Ethical disputes make the future of stem-cell research murky, but there's no question it will proceed. Proponents say it could lead to breakthroughs as spectacular as cures for Parkinson's disease and diabetes, and the ability to grow new organs and tissues to order.
Stem cells are undifferentiated cells that can grow into various types of tissue. Medicine has been using adult stem cells, in the form of bone marrow transplants, for years to treat cancer and other conditions. Other breakthroughs have also been reported, such as the treatment of incontinence through injections of the patient's own stem cells.
Most people agree that adult stem cells should be explored thoroughly. The fight is over two other elements: using more versatile embryonic stem cells (discovered in 1998), which can become any type of tissue if properly cultured, and therapeutic cloning, or inserting a person's DNA into a donor egg and then tricking the egg into turning into an embryo from which the magical embryonic stem cells can be harvested and cultured.
Either way involves destroying an embryo, which one side believes is the equivalent of killing a person. Moreover, the same techniques used for therapeutic cloning could be turned to reproductive cloning, or creating an entire person. Nearly everyone thinks that's a bad idea, but the question is where to draw the line on other stem-cell research.
The federal government has essentially banned funding for research using embryonic stem cells, though individual states, such as California, fund it on their own. Meanwhile, the search continues for "ethical" sources of stem cells that are as versatile as embryonic cells. Possible sources include umbilical cord blood, baby teeth, testicular cells or multipotent adult progenitor cells, a specific type of stem cell found in bone marrow.