Photo/IllutrationMasayo Takahashi, a researcher at Riken, presents research results by a study team that confirmed the safety of eye surgery using iPS cells from third-party donors, at the 123rd annual meeting of the Japanese Ophthalmological Society on April 18. (Kazuya Goto)

Five severe eye disease patients at risk of blindness have maintained their level of eyesight a year after receiving retina cells made from a donor’s induced pluripotent stem (iPS) cells, a Japanese study team determined.

The patients' positive condition provides the world's first confirmation that eye surgery using iPS cells from third-party donors can be safely performed, said a Riken research institute researcher, who led the project team.

“We finally climbed as far as the seventh stage,” said Masayo Takahashi, on April 18, using a mountain-climbing analogy to describe the team's achievement, at the Japanese Ophthalmological Society's 123rd annual meeting.

The safety confirmation comes about 11 years after human-induced iPS cells were first created.

The third-party iPS cells allow patients to receive transplants quicker and cheaper than using stem cells created from the patients' own bodies.

The study by the Riken team and other entities, whose objective was to ascertain the safety of the surgery, found no major rejections, cancers or other abnormalities in cells transplanted to patients with age-related macular degeneration in the year following the surgery, Takahashi said.

The study showed that cells were successfully transplanted without developing into aggressive tumors. One patient showed a mild rejection but medication was able to alleviate it.

The team put about 250,000 retina cells, which were converted from third-party IPS cells, into solutions and transplanted them through injections into the eyes of five male patients in their 60s to 80s from March to September 2017.

The donors of the cells created for the iPS cell stock possess a special type of immune system that is unlikely to trigger a transplant rejection in most Japanese patients.

The five patients the team selected for the project have a match with this system.

It is extremely expensive to create iPS cells from a patient’s skin or blood cells and then produce the nerve cells or other cells the treatment requires.

Masahiro Kinooka, professor of biochemical engineering at Osaka University, said it is more realistic to create high-quality iPS cells made from the blood of healthy donors first and then increase the number of such cells to store them for commercial use.

A stock of various types of iPS cells allows doctors to choose ones that are a match for individual patients.

Currently, many clinical studies use iPS cells from third-party donors.