Intravitreally administered AAV-mediated short-hairpin RNA against mTOR efficiently reduces neovascularization in the murine model of laser-induced choroidal neovascularization.

Abstract

Purpose : we evaluated the therapeutic effect of a self complement adeno-associated virus (scAAV)-delivered mammalian target of rapamycin (mTOR) short hairpin RNA in the laser-induced choroidal neovascularization of the mouse eye.

Methods : Self complementray adeno-associated virus (scAAV) based expression vector including GFP and mTOR shRNA (scAAV-GFP-mTOR shRNA) originally designed for the cancer treatment was used in this study.
Choroidal neovascularization was induced via laser photocoagulation (LP) in 8 week-old male C57/B6 mice (n=45). Intravitreal injection of AAV-GFP-mTOR shRNA (1μl of 5.0E+10 vg/ml) or AAV-GFP-scrambled shRNA (1 µl of 5.0E+10 vg/ml) was performed to the right eye of each animal (15 mice per each group) at 5 days after LP. Fifteen laser-treated mice with the same volume of 0.1% PBS injection were used as negative control. Transduction patterns and therapeutic effects of AAV-GFP-mTOR shRNA were evaluated at 14 days after LP. Anti-GFP antibody was used for the evaluation of the transduction efficiency into the CNV-induced retinal tissue. The expression pattern of mTOR through the chorioretinal tissue was detected with anti-mTOR antibody. Anti-LC3B and ATG7 antibodies were used to detect the autophagy. Furthermore, anti-F4/80, CD31, and Brn3 antibodies were also used. Neuroretinal injury was assessed with TUNEL staining.

Results : Expression of GFP was observed through the inner retina and cellular components in the CNV. These pattern of GFP expression were also well collocalized with CD31 (+) and F4/80 (+) cells located in the CNV tissue. In scAAV-GFP-mTOR shRNA-treated group, CNV volume was significantly reduced (p<0.05). Furthermore, CD31 and F4/80 expression were decreased . In addition, the expression of LC3B abd ATG7 were dramatically increased in the CNV sites of the scAAV-GFP-mTOR shRNA-treated eye. However, expression of these autophagic markers in the neuroretinal tissue was not significantly changed. Interestingly, the number of TUNEL (+) cells detected in the outer nuclear layer around the CNV tissue was dramatically decreased in the scAAV-GFP-mTOR shRNA-treated eye.

Conclusions : scAAV espressing mTOR shRNA along with GFP as a reporter gene did efficiently suppress laser-induced CNV in the mouse eye. These data confirm the induction of autophagy in the CNV can be used for the treatment of nAMD.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.