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HOPE OF BLINDNESS CURE

(This story reprinted from BBC ONLINE, (c) 2001 The British

Broadcasting Corporation. Reprinted with permission)

Scientists have developed a technique which they hope will restore sight

to people left blinded by retinal damage. A team in Japan has announced

that they have successfully grown the light-sensitive receptors, or rods,

that make up the eye's retina, from the iris of rats.

Although the research is at an early stage, it is already

being suggested the technique may be transferred to human beings. If that

could be achieved, rods could be grown from a blind patient's own iris and

then transplanted into the eye, ensuring the new tissue would not be rejected.

However, the new research, which is being conducted at Kyoto University,

still has some way to go, as the scientists have yet to transplants the

rods back into the eyes of blind rats. At present, there is no treatment

for retinal damage in humans, which can be caused by degenerative diseases

or by looking directly at the sun. This can result in permanent blindness,

because retina cells, once damaged, do not grow back.

Coloured diaphragm

The Kyoto team extracted cells from the iris, the coloured

muscular diaphragm at the front of the eye that controls the amount of light

entering the eye. These cells are not sensitive to light. Then, in the laboratory,

they modified them so that they became light-sensitive, and thus potentially

could be transplanted into the retina. The retina is the light-sensitive

membrane at the back of the eye made up of cells that, when stimulated by

light, trigger messages along the optic nerve, which are then interpreted

as visual images by the brain.

The cells were made light sensitive by adding a gene known

as CRX that is normally found in the mature retina. Once the gene was added

to the cells, they began to produced a light-sensitive protein called rhodopsin,

which is also found in the retina.

Although a cure for blindness is still a long way off, the

scientists are encouraged by the fact that iris and retina cells share similar

developmental characteristics.

The research is published in the journal NATURE NEUROSCIENCE.

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