Researchers at the University Hospital Bonn and the University of Bonn have converted blood-cell precursors from older donors into neural stem cells whose epigenetic “age” fell steadily over weeks. The work, in the journal Aging Cell, was done in lab dishes, not in people or animals.

The team, led by Prof. Oliver Brüstle of the Institute of Reconstructive Neurobiology, started with red blood cell precursors. Using a set of transcription factors, proteins that switch genes on and off, they reprogrammed them directly into neural stem cells, skipping the pluripotent stem cell stage that other methods use. “Using this method, we have directly converted red blood cell precursors into neural stem cells,” Brüstle said.

The researchers tracked age with epigenetic clocks, which read chemical marks on DNA that build up over a lifetime. In the university’s example, blood cells from an 80-year-old produced stem cells with a molecular age under 20 years, about 60 years younger. ScienceAlert, which reported on the study on October 20, says the team used cells from 15 donors aged from newborn to 101, and that the cells’ epigenetic age fell to roughly 5% of the donor’s age. It adds that most age-related markers had reset by about day 50. The Bonn account says the process was tracked for more than 100 days. The two reports differ on the timeline, and we could not open the paper to check.

Unlike the faster two-step method, in which rejuvenation happens quickly, the direct route did it gradually. “Rejuvenation that extends over such a long period of time is ideal as an experimental model,” Brüstle said. The authors suggest it could help identify factors that speed up or slow cellular ageing.

Brüstle pointed to a possible link with brain disease: “After all, age is the most important risk factor for neurodegenerative diseases such as Alzheimer’s!” Nerve tissue grown from a patient’s own cells might one day treat such conditions, the researchers suggest, though that is untested. Earlier work by the same group showed that neurons made this way formed connections with existing neurons after transplantation into mice.

Important limits apply. The cells were studied in vitro. A reset epigenetic clock is a measurement, not proof that the cells function like young ones, and the mechanism is not yet understood. ScienceAlert reports that the researchers also flagged possible biases in the age-estimation models and the lack of naturally aged neural stem cells to compare against.