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Margaret E. McDougal, Claire-Anne Gutekunst, Robert E. Gross; C3 Transferase Gene Therapy for Neuroprotection and Optic Nerve Regeneration. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1570.
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© ARVO (1962-2015); The Authors (2016-present)
C3 transferase (C3) is a promising treatment for glaucoma. In addition to lowering intraocular pressure (IOP), C3 protects and regenerates retinal ganglion cells (RGCs) after injury. However, these effects are limited by C3’s short duration of action and poor distribution. To address this, adeno-associated viral (AAV) vectors tagged with green fluorescent protein (GFP) were engineered to express an endogenous (e) and a secretable/permeable (sp) C3 to allow for long-term and widespread distribution of C3.
C3 gene therapy was delivered via intravitreous injection in the rat optic nerve crush (ONC) model, and animals were sacrificed at 4 and 8 weeks. RGC survival was quantified following immunostaining of the retina with an RGC-specific antibody. Optic nerves were labeled with anterograde tracer and underwent tissue clearance to allow detailed visualization of regenerating axons through the whole nerve.
In the control group, only 6% of RGCs survived 8 weeks after injury, whereas treatment with AAV-eC3GFP protected 45% of RGCs, and the widespread distribution by AAV-spC3GFP kept a remarkable 74% of RGCs alive. Robust long-distance axon regeneration was observed at 4 weeks in both treatment groups compared to controls, with a significant 38- and 24-fold increase in axon regeneration at 1 mm past the crush site for AAV-eC3GFP (p = 0.005) and AAV-spC3GFP (p = 0.02), respectively.
Modified C3 gene therapy greatly enhances RGC survival and axon regeneration after injury. These data, along with the known IOP lowering effects, suggest C3 gene therapy as an effective neuroprotective and regenerative glaucoma treatment.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Animals received an intravitreous injection of adeno-associated viral vector one-week prior to optic nerve crush and were sacrificed 4 weeks later. Confocal micrographs of cleared optic nerves were used to quantify cholera toxin subunit B (CTB)-647-labeled retinal ganglion cell axons that regenerated past the crush site (white carets). Figure is a representative two-dimensional image of the optic nerve regeneration seen in an AAV-eC3GFP treated animal. Scale bar, 100 µm.
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