Damage caused by brain vascular accidents while stem cells resume the brain

Stem cell therapy has reversed damage to strokes in mice, regenerating neurons and restoring movement.

The results bring scientists closer to human treatments which could one day transform recovery after a brain injury.

Pierced in the recovery of strokes with the stem cells

One out of four adults undergoes a stroke in their lifetime, leaving about half of them suffering from residual damage such as paralysis or speech disorders because internal bleeding or lack of oxygen supply kills brain cells irreversibly. No therapy currently exists to repair this type of damage. “This is why it is essential to pursue new therapeutic approaches to the potential regeneration of the brain after diseases or accidents,” explains Christian Tackenberg, scientific leader in the division of the neurodegeneration group of the Institute of Regenerative Medicine of the University of Zurich (UZH).

Neural stem cells have the potential to regenerate cerebral tissues, as a team led by Tackenberg and postdoctoral researcher Rebecca Weber has now been convincingly shown in two studies carried out in collaboration with a group led by Ruslan Rust from the University of South California. “Our results show that neural stem cells not only form new neurons, but also induce other regeneration processes,” said Tackenberg.

New neurons of human stem cells

Studies have used human neural stem cells, from which different types of cells in the nervous system can form. The stem cells have been derived from induced pluripotent stem cells, which in turn can be made from normal human somatic cells. For their investigation, the researchers induced a permanent stroke in mice, whose characteristics closely resemble the manifestation of stroke in humans. The animals have been genetically modified so that they do not reject human stem cells.

One week after stroke induction, the research team transplanted neural stem cells in the injured brain region and observed subsequent developments using a variety of imaging and biochemistry methods. “We have found that stem cells survived a whole period of analysis of five weeks and that most of them have turned into neurons, which even communicated with the already existing brain cells,” said Tackenberg.

Brain regeneration beyond neurons

The researchers also found other regeneration markers: a new formation of blood vessels, an attenuation of the inflammatory response processes and an improvement in the integrity of the blood-brain barrier. “Our analysis goes far beyond the scope of other studies, which focused on immediate effects just after transplantation,” says Tackenberg. Fortunately, the transplantation of stem cells in mice also reversed engine disorders caused by stroke. The proof of this was delivered in part by an analysis of the mouse march assisted by AI.

Clinical application approaching reality

When he conceived studies, Tackenberg already had his goal on clinical applications in humans. This is why, for example, stem cells have been manufactured without using animal derived reagents. The Zurich -based research team has developed a protocol defined for this purpose in collaboration with the Center for IPS Cell Research and Application (CIRA) at the University of Kyoto. This is important for potential therapeutic applications in humans. Another new overview discovered is that the transplantation of stem cells works better when carried out not immediately after a stroke but a week later, as the second study checked it. In the clinical environment, this temporal window could greatly facilitate the preparation and implementation of therapy.

Challenges, safety measures and future perspectives

Despite the encouraging studies of studies, Tackenberg warns that there is still work to do. “We have to minimize the risks and simplify a potential application in humans,” he says. The Tackenberg group, once again in collaboration with Ruslan Rust, is currently working on a sort of safety switching system that prevents uncontrolled growth of stem cells in the brain. The administration of endovascular injection cells, which would be much more passable than a brain transplant, is also under development. The first clinical trials using induced stem cells to treat Parkinson’s disease in humans are already underway in Japan, reports Tackenberg. “Stroke could be one of the next diseases for which a clinical trial becomes possible.”

Reference: “The xenogreffe of neurons contribute to long -term recovery in strokes via the molecular diaphony of the graft” by Rebecca Z. Weber, Beatriz Achón Buil, Nora H. Rentsch, Patrick Perron, Stefanie Halliday, Allison Bosworth, Mingzi Zhang, Daniela, Debora Meier, Siri L. Peter, Melanie Generali, Shuo Lin, Markus A. Rüegg, Roger M. Nitsch, Christian Tackenberg and Ruslan Rust, September 16, 2025, Nature communications.
Two: 10.1038 / S41467-025-63725-3

Never miss a breakthrough: join the Scitechdaily newsletter.
Follow us on Google, Discover and News.