Eye transplants to cure blindness are a step closer after Japanese scientists managed to "grow" a retina in the laboratory for the first time.
Researchers were amazed when stem cells in a test tube organised themselves spontaneously into a complex structure that resembled the developing embryonic eye. The development could lead to whole retinas being cultured and then transplanted, restoring sight in the blind and visually impaired.
The team from the Institute of Physical and Chemical Research in Japan first cultivated embryonic stem cells in a test tube and then added proteins to trigger their development. They hoped that they would form a recognisable organ but were stunned when over 10 days they clustered together and began to grow the "optical cup" of a retina.
Tests showed that the cells were functioning normally and were capable of communicating with each other. The research was done on the eyes of mice, but there is no reason why a similar technique would not work on humans, said experts.
They hope within 10 years to be able to start clinical trials on retina implants.
"This is an absolutely stunning achievement," said Professor Robin Ali, an ophthalmologist at University College London.
"It is a landmark not just for the retina but for regenerative medicine as a whole." More than a million people in Britain suffer from vision problems caused by damaged or malfunctioning retinas.
The retina is the part of the eye where nerve cells convert light into electrical and chemical signals that are sent to the brain down the optic nerve.
If it is not working then the eye is useless.
Professor Yoshiki Sasai, the lead author of the study, said: "What we've been able to do in this study is resolve a nearly century-old problem in embryology by showing that retinal precursors have the inherent ability to give rise to the complex structure of the optic cup."
His team, who filmed the technique as it unfolded, grew floating clusters of the mouse cells in a special tissue culture in the laboratory that had previously been successfully used to make a variety of brain cells.
By adding particular proteins they were able to encourage the cells to build a three-dimensional layered structure reminiscent of the optic cup within 10 days. The retinal neurons ultimately organised into a six-layer structure closely resembling that of a retina shortly after birth.
Prof Ali, who reviewed the research, published in 'Nature', said: "For the first time, we see unfolding in real time the beautiful events that shape the early stages of mammalian eye development. But even more remarkable is that these are not recordings from live animals, but of self-organising 3D cultures of embryonic stem cells." (© Daily Telegraph, London)