Why is there an interest in Newborn Stem Cells when other sources of cells, embryonic stem cells (ESC), induced pluripotent stem cells (iPSC), or those from either babies' teeth or adult fat, or bone marrow, are so often touted as coming to the therapeutic rescue? As the adage goes, "thumbs are not fingers, fingers are not thumbs; toes are neither fingers nor thumbs. However, fingers, thumbs and toes are all digits". So, too, one might describe stem cells. In other words, ESCs are not HSCs, HSCs are not ESCs; MSCs are neither ESCs nor HSCs. However, HSCs, ESCs and MSCs are all "stem" cells. There are two very important points to be made here. First, as discussed above, each cell population is heterogeneous (cell populations extracted from any tissue are never only one phenotype - except perhaps ESCs). As an example, cord blood cells are often called cord blood stem cells or even hematopoietic stem cells, although the vast majority of cells within such a population are not true stem cells but may facilitate the functional potency of the stem cell poo!. Similarly, mesenchymal cells derived from various tissues have been called "mesenchymal stem cells" (MSC)-although the majority of cells within such a population are not true stem cells, which has given rise to the more general term "mesenchymal stromal cell" (also abbreviated to MSC). Second, the tissue origin, number, and potency, among other characteristics of each cell population, are indicative of the clinical therapeutic potential of said population.
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