Osteoblastogenesis and osteoprotection enhanced by flavonolignan silibinin in osteoblasts and osteoclasts

J Cell Biochem. 2012 Jan;113(1):247-59. doi: 10.1002/jcb.23351.


Bone-remodeling imbalance induced by decreased osteoblastogenesis and increased bone resorption is known to cause skeletal diseases such as osteoporosis. Silibinin is the major active constituent of silymarin, the mixture of flavonolignans extracted from blessed milk thistle (Silybum marianum). Numerous studies suggest that silibinin is a powerful antioxidant and has anti-hepatotoxic properties and anti-cancer effects against carcinoma cells. This study investigated that silibinin had bone-forming and osteoprotective effects in in vitro cell systems of murine osteoblastic MC3T3-E1 cells and RAW 264.7 murine macrophages. MC3T3-E1 cells were incubated in osteogenic media in the presence of 1-20 µM silibinin up to 15 days. Silibinin accelerated cell proliferation and promoted matrix mineralization by enhancing bone nodule formation by calcium deposits. In addition, silibinin furthered the induction of osteoblastogenic biomarkers of alkaline phosphatase, collagen type 1, connective tissue growth factor, and bone morphogenetic protein-2. Differentiated MC3T3-E1 cells enhanced secretion of receptor activator of nuclear factor-κB ligand (RANKL) essential for osteoclastogenesis, which was reversed by silibinin. On the other hand, RAW 264.7 cells were pre-incubated with 1-20 µM silibinin for 5 days in the presence of RANKL. Non-toxic silibinin markedly attenuated RANK transcription and intracellular adhesion molecule-1 expression elevated by RANKL, thereby suppressing the differentiation of macrophages to multi-nucleated osteoclasts. It was also found that silibinin retarded tartrate-resistant acid phosphatase and cathepsin K induction and matrix metalloproteinase-9 activity elevated by RANKL through disturbing TRAF6-c-Src signaling pathways. These results demonstrate that silibinin was a potential therapeutic agent promoting bone-forming osteoblastogenesis and encumbering osteoclastic bone resorption.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acid Phosphatase / antagonists & inhibitors
  • Alkaline Phosphatase / metabolism
  • Animals
  • Bone Morphogenetic Protein 2 / metabolism
  • Bone Resorption / metabolism
  • Calcium
  • Cathepsin K / antagonists & inhibitors
  • Cell Differentiation / drug effects
  • Cell Line
  • Cell Proliferation / drug effects
  • Collagen Type I / metabolism
  • Connective Tissue Growth Factor / metabolism
  • Isoenzymes / antagonists & inhibitors
  • Macrophages / metabolism
  • Matrix Metalloproteinase 9
  • Matrix Metalloproteinase Inhibitors
  • Mice
  • Osteoblasts / drug effects*
  • Osteoblasts / metabolism
  • Osteoclasts / drug effects*
  • Osteoclasts / metabolism
  • Osteogenesis / drug effects*
  • Osteogenesis / physiology
  • Plant Extracts / pharmacology
  • RANK Ligand / metabolism
  • Receptor Activator of Nuclear Factor-kappa B / metabolism
  • Silybin
  • Silymarin / pharmacology*
  • TNF Receptor-Associated Factor 6 / antagonists & inhibitors
  • TNF Receptor-Associated Factor 6 / metabolism
  • Tartrate-Resistant Acid Phosphatase


  • Bone Morphogenetic Protein 2
  • Collagen Type I
  • Isoenzymes
  • Matrix Metalloproteinase Inhibitors
  • Plant Extracts
  • RANK Ligand
  • Receptor Activator of Nuclear Factor-kappa B
  • Silymarin
  • TNF Receptor-Associated Factor 6
  • Tnfrsf11a protein, mouse
  • Tnfsf11 protein, mouse
  • Connective Tissue Growth Factor
  • Silybin
  • Alkaline Phosphatase
  • Acid Phosphatase
  • Tartrate-Resistant Acid Phosphatase
  • Cathepsin K
  • Matrix Metalloproteinase 9
  • Mmp9 protein, mouse
  • Calcium