Paralyzed marmoset monkeys are walking again after a Japanese research team transplanted induced pluripotent stem cells (iPS cells) into the animals’ spines — the first time the treatment has succeeded in a primate subject.
The iPS cell transplant — carried out by researchers from Keio University and the Central Institute for Experimental Animals — had been performed on mice in the past. However, the successful application of the treatment in a species so close to humans — announced by Keio professor and group member Hideyuki Okano at the Molecular Biology Society of Japan on Dec. 7 — brings iPS transplants for spinal cord injury patients one step closer.
Spinal cord damage is an all-too common result of car crashes and other accidents, though at present there is essentially no effective treatment for such injuries. Okano and his team began their research with damaging the spinal cords of marmosets, paralyzing them from the neck down. They then transplanted cells that would become nerve tissue, produced from iPS cells, into the damaged area nine days after the injury — the most effective timing for such transplant treatment.
The researchers found that the marmosets soon began to regain some motor function, and could both stand on their hind legs and grip things with their hands around a month after the transplant. The team believes the transplanted cells did become nerve cells, regenerating the damaged spinal tissue. They used a type of iPS that has little chance of becoming cancerous — one of the primary challenges of stem cell research — and none of the marmosets had developed tumors three months after the procedure.
“The marmosets have dramatically recovered from their injuries to the extent that they can repeatedly jump,” Okano said, adding that he hoped to proceed with research into transplants using even safer types of iPS cells.
One challenge to providing the treatment to humans is timing. It takes six months or more to create iPS cells — not nearly quick enough for timely transplants to recent accident victims. To overcome this problem, the research group is also partnering with Osaka National Hospital to study the creation of an iPS cell bank that would make the stem cells available on demand.