Researchers from the Johns Hopkins University in Maryland have successfully grown human retinas inside a laboratory to figure out how humans see colors.
The goal is to provide a better understanding of human biology, specifically how cells transform into specific types responsible for certain functions. This study focuses on the three-cone photoreceptors or the specialized cells that allow people to see red, blue, and green.
The study was published in the journal Science.
The research was quite special because previous studies on vision have used either mice or fishes. However, neither animal has the same color dynamics as humans. So, researchers from the Johns Hopkins University have taken a step forward and created a human retina using stem cells.
The first to grow, according to the study, were the blue-detecting cells, followed by red, then green. The stem cells took months to develop into a full-blown human retina inside their lab.
During the study, they found that the molecular switch that occurred was based on the level of the thyroid hormone, which is independent or not controlled by the thyroid gland. Instead, the thyroid hormone was completely controlled by the lab-grown eye.
This discovery allowed researchers to manipulate the development of the retinas, creating ones that could only see blue, red, or green. How the level of thyroid hormones affects the development of cone photoreceptors also explain why some pre-term babies are more prone to having vision difficulties.
"Our research is really trying to figure out what pathways these cells take to give us that special color vision," stated Robert Johnston, a developmental biologist at the Johns Hopkins University.
Leading To Better Treatment For Vision Disorders
The researchers hope that the study will pave the way to correcting eye-related disorders. The next step is to use organoids or organ-specific tissues cultured from stem cells to learn more about the mechanisms involved in color visions and other parts of the retina. In particular, they also want to grow a new macula in a lab that might lead to the treatment of macular degeneration in the future.
"If we can answer what leads a cell to its terminal fate, we are closer to being able to restore color vision for people who have damaged photoreceptors," added lead author Kiara Eldred.