![]() Stem cells can also be modified to resist certain infections. Stem cells can be modified to produce enzymes or factors, such as insulin, before being transplanted into the body. Scientists are using genetic modification to expand the potential therapeutic applications of stem cells. ![]() Of all the adult stem cells identified so far, hematopoeitic stem cells (a stem cell from which all red and white blood cells develop) have been the most studied. Researchers are encouraging adult stem cells, such as those from the skin, to become other types of tissue, such as nerve or muscle. This research involves many biotechnology applications, such as the study of stem cell genetics, biological factors (normally occurring proteins that the body needs to function normally), receptors on the stem cells and stem cell physiology. This would allow them to create any tissue or organ in the body from a single stem cell. One of the goals of scientists is to control cell differentiation. Much research is ongoing in this area, as large numbers of cells are needed for stem cell replacement therapies. While large numbers of ES cells can be grown in a laboratory, adult stem cells are rare in mature tissues and a way to increase their numbers in cell culture has not yet been developed. Several animal and early human trials are also underway to use pluripotent or adult stem cells to repair damage to the nervous system, such as in spinal cord injury, Parkinson's disease and Alzheimer's disease. The stem cells were shown to "beat" with the surrounding heart cells. Several groups have been working on animal models in which pluripotent stem cells are grafted into damaged hearts. The stem cells of the matched donor are purified, and the patient's bone marrow is then destroyed by radiation and reconstituted with the stem cell graft. Adult blood-forming stem cells from bone marrow have been used in transplants for over 30 years. For example, adult blood stem cells have been used to treat hematologic (blood) cancers. Some diseases have already been targeted. If the differentiation of adult stem cells can be controlled in the laboratory, these cells may become the basis of therapies for many serious common diseases. ![]() Because adult stem cells have been found in many more tissues than originally thought possible, scientists have asked whether adult stem cells could be used for transplants. Research into adult stem cells has caused a lot of excitement. Unlike ES cells, which are defined by where they originated (in the inner cell mass of the blastocyst), the origin of adult stem cells in mature tissues is unknown. Some scientists are now calling adult stem cells "somatic stem cells". However, no adult stem cell has been definitively shown to be completely pluripotent. For example, scientists now believe that certain types of adult stem cells can develop into cells of another tissue (for example human blood stem cells have been shown to differentiate into liver cells if the conditions are right). The possibility that adult stem cells also have a greater "plasticity" than previously believed has resulted in new experimentation. The use of adult stem cells would also reduce the chance of transplant rejection because patients could receive transplants of their own stem cells. Research into adult stem cells has the potential to eliminate ethical concerns about experimentation or transplantation of ES cells. However, recent discoveries are pointing to new sources of stem cells within the adult body. It was long thought that adult stem cells had less flexibility than ES cells, and that they could normally form only cell types the same as the tissue of origin. They are responsible for the repair and regeneration in the body. These "adult" stem cells are found in many human tissues, such as blood, brain, intestine, skin and muscle. Multipotent stem cells can become only a certain type of cell, such as a blood cell.Īdult stem cells are found in the fetus, child and adult.Pluripotent stem cells can become almost any cell in the human body, but they cannot become placental tissue needed for development in the human uterus and.Totipotent stem cells can become any cell in the human body.Biochemical cues in different parts of the body stimulate stem cells to grow into the specific cells needed in that location.Īll stem cells have the capacity to differentiate, but to different degrees. Stem cell differentiation begins when they are exposed to certain biochemical cues - either physiological or experimental. The process by which the stem cell can become a specific cell type is called differentiation.
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