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© ALS Independence 2003-11
The Independent reports today that there is “hope for millions of
Alzheimer’s sufferers as scientists make brain cells from human skin”. It said
that “scientists had managed to convert a person's skin tissue into functioning
nerve cells – bypassing an intermediate stem-cell stage – by the relatively
simple procedure of adding a few short strands of RNA, a genetic molecule
similar to DNA”.
This is an interesting study which builds on previous research in this area. It
may enable scientists to study the behaviour of neurons (brain cells) more
easily in the future. Eventually, this might lead to the development and testing
of treatments for brain diseases in the laboratory.
However, this research is still in the early stages. Any application to the
prevention or treatment of brain disease such as Alzheimer’s in humans is
unclear. Whether converted neurons grown in the laboratory can ever be used to
replace diseased or abnormal cells in living human brains will need considerably
more research.
Where did the story come from?
The study was carried out by researchers from Stanford University,
California. Funding was provided by the Howard Hughes Medical Institute and the
National Institutes of Health. The study was published in the (peer-reviewed)
journal Nature.
The Independent reported the study accurately, although its headline claiming
that the study brings hope to “millions of Alzheimer’s sufferers” could be
misleading. Although this is exciting work, any application to the prevention or
treatment of brain disease in humans is still uncertain.
What kind of research was this?
This was an experimental laboratory study, which used genetic technology to
see if human skin cells (called fibroblasts) could be converted into neurons
(brain cells). At present, scientists find it hard to study neurons in the
laboratory because, unlike skin or blood cells for example, it would clearly be
unethical to take them from a living human.
Previously, they had found that stem cells converted from skin cells could be
transformed into neurons, but the new study aimed to find out if skin cells
could be converted directly into neurons. Earlier this year, other scientists
reported that they had managed to convert skin cells directly into neurons by
adding to them a combination of four neurogenic transcription factors.
Transcription factors are proteins that bind to specific DNA sequences,
controlling the flow of genetic information and cell processes. In this latest
experiment, scientists adopted a different technique, using genetic material
called microRNA.
What did the research involve?
In a series of experiments, the researchers used both skin cells from
neonatal foreskin and also adult skin cells. To the cells they added two short
chains of genetic material, known as microRNA (RNA is a molecule similar to DNA,
essential to all forms of life). The particular RNA molecules that they used had
previously been found to be important in triggering neural stem cells into
becoming mature neurons.
In this study, they used a virus to carry the microRNA into skin cells. The
resulting cells were then tested for neuronal activity. To do this, the
researchers examined the skin fibroblasts under the microscope to see how many
of the cells had developed the ability to transport calcium into the cells.
This ability is specific to neurons and shows that the cells had taken on the
characteristics of neurons, such as their ability to transmit electrical nerve
signals. They also looked at whether the cells contained neurotransmitters, like
neurons do.
As a further experiment they added two transcription factors to the microRNA-treated
cells used in the earlier study to see if these sped up the conversion of skin
cells into neurons. They did this to test whether it was the transcription
factor or the microRNA that was having the effect.
What were the basic results?
The researchers found that up to 2-3 % of the skin cells converted to
neurons. The cells generated the electrical signals that neurons use to
communicate with each other. They also started to grow the cell structures
(synaptic vesicles) that are needed to store neurotransmitters, the chemical
used for passing messages between brain cells.
The researchers say that the neurons were characteristic of those found in the
frontal cortex, the part of the brain involved in thinking and reasoning. Some
of them resembled “inhibitory” neurons, cells whose role is to control the
activity of other neurons.
When they added two of the transcription factors that had been used in the
earlier experiment, the number of skin cells converted into neurons rose to 20
per cent.
How did the researchers interpret the results?
The researchers say that being able to generate neurons from easily
accessible cells, such as skin cells, would make it easier to study neuronal
development, particularly in neurological diseases. They also suggest that
different types of brain cells might be made from skin cells by using different
techniques with the microRNA.
Conclusion
This work raises the possibility that neurons might be grown directly from
more easily accessible cells and could, in future, enable scientists to study
these type of cells more easily. This could lead to an increased understanding
of the abnormalities involved in various neurological diseases such as
Alzheimer’s. However, there is a long way to go before we know how far this
research can contribute to preventing or treating such diseases.
"We must remember: our character becomes our destiny." Unknown
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© ALS Independence 2003-11