Old blood cells transformed into brain stem cells that grow younger with age

Bonn researchers show direct conversion resets epigenetic age over several weeks

By LineZotpaper

Published20 October 2026

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Scientists in Germany have converted blood precursor cells from donors up to 101 years old into neural stem cells that progressively shed their biological age, eventually reaching roughly five percent of the donor's age. The findings, published in Aging Cell, offer a new experimental model for aging research and a possible route toward engineered brain cells for neurodegenerative disease.

Researchers at the University Hospital of Bonn and the University of Bonn used a direct conversion technique that skips the embryonic "blank slate" stage, transforming erythroid progenitor cells from 15 donors, aged from newborn to 101, into induced neural stem cells.

They delivered two transcription factors via a virus to trigger the change. By the 12th day, the cells had dropped their blood-like proteins and begun expressing neural proteins. Over the following 50 to 100 days, the cells kept growing biologically younger, resetting most epigenetic age-related traits by around day 50.

"We also know that this epigenetic rejuvenation ensures that the cells actually behave like young cells," said Oliver Brüstle, director of the Institute of Reconstructive Neurobiology at the University Hospital of Bonn.

The rejuvenated cells displayed less DNA damage and mitochondrial toxicity, and they continued to de-age even when their ability to divide was inhibited, suggesting the reset does not depend on cell proliferation.

The team acknowledged limitations, including potential mathematical biases in de-aging models, the absence of naturally aged neural stem cells for comparison, and possible differences between how cells behave in the lab and in a living body.

Earlier work by the same Bonn group found that similar engineered cells formed connections with existing neurons after being transplanted into the brains of mice, pointing toward future therapeutic applications. Brüstle said the slow, weeks-long reset makes the model particularly useful for studying which factors and active substances accelerate or slow down the rejuvenation process.

Analysis

Why This Matters

Shows cellular age can be reset without returning cells to an embryonic state, providing a new window into how aging works.
The extended de-aging timeline makes it possible to test which drugs or factors speed up or slow the process.
Raises the possibility of engineering brain cells for people with neurodegenerative conditions.

Background

Stem cells normally lose their flexibility as they differentiate into specific cell types, which has driven two main strategies for cellular transformation: reverting cells to a pluripotent state, or directly converting one cell type into another. The Bonn team applied the direct conversion method to blood precursor cells and tracked the epigenetic clock as it reset over several weeks. The work builds on earlier research in which similar cells, transplanted into mouse brains, connected with existing neural tissue.

Key Perspectives

The research team: Oliver Brüstle and colleagues describe the rejuvenation as genuine rather than superficial, noting the converted cells behave like young cells across multiple measures, and argue the long reset window is ideal for experimental study.

Therapeutic promise: The findings raise the prospect of engineering replacement brain cells for neurodegenerative disease, building on the team's earlier mouse transplant studies.

Researchers' own caveats: The study notes potential mathematical biases in de-aging models, the lack of naturally aged neural stem cells as comparators, and uncertainty about whether lab behaviour matches what would happen inside a living organism.

What to Watch

Whether future work includes naturally aged neural stem cells as direct comparisons.
Identification of specific substances that accelerate or slow the epigenetic reset.
Further transplant studies testing whether the rejuvenated cells integrate and function in living brains over the long term.

Sources

Old Blood Cells Have Been Transformed Into Brain Stem Cells That Get Younger As They Age · ScienceAlert

Checked

12 claims in this story checked against 1 source: 12 supported.

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SupportedBonn researchers show direct conversion resets epigenetic age over several weeksScienceAlert: “the neuronal stem cells kept getting younger as they got older... Over the following 50 to 100 days, they kept de-aging... the majority of epigenetic age-related traits resetting by around 50 days”
SupportedScientists in Germany have converted blood precursor cells from donors up to 101 years old into neural stem cells that progressively shed their biological age, eventually reaching roughly five percent of the donor's age.ScienceAlert: “The researchers used donor cells from 15 people across the age spectrum, from newborn to 101 years of age... Over the following 50 to 100 days, they kept de-aging, eventually reaching about 5 percent of the donor age”
SupportedThe findings, published in Aging Cell, offer a new experimental model for aging researchScienceAlert: “The researchers, from the University Hospital of Bonn and the University of Bonn, in Germany, described their methods in the journal Aging Cell”
SupportedResearchers at the University Hospital of Bonn and the University of Bonn used a direct conversion technique that skips the embryonic 'blank slate' stageScienceAlert: “The second method involves a 'direct conversion,' which skips the middle stage and directly transforms a cell into a different type.”
SupportedThey delivered two transcription factors via a virus to trigger the change.ScienceAlert: “The researchers used a virus to deliver two transcription factors, or proteins that attach to DNA to regulate gene activity, to get the cells to change their types.”
SupportedBy the 12th day, the cells had dropped their blood-like proteins and begun expressing neural proteins.ScienceAlert: “By the 12th day after the viral 'infection,' the cells started showing their new identity, ditching their blood-like proteins and replacing them with the expression of neural-like proteins instead.”
SupportedOver the following 50 to 100 days, the cells kept growing biologically younger, resetting most epigenetic age-related traits by around day 50.ScienceAlert: “Over the following 50 to 100 days, they kept de-aging... the majority of epigenetic age-related traits resetting by around 50 days”
Supported"We also know that this epigenetic rejuvenation ensures that the cells actually behave like young cells," said Oliver Brüstle, director of the Institute of Reconstructive Neurobiology at the University Hospital of Bonn.ScienceAlert: “"We also know that this epigenetic rejuvenation ensures that the cells actually behave like young cells," Brüstle says.”
SupportedThe rejuvenated cells displayed less DNA damage and mitochondrial toxicity, and they continued to de-age even when their ability to divide was inhibited, suggesting the reset does not depend on cell proliferation.ScienceAlert: “The cells also displayed less DNA damage and mitochondrial toxicity... they continued growing biologically younger even in conditions that inhibited their proliferation... suggesting their rejuvenation isn't dependent on their ability to split.”
SupportedThe team acknowledged limitations, including potential mathematical biases in de-aging models, the absence of naturally aged neural stem cells for comparison, and possible differences between how cells behave in the lab and in a living body.ScienceAlert: “The researchers do mention some study limitations. These include potential mathematical biases in de-aging models, the absence of naturally aged neural stem cells to use as comparisons, and potential in vitro versus in vivo behavioral differences in cells.”
SupportedEarlier work by the same Bonn group found that similar engineered cells formed connections with existing neurons after being transplanted into the brains of mice, pointing toward future therapeutic applications.ScienceAlert: “In previous Franken-mouse-like research from Bonn scientists, cells formed connections with existing neural cells after being transplanted into the brains of mice.”
SupportedBrüstle said the slow, weeks-long reset makes the model particularly useful for studying which factors and active substances accelerate or slow down the rejuvenation process.ScienceAlert: “"Rejuvenation that extends over such a long period of time is ideal as an experimental model," Brüstle emphasizes. "Since the epigenetic clocks are slowly reset over several weeks, we can use this model to investigate which factors and active substances accelerate or slow down the rejuvenation process."”