therapy, injected into the eye, to people with glaucoma or a type of optic-nerve stroke; results are not expected before 2027.^[8] It targets a specific eye disease, not ageing itself. Even if it goes well, it will give only first safety signals, from a handful of people and one small part of the body, not evidence that whole-body reprogramming is safe.

What to do

1. Don't seek it out. No reprogramming therapy is approved, and the first human trial is a small safety study in two eye diseases.
2. Be suspicious of anything sold as "reprogramming" or "epigenetic reset". Everything above is genetically engineered or gene-therapy-treated animals, cells in a dish, or one small eye trial; none of it is a pill or a clinic treatment you can buy.
3. Watch the eye trial. Its results, not expected before 2027, will be the first human safety data.

Further reading

• Lu Y, et al. Reprogramming to recover youthful epigenetic information and restore vision. Nature 2020.^[9]
• Browder KC, et al. In vivo partial reprogramming alters age-associated molecular changes during physiological aging in mice. Nat Aging 2022.^[10]
• Macip CC, et al. Gene Therapy-Mediated Partial Reprogramming Extends Lifespan and Reverses Age-Related Changes in Aged Mice. Cell Reprogram 2024 — company-run, males only.^[11]
• Abad M, et al. Reprogramming in vivo produces teratomas and iPS cells with totipotency features. Nature 2013.^[12]
• Ocampo A, et al. In Vivo Amelioration of Age-Associated Hallmarks by Partial Reprogramming. Cell 2016.^[13]