Eye in cross-section:
1 - sclera; 2 - ciliary body; 3 - iris; 4 - pupil, and anterior chamber filled with aqueous humour; 5 - optical axis; 6 - line of sight; 7 - cornea; 8 - crystalline lens; 9 - choroidea; 10 - nervus opticus; 11 - optic disc; 12 - fovea; 13 - retina; 14 - corpus vitreum
Image by MesserWoland, July 14, 2006
For the first time, researchers have been able to grow three-dimensional human tissues starting with stem cells. Hans Keirstead and his team from the University of California, Irvine have successfully used embryonic stem cells to create early-stage retinas.
Retinas form the light-sensitive inner part of the eye and are critical for vision. They are composed of many layers of different cell types, including photoreceptor cells and support cells. Functional retinas must not only include the right kinds of cells, but those cells must also be oriented in exactly the right way relative to each other. In order to achieve this engineering feat, the researchers developed microscopic gradients of solutions to coax cells into differentiating into mature cell types in precisely the right order and position.
Loss of vision due to retinal diseases affects millions of Americans each year. The scientists are optimistically testing their stem-cell retinas in animal models to see if they can restore vision.
As Keirstead says:
What's so exciting with our discovery is that creating transplantable retinas from stem cells could help millions of people, and we are well on the way.