The Effects of TGFβ2 on Uveoscleral Outflow in the Mouse Eye

Purpose: Elevated intraocular pressure (IOP) is a risk factor for primary open-angle glaucoma (POAG). Transforming growth factor beta-2 (TGFβ2) contributes to POAG pathogenesis via effects on the conventional aqueous outflow pathway. However, its effects on the uveoscleral (unconventional) aqueous outflow pathway, and effects of euthanasia and enucleation on TGFβ2 action, are unknown. Methods: We quantified the impact of overexpression of TGFβ2 on uveoscleral outflow (Fu) in mice. TGFβ2 was overexpressed in left (OS) eyes by intravitreal (IVT) injection with Ad5.CMV.hTGFβ2C226/228S (2×10-7pfu in 2?L). Right (OD) eyes were injected IVT with Ad5.CMV.null (same titer/volume). After 14 days IOP was elevated in OS (84.29%, p< 0.001). Fu was determined by perfusing the anterior aqueous chamber with FITC-dextran (2.5×10-3 M), followed by dissection of eyes into component tissues and measurement of each sample's fluorescence. Fu was inferred using a standard curve. Living animals, euthanatized animals, and enucleated eyes (exposed to air or submerged in PBS) from euthanatized animals were studied. Results: Fu was reduced in vivo in OS (0.0048±0.0017 µL/min) vs. OD (0.0987±0.0126 µL/min, p=0.025). In euthanatized mice, Fu was reduced in OS (0.0215±0.0101 µL/min) vs. OD (0.1543±0.0241 µL/min, p=0.010). In ex-vivo eyes exposed to air, Fu was reduced in OS (0.0702±0.0087 µL/min) vs. OD (0.1377±0.0106 µL/min, p=0.008). In ex-vivo eyes submerged in PBS, there was no difference between OS (0.0222±0.0065 µL/min) and OD (0.0137±0.0078 µL/min, p=0.175). Conclusions: This study quantifies TGFβ2 effects on uveoscleral outflow, providing insight on the effects TGFβ2 has on POAG pathophysiology.