Researchers at the University of California Irvine have made strides in growing retina tissue from embryonic stem cells. This marks a new step in the complexity of tissue that has been successfully created using stem cells.
The retina is the inner lining of the eye that is critical for sight. When light enters the eye, it lands on the retina where special light-receptor cells convert the light into electrical energy. This energy is sent through the optic nerve to the brain where it is translated into vision. When portions of the retina stop working, the result is partial or complete blindness. Retinitis pigmentosa and macular degeneration are just two of the many conditions that limit sight by damaging the retina. Macular degeneration effects over 10 million Americans and is the leading cause of blindness in people over age 55.
Study leader Hans Keirstead of the Reeve-Irvine Research Center and the Sue and Bill Gross Stem Cell Research Center at UCI said, “This is a major advance in our quest to treat retinal disease.” This same group of researchers also participated in the development of a stem cell based therapy for severe spinal cord injuries that is currently undergoing clinical trials.
Stem cells are unique in human development because they are building blocks that can grow into many different types of cells. Stem cells themselves are unspecialized, meaning they don’t have the particular structure to perform a job in the body, such as muscles cells or nerve cells. But stem cells have the ability to replicate themselves many times, and to differentiate or change into specialized types of cells.
Scientists have learned that the key to getting stem cells to differentiate into specialized cells is turning on or off certain genes in the cells. One complication in creating retinal tissue using stem cells is the complexity of the eye. The cells in the eye that allow for vision are not all identical to each other. Variations in these cells allow for differences is seeing “the big picture” as opposed to close up detail, and in seeing color in bright light and shades of gray in dim light.
The Keirstead team at UCI developed a technique using microscopic gradients or differences in the solution they applied to the stem cells to get them to differentiate in slightly different ways. The result is an early version of retinal tissue that is being tested in animals to try to improve poor vision that is the result of damage to the retina. If the animal trials are successful, research will progress to include human trials that may one day result in the ability to create transplantable retinas that could improve vision for millions of people.