title: Immunolocalization of Smad-4 in developing molar roots of alendronate-treated rats.
abstract: BACKGROUND
  During root formation, Smad-4 plays a key role during the epithelial-mesenchymal interactions and the Hertwig's epithelial root sheath (HERS) apical proliferation. The root formation and eruption of rat molars is impeded by alendronate treatment due to the inhibition of bone resortion by this drug. The present study aimed to examine the structures affected in the developing root and immunodetect the presence of Smad-4 in rats treated with alendronate.
  
  
  METHODS
  Newborn Wistar rats were daily injected 2.5 mg/kg alendronate (ALN) during 9, 12 and 30 days. The controls (CON) were injected with saline. The maxillae were fixed and embedded in paraffin or Spurr resin. Paraffin sections were incubated in Smad-4 antibody that was labelled with DAB. The ultrathin sections were examined in a transmission electron microscope.
  
  
  RESULTS
  In ALN, a short portion of root dentine was formed; the epithelial diaphragm (ED) and the dental follicle (DF) were disorganized by the contact of bone trabeculae. The (CON) molar roots developed normally. Smad-4 labelling was detected in the cytoplasm of fibroblasts and cementoblasts adjacent to the cementum in CON; in ALN group, few ED cells presented weak immunolabelling. Ultrastructurally, the ED and DF appeared disrupted due to the presence of thin bone trabeculae between its cells. It resulted in the lack of apical proliferation of HERS and, consequently, arrest of root formation.
  
  
  CONCLUSIONS
  The immunodetection of Smad-4 in the DF cells of ALN specimens indicates that the signalling for the differentiation of these cells into cementum-forming fibroblasts and cementoblasts occurs, despite the impairment of root elongation.
authors.affiliation: Department of Biomaterials and Oral Biology, School of Dentistry, University of São Paulo, Brazil.
authors.forename: Vivian
authors.initials: V
authors.lastname: Bradaschia-Correa
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Casado-Gomez
authors.forename: Mariana Matheus
authors.initials: MM
authors.lastname: Moreira
authors.forename: Lorraine Braga
authors.initials: LB
authors.lastname: Ferreira
authors.forename: Victor E
authors.initials: VE
authors.lastname: Arana-Chavez
mesh_terms: D019386:Alendronate / Q000009:adverse effects*; D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000187:drug effects / Q000378:metabolism; D001862:Bone Resorption / Q000209:etiology*; D002454:Cell Differentiation / Q000187:drug effects; D025021:Cementogenesis / Q000187:drug effects*; D003739:Dental Cementum / Q000187:drug effects*; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008854:Microscopy, Electron; D008963:Molar / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D051901:Smad4 Protein / Q000032:analysis* / Q000276:immunology; D014092:Tooth Root / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development; D053773:Transforming Growth Factor beta1 / Q000187:drug effects / Q000378:metabolism
chemical_list: D019485:Bone Morphogenetic Proteins; D051901:Smad4 Protein; D053773:Transforming Growth Factor beta1; D019386:Alendronate
keywords: Alendronate; Cementoblasts; Cementogenesis; Immunohistochemistry; Root formation; Smad-4