Profiling IOP-responsive genes in anterior and posterior ocular tissues in the rat CEI glaucoma model

Abstract

PurposeThe rat Controlled Elevation of Intraocular pressure (CEI) model allows study of in vivo responses to defined intraocular pressures (IOP). In this study, we use Nanostring technology to investigate in vivo IOP-related gene responses in the trabecular meshwork (TM) and optic nerve head (ONH) simultaneously from the same animals. MethodsMale and female rats (N=35) were subject to CEI for 8-hours at pressures simulating mean, daytime normotensive rat IOP (CEI-20), or 2.5x IOP (CEI-50). Naive animals, receiving no anesthesia or surgical interventions, served as controls. Immediately after CEI, TM and ONH tissues were dissected, RNA isolated, and samples were analyzed with a Nanostring panel containing 770 genes. Post-processing, raw count data were uploaded to Rosalind(R) for differential gene expression analyses. ResultsFor the TM, 45 IOP-related genes were significant in the "CEI-50 vs. CEI-20" and "CEI-50 vs. naive" comparisons, with 15 genes common to both comparisons. Bioinformatics analysis identified Notch and TGF{beta} pathways to be the most up- and down-regulated KEGG pathways, respectively. For ONH, 22 significantly regulated genes were identified in the "CEI-50 vs. naive" comparison. Pathway analysis identified defense response and immune response as two significantly upregulated biological process pathways. ConclusionsThis study demonstrates the ability to assay IOP-responsive genes in both TM and ONH tissues simultaneously. In the TM, downregulation of TGF{beta} pathway genes suggest that TM responses may prevent TGF{beta}-induced extracellular matrix synthesis. For ONH, the initial response to elevated IOP may be protective, with astrocytes playing a key role in these gene responses.