In case of colour blindness or total blindness, the cones and/or rods (cells responsible for catching light rays present on the surface of the retina) are damaged. This gene therapy targets the cells in the deeper parts of the retina to capture the light instead of depending on the dysfunctional cones and rods. Leber congenital amaurosis, which is a rare form of inherited blindness, has been specifically targeted by this approach.

In this treatment, the human gene for rhodopsin (pigment used by rod cells to detect brightness) was injected into the cells of the blind mice in the study. The idea was to give the cells present on the deeper layers the ability to produce their own light detecting pigments so that they could compensate for the loss of the natural light receptor cells of the eyes. This injection was performed using vector DNA technique, where the DNA of virus was carrying the human gene coding for rhodopsin.

“The treated mice could discriminate black and white bars, but only ones that were 10 times thicker than what sighted mice could see,” says Lucas, of the University of Manchester, UK, co-leader of the team that developed and tested the treatment.

In earlier trials, the mice could only make out object shapes in very intense light. “Our mice could respond in ordinary light, the equivalent of looking at a computer monitor under ordinary office lighting,” says Lucas, presently.

The virus used as vector to inject the pigment into the mice’s cell is approved for human use too. So the possibilities of the human trial experiment is highly anticipated in the coming 3-5 years.

“This is the most effective example yet of the use of genetic therapy to treat advanced retinal degeneration,” says Robin Ali, whose team at University College London focuses on people with Leber congenital amaurosis.

But other scientists and Robert Ali are skeptical about the lasting effects of this treatment. There have been some speculation and observations about how the effects of gene therapy on people suffering from Leber congenital amaurosis might wane over time in the last one to three years.

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Author:Technology Blog