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Thread: Perspectives on the properties of stem cells

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    Perspectives on the properties of stem cells

    http://www.nature.com/nm/journal/v11...1005-1026.html




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    Nature Medicine 11, 1026 - 1028 (2005)
    doi:10.1038/nm1005-1026 Perspectives on the properties of stem cells

    Ernest A McCulloch & James E Till Ernest A McCulloch and James E Till are at the Ontario Cancer Institute, Princess Margaret Hospital, University Health Network, Toronto, Ontario M5G 2M9, Canada. mcculloc@uhnres.utoronto.ca or till@uhnres.utoronto.ca

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    Much about stem cells is controversial. For example, even the question 'what is a stem cell?' arouses controversy. One definition of stem cells is that they are "primal undifferentiated cells which retain the ability to differentiate into other cell types...[which] allows them to act as a repair system for the body, replenishing other cells as long as the organism is alive"1. This definition is controversial for at least two reasons. First, it could be interpreted to imply that a stem cell is simply an undifferentiated cell that is able to give rise to differentiated descendants (i.e., that 'stem cell' is equivalent to 'progenitor cell'). Second, this definition neglects a crucial property of stem cells—that some of their descendants must retain stem cell properties.

    We suggested in 1963 that stem cells have two defining properties that are evident at cell division2. First, progeny arising from division may retain stem properties; that is, the stem cells have made new stem cells, the property called self-renewal. Alternatively, the progeny of stem cell division may have lost the capacity for self-renewal; instead, they may either differentiate or enter into a series of terminal divisions, finally yielding an organized tissue such as an organ or a population of functional blood cells. Beyond these two central properties, stem cells are identified and named according to the function of their descendants (for example, marrow stem cells) or their place in development (for example, adult stem cells or embryonic stem cells). Stem cells also vary in the diversity of their differentiated descendants. Those with unlimited potential are called totipotent stem cells. Equivalent designations are used for cells whose potential is limited (pluripotent stem cells, multipotent stem cells, bipolar stem cells, etc.). Much research forms the basis of these various designations, and questions about the self-renewal potential and the differentiation potential of various kinds of stem cells continue3.

    The introduction of the concept of plasticity is a good example of the general impact of stem cells throughout biology and medicine. Here we provide a few other examples, such as the impact of stem cells on the development of diversity and cancer. Furthermore, recent work in many laboratories is showing the possibility of functional uses of stem cells, especially in regenerative medicine. These experiments are controversial not only in the scientific sense, but also in their ethical consequences. These possibilities, and their accompanying debates, account in large part for the intensity of the current interest in stem cells. These controversies will be mentioned briefly here, but not considered in detail.

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    Last edited by mk99; 12-16-2005 at 08:48 AM.

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