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LaKisha Buie, Renekia Elliott, Brandon Lane, Matthew Halton Smith, Scott David Lawrence, Terete Borras; New Advances on the Gene Therapy Treatment of Steroid-induced Elevated IOP in Sheep. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5988.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate whether a safer, long term/low toxicity self-complementary AAV2 vector, scAAV2.GRE.MMP1, would also reduce IOP in the sheep model. To optimize the model by comparing sheep age, breed and steroid administrations.
The glucocorticoid-inducible expression cassette was cloned into the scAAV plasmid vector pHpa-trs-SK (mutated terminal repeat downstream from cassette) (pMG21). Plasmid pMG21 was used by the UNC core facility to generate the scAAV2.GRE.MMP1 virus. Corriedale (3 y old) and Katahdin (7 mo and 3 y) received Prednisolone, Durezol or sterile PBS drops 3X daily for 1-2 wks. One sheep received a subtenon Kenalog injection. After pressure elevation, sheep were IC-injected with 2-7 X10^12 scAAV2.GRE.MMP1 and control scAAV2.GFP viral genomes. TonoVet IOP measurements were performed 1 wk prior to corticosteroid treatment (baseline) and 2-3X a wk 1-2 h post-steroid treatment. Animals were euthanized 2-3 wks post-injection. Their anterior segments were processed for morphological and fluorescence evaluation.
A total of 7 sheep were studied. The mean IOPs at baseline were 12.5±0.8 mmHg in 7 mo Katahdin (n=4 eyes) and 15.5±0.5 mmHg in both 3 y old Katahdin and Corriedale (n=10 eyes). Young Katahdin eyes treated with Prednisolone did not experience IOP elevation while older Corriedale showed a 3.6 mmHg increase 1 wk post treatment. Eyes treated with Durezol showed a significant increase in IOPs up to 18.0±1.7 mmHg and 21.4±1.8 mmHg at 3 d (p=0.007 & p=0.0005) and 24.0±1.7 mmHg and 25.0±2.4 mmHg at 3 wks (p=0.0006 & p=0.001) in 3 yr old Corriedale and Katahdin respectively. An injection of Kenalog increased IOP to 17.3±0.9 2 wks post-injection. All 4 sheep injected with MMP1 (Ad.GRE.MMP1 n=1; scAAV2.GRE.MMP1 n=3 eyes) saw significant decrease in IOP. In a representative experiment, scAAV2.GRE.MMP1 injected eyes decreased steroid-induced IOP at 3 wks from 23.5±2.1 to 18±1.4 mmHg (n=2 eyes, p<0.05). Fluorescence microscopy showed positive GFP transduction in the TM of the Ad.GFP and scAAV2.GFP injected eyes.
Steroid type and age influenced IOP response, while sheep breeds did not. Gene transfer of MMP1 by injection of scAAV2.GRE.MMP1 into the anterior chamber of living sheep lowers steroid-induced elevated IOP making it a great candidate for long term treatment of steroid glaucoma. This gene transfer strategy will be very useful for the evaluation of lowering IOP TM drugs.
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