What Is Known About Adult Stem Cells?
• To date, published scientific papers indicate that adult stem cells have been identified in brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, epithelia of the skin and digestive system, cornea, dental pulp of the tooth, retina, liver, and pancreas. Thus, adult stem cells have been found in tissues that develop from all three embryonic germ layers. • There is no evidence of an adult stem cell that is pluripotent. It has not been demonstrated that one adult stem cell can be directed to develop into any cell type of the body. That is, no adult stem cell has been shown to be capable of developing into cells from all three embryonic germ layers. • In the body, adult stem cells can proliferate without differentiating for a long period (the characteristic referred to as long-term self-renewal), and they can give rise to mature cell types that have characteristic shapes and specialized functions of a particular tissue. • Adult stem cells are rare. Often they are difficult
