University of Bonn researchers rejuvenate human cells to under 20 years

Researchers at the University of Bonn Rejuvenate Human Cells in a Test Tube

University Hospital of Bonn and University of Bonn researchers have successfully rejuvenated human cells in a test tube by directly reprogramming red blood cell precursors into neural stem cells. During this laboratory process, the molecular clocks indicating cell age reset significantly. Blood cells taken from an 80-year-old donor transformed into stem cells possessing a molecular age of under 20 years. Because this cellular rejuvenation unfolded at a slow pace, the model provides an experimental framework for investigating underlying biological mechanisms, according to findings published in the journal Aging Cell.

The Tech TL;DR:

• Researchers at the University of Bonn converted human red blood cell precursors directly into neural stem cells without passing through an intermediate pluripotent stage.
• Epigenetic clocks on the cells were significantly reset, dropping the molecular age of cells from an 80-year-old donor to under 20 years.
• The slow, 100-day conversion process offers a controlled experimental model to investigate the biological mechanisms of cellular aging and neurodegeneration.

Epigenetic Clocks Reset During Direct Neural Conversion

All human cell types originate from a single fertilized egg and share identical genetic material, yet cellular development typically locks them into a specific fate. While skin cells or blood cells cannot naturally transform into other tissue types under normal physiological conditions, laboratory reprogramming can reverse this determination through transcription factor cocktails. Previous scientific approaches achieved this reset by taking a somatic cell, converting it first into a pluripotent stem cell with open developmental career paths, and then inducing it forward into a specific lineage like a neural stem cell. That two-step method triggers rejuvenation rapidly.

In the Bonn study, investigators bypassed the intermediate pluripotent state entirely. “Using this method, we have directly converted red blood cell precursors into neural stem cells,” stated Prof. Dr. Oliver Brüstle, Director of the Institute of Reconstructive Neurobiology at University Hospital of Bonn. Brüstle is also a member of the Transdisciplinary Research Area Life & Health at the University of Bonn. By avoiding the pluripotent shortcut, the research team observed that the rejuvenation occurred gradually over an extended observation period exceeding 100 days.

Tracking Molecular Age Over a 100-Day Window

To quantify the age transformation, researchers tracked epigenetic modifications—specifically DNA alterations that influence how frequently genetic information is read without changing the underlying genetic sequence itself. These epigenetic clocks measure biological aging. As the direct conversion of blood cell precursors to neural stem cells progressed, the epigenetic clocks wound backward. Cells originating from elderly donors exhibited molecular profiles characteristic of youth.

“In our current study, however, we focused on a different phenomenon: namely, the observation that cells become significantly rejuvenated during reprogramming.”

noted Brüstle. The gradual nature of this single-step conversion provides a continuous experimental timeline. Because the epigenetic reset spans several weeks rather than occurring instantaneously, scientists gain a window to test active substances and environmental factors that might accelerate or decelerate cellular aging. Prior animal studies by the same research group demonstrated that nerve cells produced via reprogramming successfully established functional connections after transplantation into mouse brains.

Implications for Age-Related Neurodegenerative Diseases

Cellular aging remains the most important risk factor for conditions such as Alzheimer’s disease. The ability to induce protracted fate acquisition alongside epigenetic de-aging in human blood cells creates an in vitro platform for studying neurodegeneration at a cellular level.

# Conceptual Timeline of Direct Neural Stem Cell Conversion
conversion_start_day = 0
intermediate_pluripotent_stage = None  # Bypassed in direct method
epigenetic_reset_window_days = 100
donor_starting_age = 80
resulting_molecular_age = 20

The study, authored by L. J. Berg and colleagues under the title “Protracted Fate Acquisition and Epigenetic De-Aging During Induced Neural Stem Cell Conversion of Human Blood Cells,” establishes a baseline for tracking how human cells shed molecular markers of aging under controlled laboratory conditions. The research details appear in Aging Cell (DOI: 10.1111/acel.70751).