Age-related macular degeneration has a fairly direct relationship to the accumulation of a mix of metabolic wastes called lipofuscin in long-lived retinal cells. There are other contributing causes, but that is an important one. Cell repair mechanisms are impacted, cells falter and die as a result and are not replaced, and progressive blindness follows the consequent retinal damage. Here researchers show that the overall process of degeneration can be significantly slowed via a stem cell therapy, though it is unclear as to how it affects lipofuscin accumulation versus other mechanisms:
Age-related macular degeneration occurs when the small central portion of the retina, known as the macula, deteriorates. The retina is the light-sensing nerve tissue at the back of the eye. Macular degeneration may also be caused by environmental factors, aging and a genetic predisposition. When animal models with macular degeneration were injected with induced neural progenitor stem cells, which derive from the more commonly known induced pluripotent stem cells, healthy cells began to migrate around the retina and formed a protective layer. This protective layer prevented ongoing degeneration of the vital retinal cells responsible for vision. "This is the first study to show preservation of vision after a single injection of adult-derived human cells into a rat model with age-related macular degeneration." The stem cell injection resulted in 130 days of preserved vision in laboratory rats, which roughly equates to 16 years in humans.
Researchers first converted adult human skin cells into powerful induced pluripotent stem cells (iPSC), which can be expanded indefinitely and then made into any cell of the human body. In this study, these induced pluripotent stem cells were then directed toward a neural progenitor cell fate, known as induced neural progenitor stem cells, or iNPCs. "These induced neural progenitor stem cells are a novel source of adult-derived cells which should have powerful effects on slowing down vision loss associated with macular degeneration. Though additional pre-clinical data is needed, our institute is close to a time when we can offer adult stem cells as a promising source for personalized therapies for this and other human diseases." Next steps include testing the efficacy and safety of the stem cell injection in preclinical animal studies to provide information for applying for an investigational new drug. From there, clinical trials will be designed to test potential benefit in patients with later-stage age-related macular degeneration.