Current Status of Human Stem Cell Research
"Stem cells" is a term to describe precursor cells that can give rise to multiple tissue types. There are important distinctions, however, regarding how developmentally plastic these cells are; that is, how many different paths they can follow and to what portion of a functioning organ they can contribute. Totipotent stem cells are cells that can give rise to a fully functional organism as well as to every cell type of the body. Pluripotent stem cells are capable of giving rise to virtually any tissue type, but not to a functioning organism. Multipotent stem cells are more differentiated cells (that is, their possible lineages are less plastic/more determined) and thus can give rise only to a limited number of tissues. For example, a specific type of multipotent stem cell called a mesenchymal stem cell has been shown to produce bone, muscle, cartilage, fat, and other connective tissues.