Protection of axotomized retinal ganglion cells by adenovirally delivered BDNF in vivo

Following intraorbital transection of the optic nerve (ON) in rats, more than 80% of the retinal ganglion cell (RGC) population die by apoptosis within 14 days. Repeated intraocular injection of brain-derived neurotrophic factor (BDNF) has been efficient in enhancing RGC survival following ON axotomy. The present study was designed to define a potential survival-promoting effect of adenovirally administered BDNF on axotomized RGCs. A single injection of an adenoviral vector expressing the human BDNF gene from a CMV promoter/enhancer (Ad-BDNF) enhanced RGC survival 14 days after axotomy by 40.3%. Moreover, a combinatory treatment regimen consisting of intraocular Ad-BDNF administration and systemic application of the free radical scavenger, N-tert-butyl-(2-sulphophenyl)-nitrone (S-PBN), enhanced RGC survival by 63.0%. Our data demonstrate that adenoviral delivery of neurotrophic factors to the vitreous body is a feasible approach for the prevention of axotomy-induced RGC death. Further, as shown for S-PBN, therapeutic regimens that combine local virus-mediated gene delivery with systemic administration of protective compounds, may offer promising strategies for future treatment also in human neurodegenerative conditions.