Abstract
We have investigated the effect of long-term glucocorticoid (GC) administration on bone turnover in two frequently used mouse strains; C57BL/6J and CD1, in order to assess the influence of their genetic background on GC-induced osteoporosis (GIO). GIO was induced in 12 weeks old female C57BL/6J and CD1 mice by subcutaneous insertion of long-term release prednisolone or placebo pellets. Biomechanical properties as assessed by three point bent testing revealed that femoral elasticity and strength significantly decreased in CD1 mice receiving GC, whereas C57BL/6J mice showed no differences between placebo and prednisolone treatment. Bone turnover assessed by microcomputer tomography revealed that contrary to C57BL/6J mice, prednisolone treated CD1 mice developed osteoporosis. In vitro experiments have underlined that, at a cellular level, C57BL/6J mice osteoclasts and osteoblasts were less responsive to GC treatment and tolerated higher doses than CD1 cells. Whilst administration of long-term release prednisolone pellets provided a robust GIO animal model in 12 weeks old CD1 mice, age matched C57BL/6J mice were not susceptible to the bone changes associated with GIO. This study indicates that for the induction of experimental GIO, the mouse strain choice together with other factors such as age should be carefully evaluated.
Highlights
We have investigated the effect of long-term glucocorticoid (GC) administration on bone turnover in two frequently used mouse strains; C57BL/6J and CD1, in order to assess the influence of their genetic background on GC-induced osteoporosis (GIO)
Bone marrow (BM) cells isolated from 12 weeks old C57BL/6J and CD1 mice were density separated with Lympholyte-M (Cedarlane, Burlington, USA) and the purified lymphocytes were cultured overnight at 37 °C in 5% CO2 in complete medium: α-MEM with 10% foetal bovine serum (FBS), supplemented with 50 ng/ml murine macrophage colony stimulating factor (M-CSF) (Miltenyi, Abingdon, UK) and day were plated at a density of 1 × 10^5 cells/well in 96-well plates where OC precursors were induced to proliferate and differentiate with (150 ng/ml) M-CSF and (10–100 ng/ml) receptor activator of NF-kB ligand (RANKL) (Miltenyi, Abingdon, UK) supplemented with 0–10^4 nM Dexamethasone (Dex) (Sigma-Aldrich, Gillingham, UK) as indicated
Femurs obtained from prednisolone treated CD1 mice had significantly lower elasticity and were able to withstand a significantly lesser load compared to the placebo treated mice, while C57BL/6 mice femurs biomechanical properties were not affected by GC treatment (Fig. 1a,b)
Summary
We have investigated the effect of long-term glucocorticoid (GC) administration on bone turnover in two frequently used mouse strains; C57BL/6J and CD1, in order to assess the influence of their genetic background on GC-induced osteoporosis (GIO). Whilst administration of long-term release prednisolone pellets provided a robust GIO animal model in 12 weeks old CD1 mice, age matched C57BL/6J mice were not susceptible to the bone changes associated with GIO. To research the onset and treatment options of different chronic inflammatory diseases several mouse models that carry different mutations or lack the activity of certain genes have been established[2,3,4]. Thiele and et al, have shown that long-term GC treatment in C57BL/6 animal model does not result in significant bone loss as opposed to its effects in humans or in other glucocorticoid-induced osteoporosis (GIO) susceptible mouse strains. Whilst 12 weeks old CD1 mice proved to be a robust GIO animal model with bone cells highly www.nature.com/scientificreports/
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