Even as embryonic stem-cell research took center stage in Congress this week, scientists said they are exploring an alternative that could defuse the controversy: extracting stem cells from placentas.

The Senate passed a bill Tuesday that would expand federal funding of embryonic stem-cell research to include embryos left over at fertilization clinics, which would otherwise be discarded. The House of Representatives passed the bill in 2005, but President Bush has promised to veto it.

Scientists say placentas could meet the worldwide demand for stem cells several times over without sacrificing a single embryo. They say the placenta is a rich source of stem cells capable of transforming into many types of cells in the body, holding out the hope of using them to treat many human ailments including spinal-cord injury and diabetes.

Other sources of "controversy-free" stem cells have been touted as ways to circumvent the ethical quandary destroying embryos presents. On Tuesday, members of Congress who believe the practice equals taking a life encouraged funding of research using stem cells found in bone marrow, umbilical cords and hair follicles, just to name a few ideas.

These so-called adult stem cells have less ability to morph into various types of cells for potential therapies than embryonic stem cells, studies have shown. Placental stem cells, however, are unique, according to some researchers who say they may be nearly as transformative as embryonic stem cells.

"For the life of me I can’t understand why the whole world isn’t working much more intently on adult stem cells like these," says Dr. Eve Slater, former undersecretary of health for the U.S. Department of Health and Human Services. "In my opinion they have a far greater potential to be used in therapeutics."

Celgene, a stem-cell company in New Jersey, claims to have isolated placental stem cells that have many of the same desirable properties found in the embryonic version. And the bonus, says acting CEO Bob Hariri, is they don’t come from embryos, they are more plentiful and they don’t form tumors.

Even better, Hariri says his company’s cells have unique immunological properties that suppress immune rejection. If that’s true, Celgene’s cells could reduce tissue rejection in transplant patients, and even open the door for nonhuman-to-human transplantations.

By Gretchen Cuda