Scientists from the University of Wisconsin-Madison (United States) have achieved for the first timetransform human embryonic stem cells into neurons that allow us to regain the ability to learn and remember. The experiment, carried out in mice, is the first step to implanting these stem cells in the human brain to cure neurological deficiencies.
In work by neuroscientist Su-Chun Zhang and his colleagues, published inNature Biotechnology, stem cells implanted within the mouse brain formedtwo momentous types of neurons that communicate using GABA and acetylcholine. “These two classes of neurons are involved in many aspects of human behavior, such as emotions, learning, memory or addiction, as well as in psychiatric disorders,” Zhang clarifies.
The researchers worked with rodents that had deliberately damaged neurons in an area of the brain calledmedial septum, which connects to the hippocampus via GABA and cholinergic neurons. “This circuit is critical to our ability to learn and remember,” explained the study’s lead author. However, the transplanted cells were placed in the hippocampus, a fundamental memory center, at the other end of the memory circuits. After the transferred cells implanted, they began to specialize and connect with the appropriate cells in the hippocampus. Zhang compares the process is similar to removing a section of telephone wire. “If you can find the correct route, you can connect the replacement of either end,” he points out.
The embryonic stem cells used in the implant were grown in the laboratory using molecules that promote growth in nerve cells, a field in which Zhang has pioneered for 15 years. The mice, which belonged to a special strain that does not reject transplants from other species,scored significantly better on basic learning and memory tests after transplantation. For example, after treatment they were more adept at the water maze test, in which they remembered the location of a hidden platform in a swimming pool.
Besides thatbrain repair through cell replacement is a holy grail of neuroscience, the two types of neurons used in the experiment are key to brain function, according to Zhang. “Cholinergic neurons are involved in Alzheimer’s disease and Down syndrome, but GABA neurons are involved in many additional disorders, including schizophrenia, epilepsy, depression and addiction,” says the researcher, who assures that the work will also help develop new drugs.
