Restoring visual function in animals is an important advance, but the scientists caution that it shouldn't be considered the same as restoring vision in humans. The next wave of research will focus on characterizing the mechanisms that generate photoreceptor precursors from stem cells. Swaroop believes the research has potential for developing therapies for people with retinal and macular degenerative diseases that are untreatable today.
The Swaroop research team started to develop its approach to transplantation about six years ago.
"Rather than focusing on stem cells," says Swaroop, "we believed that if we could understand how cells develop and become photoreceptors--or any other specific neuron--our transplantation efforts would meet with greater success. This technique gives us new insights in repairing damage to the retina and possibly other parts of the central nervous system."
Drs. Ali, Swaroop and their colleagues report that the transplanted cells in diseased mouse retinas have met several essential requirements: the cells survive; correctly develop into rod photoreceptors; integrate and connect in sufficient numbers to neurons that ultimately carry visual signals to the brain; and they have proven to be functional.
The photoreceptor precursors were transplanted into three different types of mice with retinal degeneration caused by distinct genetic defects involving malfunctioning or degenerating rods. The transplanted cells survived and were functional for the duration of the study. Scientists observed improvements including pupil response to light and response to light stimuli from ganglion cells, which form the circuitry to the brain.
Swaroop explains that photoreceptors constitute "the first line of information capture in vision." They are part of a complex sensory system
Source:University of Michigan Health System