Dexamethasone induces chondrogenesis in organoid culture of cell mixtures from mouse embryos

The effect of dexamethasone on morphogenesis and differentiation of cells obtained from mouse embryos grown at high density in vitro was investigated. Cells from decapitated mouse embryos of day 10 to day 13 were isolated by enzymatic treatment and grown at high density at the medium/air interface in organoid culture. After 28 days in culture, organoid-like structures such as vesicles, gland-like structures and cell aggregates had developed, dependent on the stage of the embryos. After the addition of 10(-7) M dexamethasone, cartilage had formed in cultures of cells from day-10, -11 and -12 embryos. It was maximal in cultures of day-11 cells and rare in day-10 cells. No cartilage was found in cultures of day-13 cells. Cartilage induction was similar in cultures treated with 10(-6) and 10(-7) M dexamethasone, but clearly less in cultures treated with 10(-8) M. Only minute amounts of cartilage were detectable after dexamethasone treatment of cells obtained from decapitated embryos (day-11 and -12) whose limb buds had been cut off. In organoid cultures of pure limb bud cells, 10(-7) M dexamethasone had no influence on chondrogenesis. The results indicate that the cells inducible to form cartilage by dexamethasone originate from the limb buds. Glucocorticoid induction of chondrogenesis has not been described in vivo. The dependency of both chondrogenesis and expression of glucocorticoid receptor on cell density in vitro may be the cause for this effect.