ABSTRACT
INTRODUCTION - The mechanisms underlying craniosynostosis remains unknown. However, mutations in FGFR2 are associated with craniosynostotic syndromes. We previously compared gene expression patterns of patent and synostosing coronal sutures in the nude rat and demonstrated down regulation of Noggin in synostosing sutures. Noggin expression is also suppressed by FGF2 and constitutive FGFR2 signaling [Warren et al. (2003) Nature, vol. 422, pp. 625-9; McMahon et al. (1998) Genes Dev, vol. 12, pp. 1438-52]. Thus, we therefore hypothesized that the addition of rhNoggin to prematurely fusing sutures should prevent synostosis. MATERIALS AND METHODS - Cohorts of nude rats were subjected to: 1) surgical elevation of the coronal suture (shams); 2) surgical elevation and placement of normal or FGFR2 mutant human osteoblasts onto the underlying dura (xenotransplants); or 3) xenotransplantation with co-application of heparin acrylic beads soaked with recombinant human (rh) Noggin. Eleven days post-surgery the sutures were harvested, stained, and histologically examined. RESULTS - Animals that received control osteoblasts, sham surgery, or no surgery demonstrated normal skull growth and coronal suture histology, whereas animals transplanted only with FGFR2 mutant osteoblasts showed evidence of bridging synostosis on the calvarial dural surface. Sutures treated with FGFR2 mutant osteoblasts and rhNoggin remained patent. CONCLUSION - The chimeric nude rate model is a viable model of craniosynostosis. FGFR2 mutations in osteoblasts induce bridging osteosynthesis demonstrating one of the mechanisms for premature suture fusion. Topical application of rhNoggin protein prevents craniosynostosis in the weanling nude rat xenotransplantation model of syndromic craniosynostosis.
Subject(s)
Bone Morphogenetic Proteins/antagonists & inhibitors , Carrier Proteins/therapeutic use , Craniosynostoses/prevention & control , Cystine Knot Motifs , Acrocephalosyndactylia/genetics , Acrocephalosyndactylia/pathology , Animals , Cell Line , Cell Lineage , Chimera , Cranial Sutures/pathology , Cranial Sutures/surgery , Craniofacial Dysostosis/genetics , Craniofacial Dysostosis/pathology , Disease Models, Animal , Dura Mater/surgery , Frontal Bone/pathology , Frontal Bone/surgery , Humans , Mutation/genetics , Osteoblasts/transplantation , Parietal Bone/pathology , Parietal Bone/surgery , Rats , Rats, Nude , Receptor, Fibroblast Growth Factor, Type 2/genetics , Recombinant Proteins , Skull/growth & development , Transplantation, HeterologousABSTRACT
Enamelysin is a recently isolated member of the matrix metalloproteinase (MMP) family of extracellular matrix (ECM)-degrading enzymes. Here we describe the isolation and characterization of the mouse enamelysin cDNA. Expression of mouse enamelysin was detectable only in ameloblasts and odontoblasts of developing teeth. Characterization of mouse enamelysin demonstrated that it is highly conserved in both its sequence content and pattern of expression relative to the porcine, human, and bovine homologues previously described.
Subject(s)
Cloning, Molecular/methods , Gene Expression Regulation, Enzymologic/genetics , Matrix Metalloproteinases/genetics , Amino Acid Sequence , Animals , Base Sequence , Blotting, Northern/methods , Cattle , DNA, Complementary/genetics , Humans , In Situ Hybridization/methods , Matrix Metalloproteinase 20 , Mice , Molar/enzymology , Molecular Sequence Data , Polymerase Chain Reaction/methods , Sequence Analysis, DNA , Sequence Homology, Amino Acid , SwineABSTRACT
Mouse enamelysin (Mmp20), a member of the matrix metalloproteinase (MMP) family of extracellular matrix degrading enzymes, shows a high degree of homology with other MMPs, particularly those of the stromelysin/collagenase subfamilies. It is expressed exclusively in ameloblasts and odontoblasts. The mouse enamelysin gene (Mmp20) is made up of 10 exons spanning approximately 65 kb within the MMP gene cluster at the centromeric end of chromosome 9.
