By Guest Author Linnea Schmidt
PhD Candidate, Integrated Physiology, University of Colorado Denver, Anschutz Medical Campus
Imagine you are slowly losing your sight and there is nothing you can do to stop it. This is the unsettling reality for over 170 million people worldwide with degenerative retinal diseases. If you picture the eye as a camera, the retina is the film and is the part of the eye responsible for sensing light. When the retina degenerates, or dies, the film no longer can capture the entire scene.
Causes of Degenerative Retinal Diseases
There are many causes for this type of vision loss. The most common cause in people over age 55 is age-related macular degeneration. For these folks, the center of vision is no longer clear. This makes it hard to see faces or read. People with retinitis pigmentosa experience the opposite effect. They first lose their peripheral vision, making it hard to see anything they’re not looking at directly. They may not be able to see your outstretched hand going in for a handshake or the fire hydrant that they’re about to run into.
Stem Cells as a Cure for Blindness
Until recently, these patients had little hope of halting the degeneration of their vision or getting their sight back. However, recent scientific advances have heated up the race to find a cure. There are many exciting potential treatments currently being developed. In particular, stem cell treatments show a lot of promise. Doctors are now able to tell younger patients that a cure will likely be found in their lifetime.
Research on curing blindness focuses on two different types of stem cells: embryonic stem cells and induced pluripotent stem cells. Embryonic stem cells are like clay, they can be molded by their environment to become any type of cell in the body. Like a young child, they have an unlimited number of futures available to them. Induced pluripotent stem cells, on the other hand, are cells that have undergone the “butterfly effect.” They are cells that were “adults”- their environment had already molded them into a certain type of cell. However, scientists are able to turn back time for these cells so that when exposed to a different environment they can become a different type of cell than they previously were. The key for curing blindness lies in the ability of both embryonic stem cells and induced pluripotent stem to become retinal cells. The hope is that when these new retinal cells are injected into patient’s eyes, they will be able to sense light, the “film” of the eye will be fixed, and the patient will regain sight.
Patients and their loved ones are excited about the potential of stem cell therapy because when retinal cells made from either type of stem cell are injected into the eyes of mice, they are able to integrate into the mouse retina and respond to light. Hopefully, in humans, the same thing would occur, thus restoring or preserving their sight. The question now is if the different stem cell types will differ in their success as a therapy in humans. Currently, several clinical trials are underway using both embryonic and induced pluripotent stem cells. While it remains to be seen if stem cells prove to be safe and effective, patients now can hope for a future full of light.