April 22, 2013
Human Stem Cells Injected In Mice Restore Memory, Learning Capacity
redOrbit Staff & Wire Reports - Your Universe Online
Researchers at the University of Wisconsin-Madison have successfully transformed human embryonic stem cells into nerve cells that helped mice regain their memory and the ability to learn.
Once they were inserted into the brain of the rodents, the implanted stem cells formed two common but essential types of neurons. Those neurons — which Zhang said are involved with many different types of human behavior, emotions, learning, memory, and psychiatric issues — communicate with the chemicals GABA or acetylcholine.
The embryonic stem cells used in the study were cultured in a laboratory using chemicals known to promote development into nerve cells. Zhang has worked on similar projects for the past 15 years, according to the university, and has helped pioneer research in the field.
As for the mice, they were said to be a special type which did not reject transplants from other species. An area of their brains responsible for memory and learning, known as the medial septum, were then intentionally damaged. The medial septum connects to the GABA and cholinergic neurons, Zhang said.
“This circuitry is fundamental to our ability to learn and remember,” he added.
The human cells were transplanted into the hippocampus, a key memory center located at the opposite end of those memory circuits. Following the successful implementation of the stem cells, the mice reportedly scored “significantly” better on common tests in both memory and learning.
“After the transferred cells were implanted, in response to chemical directions from the brain, they started to specialize and connect to the appropriate cells in the hippocampus,” the university explained in a statement. “The process is akin to removing a section of telephone cable“¦ If you can find the correct route, you could wire the replacement from either end.”
For the study, Zhang and his colleagues chemically directed the embryonic stem cells to begin differentiation into neural cells. They then injected those intermediate cells into the mice, ensuring that the cells would not become unwanted cell types once they entered their subjects´ bodies.
According to Zhang, it was essential that the majority of the transplanted cells turned into neural cells.
“That means you are able to predict what the progeny will be, and for any future use in therapy, you reduce the chance of injecting stem cells that could form tumors,” he explained. “In many other transplant experiments, injecting early progenitor cells resulted in masses of cells — tumors. This didn't happen in our case because the transplanted cells are pure and committed to a particular fate so that they do not generate anything else.”
While scientists have long searched for a reliable method to use stem cells to repair the brain — potentially helping to treat or cure conditions such as Alzheimer's, Down syndrome, schizophrenia, epilepsy, depression and related disorders — such medical advances are still a long way off, Zhang said.
“For many psychiatric disorders, you don't know which part of the brain has gone wrong,” he said, adding that his research will likely first be beneficial in the development of new drug-screening and detection methods.
Their findings are detailed in the latest edition of the journal Nature Biotechnology.