Inside the human eye, the retina is made up of several types of cells, including the light-sensing photoreceptors that initiate the cascade of events that lead to vision. Damage to the photoreceptors, either through degenerative disease or injury, leads to permanent vision impairment or blindness.

David Gamm, director of UW–Madison’s McPherson Eye Research Institute and professor of ophthalmology and visual sciences, says that stem cell replacement therapy using lab-grown photoreceptors is a promising strategy to combat retinal disease. The challenge is that stem cell treatments aimed at replacing photoreceptors need to first be tested in animals. Since human cells are not compatible in other species and are quickly rejected when transplanted, it’s difficult to assess their potential.

Pig and human retinas share many key features, making pigs ideal for modeling human retinal disease and testing ocular therapeutics. By testing ‘human-equivalent’ photoreceptors in pigs, we can get a better sense of what these cells can do if they are not immediately attacked by the host animal.