Introduction:: Glaucoma, a leading cause of irreversible blindness, is characterized by the prolonged degeneration of retinal ganglion cells (RGCs) and the optic nerve. Although increased intraocular pressure (IOP) is a significant risk factor, the reduction of IOP does not necessarily halt the progression of glaucomatous neurodegeneration. Current research suggests that innate and adaptive immune responses play crucial roles in glaucoma pathogenesis in both experimental mouse models and human patients. Elevated IOP has been found to trigger immune responses, leading to progressive RGC and axon degeneration in glaucoma.
Materials and Methods:: In this study, we optimized a viscobeads-induced experimental glaucoma model in adult C57BL/6 wild-type (WT) mice, following our previous experiments. Generally, the cornea of an anesthetized mouse was gently punctured near the center using a 33G needle. A bubble was then injected through this incision site into the anterior chamber to prevent possible leakage, followed by the injection of 1 μL viscobeads into the same chamber. The successful induction of unilateral experimental glaucoma in mice was validated with the IOP measurement and comparison between the glaucomatous eye and the normal eye ( > 5 mmHg). We examined the spatial distribution and temporal dynamics of microglia activation and infiltrated T cell subsets in early glaucoma, aiming to locate the initial injury site and elucidate the role of T cells in glaucomatous neurodegeneration.
Results, Conclusions, and Discussions:: By immunolabeling the retina and optic nerve head with Ionized calcium-binding adaptor molecule 1 (Iba1) antibody, we were able to visualize microglial activation, which significantly increased in intensity from day 5 post-injection and maintained activation on day 7. T cells, mainly accumulated at the trabecular meshwork and optic nerve head after 8 weeks, were traced during the first two weeks post-injection. Our preliminary data suggest the involvement of Th1 T cells at day 14 post-injection, as most T cells co-labelled with CD4 and IFN-γ but not IL-17A.
The spatial and temporal assessment of activated microglia can aid in identifying the initial injury site in experimental glaucoma. Additionally, understanding the phenotypic changes of activated microglia and the dynamics of T cell infiltration during glaucoma progression can further clarify immune mechanisms involved in glaucomatous neurodegeneration. Consequently, this research may contribute to the understanding of glaucoma pathogenesis and help identify novel therapeutic targets for treatment.
