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Karin M. Arner, Fredrik K. Ghosh; Fibronectin in the Developing Rat Retina. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2685.
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© ARVO (1962-2015); The Authors (2016-present)
To examine fibronectin (FN) expression during retinal development and possible roles during lamination formation.
FN in vivo was examined in retinas from several developmental stages ranging from E17 to adult age. To explore the role of FN during retinal lamination formation, PN5-6 full-thickness retinas were cultured for 7 days with dispase which selectively cleaves fibronectin and type IV collagen. Retinal cultures were exposed to dispase at either 0.5 U/ml for 3 or 24 hours or 5.0 U/ml for 3 or 24 hours. Eyecups and retinal explants were examined morphologically with hematoxylin and eosin staining and immunohistochemistry directed against cellular FN and vimentin.
Well labeled FN positive structures were seen epiretinally but not within the retinal layers in E17-PN8 in vivo specimens. At PN13, epiretinal labeling was not present, instead vertically arranged fiber-like structures in the innermost part of the retina were seen. From PN16 onwards, these structures were more distinct, displayed a high labeling intensity in their innermost part, and extended vertically throughout the inner and outer retinal layers. Vimentin-fibronectin double-labeling of E17-PN8 specimens revealed radially oriented vimentin positive fibers traversing the neuroblastic cell mass and separate FN positive structures epiretinally. From PN13 onwards, co-localization of fibronectin labeling along vimentin labeled Müller cells was evident. In retinas treated with 0.5 U/ml of dispase for 24 hours, retinal layers were discernible, but all specimens contained large areas of rosettes and retinal folding which was not seen in untreated controls. Vimentin labeled vertical fibers traversing the retina vertically were found, but were less organized and uniform than in the controls. Fibronectin labeling was found diffusely in the IPL, and in individual vertical fibers without any apparent organization in the outer retina. In explants treated with 5.0 U/ml of dispase for 3 or 24 hours no distinct lamination could be distinguished. 24h specimens were significantly thinner than control explants and in most parts consisted of an unorganized homogenous cell mass with randomly organized vimentin and fibronectin labeled fibers.
Fibronectin (FN) is present prior to, during, and after lamination formation in the developing rat retina. Enzymatical cleavage of FN early in the lamination process disrupts the formation of retinal layers implicating its pivotal role in this process. FN expression is closely related to Müller cells during later stages of development and may be one of the extracellular ligands with which these cells interact during retinogenesis.
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