Scientists: Zebrafish Holds Answer to Restoring Vision in Humans

A team of biologists at University of Alberta, Canada, has discovered that zebrafish’s stem cells can selectively regenerate damaged photoreceptor cells.

Zebrafish. The inset shows zebrafish cone photoreceptor mosaic: it consists of a precise reiterated arrangement of cone spectral sensitivity subtypes, extending in rows radiating toward the periphery of the retina, the micrograph demonstrates the positions of the UV- and blue-sensitive cones, shown in pseudocolored magenta and blue respectively, and the nuclei of green- and red-sensitive cones forming rows in between, shown in grey (Fraser B et al)

“For some time geneticists have known that unlike humans, stem cells in zebrafish can replace damaged cells involved in many components of eyesight. Rods and cones are the most important photoreceptors. In humans, rods provide us with night vision while cones give us a full color look at the world during the day-time,” said study leader Dr Ted Allison, who with colleagues reported the findings in the open-access journal PLoS-ONE.

“What was not known was whether stem cells could be instructed to only replace the cones in its retina. This could have important implications for human eyesight.”

“This is the first time in an animal research model that stem cells have only repaired damaged cones,” Dr Allison explained. “For people with damaged eyesight repairing the cones is most important because it would restore daytime color vision.”

To date almost all success in regenerating photoreceptor cells has been limited to rods not cones. Most of these previous experiments were conducted on nocturnal rodents, animals that require good night vision so they have far more rods than cones.

“This shows us that when cones die in a cone-rich retina, it is primarily cones that regenerate. This suggests the tissue environment provides cues to instruct stem cell how to react,” Dr Allison said.

This shows some hope for stem cell therapy that could regenerate damaged cones in people, especially in the cone-rich regions of the retina that provide daytime color vision.

The next step for the team is to identify the particular gene in zebrafish gene that activates repair of damaged cones.

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Bibliographic information: Fraser B et al. 2013. Regeneration of Cone Photoreceptors when Cell Ablation Is Primarily Restricted to a Particular Cone Subtype. PLoS ONE 8(1): e55410; doi: 10.1371/journal.pone.0055410