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Age-Related Macular Degeneration Researchers Focused
on Factor H Gene
By Tucker Sutherland, editor
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Rando Allikmets |
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Aug. 5, 2005 In March, we reported in
SeniorJournal.com that researchers had discovered a variant of the
Factor H gene is involved in the development of age-related macular
degeneration (AMD), which is the leading cause of blindness in senior
citizens. A month later, another research group found that AMD does
occur when Factor H is triggered, possibly by an infection.
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The gene, known as Factor H, encodes a protein that
regulates immune defense against infection caused by bacteria and
viruses. People who have an inherited variation in this gene are less
able to control inflammation caused by these infections, which may spark
age-related macular degeneration (AMD) later in life, this study found.
"We now understand the genetic variation that is
behind age-related macular degeneration and are beginning to target the
trigger that sets the process in motion," said Rando Allikmets, Ph.D.,
Director of the Molecular Genetics Laboratory at Columbia University,
College of Physicians and Surgeons. "By targeting the molecules involved
in inflammation and its regulation we believe we can begin to develop
therapies and diagnostic tools that could help countless people keep
their sight."
The media has continued to closely follow the work
of Dr. Allikmets, although he admits it could still take years to find a
way to prevent vision loss from AMD in older people. The researchers
continue to conduct new studies based on their results to further
understand the triggers for this gene.
More than 50 million people worldwide are estimated
to have irreversible blindness as a result of macular degeneration,
making it the most common cause of blindness for those over 60. It's
estimated that 30 percent of the population will have some form of AMD
by the time they reach the age of seventy-five. The disease is marked by
a progressive loss of central vision due to degeneration of the
macula--a region of the retina and the area responsible for fine,
central vision.
"It has been always assumed that AMD must have
environmental triggers that turn on or aid the pathological process. Our
research suggests that the trigger is a specific inducer of the
alternative complement pathway, such as an infection, systemic disease,
a vaccination, or another unusual agent. Interestingly, countries where
the vaccination rate is highest also experience an elevated rate of
AMD," said Dr. Allikmets.
"This is an area for epidemiologists to study, but
as our research progresses we should eventually be in a position to
suggest treatment that could keep many people from going blind," he
said.
Potential therapies could involve delivering
healthy Factor H directly to the eye to short-circuit the disease
process; extracting stem cells from the eye so they could be
reengineered and re-implanted; or partial transplantation of the liver -
the body's main source for Factor H.
While it would seem that "anti-inflammatory" drugs
could mitigate the inflammatory onslaught, the researchers say most do
not work on this leg of the complement system.
The genetic pre-disposition to AMD exists in
approximately half of the Caucasian population. But not everyone who has
this genetic variant gets AMD, so what causes this mechanism to
activate?
"The variation in Factor H strengthens the immune
response, keeping infections under control early, but ironically that
may contribute to a chronic disease like AMD later in life." The
scientists were able to make this connection in large measure by
studying a rare form of kidney disease called MPGN II. Patients with
this condition often share the same kind of eye lesions as individuals
with AMD. And, in fact, a genetic determinant of the two diseases had
been previously linked to the same chromosome - chromosome 1. Thus,
Factor H was thought to be a prime suspect in both diseases.
The
Voice of America recently produced a video on the progress of the
research by Dr. Allikmets. There are links below to this video. It does
require Real Player on your computer, which can be downloaded free at
http://www.real.com/ (Note free version to right of screen).
View AMD report / Real Broadband - download 
View AMD report / Real Broadband
View AMD report / Real Dialup - download
View AMD report / Real Dialup
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