In January 2009, the US Food and Drug Administration (FDA) approved the first human trial of an embryonic stem cell–based treatment. Led by the biotech company Geron (Menlo Park, California), researchers plan to test this therapy in people who have become paralyzed from the waist down due to acute thoracic (back) spinal cord injuries. The aim of the therapy, called GRNOPC1, is to help these patients regain some sensation and movement in their lower limbs.

About 48% of acute spinal injuries in humans are thoracic injuries, while 52% are cervical (neck) injuries. Due to a lack of animal data, the FDA has not approved the therapy for testing in humans with acute cervical injuries. However, researchers have now reported that this therapy helps rats with acute cervical spinal injuries.

GRNOPC1 consists of oligodendrocyte progenitor cells that are derived from human embryonic stem cells. These cells become oligodendrocytes, which form myelin, an insulating material that helps speed up nerve cell communication. The GRNOPC1 therapy traces its roots back to work done by Hans Keirstead of the University of California at Irvine and his colleagues. In 2005 Keirstead and his team reported that the therapy helped restore movement in rats with thoracic injuries (J. Neurosci., 25, 4694–4705; 2005). Now, doctoral student Jason Sharpe, Keirstead and colleagues have shown that the oligodendrocyte progenitor cell therapy helped restore motor function in rats with acute cervical spinal cord injuries (Stem Cells published online 28 October, 2009; doi:10.1002/stem.245).

The research team injured spinal cords of adult female rats at the cervical level. One week later, they injected the oligodendrocyte progenitor cell product into the spinal cords of half of the rats and a control solution into the remaining rats. They tested forelimb motor function of both groups of rats and found that the injections significantly improved forelimb motor function. Further analysis showed that injecting the oligodendrocyte progenitor cells into the injured rats helped to rebuild myelin, prevented tissue death and even prompted nerve fiber regrowth.

In August, the FDA put the GRNOPC1 trial for patients with acute thoracic injuries on hold. Pending FDA approval of additional animal data that will be submitted by Geron, the thoracic trial should be re-initiated in spring 2010. Keirstead and colleagues hope their recent results will make it more likely for the FDA to allow the therapy to also be tested in people with acute cervical injuries.