NEW YORK (Reuters Health) Dec 17 – Cortically mediated vision was restored in pigmented dystrophic rats after cells were transplanted from a spontaneously immortalized human retinal pigment epithelial cell line, according to results of a study reported in the advance online publication of Nature Neuroscience for January.
Eight weeks after transplantation, Dr. Raymond D. Lund, of the University of Utah in Salt Lake City and associates found that transplanted rats performed significantly better on tests of head tracking to moving stripes than a control group of dystrophic rats that were sham-operated. Four rats that received transplanted tracked as well as a second control group of unoperated non-dystrophic rats (normal).
The transplanted animals also performed similarly to the normal controls and significantly better than the sham control animals on perception of vertical and horizontal stripes at spatial frequencies up to 0.23 cycle/degree, in which correct choices were rewarded with food and incorrect choices were punished with a loud noise.
Electrophysiologic testing at 7 months showed that the cortex of sham-operated dystrophic rats was unresponsive to visual stimulation. At the same age, transplant rats, although performing slightly less well overall than the normal animals, exhibited normal responses for such parameters as sharpness of orientation tuning, spatial frequency cut-off, and center-surround properties.
Histological analysis showed that donor cells were distributed on Bruch's membrane in maximum densities approximately half that of normal levels. "The finding that optimal functional rescue can be achieved with less than the normal complement of photoreceptors suggests a level of adaptability within the centripetal visual processing pathway," Dr. Lund and his associates write.
The investigative team suggests that immortalized human retinal pigment epithelial cell transplants may preserve vision in patients with retinitis pigmentosa and age-related macular degeneration.
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