American company Geron Corporation (GC) has been given permission to resume its clinical trials testing the embryonic stem cell treatment GRNPOC1.

GC had originally been given permission to begin the trials in January 2009, but was then told to wait after a round of preclinical animal tests showed some worrying side effects. Researchers found that the animals given the GRNOPC1 treatment developed a higher number of cysts at the area of spinal cord injury than had been seen in previous studies. There were concerns that these cysts could produce cancerous teratomas, a detrimental side effect that could also potentially affect patients. This finding caused GC share prices to fall by 14 per cent after the trial suspension was announced. However further investigation has shown these cysts to be benign, confined to the site injury and not associated with any serious adverse effects, and so now the FDA has agreed to allow the human trials to begin.

GRNOPC1 consists of oligodendrocyte progenitor cells (OPCs), a type of neural cell derived from a human embryonic stem cell line (hESC). OPCs have the potential to differentiate into mature oligodendrocytes, which are a type of neuroglia cell responsible for coating nerve fibres with the insulating substance myelin. Loss of myelin after spinal cord injury can contribute to the loss of neural function. Just one oligodendroctye can help to insulate 50 nerve fibres, so GC aim to test if injections of these progenitor cells can improve recovery in people with spinal cord injuries.