Scientists at Johns Hopkins say they have used a type of human stem cell to create a three-dimensional complement of human retinal tissue in the laboratory, which reportedly includes functioning photoreceptor cells capable of responding to light. This represents the first step in the process of converting light into visual images.
“We have basically created a miniature human retina in a dish that not only has the architectural organization of the retina but also has the ability to sense light,” said study leader M. Valeria Canto-Soler, Ph.D., an assistant professor of ophthalmology at the Johns Hopkins University School of Medicine. She says the work (“Generation of three-dimensional retinal tissue with functional photoreceptors from human iPSCs”), reported online in Nature Communications, “advances opportunities for vision-saving research and may ultimately lead to technologies that restore vision in people with retinal diseases.”
Like many processes in the body, vision depends on many different types of cells working in concert, in this case to turn light into something that can be recognized by the brain as an image.
Dr. Canto-Soler noted that photoreceptors are only part of the story in the complex eye-brain process of vision, and her lab hasn’t yet recreated all of the functions of the human eye and its links to the visual cortex of the brain. “Is our lab retina capable of producing a visual signal that the brain can interpret into an image? Probably not, but this is a good start,” she said.
The achievement emerged from experiments with human induced pluripotent stem cells (hiPSC) and could, eventually, enable genetically engineered retinal cell transplants that halt or even reverse a patient’s march toward blindness, the researchers pointed out.
The hiPSC cells are adult cells that have been genetically reprogrammed to their most primitive state. Under the right circumstances, they can develop into most or all of the 200 cell types in the human body. In this case, the Johns Hopkins team turned them into retinal progenitor cells destined to form light-sensitive retinal tissue that lines the back of the eye.
Using a simple, straightforward technique they developed to foster the growth of the retinal progenitors, Dr. Canto-Soler and her team saw retinal cells and then tissue grow in their petri dishes, explained Xiufeng Zhong, Ph.D., a postdoctoral researcher in Dr. Canto-Soler’s lab. The growth, she said, corresponded in timing and duration to retinal development in a human fetus in the womb.
“We report that hiPSC can, in a highly autonomous manner, recapitulate spatiotemporally each of the main steps of retinal development observed in vivo and form three-dimensional retinal cups that contain all major retinal cell types arranged in their proper layers,” wrote the investigators. “Moreover, the photoreceptors in our hiPSC-derived retinal tissue achieve advanced maturation, showing the beginning of outer-segment disc formation and photosensitivity. This success brings us one step closer to the anticipated use of hiPSC for disease modeling and open possibilities for future therapies.”