Into the Fire
Back in Baltimore, Gearhart had adopted a radically different strategy-and one that appears to have propelled him to the front of the pack. He decided to sidestep the use of blastocyst-stage embryos altogether as a source of ES cells. The deciding factors were both political and scientific. The government’s funding ban, combined with the poor quality of available embryos “turned me away from that approach,” he says.
Instead, Gearhart picked up on a technique devised by cell biologist Brigid Hogan at Vanderbilt University Medical School. In 1992, Hogan showed that so-called primordial germ cells from the genital ridge (terrain destined to develop into the testes or the ovaries) of a mouse fetus could be grown in culture and acted much like ES cells. She hypothesized that the same approach might work in humans. Using aborted fetuses donated by patients, Hogan managed to isolate some interesting cells but wasn’t able to establish permanent cell lineages growing in culture-a key aim of ES research.
This alternative approach circumvented some of the funding and scientific difficulties of working with embryos. Yet in some ways it was a case of jumping out of the frying pan into the fire, since researchers using aborted fetuses are exposed to the same risk of violence from anti-abortion activists that abortion clinics face. “The threat to people working with fetal material is very real,” says Hogan.
Nevertheless, Gearhart took this strategy and ran with it-possibly all the way to the finish line. In July 1997, at the 13th International Congress of Developmental Biology in Snowbird, Utah, which was still abuzz from Ian Wilmut’s announcement that February that he had cloned a sheep named Dolly, Gearhart told a special ethics forum that he and postdoc Michael Shamblott had been growing “ES-like cells” in their lab for the preceding six months.
The connection between the ES cells and Dolly was more than just a coincidence of timing: Human ES cells could, in principle, be the vehicle for creating new breeds of human beings, as the mouse ES cells have already been used for mice. Gearhart, however, assured some attendees that neither he nor his colleagues had any intention of producing genetically altered people. His focus, he said, is strictly on the cells’ potential for saving lives by growing replacement tissues and organs and by providing important tissues for medical research. Yet even Gearhart’s colleagues understand where the fear of this new technology comes from. “It’s so easy to imagine the bad applications, since the misuse of technology, the Frankenstein myth, is already part of the vernacular,” says Pedersen, who chaired the ethics session at Snowbird.
Is Gearhart the winner in the race for the human ES cell? That’s not an easy question to answer. He and his collaborators say they have succeeded in growing “ES-like cells” from 5-to-9-week-old fetuses and are sustaining them in cell culture. But, in keeping with the field’s atmosphere of secrecy, Gearhart’s lab hasn’t yet published its results. The difference between these fetal germ cells and ES cells may well turn out to be a bone of contention among labs in the race. Gearhart, for his part, remains confident. “For all practical purposes,” he believes, these cells and ES cells will turn out to be “equivalent.”
Whether Gearhart has already won the race behind closed doors or not, the benefits for medicine of having a winner will be very large, with the largest payoff probably coming in the area of growing replacement tissues and cells.