Effects of Adeno-associated Virus-vectored Ciliary Neurotrophic Factor on Retinal Structure and Function in Mice with a P216L rds/peripherin Mutation

• Published in: Experimental eye research Vol. 74; no. 6; pp. 719 - 735
• Main Authors: Bok, Dean, Yasumura, Douglas, Matthes, Michael T., Ruiz, Alberto, Duncan, Jacque L., Chappelow, Aimee V., Zolutukhin, Sergei, Hauswirth, William, LaVail, Matthew M.
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01.06.2002; Elsevier
• Subjects: AAV; Adenoviridae - genetics; Animals; Biological and medical sciences; ciliary neurotrophic factor; Ciliary Neurotrophic Factor - genetics; Ciliary Neurotrophic Factor - physiology; CNTF; cytokine; Electroretinography; Eye and associated structures. Visual pathways and centers. Vision; Eye Proteins - genetics; Fundamental and applied biological sciences. Psychology; gene therapy; Genetic Therapy - methods; Genetic Vectors; Intermediate Filament Proteins - genetics; Membrane Glycoproteins; Mice; Mice, Inbred C57BL; Mice, Transgenic; Nerve Tissue Proteins - genetics; Peripherins; photoreceptor; Photoreceptor Cells, Vertebrate - pathology; Point Mutation; rds; rescue; Retina - physiopathology; Retinal Degeneration - pathology; Retinal Degeneration - physiopathology; Retinal Degeneration - therapy; retinitis pigmentosa; Reverse Transcriptase Polymerase Chain Reaction; Vertebrates: nervous system and sense organs; rds; cytokine; CNTF; AAV; photoreceptor; retinitis pigmentosa; gene therapy; mice; ciliary neurotrophic factor; rescue; Eye; Visual system; Neurotrophic factor; Vertebrata; Mammalia; Mouse; Rodentia; Peripherin; Retina; Mutation; Ciliary neurotrophic factor
• DOI: 10.1006/exer.2002.1176
• ISSN: 0014-4835

Past studies have shown that acute administration of ciliary neurotrophic factor (CNTF) can prolong the survival of retinal photoreceptor cells that have undergone phototoxic injury or that express gene mutations. Adenovirus-vectored CNTF has also been effective but for all of these treatments, the effect has been transient. On the other hand, adeno-associated virus-vectored minigenes offer considerable promise for long-term survival. The authors sought to provide long-term, CNTF-based protection of mouse photoreceptors expressing a dominant-negative point mutation in the rds gene by using recombinant adeno-associated virus (rAAV) to deliver minigenes that code for a secreted form of CNTF. Secreted CNTF, under control of a cytomegalovirus (CMV) or chick beta actin (CBA) promoter provided long-term, panretinal rescue of photoreceptors following single injections of rAAV vectors into the subretinal compartment. Rescue was much less effective and less reproducible when the vectors were placed in the vitreous compartment. However, there were unexpected side effects that appeared to be dose-related. One side effect was a change in rod photoreceptor nucleus phenotype, featuring an increase in euchromatin and an increase in nuclear size following subretinal injections but not intravitreal injections. These nuclear changes were panretinal when the putatively stronger CBA promoter was used but not panretinal when the CMV promoter was used. In the latter case, the nuclear changes were much more pronounced at the site of injection. Thus, chronic hyperstimulation of retinal cells with CNTF may up-regulate gene expression in photoreceptors. Based on current knowledge of retinal cell targets for CNTF, this effect may be indirect and may not represent direct stimulation of photoreceptors by CNTF. A second side effect was a paradoxical decrease in scotopic a- and b-wave amplitudes and a decrease in photopic b-wave amplitudes in the injected, rescued retina when compared to its contralateral, uninjected counterpart, in spite of the fact that these retinas had more photoreceptors than their untreated mates. The basis for these decreased ERG amplitudes may be related to changes in gene expression. The mechanisms for these side effects and proper doses of CNTF administration should be determined before human clinical trials are considered for the amelioration of inherited retinal degenerations with CNTF.