Researchers at the University of Alberta recently discovered that stem cells in zebrafish repair damaged rod and cone photoreceptors in the retina.
Rods enable humans to see at night while cones enable the perception of colour during the daytime. The retina is the light-sensitive layer of tissue at the back of the inner eye. It converts light and images into electrical signals and sends them to the brain.
If the cones get damaged, human daytime vision cannot be restored.
Led by U of A biological sciences researcher Ted Allison, the team of geneticists is studying the zebrafish to learn if human stem cells can be instructed to replace damaged cones in the retina.
“(Zebrafish) have a lot of cones for the receptors in the retina, because they use a lot of daytime vision and they are able to repair their retina,” Allison said.
“There must be some kind of genetic switches that are being turned on and off that make that happen and we are hard on the trail of figuring out what some of those are.”
Zebrafish are tropical freshwater fish that belong to the family of Cyprinidae. They are popular aquarium fish, often called zebra danio. Adult fish can grow to a length of 6.4 centimetres (2.5 inches).
Zebrafish are best known for the five pigmented, horizontal, blue stripes that run on the side of their body, reminiscent of the stripes on a zebra. Male fish have gold stripes between the blue stripes, while the females have silver stripes.
Allison said stem cell therapy is already used for other diseases such as Parkinson’s disease. Researchers at the University of Alberta are also examining the genetics of zebrafish to understand Alzheimer’s disease.
“I’ve been working on different fishes for a while but zebrafish became an equivalent to a lab rat or a fruit fly… internationally a lot of labs are using them for biomedical research now,” he said.
To date, most studies focused on regenerating rods, not cones. Researchers were able to restore vision in mice, nocturnal rodents who need more rods than cones in their retina for good night-vision.
Allison said it will take a few more years until his team is able to identify the gene in the fish that’s responsible for repairing damaged cones. After that he expects it will be at least a decade until it can be tried on human DNA.
The research was funded by the Natural Sciences and Engineering Council of Canada and was published in PLoS ONE journal.
