Photoreceptor transplant raises hope for Vision regain

In a stunning piece of research that may one day help blind people to see, British and American scientists have achieved success in restoring vision in blind mice by transplanting light-sensitive cells into their eyes.

The study was conducted on mice who suffered from eye damage called photoreceptor loss. The transplantation of retinal cells extracted from newborns into the eyes of blind mice showed signs of regained vision.

The interesting aspect of the study was that, unlike previous studies, instead of using stem cells, which develop to form into any cell type, the scientists transplanted cells which had reached a later stage of development and were surely to develop into photoreceptor cells.

Photoreceptor cells are specialized type of neurons found in the eye's retina that are capable of phototransduction. These are light sensitive cells that line the back of the eye and are essential for sight.

There are two types of photoreceptor cells in the eye namely, rods and cones. Once the rod and cone photoreceptors in a retina are lost, they cannot be replaced.

It is the breakdown of these photoreceptors which leads to diseases like retinitis pigmentosa and age related macular degeneration.
While treatments to prevent or delay the loss of these cells are underway, scientists are also seeking to help those already affected.

Under the transplantation, scientists at the Institutes of Ophthalmology and Child Health and Moorfield's Eye Hospital, London, and the University of Michigan Medical School in the United States took stem cells from the eyes of baby mice and injected them into adult mouse retinas.

These cells were extracted from three to five-day-old mice at various stages when photoreceptors are normally being generated.

Clinical examination found that cells produced within a few days after birth generated most new photoreceptors. Tests also revealed that after transplantation they connected to the retina correctly and thus helped in detecting light.

Meanwhile, mimicking similar results in humans will be possible within a decade, claim researchers.

As cells for transplantation in humans have to be extracted from fetuses in the first or second trimester of pregnancy, it would be difficult to obtain.

However, researchers are hopeful that they may soon be able to grow the correct retinal cells from adult stem cells or embryonic stem cells in the lab.