Can New Neural Cells Support an Injured Spinal Cord?
A spinal cord injury can interrupt the communication pathways that carry movement and sensory signals between the brain and body. Because the spinal cord has a limited ability to repair itself, restoring these damaged connections remains one of regenerative medicine’s biggest challenges.
A first-in-human Phase I study explored whether neural stem and progenitor cells made from induced pluripotent stem cells (iPSCs) could safely be transplanted into the injured spinal cord.
How Did the Treatment Work?
iPSCs are cells that have been reprogrammed into a flexible state where they can develop into other specialized cell types. For this study, researchers turned them into neural stem/progenitor cells, which have the potential to develop into cells found in the nervous system.
The trial included four men between 26 and 66 years old with recent, complete cervical spinal cord injuries. Each participant received a single transplant of 2 million iPSC-derived neural cells directly into the injury site approximately two to four weeks after their injury.
Participants also received temporary immune-suppressing medication and standard rehabilitation.
Safety Was the Main Goal
Because iPSC-derived therapies involve living cells capable of growth, researchers paid especially close attention to abnormal cell growth and tumor formation.
After two to four years of follow-up, researchers reported:
- No tumors or abnormal cell growth
- No serious adverse events attributed to the transplanted cells
- Stable transplant sites on long-term imaging
- No progressive neurological decline linked to the treatment
Some side effects were associated with the surgical procedure or temporary immune-suppressing medication rather than the transplanted cells themselves.
Encouraging Changes in Movement
Although the trial was primarily designed to study safety, researchers also tracked neurological recovery.
All four participants showed improvements in motor and functional measurements during the first year. The median improvement in the study’s motor score was 13 points at 52 weeks, with most of the gains occurring during the first several months.
Two participants experienced particularly notable changes in their spinal cord injury classification:
- One improved from AIS Grade A to Grade C
- Another improved from AIS Grade A to Grade D
These changes indicate that some sensory and voluntary movement returned below the original injury level.
What Makes This Approach Interesting?
The goal of the transplanted neural progenitor cells is not simply to reduce symptoms. Researchers hope these cells may eventually help create a more supportive environment for damaged neural tissue and potentially contribute to rebuilding connections within the spinal cord.
However, this study cannot prove that the transplanted cells caused the improvements. Natural recovery and rehabilitation can also contribute to neurological gains after a spinal cord injury. That is why larger controlled trials will be important.
An Important First Step
With only four participants and no randomized control group, the findings should be viewed as early clinical evidence rather than proof of effectiveness.
Still, the long-term safety results are encouraging. Researchers found no tumor formation or graft-related serious complications during up to four years of follow-up, while some participants also experienced meaningful improvements in movement and neurological function.
For regenerative medicine, this study represents an important step toward understanding whether iPSC-derived neural cells could one day help support recovery after spinal cord injury.
Source
Sugai K, Tsuji O, Fujiyoshi K, et al. An iPSC-derived neural progenitor cell therapy for subacute spinal cord injury: a phase 1 trial with long-term follow-up. Nature Medicine. 2026;32:3438–3448. Available from: https://www.nature.com/articles/s41591-026-04549-6
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