Abstract
Purpose :
To determine the transcriptomic responses of retinal microglia to elevated intraocular pressure (IOP) using single-cell (sc) transcriptomic analysis in a rat model of experimental glaucoma induced by magnetic beads.
Methods :
Animal procedures adhered to the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. Experimental glaucoma was induced in 24 Brown Norway rats via intracameral injection of magnetic microbeads. Serial IOP measurements were taken. The rats were categorized into 2 groups: moderate IOP elevation (>30-50% from baseline) and high IOP elevation (>50% from baseline). After 4 weeks, retina and optic nerve tissue were harvested for single-cell suspensions and single-cell RNA sequencing performed using Chromium (10X Genomics). Data analysis utilized the Seurat (v. 2.3.4) pipeline in R. Principal component analysis (PCA) was conducted and the first 50 principal components were used for uniform manifold approximation and projection (UMAP) visualization. Cell subpopulations were identified using the Single R tool and CellDex annotation.
Results :
The mean baseline IOP was 13.2 ±1.4 mmHg. The IOP elevations were 18.0 ±1.3 mmHg, 23.5 ±1.4 mmHg, and 21.0 ±3.6 mmHg in the moderate IOP retinal, high IOP retinal, and ON IOP groups, respectively. Single-cell microglia clusters revealed significant upregulation of CD74, CXCl13, and MHC Class II genes in the moderate IOP retinal microglia. The high IOP retinal microglia showed significant upregulation of Clec71, SPP1, and Lgals3 with concurrent downregulation of microglial homeostatic genes. ON microglia exhibited significant upregulation of APOE, Fth1, and Ctsd genes (Fig. 1).
Conclusions :
In the retina, a transcriptomic signature resembling an activated response microglia (ARM) was observed with moderate IOP elevation (37% from baseline), whereas higher IOP elevations (78% from baseline) demonstrated a neurodegenerative microglia (MGnD) signature. In the optic nerve, a signature akin to damage-associated microglia (DAM) was detected. Despite no significant difference in IOP between the optic nerve and retinal groups, the microglial signature suggests that optic nerve microglia exhibit a more damage-associated profile compared to retinal microglia, potentially serving as critical targets for glaucoma-associated neuroinflammation.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.