It's not quite Avatar, but a movie released today shows, in three dimensions, how a chaotic patch of cells grows into the beginnings of an eyeball. Even more impressive, this protoeye was grown in a laboratory dish. Scientists say the finding brings them closer to growing entire organs in the lab, including eyes that could replace those damaged by injury or disease.
In the past decade, researchers have made dramatic progress in understanding how eyes form. They have learned how to turn on and off essential genes and how to transform embryonic stem cells into retinal cells, which can be transplanted into mice to restore vision. But so far, growing an entire eyeball in the lab has eluded scientists, largely because they've been unable to recreate the "optic cup," a chalice-shaped structure that becomes the back of the eye.
Now Yoshiki Sasai of the RIKEN Center for Developmental Biology in Kobe, Japan, and his colleagues have induced embryonic mouse stem cells to spontaneously form the optic cup in a dish. The key ingredient was a mixture of jellylike proteins, called Matrigel, which forms an enticing bed on which stem cells seem to prefer to lie before turning into the eye's various structures.
In the movie, the cells—made to glow green—push out before inverting and forming two different layers: the first, the retinal cells, and the second, the neurons. This is the first demonstration that stem cells direct their own development in the eye, the team reports online today in Nature.
Knowing that stem cells can direct their own development is key if we want to grow organs without having to also grow the tissues that usually develop around them, says developmental biologist Jane Sowden of University College London, who was not involved in the study. She says that even though Sasai's team hasn't yet grown an entire eyeball in a dish, the work shows that it's possible to grow specific eye structures, such as retinas, from stem cells in a great enough quantity that they could be used in therapy. If the researchers can get the technique to work with human stem cells, she says, it could help the one in 3000 people born with a form of blindness caused by damaged retinal cells and the many more who lose their sight because of age-related disease.