Purpose : Glaucoma is a neurodegenerative disease that is a leading cause of blindness globally. Therefore, we aim to study the glial cell responses in post-mortem retinal tissues from glaucoma patients, to elucidate mechanisms contributing to disease progression and identify potential therapeutic targets.
Methods : Retinal tissues from 9 glaucoma patients and 5 controls were analyzed through immunostaining. We focused on the microglial activity and immune cells in the glaucomatous retina. Microglial activation was identified using IbA1 staining, noting changes to the cell morphology. Additional markers, including Axl, CD11b, CD45 and CD68, were employed to correlate morphological changes with functional states. Further, a panel of immune cell markers was used to identify other immune cells in the retina. We quantified these observations by measuring the median fluorescence intensity (MFI, AU) and median area covered (MAC, %). Statistical significance was determined using T-tests.
Results : Notably, there was a significant increase in Iba1 intensity in glaucomatous retina (Control: MFI: 6.29 ±1.64 AU, MAC: 0.938±0.22% vs. Glaucoma: MFI: 9.17±1.39 AU, MAC: 1.28±0.46%; p-value:0.01 and 0.02, respectively). Diverse microglial morphologies were more pronounced in glaucoma patients with an increased ameboid microglia surrounding blood vessels and the inner limiting membrane. Number of CD11b+/IbA1+ cells increased in the optic nerve head (ONH) in glaucoma patients. While CD45+/Iba1+ cells (2±1 cells/mm) in the retina were sparse, CD68+ cells were found in retinal blood vessels but not in the retina itself. No co-localisation of Axl with Iba1 was observed. CD3+ cells were detected in the retina (1.5±0.71 cells/mm), but differentiation into CD4+ T cells or CD19+ B cells could not be confirmed.
Conclusions : The observed variation in microglial morphology suggests that activated microglia in different functional states may contribute to the glaucoma progression. Although our findings indicate potential interactions between systemic immune cells and retinal glial cells, there is no clear evidence of systemic immune cell infiltration into the retinal tissue. This study underscores the need for further research to elucidate the functional roles of microglia and other glial cells, as well as the nature of immune interactions at the Blood–Retinal Barrier, in the context of glaucoma.