Monday, 22 April 2013

Human embryonic stem cells restore memory in mice

Researchers from the University of Wisconsin–Madison (UW) announced today that they have successfully used human embryonic stem cells (hESCs) to help a group of mice regain their hindered ability to "learn and remember".  The hESCs helped the mice by forming new GABA and cholinergic neurons.

The UW researchers began their study by first damaging, in a group of mice, a part of the brain known as the medial septum. Su-Chun Zhang, senior author of the study, explains that the medial septum is heavily involved in learning and memory-related processes and is connected to the hippocampus by two types of cells, known as GABA and cholinergic neurons.

"This circuitry is fundamental to our ability to learn and remember," said Zhang.

Image showing human embryonic stem cells
Human embryonic stem cells


Next, the scientists took hESCs and used special chemicals to induce them into becoming neural cells. However, they didn't transplant the cells right away. Instead they waited the hESCs to reach a partial differentiation state and then placed them,via injection, near the hippocampus area. The researchers explain that partially differentiated hESCs have the advantage of not forming unwanted cell types, like cancer 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. 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. We need to be sure we do not inject the seeds of cancer." explained Zhang.

After the transplantation, the cells continued the differentiation process and eventually formed new GABA and cholinergic neurons. This was confirmed by a series of tests, in which the mice scored significantly better than they did before the transplantation, for instance the water maze test.

Video showing the water maze test

The researchers consider their study to be very important, as in humans GABA and cholinergic neurons are crucial for many functions including:
  • Addiction
  • Emotions
  • Learning
  • Memory
  • Psychiatric issues


Furthermore, they believe that the study may have implications in treating several disorders, including Alzheimer's and Down syndrome.

"Cholinergic neurons are involved in Alzheimer's and Down syndrome, but GABA neurons are involved in many additional disorders, including schizophrenia, epilepsy, depression and addiction." said Zhang.

References
Liu, Y., Weick, J., Liu, H., Krencik, R., Zhang, X., Ma, L., Zhou, G., Ayala, M., & Zhang, S. (2013). Medial ganglionic eminence–like cells derived from human embryonic stem cells correct learning and memory deficits Nature Biotechnology DOI: 10.1038/nbt.2565

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