Light-sensitive cells found in the retina have been grown from mouse embryonic stem cells (ESCs) and successfully transplanted into the eyes of visually impaired mice, restoring some vision.
Although the technique as it currently stands would be unsuitable for use in humans, the development suggests that ESCs could one day provide a supply of these cells, called photoreceptors, to treat some forms of blindness.
The research builds on a previous study where immature retina cells were transplanted from the eyes of young mice to restore vision in visually impaired older animals. The new technique removes the need for the donor eye, with the ESCs providing a renewable source of cells.
Although he also cautioned: 'it certainly isn't a case of rolling out treatments in five years' time and providing therapies. It's taken us ten years to get here and it'll take us five years to get started in people'.
Many eye disorders arise from the irreversible loss of photoreceptors in the retina – the sheet of cells sitting at the back of the eye - including age-related macular degeneration, the most common cause of blindness in elderly people.
In the study, researchers first grew ESCs in the laboratory to create a synthetic retina. They were then able to take the light-sensitive photoreceptor cells from this retina and inject them into the eyes of night-blind mice. The mice were tested in a water maze in low light conditions and those with the injected photoreceptor cells preformed better than those without.
The photoreceptor cells were engineered to express a fluorescent protein and after three weeks scientists saw that the photoreceptors were integrating into the mice's retinas and maturing to become fully functional. The cells were still present six weeks after transplantation.
Experts were quick to praise the development. Dr Rob Buckle, director of the UK Regenerative Medicine Platform, who was not involved in the study, said: 'This study is an important milestone on the road to developing a widely available cell therapy for blindness as it proves unequivocally that embryonic stem cells can provide a renewable source of photoreceptors that could be used in treatments'.
Professor Chris Mason, chair of regenerative medicine bioprocessing at UCL, added a note of caution: 'Before human clinical trials can commence, the mouse model will require significant optimisation, for example increasing the efficiency of new photoreceptors to connect with the damaged retina'.
'However', he added, 'there is no doubt that this is a breakthrough'.