After the ES cells began to divide, they could be treated with hormones that would cause them to develop into marrow cells, which could then be returned to the patient. Similarly, islet cells could be created from the skin cells of a diabetic and returned to the patient's pancreas, where they would produce insulin. Eventually, ES cells could be turned into healthy heart or liver cells that could be used to repair tissue damaged by heart attacks or hepatitis. Congress is considering several bills, sponsored mainly by Republicans, that would ban the research that could lead to these new treatments. Stampeded by the anti-abortion lobby, congressional Republicans want to treat ES cells like human embryos, even though their ultimate form depends entirely on the intentions of the patients and doctors who create them.
Silver highlights the important distinction between growth and development.
ES cells can grow and divide into millions of identical cells, but they do not develop into any particular kind of cell until told to do so through biochemical signals. In a sense, the creation of ES cells in vitro would be like enhancing the natural production of ES cells in vivo. ES cells created from a patient's skin to treat disease are no more ethically problematic than veins taken from his legs to be used in a heart bypass operation. Both are the patient's cells, and both are being used for purposes different from their original function. Down the road, it may be possible to reset cells without using enucleated human ova.