Could scientists have found a cure for blindness?
Encouraging findings from a new "clinically significant" study suggest it's possible using embryonic stem cells.
Scientists in the US injected stem cells from human embryos into the eyes of 18 people, half of whom suffered from dry, age-related macular degeneration, and the other half from Stargardt's macular dystrophy.
Each participant had either 50 000, 100 000, or 150 000 retinal cells injected into the area just under the retina. They were then monitored for three years.
The results, published in the journal The Lancet, showed that 10 of them experienced substantial improvements in their ability to see.
There were no safety concerns, and none of them experienced negative side effects.
“About half of the patients had an improvement in visual acuity of three lines or more, which corresponds to a doubling of the visual angle, and is generally accepted as clinically significant,” said Robert Lanza, one of the main researchers involved in the study.
There are 500,000 sufferers of age-related macular degeneration in Britain, and there is currently no treatment available to prevent the inevitable loss of sight.
Should the stem cell therapy generate positive results in later stages of the clinical trial, these sufferers could all benefit from its introduction as a widely available treatment.
This finding marks the completion of the first phase of the clinical trial, the main aim of which was to assess the safety of the transplant. The eye is one of the sites in the body which does not produce a strong immune response when foreign cells are introduced, making it ideal for experimenting with embryonic stem cells.
"Embryonic stem cells have the potential to become any cell type in the body, but transplantation has often been complicated by problems including immune rejection" explained Lanza.
"Our results suggest the safety and promise of human embryonic stem cells to alter progressive vision loss in people with degenerative diseases and mark an exciting step towards using them as a safe source of cells for the treatment of various medical disorders requiring tissue repair or replacement,” said Steven Schwartz from the Jules Stein Eye Institute, co-author of the study.
The promise held by embryonic stem cells for the treatment of a large number of disorders is widely recognised.
Their ability to differentiate into any type of cell means they can generate replacement tissue for nearly all parts of the body, and it is this quality that led a group of scientists in the US to test whether they could bring sight back to patients suffering from progressive blindness.
However stem cells are not without controversy - some consider their use unethical because it requires the destruction of a human embryo.