In Vitro Effects of RU486 on Proliferation and Differentiation Capabilities of Human Bone Marrow Mesenchymal Stromal Cells

Although exogenous glucocorticoids (GC) play a role in the regulation of bone marrow mesenchymal stem/stromal cells (MSCs) proliferation and differentiation, the function of endogenous GC is not well understood. The purpose of this study was to investigate the effect of the blockage of endogenous GC using RU486, an antagonist of the glucocorticoid receptor, on the in vitro proliferation and differentiation capabilities of human MSCs. We quantitatively measured cell proliferation of human MSCs after treatment with increasing concentrations of RU486. We also evaluated multiple MSC differentiation capabilities, as well as the expression of stemness and senescence genes after proliferation of these human cells in vitro in the presence of RU486 at 10(-8)M. It was observed that RU486 treatment significantly increases the proliferation of human MSCs, although the optimal dose of RU486 for this increase in proliferation differs depending on the gender of the MSC donor. This improvement in MSC proliferation with RU486 treatment was higher in MSCs from male donors than that from females. No effect of RU486 on MSC proliferation was observed in a steroid-free medium. RU486 pretreatment significantly increased the expression of mRNA for alkaline phosphatase in human MSCs and the mRNA expression of osteocalcin of these cells up-regulated earlier after their exposure to osteogenic differentiation medium. Although no statistical significance in terms of chondrogenic differentiation markers was detected, mRNA expression for aggrecan and collagen type 2 were higher in a majority of the RU486-pretreated donor MSCs than their untreated controls. No significant difference in terms of MSC adipogenic differentiation capabilities were observed after RU486 treatment. RU486 treatment up-regulated the expressions of FGF-2 and Sox-11 in human MSCs. These results indicate that blockage of endogenous GCs may be developed as a novel approach to effectively improve the proliferation and osteochondral differentiation capabilities of human MSCs for potential clinical applications. Additional studies will be required to determine the potential long-term effects of RU486 treatment on these bone marrow cells.