A promising method for creating therapeutic stem cells without destroying human embryos has encountered a major setback, as reported this month in the journal Nature.

The research involves induced pluripotent stem cells, or iPS cells. Like embryonic stem cells, iPS cells have the ability to develop into any adult cell in the body, from bone to brain.

Their discovery by Japanese researchers in 2007 was met with great fanfare, because iPS cells can be created easily from adult cells such as skin. This method circumvents the controversy inherent in harvesting stem cells from human embryos, which many consider to be protected human life.

Alas, the iPS method might be too simplistic. University of California, San Diego researchers found that mice injected with iPS cells genetically similar to their own adult cells violently rejected the transfusion, as if it were foreign matter. Meanwhile, others accepted a similar injection of embryonic stem cells with ease.

The study doesn't spell the end of iPS cells. Rather, this work demonstrates the importance of human embryonic stem cell research, now limited by law. Without continued, complementary research on the "real thing," work on otherwise promising alternatives is futile — a concept that the U.S. government remains hesitant to accept.

Great promise

Stem cell therapy holds great promise because it offers the ability to grow new tissue to replace older, diseased tissue. The body itself employs this technique at a basic level: Adult blood stem cells, for example, churn out the various types of new red and white blood cells. Other adult stem cells create new bone or skin in response to damage.

Once a cell reaches its end point — skin, bone, blood, etc. — there's no turning back. A blood cell can't turn into a skin cell. Not even a blood stem cell can make skin.

Embryonic stem cells, however, have the ability to differentiate into all the body's cells. That, of course, is how a fetus grows. Thus, embryonic stem cells harvested from discarded, frozen embryos from fertility clinics offer the best hope for patients suffering from paralysis, Parkinson's disease, Alzheimer's disease, cancer and many other afflictions.

Oh, right, the law

Human embryonic stem cell research has been severely limited for over three decades, on moral grounds. In 1980 President Ronald Reagan instituted a moratorium on public funding, which remained in place into the George W. Bush administration. Bush allowed limited funding for embryonic cells already derived from discarded embryos but not for any new cells. This left only 20 viable cell lines, not enough to perform substantial research. [Embryonic Stem Cells: 5 Misconceptions]

President Obama lifted the funding ban when he came into office. But this action could be reversed once again in the coming months as the courts continue to debate the relevance of the 1995 Dickey-Wicker Amendment, which bans federal funding on any research that destroys human embryos. Much of the field remains as frozen as the embryos themselves, and few younger scientists are pursuing a career in stem cells.

While work on iPS cells is exciting, it is nearly useless without embryonic stem cells as a control. The iPS technique — involving a four-gene tweak of adult cells to coax them into acting like embryonic cells — was possible only through direct research on embryonic cells. And as seen in the UCSD study, conducted in part with non-federal dollars, researchers need to understand how "real" embryonic stem cells work to understand what iPS cells lack.

Pluripotent wording

The future of embryonic stem cell research and thus stem cell research in general unfortunately remains hinged upon an interpretation of legal language, not science.

The Dickey-Wicker Amendment concerns "research in which a human embryo or embryos are destroyed [or] discarded." Obama's argument that federal funding could be used on cell lines derived from embryos destroyed with non-federal dollars is just semantics. Everyone knows the intent of this conservative Christian-based law was to stop all research on human embryos — or more precisely, on a blastocyst, a collection of a few dozen undifferentiated cells — because a considerable percentage of Americans consider this human life with a soul.

Science, however, tells a different story, one in which humans evolved over the course millions of years, with no clear distinction between the last ape ancestor and the first human with a soul.

From a scientific perspective, embryos bring the potential of life — whether that life is among the approximately 150 million babies born each year, or among the approximately 25 percent of all fertilized eggs lost in a natural miscarriage, or among the countless blastocysts thrown away daily at fertility clinics, or among the millions of patients who someday could be cured through stem cell research.

Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His column, Bad Medicine, appears regularly on LiveScience.