A dozen infants who were born with cataracts have regained their sight after scientists used a radical new stem cell therapy to regenerate healthy lenses in their eyes.
The children, all aged under two, are the first to receive the treatment for a condition that remains the most common cause of blindness in the world.
The small-scale trial on babies and toddlers was approved soon after tests in animals found that the approach should both work and produce better results than conventional surgery.
“The lens regenerated remarkably well,” said Kang Zhang who led the study at the Shiley Eye Institute at the University of California in San Diego. “We restored visual function and that implies that a clear lens has regenerated.”
Doctors will now monitor the children to see whether their eyes develop normally, or grow fresh cataracts, a possibility if the stem cells that regenerated the lenses carry genetic faults that cause the lens-clouding condition.
The feat was applauded by experts in the field, with Dusko Ilic, a stem cell scientist at King’s College London, calling the work “one of the finest achievements in the field of regenerative medicine.”
“They proved it first by testing a new surgical approach in rabbits and primates before successfully treating 12 infants with congenital cataracts. It is science at its best,” he added.
When children develop cataracts at birth or soon after, they can be treated by making a large incision at the front and back of the eye. The cloudy lens is then removed and replaced with a clear artificial one. But the surgery has a number of drawbacks. It can cause inflammation that complicates healing, and about half of the stem cells that protect the lens are destroyed in the process. A further problem is that the artificial lens cannot grow as the child does.
In a series of elegant experiments, Zhang showed that stem cells found around the lens, known as lens epithelial stem cells, or LECs, can regenerate healthy lenses if they are not damaged during surgery. In animals studies, he found that minimally invasive surgery, which removed the lens without destroying a surrounding structure called the lens capsule, preserved the stem cells and allowed them to grow and form a new lens.
To treat the children in the trial, surgeons made incisions no larger than 1.5mm in both of their eyes. They then removed the cloudy lenses, taking care to leave the lens capsules intact. The incisions healed in a month, and within three months, all of the children had regrown working lenses. When compared to 25 children who had conventional surgery, the dozen in the trial had clearer lenses, less inflammation and healed faster.
Zhang, who describes his latest work in Nature, now plans to investigate whether a similar treatment can work for adults with cataracts. While replacement lenses are highly effective in older people with cataracts, many need glasses for driving or reading after surgery. In the UK, the NHS carries out more than 300,000 cataract operations a year.
“This illustrates that there a can be a new approach. We can turn on own dormant stem cells. Just imagine how powerful this could be if we can do it for heart attacks, or turn on neuronal stem cells in the brain?” Zhang said.
Graham McGeown at Queen’s University, Belfast, said the work was a clear “proof of principle” for an important new treatment for cataracts in children. “This new approach dramatically reduced the risk of sight-damaging side effects when compared with the current best practice treatment, which involves more destructive surgery followed by implantation of an artificial lens,” he said. “It is unclear, however, whether this would be of benefit in adults with cataracts, for whom current surgical techniques are usually successful.”