Mayo Clinic researchers have demonstrated they can permanently transfer a functioning gene to targeted tissues within the eye.
This success in animals is a first step in using gene therapy to treat glaucoma, a major cause of blindness worldwide. The research findings appear in the online issue of the leading vision science journal Investigative Ophthalmology and Visual Science.
Glaucoma causes pressure build up within the eyeball due to malfunctioning fluid drainage in the front of the eye. Blindness occurs when pressure progressively damages the optic nerve at the back of the eye. Eye specialists have long hoped for a permanent way to fix the malfunctioning outflow - and they may now be a step closer because of the Mayo Clinic research.
The gene that researchers transferred was a phosphorescent green protein naturally found in jellyfish. A routine procedure for ophthalmologists - a single, tiny injection through the surface of the eye (cornea) - was sufficient to introduce the jellyfish gene. The protein was encased in a specialized viral delivery system called a vector. When the vector reached the intended destination in eyes of laboratory cats, the vector’s cargo gene produced the phosphorescent jellyfish protein in the cats’ eyes. Researchers knew they were successful because the cats’ eyes turned green when viewed with ultraviolet light at the targeted area. They also knew the effect was permanent because the cats’ eyes continue to glow green more than a year after the procedure. The green-eyed cats have normal vision and are none the worse for the gene transfer.
“The main message here is that a specific kind of gene vector - a lentiviral vector - could be engineered to work really well as a delivery system to the particular tissue involved in glaucoma,” says Eric Poeschla, M.D., a virologist in Mayo Clinic’s Molecular Medicine program and the lead investigator on the project. “The next challenge is to replace the jellyfish protein with one that can safely treat glaucoma, which is what we are trying to accomplish now.”
This work has at least three important implications for gene therapy for glaucoma: