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Stephanie C Joachim, Jacqueline Reinhard, Sabrina Reinehr, Susanne Wiemann, Gesa Stute, Sandra Kuehn, Andreas Faissner, H. Burkhard Dick; Remodeling of extracellular matrix components in retinas of an autoimmune glaucoma model. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2192.
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© ARVO (1962-2015); The Authors (2016-present)
Glaucoma is characterized by death of retinal ganglion cells (RGCs) and their axons. The causes of this disease are not fully understood yet. In an autoimmune glaucoma model RGC loss is induced by immunizing with ocular antigens. To gain further knowledge about possible remodeling of extracellular matrix (ECM) proteins, immunoreactivity of the glycoprotein tenascin-C and the DSD-1-proteoglycan phosphacan were evaluated in the retina and optic nerve (ON).
Rats were immunized with optic nerve homogenate (ONA) or S100B protein (S100). The control group received sodium chloride (CO). RGC numbers were quantified using anti-Brn-3a antibody. Immunoreactivity of tenascin-C (anti-Kaf14 antibody) and phosphacan (anti-473HD antibody) was evaluated on retina cross-sections 7 (n=6/group) and 14 days (n=5/group) after immunization. Additionally, ON sections were labeled with ECM markers. Immunopositive areas of tenascin-C and phosphacan were measured using an ImageJ macro.
At 14 days RGC numbers were comparable in all three groups (p=0.9), later on, at 28 days, fewer RGCs were observed in retinas of ONA and S100 animals (p<0.001). Interestingly, regarding ECM proteins, diverse effects were noted for the immunization groups. At 7 days phosphacan immunoreactivity was significantly higher in ONA retinas (10.2±1.4%) than in controls (5.1±0.7%; p=0.0007). Here, phosphacan was mainly restricted to Müller glia processes. Phosphacan expression in S100 retinas was not altered (3.7±0.4%; p=0.09). At 14 days phosphacan staining area in ONA retinas further increased (21.3±3.5%; p=0.0007) in comparison to controls (8.2±1.4%), while S100 retinas were not affected (p=0.23). Tenascin-C immunoreactivity was significantly increased in both groups, ONA (p=0.002) and S100 (p=0.03), at 7 days. Tenascin-C immunoreactivity was found in the nerve fiber and the plexiform layers of the retina. Later on, at 14 days, tenascin-C immunoreactivity was comparable in all groups (p>0.05). Both ECM proteins could also be observed in the ON.
Our data suggest that remodeling of the ECM components tenascin-C and phosphacan occurs shortly after immunization. The drastic upregulation of tenascin-C seems to be accompanied by an early retinal degeneration immunized groups, whereas the upregulation of phosphacan in Müller glia was continuously and exclusively noted in ONA animals, possibly due to reactive gliosis.
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