Nell-1-induced bone regeneration in calvarial defects

Am J Pathol. 2006 Sep;169(3):903-15. doi: 10.2353/ajpath.2006.051210.

Abstract

Many craniofacial birth defects contain skeletal components requiring bone grafting. We previously identified the novel secreted osteogenic molecule NELL-1, first noted to be overexpressed during premature bone formation in calvarial sutures of craniosynostosis patients. Nell-1 overexpression significantly increases differentiation and mineralization selectively in osteoblasts, while newborn Nell-1 transgenic mice significantly increase premature bone formation in calvarial sutures. In the current study, cultured calvarial explants isolated from Nell-1 transgenic newborn mice (with mild sagittal synostosis) demonstrated continuous bone growth and overlapping sagittal sutures. Further investigation into gene expression cascades revealed that fibroblast growth factor-2 and transforming growth factor-beta1 stimulated Nell-1 expression, whereas bone morphogenetic protein (BMP)-2 had no direct effect. Additionally, Nell-1-induced osteogenesis in MC3T3-E1 osteoblasts through reduction in the expression of early up-regulated osteogenic regulators (OSX and ALP) but induction of later markers (OPN and OCN). Grafting Nell-1 protein-coated PLGA scaffolds into rat calvarial defects revealed the osteogenic potential of Nell-1 to induce bone regeneration equivalent to BMP-2, whereas immunohistochemistry indicated that Nell-1 reduced osterix-producing cells and increased bone sialoprotein, osteocalcin, and BMP-7 expression. Insights into Nell-1-regulated osteogenesis coupled with its ability to stimulate bone regeneration revealed a potential therapeutic role and an alternative to the currently accepted techniques for bone regeneration.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Biomarkers / metabolism
  • Bone Morphogenetic Protein 2
  • Bone Morphogenetic Protein 7
  • Bone Morphogenetic Proteins / biosynthesis
  • Bone Regeneration* / genetics
  • Calcinosis / genetics
  • Calcinosis / metabolism*
  • Calcinosis / pathology
  • Calcium-Binding Proteins
  • Craniosynostoses / genetics
  • Craniosynostoses / metabolism*
  • Craniosynostoses / pathology
  • Glycoproteins
  • Humans
  • Male
  • Mice
  • Mice, Transgenic
  • Nerve Tissue Proteins / genetics*
  • Nerve Tissue Proteins / metabolism
  • Osteoblasts / metabolism*
  • Osteoblasts / pathology
  • Osteocalcin / biosynthesis
  • Osteogenesis* / genetics
  • Rats
  • Receptor, Fibroblast Growth Factor, Type 2 / biosynthesis
  • Skull / abnormalities
  • Skull / metabolism
  • Skull / pathology
  • Tissue Culture Techniques
  • Transforming Growth Factor beta / biosynthesis
  • Up-Regulation / genetics

Substances

  • BMP2 protein, human
  • BMP7 protein, human
  • Biomarkers
  • Bmp2 protein, mouse
  • Bmp2 protein, rat
  • Bmp7 protein, rat
  • Bone Morphogenetic Protein 2
  • Bone Morphogenetic Protein 7
  • Bone Morphogenetic Proteins
  • Calcium-Binding Proteins
  • Glycoproteins
  • Nell1 protein, mouse
  • Nerve Tissue Proteins
  • Transforming Growth Factor beta
  • Osteocalcin
  • Fgfr2 protein, mouse
  • Receptor, Fibroblast Growth Factor, Type 2