Getting older is supposed to give you perspective. But for one out of five people over the age of 65, it does the opposite. Macular degeneration is a common progressive eye condition, one that thins and breaks down a tissue behind the center of the retina. Without that tissue, the light-sensing cells it supports atrophy and die, making it impossible to get a clear picture of anything straight ahead of you—like, say, the faces of your loved ones or anything past your steering wheel. Treatments can slow the loss of vision, but there’s no way to reverse it.
Which is why scientists have long been excited about the prospect of using stem cells to restore that tissue, and with it the sharp central vision necessary for driving, reading, and navigating the world. Clinical trials in the last few years have shown that injecting stem cell-derived retinal pigment cells into the eye can be done safely. But so far they haven’t been that effective, because the support cells often don’t wind up in the right place. They need a little help, a little structure.
And for the first time, that’s exactly what a group of scientists from the University of Southern California are giving them. By building a synthetic scaffold, the team of bioengineers could get retinal pigment cells derived from embryonic stem cells into a single, fixed layer that mimics the natural tissue. And when ophthalmologist Amir Kashani and Mark Humayun surgically cemented the implant beneath the retinas of four patients, the new cells didn’t just stay put—they began activating photoreceptors that had gone dormant in the damaged tissue above.
The researchers published initial results from this first human clinical trial Wednesday in the journal Science Translational Medicine. The implant successfully stopped further vision loss in all four patients in follow-ups that ranged from four months to a year. The youngest patient, a 69-year-old woman, actually got some vision back. She went from only being able to see seven letters on an eyesight test—you know, the one where the letters of the alphabet get smaller and smaller each row you go down—to being able to see 24 just four months post-surgery.
Of course, with a sample size this small it’s impossible to say whether the improvement is statistically (or clinically) significant. The study will continue enrolling until it gets 20 patients, and will follow them for five years. “We certainly need more subjects to be able to say how it works and when it works, and even why it works,” says Kashani. “But the fact we’re getting any improvement in any of these patients who have such advanced diagnoses is a pretty good sign of its potential.”
To pass regulatory muster, treatments like this one—which would be manufactured as an off-the-shelf implant—will require much bigger, longer, more prospective studies to prove their effectiveness. As more of them inch closer to commercialization, the Food and Drug Administration has begun cracking down on the more than 600 clinics across the US that hawk stem cells harvested from the blood and fat of patients, claiming they can treat everything from arthritis to autism. In 2015, doctors at one such clinic in Florida charged three elderly women with macular degeneration $5,000 each to inject these kinds of stem cells into their eyes. All three went blind.
Last August the FDA sent a warning letter to the clinic, which has since ceased administering the treatment for age-related vision loss. “Without commitment to the principles of adequate evidence generation that have led to so much medical progress, we may never see stem cell therapy reach its full potential,” wrote former FDA Commissioner Robert Califf, in an editorial that accompanied a case study of one of the Florida women in the New England Journal of Medicine.
It’s a concern that researchers like Kashani share. The implants he’s studying are the result of a decade of lab work at public research institutions and private companies in southern California. And he fears that in that decade, stem cell treatments have been tarnished by the doctors that rushed ahead to turn a quick profit. “It makes it more difficult when you lose a lot of public trust, frankly,” says Kashani. “At the end of the day you can’t develop these therapies without patient involvement.” A bonafide stem cell cure for macular degeneration is going to take more than a little perspective. It’s going to take patience, too.
Stem Cell Hopes
- Stem cells have the potential to treat a wide range of diseases, but therapies administered by stem cell clinics across the US are not FDA-approved.
- Such experimental regenerative medicines got a big boost from the 21st Century Cures Act.
- And the results can be truly astonishing: In one case, scientists used genetically corrected stem cells to grow a new skin for a boy with a rare genetic disorder.
