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55 EW RETINA February 2019 activate the stem cell state of the Muller glial cells in the mammalian retina." However, such injuries al- most completely kill retinal gangli- on cells, the only output neuron of the retina. Instead, his lab has used viruses to deliver genes directly into Muller glial cells to activate them without introducing any damage to the retina. The technique involves a two-step reprogramming process. "The first is by gene transfer to activate the Muller glial cells to stem cell state," Dr. Chen said. "Follow- ing the first step, we reprogram by gene transfer of 3 factors important for photoreceptor differentiation during early retinal development." After this, investigators found that the Muller glial cells give rise to rod photoreceptor cells that so far are indistinguishable from original rod photoreceptor cells. What's more, in the mouse model of congenital blindness, they showed that after reprogramming, newly generated rod photoreceptors were able to function. 3 "They can respond to light, and they deliver in- formation to retinal ganglion cells," Dr. Chen said. "The newly gained visual information made their way all the way to the visual cortex, enabling the congenitally blind mice to respond to light for the first time in their lives." Once this technology is ma- ture, Dr. Chen expects that it will be applicable for many forms of retinal degenerative diseases such as macular degeneration and retinitis pigmentosa. Overall, Dr. Baranov thinks that there has been great success in cell transplantation and regenerative therapies in the eye already. "I think the eye is the place to be," he said. "That's where cell transplantation studies can progress faster than in other areas because we can monitor function, we can look into the eye, and we can have good structure readouts on cellular and even sub- cellular levels." EW References 1. Oswald J, Baranov P. Regenerative med- icine in the retina: from stem cells to cell replacement therapy. Ther Adv Ophthalmol. 2018;10:2515841418774433. 2. da Cruz L, et al. Phase 1 clinical study of an embryonic stem cell-derived retinal pigment epithelium patch in age-related macular de- generation. Nat Biotechnol. 2018;36:328–337. 3. Yao K, et al. Restoration of vision after de novo genesis of rod photoreceptors in mam- malian retinas. Nature. 2018;560:484–488. Editors' note: The sources have patents related to this. Contact information Baranov: Petr_Baranov@MEEI.HARVARD.EDU Chen: bo.chen@mssm.edu Strength. COMPLEX CASE MIX. RENOWNED CLINICIANS. DISTINGUISHED FACULTY. GLOBAL ENGAGEMENT. CUTTING-EDGE TECHNOLOGY. DIVERSE SURGICAL TRAINING. EYE-ONLY EMERGENCY ROOM. MENTORSHIP AND CAMARADERIE. 840 Walnut St., Philadelphia, PA 19107 willseye.org | 877.289.4557 Believing is Seeing *Based on a Doximity clinical reputation survey for 2018-2019. Voted #1 ophthalmology residency program in the United States. *

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