Shh10, A Novel müLler Glia Cell-specific Aav Vector, Expressing Gdnf Is Neuroprotective In Murine Model Of Microbead-induced Glaucoma

Abstract

Purpose: : GDNF is a highly conserved neurotrophic factor, which promotes neuronal survival. ShH10 is a novel AAV variant that efficiently transfects Müller glia following intravitreal injection. This study aims to test if ShH10.GDNF is neuroprotective in the murine model of microbead-induced ocular hypertension.

Methods: : Polystyrene microbeads were injected into the anterior chamber of adult mice to elevate intraocular pressure. A 1μl intravitreal injection containing 1x10e9 vector genomes of either ShH10.GDNF or ShH10.GFP was administered into the same eye. Intraocular pressure was measured using a TonoLab tonometer at weekly intervals throughout the study. An enzyme-linked immunosorbent assay (ELISA) was performed at eight weeks to quantify GDNF levels in the retina and optic nerve. Mice were sacrificed at four and eight weeks and retinal ganglion cell (RGC) loss was quantified.

Results: : Increased intraocular pressure was confirmed in microbead-injected eyes by tonometer. ELISA demonstrated a significant increase in GDNF in both the retina and optic nerve in ShH10.GDNF injected eyes (retina: 75ng GDNF/mg total protein; optic nerve: 1.02ng/mg) compared to uninjected control eyes (retina: 13ng/mg; optic nerve: 0.3ng/mg). Uninjected contralateral control eyes had a mean RGC count of 288±75 cell per field (cpf). Microbead injected eyes that received ShH10.GDNF demonstrated 234±74 cpf at four weeks and 114±48 cpf at eight weeks. Microbead injected eyes that received ShH10.GFP demonstrated 100±37 cpf at four weeks and 34±26 cpf at eight weeks. Thus, microbead injected eyes treated with ShH10.GDNF contained a 234% increase in viable RGCs at four weeks and a 335% increase in viable RGCs at eight weeks compared to eyes treated with ShH10.GFP (n=5; P0.05).

Conclusions: : ShH10.GDNF results in efficient secretion of GDNF by retinal Müller glial cells and has neuroprotective effects on RGC survival. Increased GDNF expression has no effect on intraocular pressure, which is consistent with GDNF-induced neuroprotection in an environment of elevated intraocular pressure. Intravitreal ShH10.GDNF may represent a promising treatment for glaucoma by targeting the neurodegenerative aspect of this disease.

Keywords: neuroprotection • ganglion cells • cell survival