Human Retinas Grown in a Dish Reveal How Color Vision Develops

Statistics have it that 1 in 12 men and 1 in every 200 women worldwide suffer color vision deficiency (CVD) — cause by a faulty retina. Now, imagine walking into a clinic with a colorblind retina and coming out with a lab-grown color sensitive retina fitted on you to replace the faulty one. That sounds easy like replacing a car part, right?

Well, that’s where we are headed to. As in, scientists have been growing a human retina behind the scenes, from scratch, and the organ looks 100% like the natural retina. However, for now, the new retina is being used to study how cells that allow humans to see in color are made.

Why is this Super Important?

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The study lays a foundation to help researchers discover better therapies for eye diseases including CVD and macular degeneration. Top on that it could also assist in developing better lab-created “organoids,” which are a key component in the study of human development right from the cellular level. The work will soon be appearing in the journal Science.

“It’s hard to believe but what we see growing in our dish looks exactly like a normal developing eye,” said Robert Johnston senior researcher and developmental biologist, Johns Hopkins University. In other words, we now have a complete model system of the retina, which we can manipulate at the lab without necessary studying humans directly.

The Focus

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Using this model, one of the Johnston’s researchers interest has also been studying how and what determines the fate of cells. And what goes on in the womb that turns growing cells into specific cells to fit and serve at different regions of the body—one of the most unclear processes in human biology.

Nonetheless, the team is made of key scientists who are focused on exploring cells that allow people to see specific colors such as blue, red and green – representing the three cone photoreceptors found in our eyes.

The Lab Created Eye

Most vision research use mice and fish as a model to represent the human eyes. However, the two species do not have the dynamic daytime exposure and color vision we enjoy as humans. Trichromatic color vision separates us from other mammals. So the team decided to create the exact resemblance of a human eye, using stem cells.

Kiara Eldred, a graduate student of Johns Hopkins pointed out that “Our research intends to figure out the exact pathways cells take to offer us a unique color vision that is different from other animals.

As the retina grew, the team discovered that the cells which detect color blue, materialized first, then the red-detecting cells and finally the green. Now, the interesting of all findings was that the ebb and amount of thyroid hormone happen to be the molecular switch that decides the destiny of cells in the body. Top on that, the level of this hormone is controlled by the eye itself and not by thyroids gland –something that really gives lab research a leg up.

Correcting Damaged Photoreceptors

With the knowledge of how the thyroid hormone levels decided what cells turned blue, red or green, the scientists could alter the outcomes by manipulating the thyroid flow. So they came up with retinas that could only see blue, red or green, that is if they were fitted on the human eye.

These possibilities offer a great recipe that could help create red-green cones, while on the other hand offers a hint to how pre-term babies struggle with sight – linking it to the low amount of thyroid hormone from maternal supply and the increased incidences of vision complications.

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