Glycosaminoglycan chains of biglycan promote bone morphogenetic protein-4-induced osteoblast differentiation

Int J Mol Med. 2012 Nov;30(5):1075-80. doi: 10.3892/ijmm.2012.1091. Epub 2012 Aug 9.

Abstract

Biglycan (BGN) has been reported to promote bone morphogenetic protein-4 (BMP-4) stimulated osteoblastic differentiation. However, the underlying mechanism has yet to be fully elucidated. The glycosaminoglycan (GAG) chains of BGN have a variety of biological functions. In the present study, we explored the potential role of the GAG chains of BGN in promoting BMP-4-induced osteoblast differentiation. BGN knockout (KO) murine calvarial cells were transfected with adenovirus overexpressing wild-type BGN (Adv-BGN), adenovirus expressing GAG-mutant BGN (Adv-BGNm) and adenovirus without BGN (Adv-Emp). Transfected cells were treated with or without BMP-4. Subsequently, BMP-4 signaling and function were assessed by evaluating the expression of the osteoblast differentiation-related proteins, Smad1/5/8 phosphorylation and alkaline phosphatase (ALP) activity. Furthermore, the binding specificity of the transfected cells to BMP-4 was also investigated using immunofluorescence staining. Our study demonstrated that a mutant BGN lacking GAG chains decreased BGN-assisted BMP-4 signaling and osteoblast differentiation and that the expression of this mutant BGN in biglycan knockout (BGN‑KO) calvarial osteoblasts could not rescue its differentiation deficiency as efficiently as wild-type (WT) BGN. These results strongly suggest that the GAG chains of BGN promote BGN-assisted BMP-4 function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoviridae / genetics
  • Alkaline Phosphatase / metabolism
  • Animals
  • Antigens, Differentiation / metabolism
  • Biglycan / biosynthesis
  • Biglycan / genetics
  • Biglycan / physiology*
  • Bone Morphogenetic Protein 4 / metabolism
  • Bone Morphogenetic Protein 4 / physiology*
  • Cell Differentiation
  • Cells, Cultured
  • Gene Expression
  • Glycosaminoglycans / biosynthesis
  • Glycosaminoglycans / genetics
  • Glycosaminoglycans / physiology*
  • Integrin-Binding Sialoprotein / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Osteoblasts / enzymology
  • Osteoblasts / metabolism
  • Osteoblasts / physiology*
  • Osteocalcin / metabolism
  • Osteopontin / metabolism
  • Protein Binding
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / genetics
  • Signal Transduction
  • Skull / cytology
  • Smad Proteins / metabolism

Substances

  • Antigens, Differentiation
  • Biglycan
  • Bone Morphogenetic Protein 4
  • Glycosaminoglycans
  • Ibsp protein, mouse
  • Integrin-Binding Sialoprotein
  • Recombinant Proteins
  • Smad Proteins
  • Osteocalcin
  • Osteopontin
  • Alkaline Phosphatase