Osteogenesis and Embryogenesis in Zebrafish Embryo Is Differentially Modulated by Solvents and Prednisolone

Several molecules and extracts are known to have bone-specific effects. For example, the long-term use of glucocorticoids like prednisolone causes several negative effects including a loss of bone mass. Molecules like prednisolone are usually dissolved in organic solvent which are known to be toxic for zebrafish embryo in certain concentrations. Nevertheless, solvents like dimethyl sulfoxide (DMSO), ethanol and methanol have never been tested for specific skeletal effects during development in dose-dependency. Vitality assay, live fluorescence and bone-specific staining were used to evaluate solvents effects compared to prednisolone. DMSO, ethanol and methanol perturb osteogenesis starting from 1%, 1.5% and 3% respectively, concentrations in which vasculature, length and survival rate appear unaffected. This effect may be due to high sensitivity of the osteogenesis process to external chemical stimuli, especially in the trunk. On the contrary, the negative effect of prednisolone on skeletal development appears more specific since it is found at very low concentrations, far from any other developmental defects. The recommended solvent concentration to be used in zebrafish embryos osteogenesis assay was established in 0.5% for DMSO, 2% for methanol and 0.5% for ethanol. We recommend analyzing both head and trunk mineralization in zebrafish embryo osteogenesis assay.