Abstract
Purpose :
Ischemia is a common pathomechanism in various ocular diseases such as glaucoma and retinal vascular occlusion. Previously, we noted that the extracellular matrix protein tenascin-C (Tnc) is dysregulated in ischemic retinae. Tnc represents a glial scar constituent, which modulates the immune response and triggers neuroinflammatory processes. However, the role of Tnc in retinal ischemia is not fully understood yet. Hence, we established a novel Tnc knockout (KO) ischemia/reperfusion (I/R) mouse model to analyze the role of Tnc in retinal degeneration.
Methods :
I/R was induced by elevating the intraocular pressure to 90 mmHg for 45 minutes in the right eye of wildtype (WT I/R; 6 weeks old) and Tnc KO mice (KO I/R). The left eye remained untreated and served as a control. Electroretinogram (ERG) recordings were performed 7 days after I/R (n=5/group). Flat-mount retinae were dissected 3, 7, 14 and 21 days post I/R and stained immunohistochemically. The numbers of Brn3a+ retinal ganglion cells (RGCs) and Iba1+ microglia were quantified (n=6/group). In addition, the Brn3a mRNA level was determined by RTq-PCR 3 days after I/R (n=4/group).
Results :
Lower a- and b-wave amplitudes were found in both genotypes after I/R (p<0.05). However, KO I/R amplitudes were higher in comparison to the WT I/R group (p<0.05). Fewer Brn3a+ RGCs were detected in WT I/R retinae at 3 days compared to WT controls (p=0.04). Importantly, KO I/R retinae displayed similar RGC numbers as KO (p=0.69) and WT controls (p=0.24). A reduced Brn3a mRNA expression was found in WT I/R (p=0.04) after 3 days, whereas expression was not altered in KO I/R (p=0.43). At later points in time, WT I/R and KO I/R retinae displayed progressive RGC loss (p<0.05) compared to their respective control groups. Iba1+ cells were increased in WT I/R and KO I/R retinae at all examined points in time (p<0.01). Interestingly, at 3 and 7 days, KO I/R retinae exhibited a reduced amount of microglia cells compared to WT I/R (p<0.05).
Conclusions :
Our study showed a delayed RGC loss and a reduced microglia infiltration in Tnc KO mice after I/R. Absence of Tnc seems to be protective for RGCs at an early point in time. Additionally, the Tnc loss improved overall retinal functionality. Collectively, we provide evidence that Tnc represents an important player in ischemic retinal degeneration.
This is a 2020 ARVO Annual Meeting abstract.