An international team of researchers successfully put human retinal cells in primates’ eyes, forging a new path for surgical blindness treatments.
(CN) — The retinal cells from a human cadaver’s eye were successfully transplanted into the eyes of euthanized primates, an important step in perfecting surgical interventions to fight blindness, according to new medical research published Thursday.
The scientists, whose report was published in the journal Stem Cell Reports, focused their efforts on cells from the retinal pigment epithelium, or RPE, the colored region just outside the retina that transports nutrients to the retina and takes waste products away from it.
Most people who permanently lose their sight over the age of 60 can attribute their blindness to macular degeneration, one of several disorders that can occur when the RPE fails to function properly. Macular degeneration affects about 200 million people across the world.
“We have demonstrated human cadaver donor-derived RPE at least partially replaces function in the macula of a non-human primate,” said Timothy Blenkinsop, the study’s co-lead investigator and a cellular biologist at New York City’s Icahn School of Medicine at Mount Sinai, in a statement. “Human cadaver donor-derived cells can be safely transplanted underneath the retina and replace host function, and therefore may be a promising source for rescuing vision in patients with retina diseases.”
To see how adult RPEs might be repaired, the researchers took stem cells from the donated eyes of human cadavers. The cadavers’ RPE cells were transplanted under the macula of non-human primates — nine crab-eating macaques, four males and five females between 4 and 4 years old, who were sourced from Singapore’s SingHealth Experimental Medicine Center for the study.
For one week before the experiments and through their duration, the monkeys received systemic immunosuppression as an independent veterinarian monitored the macaques for dangerous body weight loss, decrease in appetite and other behavioral abnormalities.
The animals were anesthetized, the surgery was completed and the researchers euthanized the macaques with perfusion fixation, a method that protected their biological tissue from decaying while the scientists examined the transplanted retinal cells. The scientists write that their procedures were approved by the SingHealth Animal Care and Use Committee and carried out in accordance with procedures described by the Association for Research in Vision and Ophthalmology.
The scientists concluded that the portions of the RPE transplanted from human cadavers remained stable and were not attacked by the macaques’ immune system for at least three months — the duration of the experiments.
Additionally, they say that the RPE segments derived from human stem cells were able to partially take over the original RPE areas’ functions, for instance by healthily supporting the endogenous photoreceptors whose decay contributes to vision loss.
The findings suggest that human adult cadaver eyes could provide a source of transplant stem cells for treating macular degeneration in living humans.
“The results of this study suggest human adult donor RPE is safe to transplant, strengthening the argument for human clinical trials for treating retina disease,” Blenkinsop said in the statement.
The researchers note that further research on these methods are necessary and future experiments should study retinal degeneration in non-human primates over a longer time period, and consider whether cadaver-derived stem cells can restore vision in human patients or diseased primates’ eyes.
The study was a collaboration between Mount Sinai researchers as well as scientists from the Institute of Molecular and Cell Biology at Singapore’s Agency of Science, Technology and Research and the National University of Singapore. Scientists at the Singapore Eye Research Institute and Germany’s Knappschaft Hospital Saar also contributed to the paper.