Intraretinal Regeneration of Axotomised Retinal Ganglion Cells After AAV Mediated CNTF Delivery

Abstract

Abstract: : Purpose: The regeneration of axotomised retinal ganglion cells has been observed in the embryonic retina, but is generally not seen in the adult. One factor limiting regeneration might be the absence of vital neurotrophic factors, which decline in the early post–embryonic period. Viral gene transfer is a means of re–introducing high sustained intraocular levels of neurotrophic factors and might therefore facilitate regeneration. Methods: One quadrant of the adult rat retina was axotomised by a linear retinotomy between the two temporal vortex veins. An intravitreal injection of recombinant adeno–associated virus carrying CNTF or control transgenes had been given three weeks previously. The CNTF transgene was coupled bicistronically to the GFP reporter gene. For control experiments, the transgene included the GFP reporter gene only. Results: Four weeks after axotomy in the presence of CNTF, regenerating ganglion cells were identified by axonal labelling. A few axons had crossed the retinotomy and were directed towards the optic disc, but most appeared to have regenerated randomly. Growth cones could be identified at the tips of knotted axons growing out from the lesioned retina. No growth was seen in control retinas. Non–axotomised retinal ganglion cells did not show additional axon sprouting and appeared to have a relatively normal morphology when retrogradely labelled with DiI. Conclusions: Adult retinal ganglion cells regenerated axons in the presence of CNTF delivered by viral gene transfer, but the observed axon growth did not follow the normal centripetal gradient seen during development.

Keywords: ganglion cells • neuroprotection • gene transfer/gene therapy