By Robert Bazell Chief science and health correspondent
NBC News
updated 5/13/2011 2:21:35 PM ET 2011-05-13T18:21:35

New research suggests that laboratory-created stem cells might not be a solution to all the ethical problems created by stem cells from embryos, as many as hoped.

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Yang Xu, professor of molecular biology, and colleagues at the University of California, San Diego, in a paper published Friday in the prestigious British journal Nature find that so-called induced pluripotent stem cells (iPSCs) generate an immune response causing a mouse to reject them even when the iPSCs are made from the cells of that same mouse.

The term “stem cell” has many meanings, but much of the intense interest in research focuses on the stem cells that are capable of becoming any other cell in the body. This process raises the hope that they could someday be used to cure Parkinson’s, diabetes, spinal cord injury and a host of other conditions.

At first these scientists could harvest these stem cells only from human embryos that were discarded when not needed for vitro fertilization. Opponents of stem cell research argue that destroying the human embryos is a form of abortion.

But in 2006 researchers found that with genetic engineering they could take skin cells or any other cells from the body and convert them into iPSCs — cells that seem to behave like embryonic stem cells. Not only did this finding raise the possibility that the concerns over embryos could be ignored, the experiments created an intriguing new goal for research. If scientists could make iPSCs from an individual they could then transform them into kidney cells or brain cells or whatever cells were needed to treat that individual.

It's been assumed that this less controversial approach would avoid the body’s natural rejection response because it would the patient’s own cells. The latest research suggests that the genetic engineering necessary to make iPSCs changes them enough so the body rejects them as foreign.

Scientists emphasize this is only one study in mice. But it shows that scientists are yet to understand all the complexities of stem cell biology.

Another approach has been suggested for creating stem cells that would not evoke an immune response. Scientists would take a patient's DNA, put it into an emptied shell of a human egg to create an embryo and then harvest stem cells from that embryo. This “therapeutic cloning” would undoubtedly end up back in the thicket of the ethics debate.

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