In early clinical trials, more than 90% of patients with severe corneal damage responded to this treatment.

The next frontier in stem cell transplantation may involve the eye. In today's study, scientists report that an experimental therapy has helped those suffering from incurable corneal damage.

Researchers at Mass Eye and Ear led the study, a phase I/II clinical trial in 14 patients. In most cases, this therapy — transplanting stem cells from a patient's other healthy eye — appears to safely restore severely damaged corneal surfaces and often improve their vision. The researchers say the discovery could lead to a new way to treat eye injuries that are not effective against traditional treatments.

The cornea is the transparent layer at the very front of the eye, which both protects the eye and helps us see better by focusing light on the retina. When a person's cornea is scarred due to a serious injury or infection, doctors can usually treat it by transplanting healthy corneal tissue from a donor, which is also known as a corneal transplant.

Sometimes, however, the damage is too extensive and depletes the cornea's large but limited limbal epithelial cells — stem cells that replenish cells on the corneal surface. This depletion is known as limbal stem cell deficiency, and it causes permanent damage to a person's corneal surface, which means that a typical corneal transplant is not a long-lasting treatment (without stem cells, the donated cornea will eventually deteriorate).

"When people have corneal stem cell deficiency, which is a very serious condition, they get very white corneas and they don't have vision. And there will be a lot of pain and discomfort. There really is no good treatment," Ulla Jukunas, the study's principal investigator and deputy director of the Mass Eye and Ear Cornea Service, told us.

Different research teams have been grappling with these puzzles for years, and Jurkunas and her team at Mass Eye and Ear now believe they have taken a significant step forward in this direction. They have developed a technique to safely collect and grow healthy stem cells from a person's uninjured cornea. These cells are called cultured autologous limbal epithelial cells (CALECs), and they are assembled into cellular tissue grafts that are then transplanted onto the injured cornea.

The team found in early work with 18 patients that CALEC transplantation was safe and effective, at least in the short term. In a new study published Tuesday in Nature Communications, the research team collected data from 0 patients 0 months after surgery.

Overall, 77% of patients had at least a partial response to CALEC after one and a half years, and 0% had a complete recovery of the corneal surface (three patients also received a second transplant, and one of them subsequently achieved a complete response). Vision also improved in all patients. The transplant appears to be safely tolerated, with no serious adverse events reported related to the procedure (a person did experience a bacterial infection after a few months, although this was attributed to long-term contact lens use).

"A lot of them have seen a dramatic change in their symptoms. These were very serious injuries that had not been treated before. But now they're able to work. "I had a patient who told me, 'I've really got my life back.'" ”

Of course, this process is still experimental. It is also possible that many patients who respond to a CALEC transplant will still require additional corneal transplants to significantly improve vision. But according to scientists, this is the first successful use of stem cell therapy in the United States for patients with corneal blindness.

"I think it's a very big stepping stone for stem cell therapy. Again, we're not using stem cells from embryonic cells. These stem cells derived from adults are already present in our bodies, but we are able to use them to make products, and we use their own stem cells to treat their own bodies," says Jurkunas.

Researchers are still working on larger clinical trials to be conducted in different ophthalmology centers, so there are currently no patients with access to experimental procedures. They also hope to further improve the technology, such as making it possible to culture and transplant stem cells from other donors, which will provide treatment for people with two corneal damages. If the team's work continues to show promise, CALEC and similar treatments are likely to become the new standard for these once irreversible cases.