A new stem cell therapy has successfully reversed stroke damage and restored movement in mice, according to researchers at the University of Zurich. The findings offer a promising step toward regenerative treatments for severe neurological injuries that are currently considered permanent.
Stem Cell Therapy Restores Movement and Repairs Brain Damage in Mice
Stroke is one of the world’s leading causes of long-term disability, affecting about one in four adults over a lifetime. Approximately half of those who experience a stroke are left with lasting problems such as paralysis, speech difficulties, or memory loss. These disabilities occur because a stroke deprives parts of the brain of oxygen or causes bleeding that destroys brain cells. Because the adult brain has only a limited ability to replace lost tissue, the resulting damage has traditionally been permanent.
How the Transplanted Cells Rebuild the Brain
The research team was led by Tackenberg and postdoctoral researcher Rebecca Weber, in collaboration with a group headed by Ruslan Rust from the University of Southern California. The investigators utilized human neural stem cells capable of producing different types of nervous system cells. These cells were created from induced pluripotent stem cells, which are produced by reprogramming ordinary human somatic cells so they regain the ability to develop into many different cell types.
To test the therapy, the researchers induced permanent strokes in mice, creating brain damage designed to closely resemble important features of stroke in humans. Because the transplanted cells were of human origin, the mice were genetically modified to prevent their immune systems from rejecting the tissue.
Timing proved to be critical for the procedure. The researchers transplanted the neural stem cells directly into damaged regions of the brain one week after the strokes were induced. Earlier transplants tended to survive poorly because the injured brain was still overwhelmed by inflammation and toxic chemical signals. Waiting several days allowed conditions to stabilize sufficiently for the transplanted cells to take hold.
New Neurons and Broader Healing Processes
Tracking the results through imaging techniques and biochemical analyses, the research team found that the stem cells survived for the full five-week analysis period. Most of the transplanted cells transformed into neurons that communicated with existing brain cells.
Over the five-week period, the cells spread through nearby brain tissue and matured largely into functioning neurons, including specialized inhibitory brain cells known as GABAergic neurons that help regulate neural activity and are heavily depleted after a stroke. The scientists identified several major pathways involved in this cross-talk, such as neurexin, neuregulin, NCAM, and SLIT signaling, which are associated with rebuilding neural networks and guiding axons to reconnect.
Beyond replacing lost cells, the treatment triggered a broader healing response across the injured brain. Mice that received the transplants developed significantly more blood vessels near the stroke site, which improved circulation in the damaged tissue. Some of the transplanted neurons also extended long projections into areas linked to movement and sensory control.
Improvements in Movement and Coordination
The biological changes were accompanied by clear improvements in how the animals moved. The stem cell transplantation successfully reversed the motor impairments caused by the strokes in the mice.
Researchers note that this approach could provide practical advantages for future medical applications.
