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Cornelia A. Deeg, Florian Hofmaier, Christina Eberhardt, Margarete E. Swadzba, Barbara Amann, Marius Ueffing, Stefanie M. Hauck; Differences In Expression Level And Pattern Of Extracellular Matrix Proteins Osteopontin And Fibronectin In Translational Model Of Recurrent Autoimmune Uveitis. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1196.
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The extracellular matrix (ECM) is a highly dynamic structure that varies tremendously and influences the encompassing tissue. We analyze immune pathomechanisms in equine recurrent uveitis (ERU), a spontaneous model of autoimmune uveitis with proven potential for translational research. In order to assess ECM re-modeling in ERU, we investigated the expression of ECM molecules fibronectin and osteopontin in vitreous and retina samples.
In order to investigate fibronectin and osteopontin levels in ERU, we quantified protein expression in vitreous with Western blots in comparison to physiological samples. Further, we evaluated candidate expression in retinal tissue of healthy eyes and ERU cases with immunohistochemistry. To confirm retinal Müller glia associated appearance, we studied Fn and OPN expression on primary equine RMG cells and on eq-MC7, a novel equine RMG cell line.
Western blot analysis of fibronectin and osteopontin in healthy and uveitic vitreous revealed significant reduction of both proteins in ERU. Immunohistochemical expression of fibronectin in healthy retinas was restricted to the inner limiting membrane abutting vimentin positive Müller cell endfeet, while in uveitic sections, a disintegration of the ILM was observed changing the fibronectin expression to a dispersed pattern extending toward the vitreous. Retinal expression of osteopontin in control tissue was found in a characteristic Müller cell pattern illustrated by co-localization with vimentin. In uveitic retinas, the immunoreactivity of osteopontin in gliotic Müller cells was almost absent. The ability of Müller cells to express fibronectin and osteopontin was additionally shown by immunocytochemistry of primary cultured equine Müller cells and the equine Müller cell line eqMC-7.
Severe ECM re-modeling in autoimmune uveitis reported here, might affect the adhesive function of fibronectin and thus the anchoring of Müller cell endfeet to the ILM. Furthermore, the absence of osteopontin in gliotic Müller cells might represent reduced neuroprotection.
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