The impact of the immune system in glaucoma – how the complement system and microglia contribute to the damage

• Applicant: Dr. Sabrina Reinehr
• Subject Area: Ophthalmology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 437168454

Glaucoma is worldwide one of the main causes for blindness. Until now, the exact pathomechanisms are not known, however, an increased intraocular pressure (IOP) is considered as main risk factor. Nevertheless, around 30% of glaucoma patients develop glaucomatous damage IOP-independently. Unfortunately, glaucoma can remain asymptomatic until it is far progressed, hence approximately 10-50% of patients are unaware they suffer from this disease. Although IOP lowering can slow vision loss in patients, it does not completely stop disease progression. These facts emphasize the importance of discovering new treatment strategies. In the last years, a contribution of the immune system to glaucomatous damage moved more and more into the focus. Proteins of the complement system, a part of the innate immune system, and microglia response were identified in glaucoma patients and in animal models. This strengthens the hypothesis that immune alterations play an important role in glaucoma development regardless of IOP. However, new therapy strategies are currently only investigated either in models with or without elevated IOP. Hence, in this application, we will combine two established glaucoma models. Particularly, the βB1-CTGF mice model, where an overexpression of the connective tissue growth factor (CTGF) leads to an increased IOP accompanied with glaucomatous damage and the experimental autoimmune glaucoma model, where an immunization with the optic nerve antigen homogenate (ONA) provokes retinal ganglion cell (RGC) loss and optic nerve degeneration IOP-independently. First, we plan to determine whether this combination of two pathogenic factors leads to an increased glaucomatous damage, including the loss of RGCs and optic nerve axons. Since other cell types could be altered in glaucoma, different neuronal cells will be examined in this new combination model. Hence, IOP and OCT examinations will be performed after several points in time, followed by (immuno-)histological and RT-qPCR analyses. As mentioned, immune alterations play a part in glaucoma pathology. Until now, nothing is known about the immune response and the involvement in cell death in the combination model. We will investigate the responses in the combination model and will compare these results with the ONA model. Here, retinal and optic nerve tissue will be examined via (immuno-)histology, RT-qPCR, and FACS. In the last part, we want to investigate whether an inhibition of the inducible nitric oxide synthase (iNOS) can prevent retinal and optic nerve damage in the combination model. INOS is secreted from macrophages/microglia in response to inflammatory cytokines. Hence, the survival of different cell types and the immune response will be investigated via OCT, (immuno-)histology, RT-qPCR, and FACS analyses. The results from this project will help to understand the pathology of glaucoma more precisely and iNOS inhibition might be suitable as a new therapeutic approach for glaucoma patients.

• DFG Programme: Research Grants