Abstract
Purpose :
The molecular mechanisms of glaucomatous retinal ganglion cell (RGC) and optic nerve degeneration are not fully understood. The extracellular matrix protein tenascin-C (TNC) is a modulator of the immune response and triggers inflammation. In this study, we used an experimental autoimmune glaucoma mouse model to analyze the role of TNC on glial responses during retinal und optic nerve degeneration. Therefore, TNC knockout (KO) mice were compared to wild type (WT) animals.
Methods :
WT (WT ONA) and KO (KO ONA) mice (6 weeks, both sexes) were immunized with an optic nerve antigen homogenate, Freund`s adjuvant and pertussis toxin. Booster injections were given after 4 and 8 weeks. Control groups (CO) obtained sodium chloride (WT CO; KO CO). 10 weeks after immunization, we quantified the number of Brn3a+ RGCs in retinal flat-mounts (n=8/group), immunoreactivity of GFAP+ astrocytes in retina (n=8/group) and optic nerve sections (n=5/group). In addition, we investigated oligodendroglia with the markers oligodendrocyte transcription factor 2 (Olig2) and the myelin basic protein (MBP) in optic nerve sections (n=5/group). Groups were compared using one-way ANOVA followed by Tukey`s post hoc test.
Results :
A significant reduction of Brn3a+ cells was detected in ONA-treated WT (p=0.0003) and KO (p=0.01) animals. GFAP immunoreactivity was significantly increased in retina (WT ONA: 9.01 area [%]/image; WT CO: 5.39 area [%]/image; p=0.01) and optic nerve sections (WT ONA: 24.31 area [%]/image; WT CO: 12.36 area [%]/image; p=0.04) of WT ONA compared to WT CO, whereas KO ONA showed no significant changes. Furthermore, a significant loss of Olig2+ cells (p=0.01) and MBP+ signal (p=0.02) was found in WT ONA in comparison to WT CO. Interestingly, no decrease of these oligodendrocyte markers could be detected in the KO ONA group.
Conclusions :
This study showed RGC degeneration in WT and KO after immunization. The increased GFAP immunoreactivity and the reduction of oligodendrocyte marker expression is in line with the loss of RGC axons in WT ONA. In contrast, TNC deficiency resulted in a diminished glial reaction. These results indicate that TNC plays a significant role in the macroglial response during retinal und optic nerve degeneration.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.