Scientists for the first time have grown human corneas in a laboratory, a major step that could help replace controversial chemical testing on animals� eyes and perhaps one day even develop a supply of artificial corneas for patients who need eye surgery.

�They show the same function as a real human cornea� in laboratory tests, said lead researcher May Griffith of the University of Ottawa, who reports her discovery in the Journal of Science.

�This is a fundamentally new approach,� added toxicologist Rosemarie Osborne of Procter and Gamble, which helped fund Griffith�s work.

The discovery 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.

But it is only a first step toward possibly developing artificial corneas usable for human transplants, warned O�Brien and corneal expert Lore Ann McNicol of the National Institutes of Health. �It would be nice to have a tissue you could just pull out of the icebox and use� instead of searching donor banks for each eye surgery, McNicol said. �This is a very useful step toward that,� but many years of additional research are needed before lab-grown corneas could ever be used in people, she said.

Instead, the new cornea�s first use will be for medical research, in better understanding eye disease and in testing chemicals. �Maybe you could greatly reduce the numbers of animals used in eye-safety testing, O�Brien said.

In a quest to do that, Procter and Gamble, a frequent target of animal rights protests, has teamed up with competitor Unilever to figure how to mass-produce the corneas and prove they respond to toxicity testing just as rabbits� eyes do today, Griffith said. Proving the corneas� usefulness will take a few years, Osborne cautioned.

To grow the tissue, Griffith obtained a handful of healthy corneas and culled each of a cornea�s cell types from them. She inserted into the corneal cells genes from a virus that kept the cells growing indefinitely. Then she and University of Tennessee physiology expert Mitchell Watsky tested whether they still functioned like healthy eye cells.

The next step: Corneas are mostly collagen, so Griffith put each layer of cornea cells on a kind of tiny collagen �scaffolding,� first building them with a human cornea�s three main layers but then growing them with all five layers. Sitting in a special tissue culture that kept the cells moist just as tears moisten eyes, the cells took about two weeks to grow into clear, round disks.

But looking like a real cornea isn�t enough. An additional battery of test tube studies found the cornea�s endothelial cells pumped water out of eye tissue properly--they even clouded up like real corneas when exposed to certain chemicals. Still, the new corneas are not as strong as real ones, so they wouldn�t protect the eye well, and researchers are not certain whether the virus used to multiply the corneal cells is harmful or how long the corneas will last.