Embryonic stem cells (ES cells) have been used to generate a basic retina, the part of the eye that detects light and is needed for vision. The retinal tissue could be used to treat some forms of blindness, such as retinitis pigmentosa and age-related macular degeneration, and to investigate and screen potential new drugs for a range of eye diseases.
Japanese scientists grew mouse ES cells and stimulated them to develop into retinal cells, using a protein gel to support three-dimensional growth. Clusters of cells began to spontaneously form structures resembling an early stage of eye development, known as the optic vesicle. Mimicking the processes that normally occur during eye development in the embryo, the structures then folded inward and took the shape of the optic cup, a structure found at a later stage in eye development.
The cells in the inner layer of the optic cup developed into primordial retinal cells - which would normally go on to become the light-sensitive cells in the mature eye - and the outer layer cells developed into retinal support cells, reported Dr Yoshiki Sasai and colleagues at the RIKEN Center for Developmental Biology in Kobe. They hope that this technique will eventually yield cells for transplantation to treat blindness.
'In terms of regenerative medicine, we have to go beyond mouse cells. We have to make human retinal tissue from human embryonic stem cells and investigation is under way', Dr Sasai said. 'We hope that such transplantation may recover vision, at least to some partial extent, in patients who lost their eyesight'.
'I never thought I'd see the day where you have recapitulation of development in a dish', said Professor Robin Ali from the University College London Institute of Ophthalmology, who was not involved in the study. 'This is the first time anyone has been able to make a complex structure from embryonic stem cells'.
In 2006 Professor Ali and colleagues successfully transplanted retinal cells from newborn mice into adult mice, where they integrated into the adult eye and developed into functioning, light-sensitive cells. 'One big challenge with our approach is where do you get your cells from? This work shows it might be possible to grow sheets of cells to use in transplants', Professor Ali said.
The Japanese study, published in the journal Nature, showed that embryonic stem cells intrinsically possess the ability to self-organise and form intricate structures, given the right cues. 'This is just the tip of the iceberg. Hopefully it's the beginning of an important new phase of stem-cell research', said Dr Robert Lanza, chief scientific officer at the biotechnology company Advanced Cell Technology, which is currently beginning clinical trials of a stem cell treatment for blindness.