Dexamethasone treatment during the expansion phase maintains stemness of bone marrow mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) can form various mesodermal tissues when grown under appropriate conditions. Dexamethasone (Dex) is regularly used to stimulate the osteogenic potential of hMSCs and it has recently been reported to increase the cell expansion rate. In this study we have investigated the effect of low-dose Dex treatment (10(-8) M) on the multipotency of expanded hMSCs, using histological, biochemical and molecular biological techniques. Early passage (P2-3) and late passage (P6) cells were positive (>90%) for mesenchymal adhesion cell markers (CD105/CD29/CD44/CD166/CD90) and negative (<10%) for haematopoietic markers (CD34/CD45/CD14). Dex did not change the overall expression pattern of these cell surface markers. Expanded hMSCs gave rise to specialized cell lineages when grown in differentiation-promoting medium. Depending on the donor, Dex treatment improved the potency for osteogenic, adipogenic and chondrogenic differentiation of expanded hMSCs. Dex also prevented the loss of proliferative potential of hMSCs upon sequential passaging and the loss of the typical hMSCs surface phenotype. hMSCs gene expression analysis showed that low-dose Dex negatively regulated transcription of genes correlated with apoptosis and differentiation, and positively regulated genes associated with cell proliferation. In conclusion, the collective data argue that low-dose Dex preserves the stemness of hMSCs during repeated passaging, as indicated by the maintenance of the stem cell phenotype, proliferative capacity and multi-lineage differentiation potential.