In both studies, the researchers converted human embryonic stem cells (hESCs) into retinal pigment epithelial (RPE) cells, which were then injected into the eyes of patients with dry AMD. The procedure was well-tolerated and one trial reported improved vision in some patients.
'There were no serious adverse events attributable to the transplanted RPE cells, including no tumour formation,' said Dr Ninel Gregori, leader of one of the trials based at the Bascom Palmer Eye Institute in Miami, Florida.
'These trials were not designed for efficacy and there's no control group, so you have to take this with a grain of salt – but there was increased visual improvement in the treated eye,' she added.
The second trial, by researchers in Israel, also found RPE cells derived from hESCs to be well-tolerated in patients. 'We're encouraged by the results thus far, but this is just a first step in the long road towards making regenerative cell therapy a reality in macular and retinal degeneration,' said Professor Eyal Banin, at the Hadassah-Hebrew University Medical Centre in Jerusalem, who led the study.
The exact cause of macular degeneration is unknown, but it involves the loss of RPE cells in part of the retina called the macula. These cells deliver nutrients and remove waste products from the light-sensitive rod and cone cells. Without RPE cells, the rods and cones in the macula gradually die and central vision – essential for tasks such as reading, driving and facial recognition – deteriorates.
AMD currently affects more than 600,000 people in the UK and is the leading cause of vision loss. Approximately 1 in 10 people over the age of 65 have some degree of AMD.
Experts in regenerative medicine believe that macular degeneration will be one of the first conditions treated with stem cell therapy. RPE cells grown in the laboratory are very similar to those found naturally in the eye, and can be easily grown in large numbers. Furthermore, the risk of immune rejection is relatively low, as the cells are injected into an immune-privileged area of the eye.
Results from both trials were presented at the American Academy of Ophthalmology's annual conference in New Orleans, Louisiana last week.