Few drugs generate bone-stimulatory effects via epigenetic mechanisms. Modulation of CpG-residues hydroxymethylation in gene-promoters of key osteoblast-related factors (e.g., DLX5) induces their expression and increases osteoblast differentiation in vitro. The chemical properties of sulforaphane (SFN), a natural compound abundantly present in cruciferous vegetables like broccoli, suggest that it may have similar molecular and biological effects. Previous studies suggest that SFN blocks nuclear factor-kappaB and thus osteoclastogenesis in vitro.
Here, we evaluated the effect of SFN on biological properties of osteoblasts and osteoclasts in cell culture models. Mouse MC3T3-E1 osteoblasts, RAW-264.7 osteoclasts, MLO-Y4 osteocytes, murine bone marrow-derived mesenchymal stem cells (mBMSCs), human adipose-derived mesenchymal stem cells (hAMSCs), mouse pre-osteoclasts (mOC) and mouse calvaria were treated with increasing concentrations of SFN for up to 6 weeks. The in vivo relevance of SFN in promoting bone mass was examined in C57Bl6/J mice (at 8 weeks) treated intraperitoneally with SFN for 5 weeks.
After 24 h, 3 μM SFN inhibits cell proliferation and activates caspases 3/7 and 8 significantly stronger in pre-osteoclastic RAW-264.7 cells than in MLO-Y4 and MC3T3-E1 cells. Furthermore, mOC-resorption on ivory is significantly inhibited (~40%) after 12 days. Consistently, SFN significantly decreases expression of RANKL/TNFSF11 in MLO-Y4 cells and mice calvaria. Direct anabolic effects of SNF are reflected by significantly increased expression of bone markers (e.g., Bglap2, Runx2, Col1a1) in MC3T3-E1 cells (after 14 days) and mBMSC (after 20 days). In hAMSCs, SFN transiently stimulates expression of selected markers (e.g., BGLAP2, OPG/TNFRSF11B, SATB2) with increased alkaline phosphatase deposition after 13 days. Furthermore, all cell-types and mice calvaria exhibited robust stimulation of extra cellular matrix mineralization after SFN exposure. As measured by μCT, SFN significantly increases trabecular number in bone and an increasing trend (P=0.07) was observed in trabecular bone volume in C57Bl6/J mice.
Our findings suggest SFN as potential bone-anabolic mediator suppressing osteoclast function and promoting osteogenic differentiation.
17 May 2014 - 20 May 2014