Scientists from Johns Hopkins University have successfully grown human retina tissue from scratch in a lab. The work could help with the development of new therapeutics related to eye diseases. These lab-grown retinal cells won’t be used for transplants, however. Instead, they are being used by researchers to gain a better understanding of the way in which the color-detecting cells in the eye function.
“We believe that there are hundreds of different cell types in the human retina,” Robert Johnston, an assistant professor in the Department of Biology at Johns Hopkins, told Digital Trends. “What I wanted to do was to try to figure out more about the color-detecting cone cells.”
The retinas were grown from stem cells called retinal organoids. Growing organoids in a Petri dish in this way means that you do not have to directly study humans, and instead focus on model systems which function in the same way. Nonetheless, the growth process took place on the same timescale as human fetal development, meaning that anything that went wrong could have cost the researchers up to a year of patient waiting.
During the growth process, the retina’s blue-detecting cells were the first to grow. These were followed by the red-detecting cells, and finally the green-detecting ones. The researchers discovered that the release of thyroid hormone dictates whether cells become blue, red, or green detectors. The levels of this hormone are controlled by the eye tissue. Early on in the development of the retina, they hypothesize that thyroid hormone levels are low, since this is when blue cells are created. Later on, it gets higher to make the red and green cells. As a result, the team believes that children who are born with decreased thyroid hormone may be more prone to develop color blindness.
The work demonstrated that it is possible, through CRISPR gene editing, to make only blue or only red and green cells. The researchers hope to use this knowledge in the future to develop therapeutic applications that involve these color-detecting cells. In particular, they aim to use the scientific and technological breakthrough to help treat macular degeneration, the leading cause of vision loss.
A paper describing the research was recently published in the journal Science.