Eyeworld

I SEPTEMBER 2020 | EYEWORLD | 37 Stem cell replacement therapies for the eye by Liz Hillman Editorial Co-Director At a glance • Stem cell-derived therapies for corneal and retinal conditions are in clinical trials in the U.S. • A replacement cell therapy using stem cell-derived eye tissues could be useful when the patient's own eye cells are damaged or dead. • Researchers are looking at cultivated stem cells for limbal stem cell deficiency as well as replacement photorecep- tor cells for transplant for retinal conditions like retinitis pigmentosa and dry AMD. S tem cell-derived therapy is an attrac- tive treatment option in situations when there is not necessarily a genetic component to the disease to correct (though there could be) and/or if the cells are not healthy enough for a gene therapy to correct a condition. A few options are currently in clinical trials for ocular disorders. "Replacement cell therapy using stem cells is aimed at later stages of disease when cells are terminally damaged or dead, in which case gene therapy would not work," said David Gamm, MD, PhD. In the eye, stem cell therapy has been in the works for more than 2 decades, with Pellegrini et al. describing transplant of cultivated lim- bal stem cells for limbal stem cell deficiency (LSCD) in 1997. 1 While such stem cell therapies have been available to patients in Europe and Asia, they are still in clinical trial stages in the U.S. Ula Jurkunas, MD, described research for cultivated limbal stem cells as the first stem cell trial funded by the National Eye Institute (NEI) for the cornea. "The way it works, in general, is you take a small biopsy from the healthy eye of the limbus. Expand the cells with various techniques in the laboratory. … After growing them and making more of those cells, you take them back to the surgeon—it takes about 2 weeks for the cells to grow—and transplant them on an unhealthy eye, the eye that has limbal stem cell deficiency," Dr. Jurkunas said, noting that the cells they are cultivating in the U.S. clinical trial are with good manufacturing practice (GMP) products. "This isn't new; it was first described in 1997. It just took a while to develop consistent manufactur- ing using qualified and validated reagents and make them into the FDA-ready product here in the U.S." Dr. Jurkunas explained how stem cell thera- py for LSCD might be advantageous over other techniques. Unlike corneal limbal allografts, which require systemic drugs to reduce chance of rejection, limbal stem cells come from the continued on page 38 A magnified portion of lab-grown, human induced pluripotent stem cell (iPSC)-derived retinal organoid immunostained for cone (yellow) and rod (red) photoreceptors Source: Dr. Beth Capowski, Gamm Lab

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