Senescence of bone marrow mesenchymal stromal cells is accompanied by activation of p53/p21 pathway in myelodysplastic syndromes.

The contribution of bone marrow mesenchymal stromal cells (BMMSCs) to the pathogenesis of myelodysplastic syndrome (MDS) has created controversies. In this study, we confirmed that BMMSCs from MDS patients showed prominent features of senescence, which were characterized by increased cell size, decreased proliferation and colony-forming potential, alteration of cytoskeleton, and increased senescence-associated β-galactosidase (SA-β-Gal) activity. Interestingly, the apoptosis assay results showed that the percentage of apoptosis cells was very low and the difference was not significant between MDS patients and normal controls. Moreover, the osteogenic differentiation potential of BMMSCs from lower risk but not higher risk MDS was impaired, indicated by cytochemical stainings and reduced expressions of RUNX2. In addition, BMMSCs from MDS patients had impaired hematopoietic supporting function. Furthermore, the expression of p53 and p21 which played an important role in regulating the senescence progress of BMMSCs was significantly increased, whereas levels of p16 and pRb expression were not changed in the BMMSCs from MDS patients. Taken together, our comprehensive analysis shows that BMMSCs from MDS patients exhibited senescent behavior and activation of p53/p21 pathway probably played an important role in the senescence process.