Stem cell implant improves dry macular degeneration

A stem cell implant appears to be safe, suggest the results of a clinical trial for the dry form of age-related macular degeneration (AMD). 

In dry AMD, a layer of cells beneath the retina that provide light-sensing cells in the eye with nutrients begin to thin. Eventually, the light-sensing cells can die and lead to partial blindness. 

In a study published in Science Translational Medicine, researchers grew a layer of embryonic stem cells on an ultra-thin membrane to replace the lost cells beneath the retina. The stem cell layer was implanted under the retina of four patients at an advanced stage of the condition. 

Dr Amir Kashani from University of Southern California's Roski Eye Institute, lead author of the study, said he did not expect an improvement in vision due to the patients advanced stages of disease. 'But after surgery, one patient could read 17 more letters on an eye chart than before surgery,' he told Wired. 

In follows-ups completed up to 12 months after the procedure, no further vision loss was reported. In one case, the implant improved the patient's vision within four months of surgery. 

The study was small and did not include control subjects, which would confirm statistical and clinical relevance. However, the results mark a huge step towards finding a cure for dry AMD, the most common cause of blindness in the UK. Nearly 200 million people worldwide are expected to suffer from a form of AMD by 2020, according to the US non-profit organisation, the BrightFocus Foundation. 

The trial is now being extended to study 20 patients over a five-year period to test the effectiveness of the implant. The research team has hopes that the implant will be more effective in restoring vision for people in earlier stages of the disease. 

The trial follows the success of a similar recent stem cell treatment for the wet version of AMD (see BioNews 943).