Cataract
surgery includes making large incisions in the front as well as the
back of the eye. The cloudy lens is then removed and replaced with a
clear, artificial one.The
standard surgical procedure with children with cataracts is cutting a
6-millimetre slit in the center of the lens capsule which results in the
loss of many LECs.(B) This form of surgery is very risky especially on
younger patients because the artificial lens does not grow as the child
grows. Future cataract surgery is in the horizon for the younger
patients. (Patients have known to get inflammation around the
incisions). (A)
Stem
cells in the science of research and medicine are known as revolutionary. The
Nature study conducted in China revealed that the use of activated stem cells
within the eye cured blindness in a dozen children where these stem cells were
able to grow a completely new lens. Stem cells have also been known to restore
damaged heart tissue and generate insulin-manufacturing cells in a
malfunctioning pancreas. Twenty million people worldwide are blind because of
cataracts (i.e. cloudy lenses). Although cataracts is common in older people
but newborns are at risk shortly after birth. (A)
Experiments
with rabbits and macaque monkeys study was specifically targeted on
their lens capsule. A lens capsule is where stem cells line part of the
eye that surrounds the lens itself. These lens epithelial stem cells
(aka:LECs) were frequently destroyed during conventional cataract
removal surgery. However, what the results from these earlier
experiments showed that if the lens were left intact they were able to
regenerate healthy lenses. (A) The scientists began a series of animal
studies to assess whether
lens epithelial stem/progenitor cells (LECs) that exist naturally in a
fully formed mammalian eye can produce a new lens. Encouraged by the
results, the team developed a surgical technique and tested it in
rabbits, macaque monkeys and, finally, 12 human infants.(B)
Twelve children under the age of two were chosen for a new type of
minimally-invasive cataract removal surgery based on these LECs.
Surgeons made 1.5 millimeter-long incisions in both their eyes, and the
cloudy lenses were removed as before. This time, care was taken to leave
the lens capsules and their LECs intact.(A) In the new method, surgeons slice a 1.5-millimetre opening in the
side of the lens capsule to remove the diseased lens, prompting the
eye’s LECs to grow a new one. In initial tests, this approach produced a
much lower rate of complications — 17% — than the 92% seen after
typical cataract surgery. And the lenses generated did not grow opaque
as artificial lenses tend to do. (B)
The
first
infant treated using the method underwent surgery two years ago and
still has good vision, says Zhang. He says that the regenerated lens
should grow as the child grows, which could reduce later
complications.(B) Within four weeks time the incisions were completely
healed. In three months the children had regrown fully operational
naturally grown lenses. By the eight month these children's sight was
completely restored as their new lenses fully grew back to the size of
their originally cloudy ones. (A)
Compared
to conventional cataract surgery the dozen children had clearer lenses,
noticeably less inflammation, and an incredibly shorter healing period.
The reason as to why this surgery was specifically aimed at children is
because their LECs are much more youthful and more likely to
successfully regenerate a new lens than an adult with LECs. Because of
the results from these experiments, new approaches are now far more
possible than ever before as we can now turn our own dormant stem cells.
powerful this could be if we can do it for heart attacks, or turn on
neuronal stem cells in the brain. (A)
Sight
has also been restored to rabbits from discs made of multiple types of
eye tissue that have been grown from human stem cells. Induced
pluripotent stem cells which are stem cells generated from adult cells
is the future in replacing corneal or lens tissue for human eyes. These
discs can also be used to study how eye tissue as well as congenital eye
diseases develop. (A) Another surgical procedure activates the body's
own stem cells to regenerate a clear functioning lens in the eyes of
babies who are born with cataracts. From Osaka University Graduate
School of Medicine in Japan, Kohii Nishida conducted the first study
with this form of surgical procedure. Nishida was able to cultivate
human iPS cells to produce discs that contained several types of eye
tissue. (B)
Nishida's
team noticed that the cells grew in distinct regions. Because of this,
it made it easier for the researchers to extract and purify specific
types of cells including those found in the cornea, retina, and lens.
They were able to remove cells from one region of the disc to grow
sheets of corneal epithelium. Then they were able to successfully
transplant into the defective corneas of rabbits. (B)
Although
there have been many studies where retina or cornea tissues were
produced using iPS cells, none have produced different types of eye
cells. Cells made from recipients own cells using the disc method could
one day supply tissue repair to damaged eyes without the threat of
rejection by the immune system. (B)
By contrast, the
cataract paper could have an almost immediate impact on treatment, says
James Funderburgh, a cell biologist at the University of Pittsburgh
School of Medicine in Pennsylvania. The technique described does not
involve culturing cells outside the body or transplanting material that
would require regulatory approval. The research was inspired by a
typical side effect of implanting artificial lenses to treat cataracts:
the new lenses often become cloudy as the recipient’s own cells grow
over them. A team led by ophthalmologists Khang Zhang of the University
of California, San Diego, and Yizhi Liu of Sun Yat-sen University in
Guangzhou, China, decided to find out whether this regrowth signalled
that the body is capable of regenerating an entire lens.(B)
But
there are still difficulties to be worked out. Babies born with
cataracts often have genetic mutations that will cause a new lens to
become cloudy again. And surgery alone may not work for elderly adults —
the people most likely to suffer from cataracts — because their cells
regenerate relatively slowly. (Even in babies treated with the method,
growing a new lens takes three months.)
Still, Funderburgh is enthusiastic about the technique. “Even if it’s only for kids, it’s fantastic,” he says.(B)
LINKS:
(A) http://www.iflscience.com/health-and-medicine/revolutionary-stem-cell-surgery-restores-sight-children-cataracts
(B)http://www.nature.com/news/sci-fi-eye-experiments-improve-vision-in-children-and-rabbits-1.19535
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