Dose-dependent rescue of axotomized rat retinal ganglion cells by adenovirus-mediated expression of glial cell-line derived neurotrophic factor in vivo

Adult rat retinal ganglion cells undergo degeneration after optic nerve transection. Repeated intraocular injection of glial cell-line derived neurotrophic factor (GDNF) has been shown to be efficient in enhancing retinal ganglion cell survival following optic nerve axotomy. In the present study we evaluated the potential survival-promoting effect of adenovirally administered GDNF on axotomized retinal ganglion cells. A single intravitreal injection [7 x 10(7) plaque-forming units (pfu) or 7 x 10(8) pfu] of an adenoviral vector expressing the rat GDNF gene from a cytomegalovirus promoter enhanced retinal ganglion cell survival 14 days after axotomy by 67 and 125%, respectively, when compared to control animals. Intraocular administration of the vector rescued 12.6 and 23%, respectively, of the retinal ganglion cells which would otherwise have died after axotomy. An increase in retinal GDNF protein and specific virally transduced GDNF mRNA expression was detected following intraocular vector application. Our data support previous findings showing that adenoviral delivery of neurotrophic factors to the vitreous body is a feasible approach for the prevention of axotomy-induced retinal ganglion cell death in vivo and may constitute a relevant strategy for future treatment in traumatic brain injury and ensuing neurodegeneration.