**Molecular Assessment of Epiretinal Membrane: Activated Microglia, Oxidative Stress and Inflammation**

**Sushma Vishwakarma 1,2,**†**, Rishikesh Kumar Gupta 1,**†**,**‡**, Saumya Jakati 3, Mudit Tyagi 4, Rajeev Reddy Pappuru 4, Keith Reddig 5, Gregory Hendricks 5, Michael R. Volkert 6, Hemant Khanna 7, Jay Chhablani 4,\*,§ and Inderjeet Kaur 1,\***


Received: 27 June 2020; Accepted: 21 July 2020; Published: 23 July 2020

**Abstract:** Fibrocellular membrane or epiretinal membrane (ERM) forms on the surface of the inner limiting membrane (ILM) in the inner retina and alters the structure and function of the retina. ERM formation is frequently observed in ocular inflammatory conditions, such as proliferative diabetic retinopathy (PDR) and retinal detachment (RD). Although peeling of the ERM is used as a surgical intervention, it can inadvertently distort the retina. Our goal is to design alternative strategies to tackle ERMs. As a first step, we sought to determine the composition of the ERMs by identifying the constituent cell-types and gene expression signature in patient samples. Using ultrastructural microscopy and immunofluorescence analyses, we found activated microglia, astrocytes, and Müller glia in the ERMs from PDR and RD patients. Moreover, oxidative stress and inflammation associated gene expression was significantly higher in the RD and PDR membranes as compared to the macular hole samples, which are not associated with inflammation. We specifically detected di fferential expression of hypoxia inducible factor 1- α (*HIF1-*α), proinflammatory cytokines, and Notch, Wnt, and ERK signaling pathway-associated genes in the RD and PDR samples. Taken together, our results provide new information to potentially develop methods to tackle ERM formation.

**Keywords:** human retina; epiretinal membrane; internal limiting membrane; vitreoretinal surgery; macular hole; proliferative diabetic retinopathy
