SMARTER STRATEGIES

Replacement Retina Fabricated from Embryonic Stem Cells

R. Colin Johnson | Date: 06-14-10 | Comments

Scientists have created the world's first human retina from embryonic stem cells, holding out the promise of restoring sight to millions of blind patients with transplant-ready living retinas.

Much has been made about artificial retinas restoring sight to the blind by establishing wireless communications between an eye-glasses-mounted video camera and semiconductors implanted inside a patient's eye. However, all those efforts could become obsolete before they get started as a result of researchers who recently created a new living retina out of embryonic stem cells.

University of California at Irvine (UCI) scientists recently revealed that they had successfully created a living retina aimed at curing blindness caused by the same maladies that the electronic implants are being designed to cure�retinitis pigmentosa and macular degeneration�but without inserting semiconductors inside the eye. Still in the experimental stages, these new living retinas could restore sight to 10 million Americans.

The living retina was constructed by painstakingly assembling eight layers of embryonic stem cells into a three-dimensional tissue structure remarkably similar to the architecture of natural retinas.

UCI researchers used human embryonic stem cells to create these retinal progenitor cells, which later developed into a three-dimensional tissue sheet for their living retina.

Constructed at the Stem Cell Research Center at UCI by project leader Hans Keirstead, the retina was preceded by spinal cord injury studies there. Those studies proved that stem cells are capable of being directed to differentiate into specific cell types. For the retina, it was necessary to create many different types of cells to duplicate the intricate construction of human retinas. The effect was realized by mimicking the early-stage development of natural retinas and using microscopic gradients of solutions, which coax the stem cells to initiate the correct differentiation path. The process, engineered by Dr. Gabriel Nistor, is the world's first to successfully demonstrate that such gradient solutions can be used to create complex multilayer tissues.

The human retina is the layer of the eye that senses incoming light and generates signals that pass down the optic nerve to the brain. Maladies like macular degeneration and retinitis pigmentosa are progressive eye disorders that render these cells useless without damaging the optic nerve. By substituting an early-stage retina for the original, the researchers hope to provide a new means of sensing light and passing the resulting information to the optic nerve. The researchers believe that, after a period of adjustment, the new retinas will grow into the tissues of the eye and provide the brain with information it can substitute for that missing from the original retina.

The next stage of the research will be to implant the newly minted early-stage retinas into animals to prove that they can successfully integrate and attach to existing optic nerves. If the transplanted retinas can be shown to improve the vision of blind mice, then the next stage will be clinical trials with blind humans.