San Francisco— When researchers first demonstrated in 2007 that human skin cells could be reprogrammed to behave like stem cells that can fully differentiate into other cells, scientists and politicians alike rejoiced. All the potential of embryonic stem cells might be harnessed with the new techniques—without the political and moral controversy associated with destroying a fertilized egg.

That optimism, however, may be misplaced; these transformed cells, known as induced pluripotent stem cells (iPS cells), actually present equally troubling ethical quandaries, according to bioethicists who met at the International Society for Stem Cell Research annual meeting in June. Not only do many of the ethical challenges posed by embryonic stem cells remain, but the relative ease and low cost of iPS techniques, combined with the accessibility of cells, accelerate the need to address futuristic-sounding possibilities such as creating gametes for reproduction. Scientists have already reported progress in growing precursor cells for eggs and sperm from both iPS and embryonic stem cell lines.

Although perfecting the process may take another decade, “we should start thinking carefully about this now,” said Kazuto Kato, a bioethicist at Kyoto University in Japan. To make sure the gametes work normally, for instance, researchers will need to grow embryos and then destroy them, a morally contentious practice with prohibitions and policies differing around the world. Sperm and egg from skin cells eventually might be used for reproductive purposes, enabling parenthood at any age using tissue from either the living or dead. In fertility clinics, iPS cells could enable prospective parents to choose embryos for desired traits more easily than they can with conventional assisted-reproduction technologies. The possibilities raise a radical question about the moral status of human cells, noted Jan Helge Solbakk, head of research at the Center for Medical Ethics at the University of Oslo in Norway and chair of the society’s ethics and public policy committee.

Although Kato called human reproductive cloning directly from iPS cell lines “very hypothetical,” he pointed out progress for that possibility when he noted that three teams had produced mouse clones from iPS cells. Less expensive and more efficient than the process that produced Dolly the sheep, the iPS approach also would skirt the language of many current prohibitions against human reproductive cloning. Some bioethicists have called for a new international ban that would clearly prohibit the implantation of a human clone in part because of the tantalizing research uses for nascent embryos.

More immediate concerns have to do with control of the original donation and tissue grown from iPS cells. “Biobanks” all over the world already store biological material and related data for research, and many do not seek consent for future work as long as the material cannot be connected back to the donor. The far-reaching potential of iPS research, combined with a higher likelihood that cell lines will stay linked to a single donor (and that donor’s health history), heightens the need for consensus, said Timothy Caulfield, research director of the Health Law Institute at the University of Alberta in Edmonton.

Yet such consensus may be hard to achieve. In research on attitudes, Caulfield has noticed a trend: clinical researchers, patient participants, privacy experts and the general public disagree about whether consent should be necessary for each new use of donated tissue or whether blanket consent will do. And how will a disillusioned cell donor withdraw when iPS cell lines have been distributed all over the world? Bedrock international research norms of consent and withdrawal may no longer be workable. “We have to recognize all the complicated issues that iPS research is engaging and get a sense of how existing laws and policies play out,” Caulfield said.

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Some ethicists suggest that tissue donors deserve a share of the tremendous commercial potential of iPS cell lines as disease models, drug-testing platforms or treatments. New partnerships could acknowledge the contributions of both the cell provider and the laboratories that grow and sustain iPS cell lines. Donors might share in some monetary rewards and be able to opt out of certain uses for iPS cells, such as for creating gametes or mixed species, or have a say in the overall direction of research, Solbakk suggested.

The stem cell society’s ethics committee is working on a paper that would explore the rights of tissue donors and make recommendations by the end of the year. Solbakk also hopes to hold more public forums that could clarify research advances while also stimulating reflection on ethical challenges. He said the society would continue its efforts to reduce hype in the field. A new Web site aims to help patients evaluate claims by clinics that offer stem cell treatment and even submit a clinic for review by the society. “The most vulnerable resource,” Solbakk said, “is trust.”