Photoreceptors are cells in the retina which convert light into nerve impulses. Because of them, we can see the world around us. The two types of photoreceptors are rod cells and cone cells. Rod cells are responsible for peripheral and night vision, and cone cells are responsible for central and color vision under bright conditions.
Science has been looking at stem cells as a possible replacement for degenerated photoreceptors, but new research reported in the April 2020 issue of Nature has shown that rod cells can also be grown from skin cells, specifically, fibroblasts, the principal active cells of connective tissue. Researchers at the University of North Texas bathed fibroblasts of mice with a set of five small molecules to chemically induce the transformation of fibroblasts into rod photoreceptor-like cells.
The transplantation of these cells into the subretinal space of rod-degenerated mice led to partial restoration of the pupil reflex and visual function. Within a month, six of 14 (43%) showed a significant reaction to low light compared to none of the untreated mice. And at three months, further examination confirmed not only the survival of the new photoreceptors, but their growth of connections (synapses) to surrounding cells.
This is important research in view of the fact that it may allow scientists to bypass the use of stem cells in growing new photoreceptors, considerably shortening the wait for future clinical therapy of retinal diseases like macular degeneration, diabetic retinopathy, and retinitis pigmentosa.
Further research with animal models is necessary before applying the protocol to humans. This will be conducted by CIRC Therapeutics, a start-up company that plans to commercialize treatments using the technology.
SOURCE: Mahato, B., Kaya, K.D., Fan, Y. et al. Pharmacologic fibroblast reprogramming into photoreceptors restores vision. Nature (2020). https://doi.org/10.1038/s41586-020-2201-4