THE first treatment derived from embryonic stem cells might soon undergo clinical trials. The cells would be used to help repair damaged spinal tissue.
One of the main concerns with embryonic stem cell (ESC) treatments has been the possibility that the recipient’s immune system will see the transplanted cells as foreign and attack them.
Now Geron in Menlo Park, California, claims to have shown that this might not be a problem, at least for spinal repair treatment.
"I’m confident that we will be in the clinic next year with the first human ESC-derived product," said Tom Okarma, chief executive of Geron, at a conference in London last week. The company will soon be seeking permission from the US Food and Drug Administration to begin the trial.
Treatments with cells derived from human ESCs have been keenly awaited since 1998 when the cells were first cultured in the lab, providing a potentially inexhaustible supply. They have great clinical potential because they can grow into all types of body tissues, and so could in theory be used to generate new tissue or even entire new organs.
Geron’s plan is to treat people that have acute spinal injuries with oligodendrocyte progenitor cells grown from human ESCs. Oligodendrocyte cells support neurons in the brain and spine by sheathing them in myelin, a fat that helps neurons to transmit signals.
Spinal "crush" injuries often cause a loss of myelin, and so destroy the capacity of nerves to transmit signals. Previous experiments carried out by Geron in rats with damaged motor nerves suggested that oligodendrocyte progenitor cells injected into the spine can redress this, helping to restore movement.
The company now says it has evidence from cell-culture experiments that the treatment will not cause harmful immune reactions, though it has yet to release details of the research. "The oligodendrocyte progenitor cells don’t elicit major immune responses, at least in vitro," says Okarma, adding that the full results will be presented later this month in Toronto, Canada, at the annual meeting of the International Society for Stem Cell Research.
The finding will not make other stem cells treatments more likely, though, as immune responses from brain and spinal cord tissue are often mild or non-existent. Compared with other tissues, these organs have a relatively inactive immune system.
Some researchers have doubts about the claims. "We still don’t know how immunogenic these cells are, either when undifferentiated as human ESCS, or differentiated, like the oligodendrocytes," says Stephen Minger of King’s College London. "The evidence is all over the place."
