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Diana C Lozano, Hari Jayaram, Tiffany Choe, William Cepurna, Shandiz Tehrani, Elaine Johnson, John C Morrison; Elevated Intraocular Pressure (IOP) Induced Optic Nerve Head (ONH) Gene Expression Responses: Two Experimental Models and Two Analysis Platforms. Invest. Ophthalmol. Vis. Sci. 2019;60(9):675.
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Previously we used microarray analysis to determine gene expression changes in ONH with small, focal optic nerve lesions from chronic IOP elevation (PMID: 20847120). We have now used RNAseq to track the time course of gene expression changes in ONH with similar lesions 10 days after a single Controlled Elevation of IOP (CEI) (2018 ARVO E-Abstract 3740). This study compares responses between these two models.
Early Injury Arrays: Chronic IOP elevation was produced in rats by unilateral episcleral vein injection of hypertonic saline. IOP was measured frequently and RNA from ONH with focal optic nerve lesions was studied by microarray (N=9). CEI-RNAseq: Following an anesthetized 8-hr, 60 mmHg CEI, rat ONHs were collected 0-10 days (N=6/time) and subjected to RNAseq. Expression levels were compared to those in control ONH. Differentially expressed genes in the array data were compared to those identified by RNAseq.
For the array Early Injury group, mean and peak IOPs were 3.1 and 9.4 mmHg above control values. Of 877 significant genes in the Early Injury array study, 787 met detection criteria (>10 reads) for inclusion in the RNAseq differential expression analysis. Of these, 40% were significant (>130% or <77%, false-discovery-rate<0.2) at any one time point following CEI. The majority of significant genes were found at 0hr (198 genes), 3 days (79 genes), and 10 days (99 genes) post-CEI. Expression change direction agreement with that seen in the array was 95%, 99% and 100% at 0, 3 and 10 days respectively. DAVID Bioinformatics analysis of significantly regulated gene categories in both studies identified upregulation of cell cycle and cytokine expression and down regulation of axonal/synaptic genes. Following CEI, cytokine expression peaked at 0 and 10 days, cell cycle gene expression gradually increased between 2 and 10 days and axonal/synaptic genes reached sustained minimal values at 3-10 days.
The excellent agreement of our RNAseq results at each time point following CEI with the chronic model Early Injury ONH array analysis confirms that a single, short-term IOP exposure can be used to successfully model the sequential events of chronic glaucoma. Gene expression responses in chronic glaucomatous optic nerve damage represent a composite of events that accompany and follow axonal injury.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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