ABSTRACT
Adult stem cells are undifferentiated cells that are present in an otherwise differentiated tissue or organ. They renew themselves throughout their life, producing either identical copies of themselves or differentiating into specialized cells of the respective tissues (Watt & Hogan 2000: 1427−30). Adult stem cells have been discovered in a variety of organs and tissues: bone marrow, brain, epidermis, blood, liver, skin, eyes, intestine, pancreas and skeletal muscle. The use of adult stem cells
as therapy for human diseases would be of interest for several reasons. one reason is that it is the function of adult stem cells to build different cell types of a particular tissue. Ideally, it should then be possible through the transplantation of adult stem cells to regenerate all these different cell types. Among other findings, it has been shown that at least a few stem cells can migrate to impaired tissues (Aboody et al. 2000: 12846−51). This would ease surgery significantly because the transplanted tissues would need to match the target tissue less precisely. in addition, it was proven (at least for neural stem cells) that stem cells secrete growth factors that possibly protect or even mobilize other cells in affected tissues (Noble 2000a: 369−70, and 2000b: 12393−5). Should this discovery prove generally valid, the healing of affected tissues could be made easier through this method. It may even be possible to activate stem cells to produce more growth factors before the transplantation or to change them genetically so that they build important substances for regenerating the tissue.
