A research team from the University of Zurich in Switzerland has made a breakthrough: in animal experiments, stem cell transplantation has reversed brain damage caused by stroke - not only promoting neuronal regeneration, but also significantly restoring motor function. This marks a crucial step forward for regenerative medicine in the field of brain repair. The relevant research was published in the latest issue of Nature Communications. One quarter of adults will experience a stroke in their lifetime, with about half of them leaving long-term sequelae such as paralysis or language disorders. This is because cerebral hemorrhage or hypoxia caused by stroke irreversibly kills a large number of brain cells, and there is currently no effective therapy to repair this structural damage. Therefore, exploring new methods to promote brain regeneration has become an urgent need in the medical community. This time, the team used neural stem cells derived from human induced pluripotent stem cells, which can be reprogrammed from ordinary somatic cells and have the ability to differentiate into various nervous system cells. To simulate human stroke, they induced permanent brain damage in the brains of mice that was highly similar to that of humans. These mice have been genetically modified to not reject transplanted human cells. One week after the stroke, the team accurately transplanted neural stem cells into the damaged brain area and tracked the subsequent changes for up to 5 weeks using various imaging and biochemical techniques. The results showed that the transplanted stem cells successfully survived in the damaged brain area, with most of them differentiating into mature neurons and establishing functional connections with the host's existing neural network, achieving the transmission of electrical signals. This indicates that the newly generated neurons have truly integrated into the brain's operational system. What is even more exciting is that the team also observed a widespread regenerative effect: new blood vessels were formed in the damaged area, the inflammatory response in the brain was significantly reduced, and the integrity of the blood-brain barrier was restored. These changes collectively reveal how transplanted cells activate the entire brain's' regenerative program '. The team collaborated with the iPS Cell Research and Application Center at Kyoto University in Japan to ensure that all stem cells were prepared without using animal derived reagents, laying the foundation for safe future applications in the human body. Another key finding is that transplantation is not performed immediately after a stroke, but is more effective one week later, providing a valuable preparation period for clinical treatment. Despite the encouraging results, the team remains cautious. They stated that it is still necessary to minimize potential risks and optimize technology to simplify its application in humans. At present, they are collaborating to develop a "safety switch" system that can terminate stem cell proliferation when necessary to prevent abnormal growth. This study has opened up a new clinical prospect, with the significance of achieving biological repair of structural brain injury for the first time, rather than just relieving symptoms. Through stem cell transplantation, the overall regeneration environment of the brain has been activated, providing a reference therapeutic paradigm for other neurodegenerative diseases such as Parkinson's or spinal cord injury. The "one week delayed transplantation" window period discovered in the study is clinically feasible, taking a crucial step towards the practical application of the technology. If the efficacy can be verified in the human body in the future, it may completely change the pattern of neurological rehabilitation medicine. (New Society)