What are the basic sources of stem cells for medical treatments?
Adult stem cells are found in body tissues, including bone marrow and certain other tissues in the bodies of adults and in discarded umbilical cord blood. ES cells are available from two basic sources. One source is leftover fertility clinic blastocysts that would otherwise be discarded and destroyed. The other source is a process called Somatic Cell Nuclear Transfer (SCNT), which provides a way to use a patient’s own cell and an unfertilized human egg to make ES cells in a lab dish. A NOTE ON TERMINOLOGY: Although laymen and news reports often refer to blastocysts as “embryos,” the scientific definition of an “embryo” more correctly applies to the stage of development that comes after a fertilized egg has passed through the zygote, morula and blastocyst stages of development and the blastocyst has been implanted in a uterus. Blastocysts used for ES cell research are microscopic balls of undifferentiated cells that have not been implanted and never will be implanted in a woman’s uterus
