A cornea that's got some nerve.

Scientists have developed a technique to grow corneal tissue that includes nerve cells, an advance that may enable researchers to test consumer products in lab dishes rather than in live animals.

Previously, scientists had created tissues that in many respects mimic the human cornea, says Rosemarie Osborne, a cell biologist with Procter & Gamble in Cincinnati. When exposed to chemicals for extended periods, those substitutes become cloudy and inflamed and show other signs of irritation, just as human corneas do. However, because those tissues lacked nerve cells, researchers couldn't monitor cellular activity associated with pain. Also, corneal tissue without nerves doesn't heal as quickly as a wounded human cornea does.

Now, by carefully controlling the chemical environment in their petri dishes, Osborne and her colleagues have added nerve cells to their cornea recipe. Those cells spread their fibers through the tissue in a pattern similar to the one found in natural corneas, she notes. The nerve fibers respond to stimuli, carry electrical signals, and release nerve-signaling chemicals. The innervated tissues also heal as quickly as corneas do, she notes.

Osborne says that the team's new tissue-making technique might also lead the way to lab-grown corneas suitable for human transplants.--S.P.