Reduction of fibronectin expression by intravitreal administration of antisense oligonucleotides

We have investigated whether antisense oligonucleotides delivered intravitr eally could reduce gene expression specifically in the retina. In this stud y, phosphorothioate antisense oligonucleotides targeted to fibronectin tran scripts were coupled to a novel carrier and used to specifically reduce fib ronectin (FN) expression in retinal vascular cells. Using confocal microsco py, fluorescence from fluorescein isothio-cyanate-labeled FN-oligonucleotid es was detected in retinal vascular cells at 24 h postinjection and persist ed until day 6 (the end point of this study). The fibronectin mRNA level wa s consistently decreased to 86.7% +/- 7.9% of control (p<0.05) at day 2, an d 46.7% +/- 4.9% of control (p<0.01) at day 6. In contrast, the p-actin mRN A level, an internal control, was unaltered in rat retinas that received FN -oligonucleotides. Fibronectin protein level at day 6 was also significantl y reduced to 61.4% +/- 16% of control (p<0.01). No toxic effect resulting f rom the carrier was detected histologically. Thus, intravitreal delivery of antisense oligonucleotides to modulate abnormal gene expression in retinal diseases may he an effective approach for ocular gene therapy.