Peripheral inflammation effects on retinal phagocytic system

Abstract

AbstractPurposeTo study how a unilateral arthritic inflammatory process, affecting the peripheral nervous system, can activate the mononuclear phagocytic system at retinal level.MethodsAn experimental model of peripheral inflammatory process produced by an intraplantar injection of Freund's complete adjuvant (FCA) in the left hind limb was induced to adult C57BL/6J lysozyme M‐eGFP‐knock‐in (LysM‐eGFP) mice that express LysM‐eGFP selectively in myelomonocytic cells. FCA, sham and naïve mice were processed at different survival times (ranging 1–10 days post‐lesion). Retinas were prepared as whole‐mounts and histologically analyzed for microglia markers and LysM‐eGFP expression.ResultsAfter FCA administration morphological signs compatibles with microglial activation were observed in the eGFP+ cells in the innermost layer of the retina, persisting along the time‐course of study. The three sub‐population of eGFP+ cells identified, amoeboid, ramified and peripheral, showed significant and relevant changes in the distribution pattern respect to that observed in untreated retinas from sham or naïve mice. The quantitative analysis showed statistically significant changes in the expression of eGFP+ and Iba‐1+ for all cell sub‐population in the course of time. However, the number of eGFP+ and Iba‐1 immunonegative amoeboid cells was constant and similar to those of sham or control retinas.ConclusionsInduction of a peripheral inflammatory process by administration of FCA elicits a response from the peripheral bone marrow‐derived monocyte‐macrophage population at retinal level, where these cells are recruited and transformed into microglia.