A Canadian-led research team has created the first laboratory-grown human corneas, prompting excitement that the tissue could replace some chemical testing on animals' eyes and marking a major step toward one day developing artificial corneas for transplant.
"They show the same function as a real human cornea," said lead researcher May Griffith of the University of Ottawa. Griffith said she tried growing corneas from human eye cells when she couldn't find enough donated corneas to perform important medical research.
The cornea is a window into the eye, a transparent protective covering that also focuses light to the proper spot for vision. Some 40,000 corneal transplants are performed each year in the United States using corneas donated at death, enabling people whose corneas became damaged or clouded to see again.
But there are barely enough donations to fill that need, leaving little for researchers to use in studying eye diseases. The short supply also means manufacturers often must test the toxicity of chemicals and medications on animals, usually rabbits' eyes, prompting protests from animal-rights activists.
Previous attempts to grow human corneas have failed. But Griffith's success, to be reported in Friday's edition of the journal Science, "is very encouraging," said Dr. Terrence O'Brien, director of refractive surgery at Johns Hopkins University's Wilmer Eye Institute. "This brings us to a new level" in eye research.
It is only a first step toward one day developing a supply of artificial corneas to have on hand for eye surgery, he stressed; that will take years of additional research.
Instead, the artificial cornea's first use probably will be for medical research. Manufacturers are studying whether the corneas could be mass-produced and properly respond to toxicity testing, in hopes that they could replace some animal testing.
Griffith culled each of the cell types that make up a cornea's different layers from a handful of healthy donated corneas, and painstakingly grew each layer in a lab dish. In about two weeks, the cells grew into clear, round disks that looked like real corneas and further chemical, genetic and physiological testing showed they function like real ones, Griffith reported.
But they are not as strong as real corneas, so they wouldn't protect the eye as well, Griffith said. She is working to correct that.