Researchers at the Icahn School of Medicine at Mt. Sinai in New York City recently used stem cells to induce the retina to regrow rod cells in an animal model of congenital blindness. The report was published in the August 15 online issue of the journal Nature.
The paper notes that cold-blooded vertebrates like the zebrafish can use Müller glial cells to regenerate any type of retinal neuron. In mammals, however, the MGCs stay quiet and don’t allow regeneration in retinal degenerative diseases. “We’re trying to reactivate this regenerative capability in the mammalian retina to regenerate photoreceptors,” says lead investigator Bo Chen, PhD, associate professor of ophthalmology and director of the Ocular Stem Cell Program at Icahn.
Dr. Chen says the process involved two steps: “First, we used adeno-associated virus as a tool to deliver a gene to the MGCs by way of intravitreal injection,” he explains. “This gene transfer induced the MGCs to re-enter the cell cycle, to divide and produce daughter cells. Then, two weeks later, we used another gene transfer to transfer transcription factors and help guide the MGCs to become photoreceptors.” These newly created rods integrated into the existing retinal structure, and the researchers say there’s no difference between them and naturally occurring rod cells. Four to six weeks after the gene transfer, the mice regained vision, though the researchers weren’t able to measure the exact degree of visual improvement.
“Our goal is to one day have our work benefit humans,” Dr. Chen avers. “We’re currently working with clinicians to see if we can get human retinal samples from patients who have undergone enucleation. We could then culture the retinal samples and work with them.”
FDA Approval Watch
August brought several new nods from the FDA:
• Ivantis Hydrus. Surgeons have a new tool for their anti-glaucoma arsenal in the form of this canal-based microstent. We take a closer look at the Hydrus and the new iStent inject, in this month’s Technology Update.
• Sun Pharma’s Cequa 0.09%. This cyclosporine A solution is a new option for dry-eye patients. Sun says that Cequa provides the highest FDAapproved concentration of CsA and is the first approved CsA product to use a nanomicellar technology to help overcome solubility challenges.
• Eylea (aflibercept) labeling. The FDA approved a label change for Eylea in patients with wet AMD. The approval was based on second-year data from the Phase III VIEW 1 and 2 trials in which patients were treated with a modified 12-week dosing schedule. These data are now on the label.
• MeiraGTx AAV-CNGA3. The FDA granted orphan drug designation for AAV-CNGA3 gene therapy for the treatment of achromatopsia caused by mutations in the CNGA3 gene. AAVCNGA3 is an investigational gene therapy delivered to the cone receptors via subretinal injection.
• Dompé’s Oxervate. Oxervate received orphan-drug designation for the treatment of neurotrophic keratitis, becoming the first topical biologic in ophthalmology and the first drug approved specifically for NK.
• Kala’s Inveltys. Inveltys (loteprednol etabonate ophthalmic suspension) 1% was approved for postop inflammation and pain following ocular surgery. It’s the first b.i.d. ocular steroid approved for this indication. REVIEW