Mini ReviewMesenchymal stem cell aging
Introduction
It is commonly believed that stem and precursor cells are involved in continuous maintenance and repair of most tissue types. Taken into consideration that stem cells are capable of self-renewal and that they share the ability to differentiate in multiple lineages, this class of cells is of paramount importance for an organism, not only during development, but also during adulthood with respect to cellular homeostasis. In contrast to higher animals, the life span of microorganisms as well as simple multi-cellular animals is believed to correspond to cellular longevity. As long as damaged cells within a specialized organ are replaced, proper physiological function will be maintained which would contribute to longevity of the whole organism (Van Zant, 2003, Young et al., 2004). Consequently, stem cells must have life spans that may be equal to that of the organism they reside in (Van Zant and Liang, 2003). Therefore, they have to face long replicative histories and thus accumulate genetic damage. In addition to this, they are certainly subject to damage from intracellular and extracellular sources such as reactive oxygen species (Hasty et al., 2003).
Section snippets
Properties of mesenchymal stem cells
Stem cells for non-haematopoietic tissues, which can be derived from bone marrow are commonly termed mesenchymal stem cells (MSC). This definition (first coined by Arnold Caplan, 1991) and many other terms (marrow stromal cells, precursors of non-haematopoietic tissue, colony forming unit fibroblasts or multipotent adult progenitor cells) have been introduced in the field and refer to differences of isolation and cultivation or epitope characterization. The basal term ‘mesenchyme’ was first
Senescence of mesenchymal stem cells
MSC in culture show replicative senescence phenotypes depending on the species they have been derived from. For instance, human MSC cease growth rather early (around 40–50 population doublings) (Stenderup et al., 2003), whereas murine MSC can be passaged for more than hundred population doublings (Meirelles Lda and Nardi, 2003). In vitro senescence of MSC is paralleled by a progressive loss of clonal multipotentiality. By and large, this supports a hierarchical model, with a pathway of
Acknowledgements
GL is an APART fellow of the Austrian Academy of Sciences. He is further supported by the Jubilee Fund of the Austrian National Bank, project 10481 and by the Austrian Science Fund (FWF), project S9309-B09.
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