Gene Therapy Treatment Reverses Vision Loss

(Photo: Petr Novák, Wikipedia)

Scientists at the University of Pennsylvania may have found a way to prevent, and even reverse, a serious inherited eye disease which leads to blindness.

The disease, called X-linked Retinitis Pigmentosa (XLRP),  causes early, severe and progressive vision loss.

It is one of the most common inherited forms of retinal degeneration in people.

Peoples with XLRP experience a gradual decline in their vision as  the eye’s photoreceptor cells die off.

At first, XLRP usually impacts the ability to see in dimly-lit areas.  Later, sufferers notice a reduction in their visual field,  a sort of  “tunnel vision,” as though they’re looking at things through a narrow tunnel.

Over the years, as the disease advances, the ability to see in even normally-lit conditions, or day vision, progressively dies, leading to complete blindness.

A scene as it might be viewed by a person with retinitis pigmentosa. (Photo: National Eye Institute, National Institutes of Health)

The University of Pennsylvania research was conducted on dogs.

However, the scientists say there are enough similarities between humans and dogs – in terms of eye anatomy, physiology and disease characteristics – that the positive results with gene therapy raise hope of developing similar therapies for humans.

Past research shows XLRP is caused by defects in the RPGR gene.  Scientists discovered a region on the X chromosome, where the RPGR gene is located, which tends to be very susceptible to damage.

Consequently, when there is a replication of cells in a part of the RPGR gene called ORF-15, that replication can be faulty, producing a mutated gene.

To correct or repair the mutated gene, the researchers developed a therapeutic version of it, which is actually a healthy human RPGR gene.

Using a viral vector, a common tool scientists use to deliver genetic material into individual cells which can specifically deliver the therapeutic gene to only the diseased or damaged cells, the researchers were able to repair, not only the damaged photoreceptor cells, but also the connectors which send signals from the photoreceptors to the brain.

Dr. Gustavo D. Aguirre (left) and Dr. William A. Beltran (right) (Photo: University of Pennsylvania School of Veterinary Medicine)

The researchers call the results of this treatment “dramatic.”

In dogs that already had the disease, scientists   were able to stop the retinal degeneration completely. The previously-damaged cells were able to function normally and scientists were able to prevent XLRP altogether if the retina was treated before the disease had a chance to develop.

The findings of the team’s research were recently published in the journal Proceedings of the National Academy of Sciences.

Dr. Gustavo Aguirre, senior author of the study and the paper’s lead author, Dr. William Beltran,  both of the University Of Pennsylvania School Of Veterinary Medicine, join us this weekend on the radio edition of “Science World.”

They’ll talk about how their findings could help those suffering from X-Linked Retinitis Pigmentosa. Tune in (see right column for scheduled times) or check out the interview below.

Other stories we cover on the “Science World” radio program this week include:

• Dependability of Russian space program questioned
• Different blood pressure readings in each arm could signal trouble ahead
• Ancient amber sample shows ages-old natural alliance between fungi and modern forests
• IBM reveals its latest technology predictions
• World’s poor may soon benefit from mobile phone apps