Retinitis pigmentosa is the leading cause of blindness worldwide, but scientists from the University of Manchester have discovered how to cure mice with the disease by transforming cells that can’t sense light into those that can.
Retinitis pigmentosa, which affects around 1.5 million people worldwide, involves the breakdown and loss of the cells in the eye used to detect light and color—rods and cones. The rest of the cells necessary for vision are still intact, but the very first cells you need to see are gone, causing blindness.
Most research on the disease focuses on prevention or repairing the damaged cells, but this study took a unique approach—it skipped over the lost cells and went straight for the next ones in line. These cells are known as ganglion and bipolar cells, and are responsible for processing the signals given off by the “seeing” cells when they’re functional.
That is, until the researchers turned them into seeing cells themselves. Rods use a pigment known as rhodopsin to sense light, and by using viruses, they were able to insert the gene that produces rhodopsin into the non-seeing ganglion and bipolar cells. (This is a technique known as gene therapy.)
When this happened, the previously blind mice regained several aspects of vision. They could distinguish light from dark and flickering from steady light, and when shown a movie of a swooping owl, they ran away.
Limitations and human trials
“You could say they were trying to escape, but we don’t know for sure,” said Rob Lucas, co-leader of the team that developed and tested the treatment, to New Scientist. “What we can say is that they react to the owl in the same way as sighted mice, whereas the untreated mice didn’t do anything.”
Only sensitivity to light was restored (color vision requires different pigments than rhodopsin), and the restoration was somewhat limited: “The treated mice could discriminate black and white bars, but only ones that were 10 times thicker than what sighted mice could see,” said Lucas.
However, according to researcher Robin Ali of the University College London, this is the most effective use of a gene therapy in this disease to date. Further, the virus used to deliver the rhodopsin is already approved for use in humans; Lukas hopes human trials can begin in a few years.
The paper can be found in Current Biology.
(Image credit: zhouxuan12345678 / Flickr Creative Commons)
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