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Kazuya Oikawa, Julie A. Kiland, Odalys Torne, Shawna Gloe, Virginia Mathu, Brenna Wetherbee, Gillian J McLellan; Optic nerve head (ONH) glial activation molecular signature across disease stages in a feline glaucoma model. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2373.
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© ARVO (1962-2015); The Authors (2016-present)
Mechanisms of axonal insult within the ONH in glaucoma are not fully understood. This study aimed to delineate ONH molecular alterations in chronic stages of glaucoma, in an inherited feline model with ONH structure comparable to humans.
ONH tissues from 10 LTBP2mut/mut cats with glaucoma and 5 wt control cats (age 1-3 yrs) were used to generate cDNA libraries for RNAseq. Weekly intraocular pressure (IOP) data and optic nerve axon counts were available for all subjects. Differentially expressed genes (DEGs) were identified using DESeq2 (false discovery rate < 0.05), and g:Profiler was used for functional enrichment analysis. DEGs in chronic glaucoma were compared to DEGs in an RNA-seq dataset generated by our lab from ONH tissues of LTBP2mut/mut cats prior to axon degeneration. Transcriptomic findings were validated by RNAscope in situ hybridization (ISH) and by immunolabeling (IF) of archived ONH tissue sections. For confirmatory studies, data were compared between groups by two-tailed unpaired t-test or ANOVA (p < 0.05 considered significant).
Mean and cumulative IOP over 10mths prior to tissue collection were consistently higher in LTBP2mut/mut than in wt cats. Stratifying subjects by optic nerve damage based on histological evaluation (mild [MLD], moderate [MOD] and severe [SEV] damage), 77, 882 and 1878 DEGs were identified, respectively, in glaucoma relative to age-matched controls. Functional analysis of DEGs in chronic, established glaucoma (MOD and SEV groups) identified upregulated DEGs ascribed to cell adhesion, immune/inflammatory responses, and MAPK cascade, and downregulated DEGs associated with metabolism, fatty acid synthesis, actin cytoskeleton and myelination. Comparing these DEGs in established chronic glaucoma to those in pre-degenerative, early-stage disease, 111 DEGs were shared between stages, including significant upregulation of HP and TNC. ISH confirmed expression of HP and TNC in the ONH, but with sub-regional differences in expression. TNC was highly expressed in the prelaminar - laminar regions and HP in the laminar and retrolaminar regions. ISH and IF identified astrocytes as the predominant ONH cell-type expressing these gene products.
Early and chronic stages of glaucoma share a reactive astrocyte molecular signature. Gene expression changes are more complex and enhanced in chronic glaucoma.
This is a 2021 ARVO Annual Meeting abstract.
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