Stem cells used to grow light-sensitive retina in lab

Baltimore, MD-Using human stem cells, researchers at Johns Hopkins have created a three-dimensional complement of human retinal tissue with functioning photoreceptor cells.

Lead researcher M. Valeria Canto-Soler, PhD, cautions that photoreceptors are only part of the complex eye-brain process of vision, and the lab hasn’t recreated all of the functions of the human eye and its links to the visual cortex of the brain.

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“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,” says Canto-Soler, an assistant professor of ophthalmology at the Johns Hopkins University School of Medicine.

“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 says.

Researchers say they worked with human induced pluripotent stem cells (iPS, which could, in the future, allow for genetically engineered retinal cell transplants that halt or even reverse a patient’s march toward blindness.

Under the right circumstances, iPS cells 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.

Postdoctoral researcher Xiufeng Zhong, PhD, said that the growth of the retinal tissue in the lab corresponded in timing and duration to retinal development of a human fetus in the womb. Researchers tested the lab-grown retinal tissue by placing an electrode into a single photoreceptor cell and then giving a pulse of light to the cell, which reacted in a biochemical pattern similar to the behavior of photoreceptors in people exposed to light.

“We knew that a 3-D cellular structure was necessary if we wanted to reproduce functional characteristics of the retina, but when we began this work, we didn’t think stem cells would be able to build up a retina almost on their own. In our system, somehow the cells knew what to do,” says Canto-Soler.

Canto-Soler says that the system gives researchers the ability to generate hundreds of mini-retinas at a time directly from a person affected by a particular retinal disease such as retinitis pigmentosa. In the long term, the potential is also there to replace diseased or dead retinal tissue with lab-grown material to restore vision.