Ben Yi Tew ¹ Gerald C. Gooden ¹ Pei-An Lo ¹ Dimitrios Pollalis ¹ Brandon Ebright ¹ Alex J. Kalfa ¹ Alejandra Gonzalez-Calle ¹ Biju Thomas ¹ David N. Buckley ¹ Thomas Simon ¹ Zeyi Yang ¹ Ege Iseri ¹ Cody L. Dunton ² Vadim Backman ² Stan G. Louie ¹ Gianluca Lazzi ¹ Mark S. Humayun ¹ Bodour Salhia ^1*

• ¹ University of Southern California, Los Angeles, United States
• ² Northwestern University, Evanston, Illinois, United States

Background: Retina degeneration is a major cause of irreversible blindness. Stimulation with controlled low-level electrical fields, such as transcorneal electrical stimulation (TES), has recently been postulated as a therapeutic strategy. Despite some promising results, there is insufficient molecular characterization of the therapeutic effects of TES.Methods: Controlled, non-invasive TES was delivered using a custom contact lens electrode to the retinas of Royal College of Surgeons (RCS) rats, a model of retinal degeneration. DNA methylation in the retina, brain and blood plasma was assessed by reduced representation bisulfite sequencing (RRBS) and gene expression by RNA sequencing.Results: TES induced DNA methylation and gene expression changes implicated in neuroprotection in the retina of RCS rats. Using an epigenomic retinal health score derived from DNA methylation changes observed with disease progression in RCS rats, we showed that TES improved the epigenomic health of the retina. TES also induced DNA methylation changes in the superior colliculus: the brain region integrating visual signaling. Lastly, we demonstrated that TES-induced retinal DNA methylation changes were detectable in cell-free DNA derived from plasma.TES induces DNA methylation changes with therapeutic effects, which can be measured in circulation. These findings shed light on the therapeutic potential and molecular underpinnings of TES, and provide a foundation for the further development of TES to improve the retinal health of patients with degenerative eye diseases.