Clinical uses of neural stem cells
Neural stem cells may hold the
key for treating many diseases of the central nervous system. These include
Parkinson's disease,
Huntington's disease, Epilepsy, Alzheimer's disease and strokes. Many of these diseases
are neurodegenerative
disorders that are caused by groups of cells
either dying, or beginning to malfunction. These disorders are difficult
to treat because generally, once neurons die, the function they previously
performed is permanently lost. Because of this, treatments for these diseases
involve relieving symptoms of pain or discomfort, but cannot bring patients
back to the health of a normal individual.
Neural stem cells could provide a treatment
for these diseases that would allow patients to regain some of their lost
abilities. If neural stem cells could be implanted into the adult brain
and successfully differentiate into neurons, these new neurons would provide
the same inputs and outputs as the diseased neurons. In a sense the patient
relearns the lost abilities. As the neural stem cells make more connections
and become more and more integrated into the brain, the person will see
increased improvement in their skills (See the technical section on implantation).
The neural stem cells that are transplanted
into the brain are not the ones that are taken directly from embryo's. Instead,
the original embryonic stem cells need to be cultured so that there can
be more of them and so that they will grow into the right kind of tissue
(For more information on this see Cell Differentiation).
If the stem cell implantation treatment works
correctly, it almost seems like the stem cells fix the problem themselves.
They integrate themselves into the brain and differentiate into both neurons,
the cells in the nervous system responsible for thinking, and glial cells
which provide support for the neurons. If the stem cells work as planned,
they will also send out projections to the appropriate brain regions, in
the form of dendrites and axons. In making these connections, these new
neurons will have to "relearn" the old connections of patterns.
If they can replicate these old patterns they will be able to bring back
the functions that were lost.
However, research into clinical uses of neural
stem cells is a very young field. It may be necessary to discover some tricks
that help the stem cells develop into the proper type of cells. It is also
necessary to understand the disease that is being treated. The stem cells
cannot just be implanted anywhere into the brain: they have to be placed
in a specific area so they will develop into the right kind of neuron and
interact with the appropriate areas. Because of this limitation, diseases
whose actions are well understood and that act on a specific area of the
brain are the prime candidates for neural stem cell treatment.
I focus much of my discussion on The movement
disorders Huntington's disease and Parkinson's disease, because the stem
cell therapies are most promising for these diseases. I also present proposed
treatments for other diseases.
Italicized words take you to the Glossary