“The most sobering thing about [hES] cells is their power,” says neuroscientist Clive Svendsen of the University of Wisconsin, Madison, who works with both fetal and embryonic stem cells. The extreme flexibility and capacity for growth characteristic of ES cells makes them ideal for producing large quantities of therapeutic cells to treat, say, diabetes or spinal cord injuries. But these same traits also increase the risk that renegade cells could, as they have in animal studies, cause unwanted side effects, ending up in the wrong place or even sparking cancerous growth. “You have to learn to control that power in the dish” before thinking about putting the cells into patients, says Svendsen.
Office of Strategic Communication