Eye Disorders - Treatment Using Various Stem Cells - Printable Version
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Eye Disorders - Treatment Using Various Stem Cells - nihila - 10-03-2012
Visual impairment and blindness are the major health problems presently. The most common reason for eye disorders is age-related retinal degeneration. As there is lack of effective treatment for degenerative retinal diseases, stem cell-based therapy can provide a promising approach in restoring and sustaining retinal function and prevent blindness, thus holding great hope for many people. Stem cell therapy holds great promise for the treatment of retinal diseases. The source of stem cells for a particular therapy is a major issue. Not all stem cell types can be induced to differentiate into cell types needed for treatment. It is encouraging that a number of different sources and types of stem cells and precursor cells have been identified from which relevant cell types for ocular stem cell therapy can be derived. These include fetal stem cells, cells from brain, limbus, conjunctiva, corneal endothelium, and retina.
Researchers have identified, stem cells of central nervous system in a single layer called the retinal pigment epithelium, or RPE, which lies behind the retina and which may provide a way to repair the damage from age-related macular degeneration, or AMD, the leading cause of vision loss in people over 60. Researchers say, cell types generated from the stem cells can be used for testing drugs for AMD and other eye diseases, but the ultimate goal would be to regenerate eye tissue destroyed by AMD so sight could be restored. Tests have suggested that the cells are stable and do not appear to cause tumors, a potential danger inherent in some types of stem cells. More studies are needed to determine whether the cells can restore lost vision or not.
An American Retinal Surgeon has treated 7 patients with a new technique for administrating adult stem cells for eye disease. Adult Stem Cells are stem cells are typically obtained from the bone marrow of the patients itself, where there is a high concentration of specific types of stem cells found to be useful for many diseases. At times they are obtained from the blood directly. The patients range from 2 years to 87 years and suffered from a variety of eye diseases including AMD or Age Related Macular Degeneration, Myopic Macular Degeneration, Bulls Eye Retinopathy- a type of hereditary retinal disease, Retinitis Pigmentosa, and Optic Nerve Disease. Previously the stem cells were injected behind the eye to treat ophthalmic problems but the exact location and how far they might be from the targeted retinal or optic nerve tissue was not always known but now with the new technique the stem cells can be placed precisely adjacent to the eye in a very safe manner.
Embryonic stem cell therapy used to treat degenerative form of blindness has showed no signs of any adverse effects. Embryonic stem cells are extraordinarily versatile cells that are found in early-stages of embryos that can differentiate into any tissue of the body. Scientists have been trying using them as a replacement for tissue lost through disease or lost in accidents or war. Advanced Cell Technology (ACT) Inc. has conducted experiments to treat eye diseases using embryonic stem cells. Around 50,000 embryonic stem cells that diversified into replacement cells for the pigmented layer of the retina were transplanted into two blind volunteers one with dry age-related macular degeneration, the leading cause of blindness in the developed world, the other who had Stargardt's macular dystrophy, the commonest form of vision loss among young people. For six weeks, the patients received treatment to prevent their immune systems from attacking the implanted cells. In the first four months, no signs of cancer, rejection or other safety concerns emerged and both patients recovered a little vision.
Although results achieved on applying stem cell technology to treat eye disease has a shown good results more work is required. The main issues that require focus are identification of the optimal precursor cell types, establishment of growth and differentiation conditions that meet safety and effectiveness standards, and the manipulating surrounding environment to allow transplanted cells to survive and function. Transplanted neuronal precursors can connect into the inner plexiform layer and optic nerve head. But directing their axons to appropriate targets is yet to be explained. A substantial progress in this aspect and other areas is needed to be achieved.