Content area
Full Text
'...the revolution of using stem cells for regenerative medicine has begun.'
Stem cells with the potential for the treatment of a wide range of degenerative disorders may be obtained from a variety of sources but, for practical reasons, some of them are more likely to find earlier clinical application than others. The main types that have been studied in the context of stem cell therapy are embryonic stem cells, fetal stem cells and adult stem cells.
Embryonic stem cells and, to a lesser extent, fetal stem cells have the potential to repair many types of tissue because they are totipotent [1]. Embryonic stem cells can be greatly increased in number in culture as cell lines in vitro and may be immuno-priviledged. These attributes mean that they can be used to treat multiple patients. However, their use has been confounded by serious ethical issues [2] and the very real likelihood that, being immortal, they will form tumors after they have been transplanted into patients [3]. Undoubtedly, however, these barriers to widespread application will be overcome in the future.
Adult stem cells exist in many tissues and organs and these stem cells have differentiation potentials beyond those required to regenerate the tissue or organ in which they reside [4]. Clearly, some of these sources of adult stem cells, like brain stem cells, are less accessible than others, such as bone marrow stem cells. The use of bone marrow-derived stem cells for tissue and organ repair has the additional advantage that there is considerable experience in the clinical application of bone marrow transplantation for the regeneration of the hemopoietic system, dating from the 1970s when relatively large clinical studies were initiated. By 2002, 20,207 hemopoietic stem cell transplants had been performed in Europe by 586 teams in 39 countries. This clinical experience has been accompanied by a wealth of laboratory studies on hemopoietic stem cells and transplantation biology.
In general, two distinct stem cell populations are thought to reside in hemopoietic tissue. These are hemopoietic stem cells and the mesenchymal stem cells. Classically, hemopoietic stem cells are the precursors of all of the blood cell lineages [5] and the mesenchymal stem cells are the source of the supporting stromal cells...