Mammalian astrocyte cell

Credit: Edward Nyatia and Dirk Lang

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LONDON: A novel method for producing large amounts of astrocyte cells - which assist in regulating the extracellular composition of brain fluid - from human stem cells has been achieved by scientists in the U.S.

The hope is that this will enable scientists to gain new insight into how astrocytes function in the nervous system and could provide them with information to help produce new therapies and drugs for neurological disease.

"Astrocytes wrap around nerve cells to protect them and keep them healthy. They participate in virtually every function or disorder of the brain. Without the astrocyte, neurons can't function," said lead researcher Su-Chun Zhang, professor of neuroscience in the UW-Madison School of Medicine and Public Health.

The humble astrocyte

Astrocytes are the most common cells in the human nervous system but they have long been in the shadows of the more obviously interesting neurons. However, the tides appear to be turning and the once ignored astrocyte is starting to be noticed.

They are now thought to be just as important as neurons and have been found to play a role in regulating blood flow, cultivating an optimum environment for neuronal function and helping maintain the protective blood brain barrier to ensure dangerous molecules are kept away from the brain.

The ability to direct human stem cells into new cell types is something of great interest but it has proven difficult to pinpoint what is needed to make them turn into different cell populations.

Treatment of neurological conditions

In the past they have been successfully directed into neuronal cell types but the protocol needed to make them turn into astrocytes was unknown. Now Zhang's group have demonstrated that within six months it is possible to take one human stem cell and turn it into twenty-eight-hundred-billion astrocytes.

"The ability to forge astrocytes in the lab has several potential practical outcomes," said Zhang.

"They could be used as screens to identify new drugs for treating diseases of the brain, they can be used to model disease in the lab dish and, in the more distant future, it may be possible to transplant the cells to treat a variety of neurological conditions, including brain trauma, Parkinson's disease and spinal cord injury."

Clinical hope

According to their study, published in the current issue of Nature Biotechnology, Zhang and his group have identified the two chemical growth signals needed to turn human stem cells into astrocytes. These growth signals called EGF and FGF2 can be added to the stem cells in the lab, making them grow and change to produce uniform cultures of astrocytes.

Zhang also found the astrocytes the group could grow in the lab express the same characteristics as the astrocytes in our nervous system and that when they are implanted into a mouse brain they can function the same way the astrocytes in our nervous system do.