[access-uk] FW: vip-l: Article: Scientists Regenerate Optic Nerve for the First Time
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- Date: Fri, 25 Mar 2005 14:24:05 -0000
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From: Christo [mailto:orrick@xxxxxxxxxx]
Sent: Friday, March 25, 2005 12:29 PM
To: monique hofschneider
Subject: Fw: vip-l: Article: Scientists Regenerate Optic Nerve for the First
Time
Scientists Regenerate Optic Nerve for the First Time
BOSTON, Mar. 7 -- For the first time, scientists have regenerated a damaged
optic nerve -- the nerve that connects the eye to the brain. This
achievement, which occurred in laboratory mice and is described in the March
1, 2005 issue of the Journal of Cell Science, holds great promise for
victims of diseases that destroy the optic nerve and for sufferers of
central nervous system injuries. "For us, this is a dream becoming reality,"
says Dr. Dong Feng Chen, lead author of the study, assistant scientist at
Schepens Eye Research Institute and an assistant professor of ophthalmology
at Harvard Medical School. "This is the closest science has come to
regenerating so many nerve fibers over a long distance to reach their
targets and to repair a nerve previously considered irreparably damaged."
This research, supported in part by grants from the National Institutes of
Health, the Department of Defense and the Massachusetts Lions Club, has
always been a priority of the institute, but recently the urgency around it
has increased, according to Dr. Michael Gilmore, director of research at
Schepens Eye Research Institute and professor of ophthalmology at Harvard
Medical School. In addition to the thousands of Americans blinded by
glaucoma and injuries that destroy the optic nerve, "We were hearing stories
of soldiers in the Middle East whose lives were saved by body armor, but who
were returning with severe damage to limbs and eyes," he says. "At the same
time, we learned of the untimely death of Christopher Reeve. It was,
therefore, a priority for us to redouble our efforts to find ways to restore
damaged nerves."
Many tissues in the body continually renew themselves if injured. However,
this is not true for nerve cells or their fibers (axons) in the Central
Nervous System (CNS). The optic nerve, which is part of the CNS, loses this
ability shortly before birth. So for those afflicted by glaucoma, which
destroys the optic nerve through excessive internal pressure, or those with
injuries that sever the optic nerve after birth, destruction can be
permanent and blinding.
Chen and her research team dedicated themselves to learning the reasons why
CNS tissue stops regenerating and to finding ways to reverse that process,
using the optic nerve as their research model. The optic nerve consists of
millions of nerve cells which transmit visual information from the retina to
the brain for interpretation. In earlier research, Chen's team discovered
several processes that they believed "locked up" the optic nerve's ability
to regenerate. The first lock, they found, was the turning off of a specific
gene - BCL-2 - which, when turned on, activates growth and regeneration. The
second lock, they theorized, was a scar on the brain created shortly after
birth by "glial" cells. (Glial cells have many functions in the brain, one
of which is to create this kind of scar tissue). The researchers believed
that the scar puts up a physical as well as molecular barrier to
regeneration. Athough there may be other "locks" to the regeneration door,
Chen and her colleagues believed these two were the most important. In the
current research, Dr. Kin-Sang Cho, research associate in Chen's laboratory
and the first author of the paper, tested two keys to unlock regeneration.
The first key involved the development of a mouse model in which the BCL-2
gene is always turned on (or is overexpressing). The second key was the use
of a mouse line carrying mutations of "glial specific genes" that lead to
the reduced "glial scar" formation. By unlocking the regeneration with the
first key, they observed robust optic nerve regeneration in postnatal mice,
whose nerves grew rapidly and reached from the eye to the brain in four
days. But the regeneration happens only in the younger mice whose brains had
not yet formed a "glial scar." In the mice that were slightly older and had
developed the "glial scar," regeneration failed again. Dr. Cho then added
the second key by combining BCL-2 overexpresser with the "glial gene"
mutation to prevent the development of the "glial scar" in the older
transgenic mice. He found that the combination of the turned-on BCL-2 and
the mutation of "glial specific genes" caused the optic nerves to return to
an embryonic state and stimulated rapid, robust regeneration of the optic
nerve within only a few days.
"We could see that at least 40 percent of the optic nerve had been
restored," says Chen. "But we believe that an even higher percentage
actually regenerated."
The next step for Chen and her colleagues is to determine if the regenerated
optic nerves were functional. In other words, did they cause the mice to see
again?
To obtain a copy of the study, "Reestablishing the Regenerative Potential of
the Central Nervous System Axons in Postnatal Mice," e-mail Patti Jacobs at:
pjacobs12@xxxxxxxxxxxx
Updated: 3/10/2005 3:30:26 AM
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