Harvard Medical School have managed to restore partial vision and balance in mice born
with a genetic disease that affects both.
The new model exceeds the length of the barrier to the hair cells, sensors in the ear that
captures the sound and movement of the head and becomes the auditory nerve and the
balance of the signal. These cells have been very difficult to treat with gene-entrega
technical advance.
The results of the team, which was published in the February issue of molecular therapy,
suggesting that the treatment leads to remarkable progress in the public and allows that
your rat tend to be completely deaf to hear the equivalent of a powerful conversation. This
approach also increases the balance of flavor.
The same themes appeared in the commentary accompanying the study.
The attention of researchers approach is used in humans, but brought the promise of gene
therapy to restore hearing in people with various forms of genetic and acquired deafness.
Approximately 30 million Americans suffer from hearing loss and every year about one in
1000 babies are born with hearing loss, according to the Center for control and prevention.
In its effort to restore hearing through gene therapy, scientists have been looking for
ways to improve the delivery of genes in the cells of the hair. Anterior approach only
slightly effective because they reached a set of hair cells in the inner ear, but equally
critical convincing subset of others remain largely impenetrable.
"To treat most forms of hearing loss, we need to find a delivery mechanism that works for
all types of hair cells," says Neurobiology David Corey, lead researcher and author
Professor of translational medicine at HMS Bertarelli of the study.
To achieve this, the researchers used a general adeno-associated virus (AAV). The virus has
been used as a delivery vehicle for the disruption of the gene of the retina but so far has
proved to be much more effective in penetrating the hair cells.
Loading super AAV as the carrier of the genes in the inner ear, the team used a form of the
virus is wrapped in a protective bubble called exosomes, approaches developed by other
researchers studying Casey Maguire, HMS Assistant Professor of Neurology at mass General
and Xandra Breakefield, a Professor of Neurology at the HMS public masses.
Maguire and his colleagues grew the virus in AAV ordinary cells. cells naturally yellow
exosomes small bubbles made of virus carriers of cell membranes. Wrap the membrane of
viruses with proteins that bind to cell receptor., said Maguire, may be the reason why this
form of bubbles wrapped AAV, or exo-AAV, join more easily the surface of the hair cells and
penetrate more efficiently...
"Unlike current approaches in the field, not to alter or modify the virus directly. On the
other hand, gave us a vehicle to travel, the better able to navigate the area in the inner
ear and access to previously resistant cells, "said Maguire, who is also a co-author of the
study.
Experiment laboratory at the source, exo-AAV penetrated successfully 50-60 per cent of the
ciliated cells, the researchers said. On the other hand, a single AAV is only 20% of the
hair cells.
To test the approach in a live animal, the researchers worked with mice born without a gene
that is essential for cell function. These animals usually not the strongest voice is heard
and shows poor balance.
Researchers Ali György and wise Cyrille, first author of the study, injection of exo AAV
loaded with a gene that is lost in the inner ear of offspring of mouse, shortly after
birth.
After treatment, the tests showed that the gene was introduced between 30 and 70 per cent
of the hair cells, the cells to achieve inner and outer hair.
One month after treatment, nine of the 12 rats have some hearing level is reset and can be
hit by a strong slap, conduct of spectators test standards. Four could hear the intensity
of the sound of the 70 and 80 decibels, the equivalent of a rude conversation in a noisy
restaurant.
Because the hair cells are also fundamental to a sense of balance, a mouse with hair cells
are damaged or are missing shows abnormalities of the balance. Treated rats has been
mainly to improve the balance, compared with their counterparts who were not treated,
offers much less head or walking in a circle, the second marker of instability or disorientation.
The team now plans to improve the techniques of gene delivery in efforts to achieve a
higher proportion of hair cells. Scientists will test the approach in other forms of
deafness, including conditions that cause deafness and blindness.
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