title: Differential expression of sclerostin in adult and juvenile mouse calvariae.
abstract: BACKGROUND
  An understanding of the molecular mechanisms controlling bone formation is central to skeletal tissue engineering efforts. The observation that immature animals are able to heal calvarial defects while adult animals are not has proven to be a useful tool for examining these mechanisms. Thus, the authors compared expression of sclerostin, a bone inhibitor, between the calvariae of juvenile and adult mice.
  
  
  METHODS
  Parietal bone was harvested from juvenile (6-day-old; n = 20) and adult (60-day-old; n = 20) mice. Sclerostin transcript and protein levels were compared between the parietal bone of juvenile and adult mice using polymerase chain reaction, Western blotting, and immunohistochemistry. Finally, osteoblasts from the parietal bone of juvenile and adult mice were harvested and cultured under osteogenic differentiation conditions with and without recombinant sclerostin (200 ng/ml). Terminal osteogenic differentiation was assessed at 21 days with alizarin red staining.
  
  
  RESULTS
  Polymerase chain reaction, Western blot analysis, and immunohistochemistry all confirmed greater expression of sclerostin in the parietal bone of adult mice when compared with that of juvenile mice. Osteoblasts, whether from juvenile or adult parietal bones, demonstrated reduced capacity for osteogenic differentiation when exposed to recombinant sclerostin.
  
  
  CONCLUSIONS
  Given the role of sclerostin in inhibiting bone formation, the authors' findings suggest that differences in expression levels of sclerostin may play a role in the differential regenerative capacity of calvariae from juvenile and adult animals. These findings suggest it as a potential target to abrogate in future tissue engineering studies.
authors.affiliation: Stanford, Calif. From the Hagey Laboratory for Pediatric Regenerative Medicine, Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Kwan
authors.forename: Natalina
authors.initials: N
authors.lastname: Quarto
authors.forename: Deepak M
authors.initials: DM
authors.lastname: Gupta
authors.forename: Bethany J
authors.initials: BJ
authors.lastname: Slater
authors.forename: Derrick C
authors.initials: DC
authors.lastname: Wan
authors.forename: Michael T
authors.initials: MT
authors.lastname: Longaker
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000375:Aging / Q000502:physiology; D000818:Animals; D015153:Blotting, Western; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D001861:Bone Regeneration / Q000502:physiology*; D002454:Cell Differentiation; D005819:Genetic Markers; D006023:Glycoproteins; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D010006:Osteoblasts / Q000378:metabolism; D010294:Parietal Bone / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D023822:Tissue Engineering
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D019485:Bone Morphogenetic Proteins; D005819:Genetic Markers; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; C486030:Sost protein, mouse