By Ron P. Gallemore, M.D., Ph.D.
Stem cells are the building blocks of the body. All the tissues of the body—the heart, lung, brain and even the eye—can be made from the same stem cell. Because stem cells have the potential to create any cell type, they can be used to cure any inherited disease. In the case of most retinal diseases such as macular degeneration and retinitis pigmentosa, the main cells damaged are the photoreceptors—the cells that convert light to an electrical signal that is sent to the brain, where the image we see is created. The latest research and how we are beginning to treat blinding diseases with stem cell therapy are is exciting and encouraging.
Stem cells are undifferentiated cells that have the potential to become any cell in the body. When they are placed in the tissue they need to repair, the surrounding cells release signals that direct the stem cells to develop into the correct cell type. In the case of the retina, placing a stem cell in the deep layers of the retina leads to the creation of photoreceptors, as the surrounding cells release the right factors to produce this cell type.
An impediment to stem cell research has been the need for fetal tissue, where stem cells are normally found. There remain significant social and political barriers to the use of fetal tissue. Fortunately, recent discoveries show that adults also carry stem cells. A bone marrow biopsy is a common means for collecting stem cells. More recent studies have shown that stem cells are also found in circulating blood, and blood donation alone is adequate for collecting stem cells in some cases! In addition, stem cells collected in adults from the “limbus”—the tissue next to the cornea at the front of the eye—have now been used to grow cells for corneal transplantation as well as to grow photoreceptor cells for retinal transplantation!
A number of blinding diseases have now been treated with stem cell research. Neuronal ceroid lipofuscinoses (NCLs) are a common cause of brain damage and blindness in children. A mouse model of the disorder, mouse neuronal degeneration (MND), was treated with transplantation of stem cells into the retina by simply injecting the cells into the eyeball. The cells migrated into the retina and made connections that allowed the retina to function when it was normally destroyed. Traumatic retinal injury has also been treated in a rat model of retinal damage by using a similar approach. Closer to humans, a mouse model of retinitis pigmentosa and macular degeneration has been successfully treated with stem cells derived from human bone marrow. Recently, stem cells have been used to treat an adult patient with retinitis pigmentosa for the first time, and we are awaiting the follow-up results of this study.
Blinding eye diseases have now been treated in animal models, and new treatment strategies have been developed for human conditions including retinitis pigmentosa, macular degeneration, diabetic retinopathy, corneal disorders and glaucoma. Clinical trials are in development. Your eye doctor may refer you for appropriate evaluation in a clinical study and help you or your family member affected by these disorders get the best possible care now and in the future.
For more information, please contact Dr. Ron P. Gallemore, M.D., Ph.D., Director and Founder, Retina Macula Institute, 4201 Torrance Blvd., Ste. 220, Torrance, CA 90503, (310) 944-9393.
About Dr. Gallemore
Ron P. Gallemore, M.D., Ph.D., practices as an ophthalmologist at Retina Macula Institute in Torrance, California. He graduated from the University of California, San Francisco, with a certification from the American Board of Ophthalmology and earned a Vitreoretinal Surgery Fellowship from Duke University Medical Center. Dr. Gallemore maintains affiliations with numerous hospitals throughout the greater Los Angeles metropolitan area.