15 Nov Stem Cell Therapy for Macular Degeneration
Age-related Macular degeneration (AMD) is the leading cause of legal blindness in Americans over 65. AMD is characterized by the loss of photoreceptors cells that transmit light stimulus to the optical cortex. These photoreceptor cells rely on retinal pigmented epithelial (RPE) cells for nourishment and structural support. Thus, when RPE cells fail, loss of photoreceptors occurs, and vision deteriorates.
There are two distinct types of AMD, both of which result in the deterioration of the macula – wet and dry AMD. Wet AMD affects 10% of the patients, is more aggressive of the two, and is treated with anti-VEGF medication. However, there are no approved therapies for dry AMD.
There has been a lot of buzz about stem cell therapy for AMD. However, it is still in the experimental phase. CPBE-RPE1, a cell-based treatment for late-stage dry AMD is currently under study.
It has been shown that retinal pigment epithelium cells (RPE) can be regenerated from human embryonic cells. It is also possible to introduce a bioengineered synthetic cellular membrane that replaces the damaged Bruch’s membrane, on which the RPE rest.
Stem cell research is helping scientists understand how the different cell types in the retina function and how rods and cones can be replaced and connections established with the optic nerve. This is an extremely complex challenge. New RPE cells don’t need to connect with nerve fibers and can replace diseased RPE cells. If the stem cell transplant is done before rods and cones have degenerated, new RPE cells may be able to prevent that stopping the progression of the disease. RPE cells also help form uniform cell type from stem cells.
Various kinds of stem cells can be used to create these new RPE cells. Induced pluripotent stem cells (iPS), — tissue-specific cells or embryonic cells are being programmed to grow rods and cones or RPE cells. Other groups are using human embryonic stem cells grown from the adult RPE. In general, the less mature these transplanted stem cells are the more self-renewal properties and possibly more potential they have to integrate. Novel delivery systems are also being devised to transplant these stem cells into the eye. The key question is whether these cells will integrate well with the patient’s own RPE cells.
In a recent study performed at UCSB, researchers created a retinal patch from human embryonic stem cells. The RPE layer was placed on a synthetic patch that is implanted under the patient’s retina to replace the damaged cells. The stem cell-based eyepatches are being implanted in patients with severe vision loss caused by the wet AMD in a major trial in the UK as well.
More trials like these will need to take place to validate this novel approach. Its safety and efficacy has yet to be successfully proven, but stem cells may well be the potential cure for AMD-related blindness.