Cellular responses to short-term intraocular pressure elevation in a porcine eye explant model

Cost-effective glaucoma models are needed in animals whose optic nerve head lamina cribrosa (LC) is similar to the human, such as pigs. We studied responses to acute intraocular pressure (IOP) elevation in porcine eye explants in which eyes were cannulated to maintain IOP at 10 or 50 mmHg for 4, 16 or 24 h. Quantitative fluorescence imaging of amyloid precursor protein (APP) found localized axonal transport at the LC in explant tissue after IOP elevations for 4 and 16 h, as do primate glaucoma and human glaucoma eyes (both P ≤ 0.001, Mann Whitney). Immunofluorescent labeling identified which cells express molecules in the transforming growth factor β and integrin signaling pathways. Quantification of mechanosensitive pathway molecules was performed at 4 and 24 h on micro-dissected retina, prelamina, LC and optic nerve. LC RhoA increased at 24 h (P = 0.03, t-test), myelinated optic nerve ratio of p-cofilin to total cofilin increased at 4 h (P = 0.05, t-test), and LC p-Smad2/3 increased at 24 h (P = 0.01, t-test). Integrin β1 and vinculin decreased at 4 h in the LC (P = 0.004 and P = 0.04, respectively, t-tests). At 24 h, LC integrin β1 returned to baseline, while vinculin increased (P = 0.004). Explants demonstrate dynamic changes in axons and astrocytes during at least 24 h post mortem. Mechanosensitive signaling pathways can be studied in porcine eyes with large sample sizes at low cost.