Induction of gene into the rabbit eye by iontophoresis: preliminary report

To assess the transfer of 6-carboxyfluorescein (6-FAM)-labeled phosphorothioate oligonucleotides(S-ODNs) into the ocular tissues, their stability, and possibility of injury to the ocular tissues.

The S-ODNs(2 mL/eye)were transduced noninvasively into albino rabbit eyes.The iontophoresis group consisted of 6 rabbits (12 eyes); the control group consisted of 2 rabbits (4 eyes) given eye drops containing S-ODNs. Aqueous humor and vitreous humor were collected after iontophoresis, subjected to electrophoresis with a fluorescence DNA sequencer and analyzed by the Gene Scan program. Frozen sections, 10-microm thick, were prepared for observation under a fluorescence microscope. A plasmid 4.7 kbp in size that expresses green fluorescent protein (GFP) was induced into the 18 eyes of 9 rabbits by the same procedure.

In the iontophoresis group, S-ODNs were detected in the anterior chamber 5 minutes after electrophoresis began and in the vitreous after 10 minutes. These S-ODNs maintained the same length as at the initial synthesis. The S-ODNs could also be detected in the posterior retina 20 minutes after electrophoresis. No evidence of degeneration or inflammation due to the above procedure was found in the ocular tissues. Fluorescence showing GFP gene expression was found in the cornea, the anterior chamber angle, and the ciliary subepithelial tissues.

These findings show that iontophoresis is an effective method to induce genes into the rabbit eye.