On Mar. 24, 2025, Hideyuki Okano, a stem-cell scientist at Keio University in Tokyo, and his colleagues announced in Nature that a paralysed man can stand on his own after receiving an injection of neural stem cells to treat his spinal cord injury.

The Japanese man was one of four individuals in a first-of-its-kind trial that used reprogrammed stem cells to treat people who are fully paralysed. Another man can now move his arms and legs following the treatment, but the two others did not show substantial improvements.

The results, which were announced at a press conference on March 21 and have not yet been peer reviewed, suggest that the treatment is safe, say researchers. In 2019, roughly 0.9 million people globally experienced a spinal cord injury, and some 20 million people were living with the condition.

Reprogrammed or induced pluripotent stem (iPS) cells are created by reverting adult cells to an embryonic-like state, from which they can be coaxed to develop into other cell types.

In this trial, iPS cells derived from a donor were used to create neural precursor cells. Two million of these were injected into each patient’s injury site, in the hope that they would eventually develop into neurons and glial cells. The results are the latest in a series of small human trials testing the potential of iPS cells to regenerate tissue and treat disease.