iPS Cell Transplantation Helps 2 Paralyzed Patients Improve Motor Functions; Research Team Says Cells ‘Repaired Damage’

The Yomiuri Shimbun

17:17 JST, March 22, 2025

A research team in Japan unveiled Friday that two of four paralyzed patients who received transplantations of cells derived from induced pluripotent stem (iPS) cells saw improvement in their motor functions.

The two patients can now eat by themselves, and one is able to stand.

The team, which consists of researchers from Keio University and other institutions, believes “the transplanted cells may have repaired the damage.”

The clinical study, which is the first of its kind, was conducted by a team led by Masaya Nakamura, a professor of orthopedic surgery at Keio University, and Hideyuki Okano, a professor of physiology at the university.

The results were reported at a meeting of the Japanese Society for Regenerative Medicine held in Yokohama.

According to the team’s presentation, the four patients were aged 18 or older and two to four weeks out from suffering a spinal cord injury, which resulted in a loss of motor functions as well as sensory paralysis below the neck or chest.

The team produced cells that would become nerves from healthy human iPS cells and transplanted approximately two million of them into each patient’s spinal cord from 2021 to 2023.

The patients also underwent regular rehabilitation and other treatments to promote their recovery.

A test to evaluate the efficacy of the transplantations was conducted about one year later. It showed that one patient’s motor functions had improved three ranks and another patient’s had improved two ranks on a five-level scale.

The remaining two patients had the same rank as before their transplantation but reportedly showed some improvement, meaning that 50% of the patients showed recovery.

This latest clinical study was aimed chiefly at confirming the safety of the transplantation, and no serious adverse health effects were observed. The efficacy of the procedure will be further examined. The team said they also plan to conduct a clinical trial on patients with chronic paralysis in 2027.

There are approximately 6,000 new patients every year in Japan suffering from spinal cord injuries caused by such things as traffic accidents. There are estimated to be more than 100,000 patients with chronic paralysis in the country.

One patient practices walking

“I feel like I can see a beacon of hope,” said Makoto Ohama, chairman of the Japan Spinal Cord Foundation, a Tokyo-based group of patients with spinal cord injuries, after he listened to the research team’s presentation at the Yokohama meeting.

People who suffer spinal cord injuries and become paralyzed below the neck or chest are still conscious but lose sensation in their hands and legs, making it difficult for them to eat, bathe and use the bathroom.

Spinal cord injuries are ranked on a five-level scale, from grade A (complete paralysis) to grade E (normal motor function). Some studies have shown that rehabilitation helps about 10% of patients improve their motor functions from grade A to grade C (limited motor function) or grade D (some motor function, such as ability to stand).

One of the two patients who showed recovery in the trial, an elderly person whose motor functions improved to grade D, has reportedly begun practicing walking while also undergoing rehabilitation.

“We believe it is quite rare [for patients with spinal cord injuries to see their rank] improved from grade A to grade D,” said Nakamura.

Nerves may have increased

The team said one patient’s magnetic resonance imaging scans showed that a damaged area that had been hollow before the treatment was found to be filled about one year later.

“It’s possible that the [transplanted] cells have engrafted and are increasing the number of nerves,” said Prof. Toru Ogata of the University of Tokyo, who is familiar with spinal cord impairment. “Even though it is only one person, it’s amazing that a grade-A patient is now able to stand and can start practicing to walk. The outcome is groundbreaking.”

All the patients received transplantation during the subacute stage — between two and four weeks after their spinal cord was damaged. Patients in the subacute stage are said to have a greater chance of recovery than patients in the chronic stage. Even if a patient’s nerves seem ruptured, making them completely paralyzed, the nerves can still be connected in some cases.

In this regard, Kota Suda, director of the Hokkaido Spinal Cord Injury Center, has a high evaluation of the latest study. “The Keio University team chose difficult cases from among completely paralyzed patients,” he said.

Number of cases will be the key

On the other hand, the clinical study was unable to confirm the treatment’s efficacy in two of the four patients. The injury of one of the two patients was extremely severe before the transplantation. Although all four of the patients were completely paralyzed, the degree of their injuries likely differed.

The treatment was performed as a clinical test to ensure its safety, and the number of patients was limited to four. The team limited the number of cells transplanted to two million because animal testing confirmed that figure to be safe, without risk, for instance, of causing tumors to develop.

Nakamura said the current phase of the study shows that the treatment may be effective. He went on to say that the team plans to continue to conduct clinical tests on patients in the subacute phase. “We think we need to increase the number of transplanted cells,” he said.

Prof. Kinichi Nakashima of Kyushu University pointed out that the transplantation of cells into patients in the subacute phase may have prolonged the survival of existing cells. “The key will be whether the team can prove the treatment’s efficacy by increasing the number of successful cases,” he said.