Abstract
Purpose :
It seems that, among others, immune processes, elevated intraocular pressure (IOP), or a combination of these factors are responsible for glaucomatous damage. Here, we combined two glaucoma models to examine if multifactorial risk factors (IOP and immune response) lead to a more severe damage of retinal ganglion cells (RGCs) and additional microglia activation.
Methods :
Six-week-old wildtype (ONA) and βB1-CTGF mice (combination), a genetic OHT model, were immunized with 1 mg ONA (optic nerve antigen). A wildtype (control) and a βB1-CTGF control group (CTGF) received NaCl instead. 6 weeks after immunization, retinae were evaluated for RGCs (RBPMS), microglia/macrophages (Iba1), and microglia (Iba1 and Tmem119) via immunohistology. Further, mRNA levels of corresponding genes were analyzed via RT-qPCR.
Results :
A significant RGC loss was noted in ONA (p=0.02), but not in CTGF mice (p=0.60) compared to controls. In the combination group, significantly fewer RGCs were noted compared to WT (p<0.001) and CTGF mice (p=0.03). The Pou4f1 mRNA levels (RGCs) were significantly downregulated in CTGF and combination retinae (both: p=0.04) compared to controls, while only a trend towards a downregulation was noted in ONA animals (p=0.055). The number of Iba1+ cells in the ganglion cell layer (GCL) was significantly increased in CTGF (p<0.05) and combination mice (p<0.001) compared to control and ONA animals. Significantly more Iba1+ and Tmem119+ microglia were only found in the GCL of combination retinae (1.93±1.30 cells/mm) compared to control (0.29±0.44 cells/mm) and ONA mice (0.38±0.43 cells/mm; both p<0.001). The number of Iba1+ and Tmem119+ cells was also increased in the combination group compared to CTGF retinae (0.48±0.64 cells/mm; p=0.001). Similar results for Iba1+ and Iba1+ and Tmem119+ cells were observed when counting from GCL to outer plexiform layer. The mRNA expression levels of Iba1 showed no difference within the groups, while a significant upregulation of Tmem119 mRNA could be observed only in CTGF retinae (p=0.02).
Conclusions :
We revealed an enhanced RGC degeneration accompanied by an increased microglia activation. These results underline the important role of immunological processes, not only in autoimmune glaucoma, but also in IOP-dependent pathologies. Hence, this new model could help to study the pathomechanisms of this multifactorial disease more precisely.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.