What is an adult (tissue-specific) stem cell?
Perhaps better referred to as a tissue-specific stem cell, these cells are found in tissues that have already developed. Tissue-specific stem cells can be isolated from many tissues, including brain. The most common source of tissue-specific stem cells is the bone marrow, located in the center of some bones. There are different types of stem cells found in the bone marrow, including hematopoietic or blood stem cells, endothelial stem cells, and mesenchymal stem cells. It is well established that hematopoietic stem cells form blood, that endothelial stem cells form the vascular system (arteries and veins), and that mesenchymal stem cells form bone, cartilage, muscle, fat, and fibroblasts.
