Abstract
Purpose :
The neurodegenerative processes leading to glaucoma are complex. Despite elevated intraocular pressure, an involvement of immunological mechanisms is most likely. In the new multifactorial glaucoma model, a combination of high intraocular pressure (IOP) and ocular antigen immunization leads to an enhanced loss of retinal ganglion cells (RGCs), mimicking glaucoma disease better. Here, we evaluated the immune response in this new model.
Methods :
Six-week-old wildtype (ONA) and CTGF mice (COMB), a genetic OHT model, were immunized with 1 mg ONA (optic nerve antigen). A wildtype (control) and a CTGF control group (CTGF) received NaCl instead. 6 weeks after immunization, retinae were processed for flow cytometry to analyze microglia (CD45, CD11b). Further, immunohistological analyzes of the complement factor C1q and corresponding RT-qPCR analyses of C1q subunits and inflammatory factors (Il1b, Tnf, Nos2) were performed. Lastly, the number of CD3+ T-cells in the ganglion cell layer (GCL) was assessed via immunohistology.
Results :
While no changes were noted in ONA animals, the percentage of CD45+ cells was significantly higher in CTGF (p=0.01) and COMB retinae (p=0.03) compared to controls. Corresponding results were noted for the fluorescent intensity of CD11b (CTGF: p=0.01; COMB: p=0.001). C1q, as part of the complement system, is bound to microglia. We noted significantly more C1q+ cells in the GCL of CTGF and COMB mice (both: p=0.03), while no changes occurred in ONA retinae compared to controls. RT-qPCRs analyses confirmed a significant upregulation of C1qa, C1qb, and C1qc in CTGF and COMB animals (all: p<0.05). Moreover, the mRNA expression levels of Tnf and Nos2 were upregulated in CTGF (both: p<0.01) and COMB (both: p<0.05), but not in ONA retinae. Higher Il1b expression levels were observed in all glaucoma groups (all: p<0.05). The number of CD3+ T-cells did not differ in ONA and CTGF mice, while significantly more CD3+ cells were counted in COMB retinae (p=0.03).
Conclusions :
Despite a more pronounced RGC loss in COMB animals, the expression of immune markers was comparable in all glaucoma groups, with no additional effects in COMB mice. Contrary, the number of T-cells was solely increased in COMB mice. It seems that the combination of two risk factors causes an over-aggregation of T-cells leading to a more persistent pathology in these animals.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.