Making eyes

时间:2019-03-07 01:16:05166网络整理admin

By Alison Motluk in Toronto IF YOU can’t get them, grow them. Faced with a shortage of fresh human corneas, scientists in Canada and the US have made their own. The artificial corneas can not only be used for research, but may also save millions of rabbits from cosmetic or medical tests. One day they may even help restore the sight of blind people. May Griffith of the University of Ottawa Eye Institute and Mitchell Watsky, now of the University of Tennessee in Memphis, were studying how the eye heals after being injured by splashes of chemicals. Since good quality corneas are always in demand for transplants, there were never enough fresh ones available. “In desperation, we decided to make our own,” says Griffith. The cornea is the eye’s transparent cover. It not only protects the pupil and iris from the elements, but also helps to focus images on the retina. Other groups have tried to recreate it, some using polymers, but none has been able to mimic the human model accurately. The human cornea is made up of three major cell layers and the researchers harvested cells from each of these layers from human corneas. They infected the cells with viruses that made them keep on dividing indefinitely, a process known as “immortalisation”. This provides a constant supply of a desired cell type. Then they tested each of these tissue types rigorously, to make sure they resembled human corneal tissue in structure, biochemistry and the way they conduct electrical signals. Griffith and Watsky used a synthetic scaffold, made of a mesh of collagen cross-linked with glutaraldehyde, to anchor the three separate corneal layers. Any unbound glutaraldehyde has to be removed with glycine, as glutaraldehyde is toxic. They placed cells on top, within and underneath the scaffolding. The researchers say that their fake corneas, which took five years to develop, resemble real ones in every important way. They even mimic human corneas in how cloudy they get when splashed with substances such as detergents, hair conditioners and cleaning solutions, says Griffith. The chemicals company Procter & Gamble has also taken an active part in the research and is already working out how to use the corneas to reduce animal testing. The University of Ottawa Eye Institute is encouraging Griffith to take the artificial cornea a step further and develop one that could be used for human transplant. “This might just be the solution we need to meet future demands and restore sight to many blind eyes,” says Bruce Jackson, the institute’s medical director. But Griffith says that there is still much work to be done, such as strengthening the scaffolding. “It’s not mechanically strong enough,” she says. “People can get poked in the eye accidentally.” Griffith chalks the success up to the optimism of new graduates. “We were postdocs,