What are human embryonic stem cells?<br />Stem cells are cells that have the remarkable potential to develop into many different cell types in the body. Serving as a sort of repair system for the body, they can theoretically divide without limit to replenish other cells for as long as the person or animal is still alive. When a stem cell divides, each "daughter" cell has the potential to either remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell.<br /><br />Why not use adult stem cells instead of using human embryonic stem cells in research?<br />Human embryonic stem cells are thought to have much greater developmental potential than adult stem cells. This means that embryonic stem cells may be pluripotent that is, able to give rise to cells found in all tissues of the embryo except for germ cells rather than being merely multipotent--restricted to specific subpopulations of cell types, as adult stem cells are thought to be. <br /><br />Have human embryonic stem cells been used successfully to treat any human diseases yet? <br />Scientists have only been able to do experiments with human embryonic stem cells (hESC) since 1998, when a group led by Dr. James Thompson at the University of Wisconsin developed a technique to isolate and grow the cells. Moreover, Federal funds to support hESC research have only been available since August 9, 2001, when President Bush announced his decision on Federal funding for hESC research. Because many academic researchers rely on Federal funds to support their laboratories, they are just beginning to learn how to grow and use the cells. Thus, although hESC are thought to offer potential cures and therapies for many devastating diseases, research using them is still in its early stages.<br /><br />Adult stem cells such as blood-forming stem cells in bone marrow (called hematopoietic stem cells, or HSCs) are currently the only type of stem cell commonly used to treat human diseases. Doctors have been transferring HSCs in bone marrow transplants for over 40 years. More advanced techniques of collecting, or "harvesting", HSCs are now used in order to treat leukemia, lymphoma and several inherited blood disorders.<br /><br />The clinical potential of adult stem cells has also been demonstrated in the treatment of other human diseases that include diabetes and advanced kidney cancer. However, these newer uses have involved studies with a very limited number of patients.<br /><br />
if ya know what I mean. 
