Regenerative medicine offers new hope for returning sight to those who are going blind due to retinitis pigmentosa (RP).
Retinitis pigmentosa or RP is a degenerative eye disease that slowly causes vision loss over a span of many years, eventually resulting in near or total blindness. Although current statistics are not available, it is generally estimated that the disorder affects roughly 1 in 4,000 people, both in the United States and worldwide. While relatively rare, for those that suffer from RP, there is little that can be done to avoid a slow but steady trek into darkness.
Such was the case of a 58-year-old man until a team of scientists restored useful sight by injecting “genetically engineered viruses” into his eyes. The man went from having no vision for the last two decades to being able to see small objects such as a notebook and a staple box with the help of light-stimulating goggles.
The breakthrough was described in a paper published in the journal Nature Medicine. The technique employed was one from the emerging science of regenerative medicine known as “optogenetics.” Optogenetic therapies to restore vision involve the use of modified genetic material to make new areas in the eye sensitive to light to replace those light-sensitive cells that have been damaged by diseases such as RP. In this case, scientists injected these genes into the man’s retina’s remaining functional ganglion cells, causing them to create the light-sensitive protein ChrimsonR.
Normally the rods and cones are photosensitive, but given that RP had essentially damaged and destroyed the patient’s rods and cones, the ganglion cells (that mainly focus on carrying electrical charges generated by those photoreceptive cells) would have to be modified. To do this, the researchers isolated a gene from a light-sensing species of green algae into one of the patient’s eyes.
Speaking to Forbes, David Birch, a retinal degeneration expert at the Retina Foundation of the Southwest in Dallas, said, “It’s exciting. It’s really good to see it working and getting some definite responses from patients.” Birch has conducted clinical trials of other optogenetic therapies but was not involved in this study.
This is the first reported case of partial functional recovery in a neurodegenerative disease after optogenetic therapy. However, this current study is a very preliminary start to this form of therapy. Before optogenetics can become a standard treatment for RP and other forms of degenerative blindness, further positive clinical trial findings are needed.
The lead researchers in this study stress that the therapy is not a cure for blindness. “For now, all we can say is that there is one patient … with a functional difference. It’s a milestone on the road to even better outcomes.”