INDUCIBLE MMP-3 EXPRESSION IN A STEROID-INDUCED MURINE MODEL OF GLAUCOMA

Abstract

Purpose : We have previously reported on the efficacy of AAV-2/9-mediated expression of matrix metalloproteinase 3 (MMP-3) from the corneal endothelium, expressed both constitutively and induced by periodic topical administration of doxycycline in wild type mice (O’Callaghan et al. 2017, Hum. Mol. Genet.). MMP-3 secretion results in significantly increased outflow facility, with concomitant remodelling of the extracellular matrix and a reduction in intraocular pressure (IOP). We report here results obtained from using this approach in a widely accepted murine model of steroid-induced glaucoma.

Methods : Animals were intracamerally inoculated with inducible AAV-MMP-3 or contralateral AAV-eGFP as a control. 2 weeks later, animals were implanted with a micro-osmotic pump containing either cyclodextrin (vehicle control group) or dexamethasone (DEX) at 2 mg/kg/day for 4 weeks. Virus was activated by topical administration of doxycycline eye drops (0.2%) 2 weeks after micro pump implantation. Tonometric IOP readings were taken every week and facility was measured ex vivo using iPerfusion 2 weeks after induction.

Results : MMP-3 impeded the increase in IOP observed in response to systemically-administered DEX. For the DEX cohort: in eGFP injected eyes, IOP increased by 3.5 ± 1.9 mmHg (median ± median absolute deviation) (p=<0.001, N=14) over the 6 weeks, and in MMP-3 treated eyes, IOP increased by 2.1 ± 1.4 mmHg (p=0.008, N=14) over the same period. At the experimental endpoint, IOP had a median decrease of 1.9 ± 0.1 mmHg in the MMP-3 treated eyes as compared to eGFP treated eyes (p=0.002, N=14). No significant changes in IOP were observed between MMP-3 and eGFP-treated eyes in the control group (N=10). Facility in MMP-3 treated eyes was an average of 45% [18, 78%] (p=0.005, N=8) higher than in eGFP-injected eyes in the DEX cohort, and an average of 59% [26, 100%] greater in the control cohort (p=0.002, N=8). Electron microscopy showed a significant increase in optically empty spaces in MMP-3 treated eyes at the sub-endothelial region around the circumference of the Schlemm’s canal of 16% [5, 27%] (p=0.017, N=4).

Conclusions : Doxycycline-induced AAV-mediated expression of MMP-3 from the corneal endothelium significantly increases outflow facility and reduces IOP in hypertensive animals by degradation of ECM.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.