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The next frontier of stem cell transplantation might involve the eyes. In research out today, scientists report that an experimental therapy has helped people with otherwise untreatable injuries to their corneas.
Researchers at Mass Eye and Ear led the study, a Phase I/II clinical trial of 14 patients. In most cases, the therapy—a transplant of stem cells from the person’s other healthy eye—appeared to safely restore the surface of people’s severely damaged corneas, often improving their vision as well. The findings could lead to a novel treatment for eye injuries that don’t respond to conventional options, the researchers say.
The cornea is the transparent frontmost layer of the eye that both protects it and helps us see clearly by focusing light on the retina. When people’s corneas are scarred by serious injury or infection, doctors can usually treat it by transplanting healthy corneal tissue from a donor, also known as a corneal graft.
But sometimes, an injury is so extensive that it depletes the cornea’s large but limited supply of limbal epithelial cells—the stem cells that replenish the cells on the cornea’s surface. This depletion is called a limbal stem cell deficiency and it leaves people with a permanently damaged corneal surface, meaning that a typical corneal graft can’t be a lasting treatment (without the stem cells, the donated cornea will eventually deteriorate).
“When people have a corneal stem cell deficiency, which is a very devastating condition, they can have a really white cornea and no vision. And there’s a lot of pain and discomfort. There are really no good ways to treat that,” lead study researcher Ula Jurkunas, associate director of the Cornea Service at Mass Eye and Ear, told Gizmodo.
Stem cells in culture collected from the first patient given a CALEC transplant. © Mass Eye and Ear Various research teams have been working for years to solve these difficult cases, and Jurkunas and her team at Mass Eye and Ear now believe they’ve made a major step forward in doing so. They’ve developed a technique to safely collect and then grow healthy stem cells from a person’s uninjured cornea. These cells, called cultivated autologous limbal epithelial cells (CALEC), are assembled into a cellular tissue graft, which is then transplanted over to the person’s injured cornea.
The team’s earlier work in four patients had found that CALEC grafts could be safe and effective, at least in the short term. In its new research, published Tuesday in Nature Communications, the team collected data from 14 patients up to 18 months after their procedure.
Overall, 92% of patients showed at least a partial response to CALEC a year-and-a-half later, with 77% experiencing a complete restoration of their corneal surface (three patients also received a second graft, with one achieving a complete response afterward). All of the patients experienced at least some improvement in their visual acuity as well. And the transplant appeared to be safely tolerated, with no serious reported adverse events tied to the procedure (one person did experience a bacterial infection several months later, though this was attributed to chronic contact lens use).
“A lot of them have had a great transformative change in their symptoms. And these were really severe injuries with no current treatment beforehand. But now they’re able to function,” Jurkunas said. “I had one patient tell me, ‘I actually got my life back.'”
This procedure is still experimental, of course. It’s also likely that many patients who respond to a CALEC graft would still need an additional corneal graft for their vision to substantially improve. But according to the scientists, this is the first stem cell therapy of its kind in the U.S. to be used successfully in people with corneal blindness.
“I think that this is a very big stepping stone for stem cell therapy in general. Again, we’re not using stem cells from embryonic cells. These are adult-derived stem cells that already exist in our bodies, but we’re able to harness them and to create products where we treat the person’s own body with their own stem cells,” Jurkunas said.
The researchers are still trying to get larger clinical trials underway that can be performed at different eye centers, so the experimental procedure isn’t available to any patients for the time being. They’re also hoping to improve the technology further, such as making it possible to cultivate and transplant stem cells from other donors, which would then open up the therapy to people with two damaged corneas. Should the team’s work continue to show promise, CALEC and similar treatments could very well become a new standard of care for these once-irreversible cases.
