Senescence in mesenchymal stem cells: the effects of reduced culture temperature and media glucose concentration
A. Stolzing, A. Scutt
Centre of Biomaterials and Tissue Engineering, Department of Engineering Materials, University of Sheffield, UK
Mesenchymal progenitor cells (MPC) show great promise for use in a
variety of cell-based therapies. As isolated primary MPC are low in
numbers, in vitro expansion is necessary. However the expansion
potential is limited and in vitro aging leads to loss of multipotency
and to replicative senescence. Stress induced by the culture conditions
is thought to be one of the driving reasons for replicative senescence
and might also influence multipotency of MPC. Optimisation of culture
conditions might be able to improve the expansion of MPC in cultures.
Temperature reduction was shown to be beneficial in somatic cell
cultures by reducing oxidative stress. We therefore monitored the
growth of MPC from rats and humans at 37C and 32C. We found that the
in vitro lifespan of MPC was not affected but less damage was
accumulated at the lower temperature and the MPC preserved their
differentiation potential for a longer time. This suggests that MPC
expanded in vitro for engraftment or tissue engineering purposes should
be maintained at a lower temperature to avoid the accumulation of
damage and possible reduction of tissue construct quality. However this
was only true for MPC derived from 'young' subjects with MPC derived
from 'aged' subjects showing no such improvements.
The second half of our studies involved a model of caloric restriction;
the only established method to delay aging and extending the lifespan.
Studies of in vitro caloric restriction are rare, but showed some
beneficial effects. We therefore investigated the effect of culture
medium glucose concentration on the proliferative and differentiation
potential of MPC. Reduction in glucose concentrations lead to a
decrease in apoptosis levels and an increase in the rate of
proliferation. Similarly, reduced glucose concentration increased the
number and size of fibroblastic colonies in the colony forming unit
assay.
Conclusion: These data suggest that culture conditions such as
temperature or glucose concentration can have profound effects on MPC
growth and senescence. The reason for the differential effect of
temperature on young and aged cells is at present unclear but may be of
great importance for the use of MPC in cell-based therapies.
Key words:
mesenchymal stem cells, aging, senescence
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