Photo/Illutration Koji Nishida, professor of ophthalmology at Osaka University, speaks at a news conference in Osaka Prefecture on April 4 about the clinical trial in which corneal cells made from iPS cells were transplanted into patients suffering from a stem cell deficiency. (Fumi Yada)

Transplanting corneal cells made from human induced pluripotent stem (iPS) cells into patients with a vision-impairing disease didn’t cause any serious side effects, researchers announced on April 4.

Some of the patients’ eyesight even improved as a result of the clinical trial, the team at Osaka University said.

“This could be a revolutionary treatment that could overcome the challenges that existing treatment has faced, such as a shortage of cornea donors or transplant rejection,” said Koji Nishida, a member of the team and professor of ophthalmology at the university, at a news conference.

The team transplanted corneal cells into four patients with serious cases of corneal epithelial stem cell deficiency--a disease that occurs when stem cells comprising the cornea are lost due to an injury or for other reasons.

The disease causes a patient’s cornea to become cloudy and can lead to loss of vision.

The team didn’t note any side effects one year after the operations, including the cells becoming cancerous, or any sign of transplant rejection in the patients.

In the trial, the team first created corneal cells from iPS cells that had been generated from third-party donors. They then shaped the corneal cells into sheets 0.03 to 0.05 millimeter thick.

From July 2019 to December 2020, the team transplanted the sheet-like corneal cells into the four patients in their 30s to 70s suffering from corneal epithelial stem cell deficiency.

The aim was to maintain corneal transparency in the patients' eyes by allowing the sheet-like corneal cells to continuously create corneal epithelium.

Although the deficiency could be treated by transplanting another person's cornea into a patient, donors are in short supply in Japan. It can also cause transplant rejection in some patients.

Two of the four patients in the clinical trial completed the transplant process without needing to be injected with an immunosuppressant, a drug that prevents rejection after transplant surgeries.

The four patients' corneas are also less cloudy after the transplant, although how clear they are varies between them, Nishida said. 

He also reported that the corrected eyesight for three of the four patients was 0.04 on the Japanese optometric system scale before the transplant, but it improved to 0.3 after the operation.

The aim of the clinical trial was to ensure the safety of the treatment.