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Alfred K. Yu, Krisztina I. Forward, Shawn A. Morales, Lynn K. Gordon, Lawrence S. Morse, Susanna S. Park, David G. Telander; EMP2 Expression in Human Proliferative Vitreoretinopathy (PVR) and Spontaneous Epiretinal Membranes (ERM). Invest. Ophthalmol. Vis. Sci. 2011;52(14):4919.
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Previous studies have shown that Epithelial Membrane Protein 2 (EMP2) is upregulated in pre-retinal membranes. The purpose of this study is to better characterize EMP2 expression when comparing pre-retinal membranes of different etiology. The staining intensity (SI) and percentage of positive (PP) cells were compared in idiopathic epiretinal membranes (ERM) and proliferative vitroretinopathy (PVR) membranes. In addition, we compared retinal detachment-induced PVR and trauma-induced PVR. We also wanted to determine if there is any correlation between the duration of PVR and EMP2 SI. Understanding EMP2 expression in retinal disease will aid designing possible therapies.
Pre-retinal membranes were collected from patients during surgical pars plana vitrectomy with consent. The membranes were fixed and processed for paraffin embedding. The membranes were sectioned and protein expression of EMP2 was evaluated by immunohistochemical analysis. Four masked observers rated SI and PP cells based on a previously described protocol. Membranes were then categorized based on cause and type of pre-retinal membrane. The duration of the membrane was recorded based on time of diagnosis to date of surgical membrane retrieval.
EMP2 expression varied in pre-retinal membranes of different etiologies. PVR membranes and idiopathic ERMs were compared. Pre-retinal membranes were also compared based on the type of cause. 100% of the studied membranes expressed EMP2. PVR-induced membranes showed greater expression of EMP2 (higher SI and PP) than spontaneous ERMs; however the difference was not statistically significant. When comparing duration of PVR membrane and expression of EMP2, no correlation was determined. Trauma-induced PVR also showed a trend of even higher EMP2 expression (increase SI and PP) compared to PVR induced by retinal detachments.
Comparison of different etiologies of pre-retinal membranes revealed a trend of increased EMP2 expression in PVR when compared with spontaneous ERMs. Further studies with a larger population will aid in determining if a correlation exists between the duration of PVR and EMP2 SI. Based on the results of this study, targeting EMP2 may be a therapeutic option for all pre-retinal membranes.
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