By Amy Norton
In an early study of infants born with cataracts, researchers used a minimally invasive approach to remove the eye's damaged lens -- while keeping the native stem cells intact. Stem cells are primitive cells that give rise to different types of mature tissue.
Those stem cells were then able to form a new lens, the researchers reported March 9 in the online edition of the journal Nature.
Experts cautioned that more research is needed to know whether the approach is better than the standard treatment for infantile cataract.
And it's not clear whether it could be used for the much more common type of cataract that affects older adults, said Dr. Ali Djalilian, a clinical spokesperson for the American Academy of Ophthalmology, who was not involved in the research.
"But are these findings interesting and exciting? Definitely," said Djalilian, who also directs the corneal epithelial biology and tissue engineering lab at the University of Illinois School of Medicine, in Chicago.
A cataract is a clouding of the eye's lens, usually caused when proteins in the lens start to clump together as a person ages. But it's also possible for infants to be born with a cataract in one or both eyes. About three out of every 10,000 children have cataracts, according to the American Association for Pediatric Ophthalmology and Strabismus.
Right now, doctors may perform surgery to remove a baby's cataract, but there is controversy about whether the lens should be replaced with an artificial lens -- which is standard for adults. The other options are contact lenses or glasses.
"There's a huge need for better treatments for congenital cataract," said researcher Dr. Kang Zhang, founding director of the Institute for Genomic Medicine at the University of California, San Diego.
Zhang said his team's approach -- tested in animals and 12 babies with congenital cataracts -- could offer a way to harness the body's own healing capacity.
The eye's lens contains so-called epithelial stem cells, which generate replacement lens cells throughout life -- though that declines with aging, according to Zhang.
During traditional cataract surgery, most of those stem cells are removed, Zhang explained. So, his team developed a less invasive approach that preserves the lens "capsule," a membrane that gives the lens its shape.
That essentially "left the bag intact," Zhang said, and the resident stem cells were able to regenerate a clear lens in all 12 babies over three months.
The investigators also reported less inflammation in the eyes and less lens clouding, compared with 25 babies who had standard cataract surgery.
Still, Djalilian said, the study followed the children for only a short time, and it's not clear what the long-term effects on vision will be.
One risk, he said, is that the cataract will come back in the new stem-cell-generated lens.
That is a possibility, Zhang agreed. He acknowledged that much more research is needed before the stem cell approach can become standard therapy.
Other researchers are trying to use stem cells to treat various eye diseases. In another study in the same issue of Nature, scientists reported that they were able to use human stem cells to generate several types of eye tissue.
The researchers then transplanted some of that tissue into rabbits blinded by damage to the cornea. Eventually, the transplanted tissue repaired the animals' eyes and restored their vision.
Zhang sees his team's approach as particularly promising because there is no transplanted tissue.
"Our work focuses on using stem cells that are right at the place of injury," he said, a fact that could avoid potential problems such as infection transmission or immune system rejection.
Zhang said he does plan to test the approach in treating age-related cataract -- a very common condition that affects more than half of Americans who live to age 80, according to the U.S. National Eye Institute.
Djalilian had some caveats, however.
The idea of trying the treatment on adults "isn't too far-fetched," he said. But, he also pointed out that regenerating a lens in a baby and regenerating one in a 70-year-old are two different things.
The "environment" of a baby's eye is designed for growth and development, Djalilian explained. With an older adult, he said, regenerating a lens would likely take more "manipulation," such as using proteins called growth factors.
Plus, even though there is room for improvement in age-related cataract treatment, Djalilian said, the current treatments are "usually quite successful."