Proteomic analysis of proteins associated with cellular senescence by calorie restriction in mesenchymal stem cells

Mesenchymal stem cells (MSCs) hold great promise for use in cell-based therapies because of their multipotency and simple methods for in vitro expansion. However, during in vitro expansion, MSCs will age and lose their multipotency and proliferation capability. Previous studies have reported that calorie restriction (CR) increases proliferation of MSCs and decreases apoptosis. Therefore, in this study, we examined the effect of low glucose (LG) on human bone marrow-derived MSCs. Proliferation under low glucose (LG, 1.4 mM) conditions was compared with that under normal glucose (NG, 5.5 mM) conditions. In addition, comparative studies of population doubling (PD), β-galactosidase (β-GAL) activity, reactive oxygen species (ROS) generation and differentiation capacity (osteocytes and adipocytes) in NG and LG conditions were performed. In addition, protein expression patterns were compared between NG and LG conditions and several proteins were found to be up- or down-regulated under the glucose restriction condition (LG condition). As a result, CR does not seem to have a significant effect on proliferation, ROS generation, glucose consumption concentration, population doublings, and adipogenic differentiation of MSCs. Interestingly, however, the differentiation potential into osteocytes was maintained under CR and a lower senescence-associated β-galactosidase (β-GAL) activity was observed under CR than under the NG condition. In addition, we determined three up-regulated proteins (aldehyde dehydrogenase, neuropolyprptide h3, and prolyl 4-hydroxylase alpha subunit) and seven down-regulated proteins (laminin-binding protein, actin, sec 13 protein, alpha soluble N-ethylmaleimide-sensitive fusion protein (NSF)- attachment protein (SNAP), manganese superoxide dismutase, proteasome alpha 1 subunit, and ribosomal protein S12) via two-dimensional electrophoresis analysis. These results imply that differentially expressed proteins under the LG condition may provide further information on the aging and differentiation of stem cells.