Researchers have grown human retinal cells in the laboratories and thus attempted to understand the basis of color vision and its development in humans. The results showed that certain hormones are essential for the development of color vision in humans and were published in the latest issue of the journal Science.
Researchers at the Johns Hopkins University believe that a deeper understanding of color vision among humans could help in devising treatment for color blindness and also macular degeneration. Development of color vision was difficult to study as it occurs in the fetus while it is still within the uterus. The two scientists conducting this research overcame this hurdle by creating retinal cells grown in the labs. These were termed “retinal organoids”.
First author of the study, graduate student at Hopkins Kiara Eldred said that these retinal organoids were difficult to grow and sustain and it took nearly a year before the organoids were fully functional. Robert Johnston, assistant professor in the biology department and part of this study said that these clusters of immature retinal cells slowly developed into a 3D structure and it started acting like a “developing retina that you would see in a baby.” Johnston explained that they needed human retinal cell organoids for this study since lab animals or mice could not see colors and thus were not appropriate study subjects.
The clusters of embryonic retinal cells along with some pluripotent cells were allowed to grow, Johnston explained. Pluripotent cells are stem cells that can be coaxed to become any cell of the body. Certain growth factors were added to allow the growth of the cells. Johnston said that the organoids took 9 months to develop just like a fetus would within the womb.
It is known that thyroid hormone plays a role in development of the vision. The researchers then added thyroid hormone to the petri dishes carrying immature retinal cells. They noted that the organoids developed more red-green cones when the hormone was added. The future of this research, Johnston says it to find how and why the hormone works as it does. He added that they plan to understand why some cones become specialized to detect only red while some detect only green.
The team hopes that clearer understanding of development of color vision could help in development of treatment for color blindness. Johnston says that gene therapy and its potential in treatment of color blindness would be studied next.
The team is also looking at the causes and possible management of macular degeneration that leads to blindness in thousands of individuals. He explained that mice do not have a macula which is a region of the retina that can provide clear high resolution vision to humans. Macular degeneration damages this region of the retina. Up until now it has been difficult to study macular degeneration in the labs he said. With these retinal and macular organoids they could not study macular degeneration, its possible pathology and probable treatment.