Subconjunctival Administration of an Adeno-Associated Virus Expressing Stanniocalcin-1 Provides Sustained Intraocular Pressure Reduction in Mice

Abstract

PurposeTo investigate subconjunctival administration of a single-stranded, adeno-associated virus, serotype 2, engineered to express Stanniocalcin-1 with a FLAG tag (ssAAV2-STC-1-FLAG) as a novel sustained intraocular pressure (IOP) lowering agent with a reduced ocular surface side effect profile. DesignIn vivo pre-clinical investigation in mice SubjectsC57BL/6J, DBA/2J, FP receptor knockout mice MethodsNormotensive C57BL/6J mice were treated with a subconjunctival injection of ssAAV2-STC-1-FLAG (2 μL; 6 x 109 viral genomes [VGs]) in one eye and the same volume and concentration of ssAAV2-GFP or the same volume of PBS in the fellow eye. Ocular hypertensive DBA/2J mice were subconjunctivally injected with 6 x 109 VGs of ssAAV2-STC-1-FLAG or ssAAV2-GFP. Steroid-mediated ocular hypertension was induced in C57BL/6J mice with weekly injections of dexamethasone into the conjunctival fornix, and mice were then injected subconjunctivally with 6 x 109 VGs of ssAAV2-STC-1-FLAG or ssAAV2-GFP. FP receptor knockout mice were injected subconjunctivally with 6 x 109 VGs of ssAAV2-STC-1-FLAG or PBS. An identical vector was constructed without the FLAG tag (ssAAV2-STC-1) and evaluated in normotensive C57BL/6J mice. IOP was assessed using the Tonolab tonometer for all experiments. Tumor necrosis factor alpha (TNFα), a marker of ocular surface inflammation, was compared between subconjunctivally delivered ssAAV2-STC-1 and other treatments including daily topical latanoprost. Main outcome measuresIOP assessment ResultsSubconjunctival delivery of ssAAV2-STC-1-FLAG significantly reduced IOP for 10 weeks post injection in normotensive mice. Maximal IOP reduction was seen at week 2 post injection (17.4%; 17.1 ± 0.8 vs 14.1 ± 0.8 mmHg, P<0.001). After the IOP-lowering effect had waned, a second injection restored the ocular hypotensive effect. Subconjunctivally delivered ssAAV2-STC-1-FLAG lowered IOP in DBA/2J mice (16.9%; 17.8 ± 2.0 vs 14.8 ± 0.9 mmHg, P<0.001) and steroid-mediated ocular hypertensive mice (19.4%; 18.7 ±0.9 vs 15.1 ± 0.5 mmHg, P<0.001) over the experimental period. This construct also reduced IOP to a similar extent in wild type (15.9%) and FP receptor knockout (15.7%) mice compared to the fellow eye. A related construct also lowered IOP without the FLAG tag in a similar manner. Reduction in conjunctival TNFα was seen when comparing subconjunctivally delivered ssAAV2-STC-1-FLAG to daily topical latanoprost. ConclusionsSubconjunctival delivery of the STC-1 transgene with a vector system may represent a novel treatment strategy for sustained IOP reduction and improved ocular tolerability that also avoids the daily dosing requirements of currently available medications.