Effects of continuous dexamethasone treatment on differentiation capabilities of bone marrow-derived mesenchymal cells

Human bone marrow-derived mesenchymal cells (hBMMCs) originate from cell populations in the bone marrow and are capable of differentiating along multiple mesenchymal lineages. To differentiate hBMMCs into osteoblasts, adipocytes and chondrocytes, dexamethasone has been used as a differentiation reagent. We hypothesized that dexamethasone would augment the responsiveness of BMMCs to other differentiation reagents and not define the lineage. This study investigated the effect of continuous treatment with 100 nM dexamethasone on the differentiation of BMMCs into three different lineages. hBMMCs cultured with continuous dexamethasone treatment (100 nM) exhibited higher mRNA expression levels of osteogenic markers and higher positive rates of colony forming unit assays for osteogenesis compared to hBMMCs treated with dexamethasone only during the differentiation culture. Furthermore, continuous dexamethasone treatment augmented bone formation capability of monkey-derived BMMCs in a bone induction experimental model at an extra skeletal site. In addition, continuously dexamethasone-treated hBMMCs formed larger chondrogenic pellets and expressed SOX9 at higher level than the control BMMCs. Likewise, continuous dexamethasone treatment facilitated adipogenic differentiation based on mRNA level and colony forming unit analysis. To investigate the mechanism of the augmentation of differentiation, further studies on apoptosis were conducted. The studies indicated that dexamethasone selectively induced apoptosis of some populations of hBMMCs which were thought to have poor differentiation capability.