Defining Microglia Homeostatic and Functional Phenotypes in Glaucomatous Injuries: Beyond Single-Cell Transcriptomics

Abstract

Presentation Description : The resident neuroprotective lipoxin circuit is impaired during retinal stress that include exocytotoxic- and ocular hypertension-induced neuropathy. Lipoxin B₄ produced by homeostatic astrocytes directly acts on retinal ganglion cells to increase survival and function in ocular hypertension-induced neuropathy. Homeostatic roles and cellular targets of LXB₄ in the retina and optic nerve are a critical gap in knowledge. We have identified microglia in the retina and optic nerve as novel cellular targets for the homeostatic action of LXB₄ using bulk and single-cell RNA analysis. Microglia are highly dynamic and undergo rapid phenotypic, morphological and functional changes that are tissue-specific. These rapid functional changes are not captured in transcriptomic analyses or in in vitro experiments. We employed and optimized a novel MorphOMICS method to fully measure the complete morphology of all microglia in the retina and optic nerve. The methods enabled us to define distinct microglia populations and their transition over time to distinct functional homeostatic and reactive phenotypes during retinal hypertension injury and LXB₄ treatment. The MorphOMICS analysis revealed temporally defined microglia functional phenotypes during the time course of sustained hypertension in the retina and, unexpectedly, the distal myelinated optic nerve. LXB₄ treatment resulted in the transition of microglia from a reactive towards a distinct homeostatic phenotype. This regulation of microglia phenotypes by LXB₄ in the distal optic nerve correlated with downregulation of specific diseases associated microglia pathways that were identified by RNA sequencing and immunohistochemistry. In summary, analysis of morphological phenotypes of microglia populations in the retina and optic nerve is a powerful method to define the dynamic functional changes in distinct microglia populations and define novel action for LXB₄ in maintaining microglia homeostatic function.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.