![]() It was not until the 1990s that scientists agreed that the adult brain does contain stem cells that are able to generate the brain’s three major cell types-astrocytes and oligodendrocytes, which are non-neuronal cells, and neurons, or nerve cells. In the 1960s, scientists who were studying rats discovered two regions of the brain that contained dividing cells that ultimately become nerve cells, but despite these reports most scientists believed that the adult brain could not generate new nerve cells. ![]() These non-hematopoietic stem cells make up a small proportion of the stromal cell population in the bone marrow and can generate bone, cartilage, and fat cells that support the formation of blood and fibrous connective tissue. Types of adult stem cellsīone marrow stem cells are also called mesenchymal stem cells, and were discovered a few years later. Bone Marrow stromal stem cells are a multipotent subset of bone marrow stromal cells that are able to form bone, cartilage, stromal cells that support blood formation, fat, and fibrous tissue. Hematopoietic stem cells form all the types of blood cells in the body. In the 1950s, researchers discovered that the bone marrow contains at least two kinds of stem cells. The history of research on adult stem cells began more than 60 years ago. If the differentiation of adult stem cells can be controlled in the laboratory, these cells may become the basis of transplantation-based therapies. Scientists now have evidence that stem cells exist in the brain and the heart, two locations where adult stem cells were not at first expected to reside. In fact, adult hematopoietic-or blood-forming-stem cells from bone marrow have been used in transplants for more than 40 years. This finding has led researchers and clinicians to consider whether adult stem cells could be used for transplants. Scientists have found adult stem cells in many more tissues than they once thought possible. Research on adult stem cells has generated a great deal of excitement. Unlike embryonic stem cells, which are defined by their origin (cells from the preimplantation-stage embryo), the origin of adult stem cells in some mature tissues is still under investigation. Scientists also use the term somatic stem cell to describe adult stem cells, where somatic refers to cells of the body (not the germ cells, sperm or eggs). The primary role of adult stem cells in a living organism is to maintain and repair the tissue in which they are found. The adult stem cell can renew itself and can differentiate to yield some or all of the major specialized cell types of the tissue or organ. ![]() An adult stem cell is an undifferentiated cell, found among differentiated cells in tissue or an organ.
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