title: Doxycycline reduces the expression and activity of matrix metalloproteinase-2 in the periodontal ligament of the rat incisor without altering the eruption process.
abstract: OBJECTIVE
  Doxycycline is an antibiotic agent that inhibits the activity of matrix metalloproteinases (MMPs) present in the extracellular matrix. In this study, the rat incisor was submitted to a hypofunctional condition, and the effects of doxycycline (80 mg/kg/d) on the expression and activity of MMP-2, as well as on eruption rate, were determined in the odontogenic region and in the periodontal ligament for 14 d.
  
  
  METHODS
  Rats were distributed into four groups: normofunctional (NF); doxycyline normofunctional (DNF); hypofunctional (HP); and doxycyline hypofunctional (DHP). The left lower incisors of 10 rats were shortened every 2 d, using a high-rotation drill, to produce the HP and DHP groups, after starting doxycycline treatment (80 mg/kg) by gavage. Eruption was measured using a millimeter ocular, from the gingival margin to the top of the tooth in the HP and DHP groups, and also by a mark made in the tooth previously, in the NF and DNF groups. The hemimandibles were removed and the teeth were extracted to collect the periodontal and odontogenic tissues for immunohistochemical analyses and zymography.
  
  
  RESULTS
  The eruption rates were higher in the HP and the DHP groups than in the NF and DNF groups, respectively (p < 0.05). In the odontogenic region, neither of the treatments changed the expression and activity of MMP-2. In the HP group, the shortening treatment decreased the expression, but not the activity, of MMP-2, while doxycycline was able to inhibit the increase of expression and activity of MMP-2.
  
  
  CONCLUSIONS
  We conclude that the inhibition of MMP-2 by doxycycline, during incisor shortening, was not enough to alter the eruption rate, which suggests that MMP-2 may have an important role in the turnover of extracellular matrix of the periodontal ligament during the tooth-eruption process.
authors.affiliation: DEBIOGEM, Ponta Grossa, Brazil.
authors.forename: J R
authors.initials: JR
authors.lastname: Gomes
authors.affiliation: UEPG-DEBIOGEM, Ponta Grossa, Brazil.
authors.forename: N F
authors.initials: NF
authors.lastname: Omar
authors.affiliation: Universidade Estadual de Campinas Faculdade de Odontologia de Piracicaba, Piracicaba, Brazil.
authors.forename: J D S
authors.initials: JDS
authors.lastname: Neves
authors.affiliation: Universidade Estadual de Campinas Faculdade de Odontologia de Piracicaba, Piracicaba, Brazil.
authors.forename: P D
authors.initials: PD
authors.lastname: Novaes
mesh_terms: D000818:Animals; D004318:Doxycycline / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D007180:Incisor / Q000187:drug effects / Q000254:growth & development*; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000187:drug effects*; D061965:Matrix Metalloproteinase Inhibitors / Q000494:pharmacology*; D010513:Periodontal Ligament / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D017208:Rats, Wistar; D014078:Tooth Eruption / Q000187:drug effects*
chemical_list: D061965:Matrix Metalloproteinase Inhibitors; D020778:Matrix Metalloproteinase 2; D004318:Doxycycline
keywords: matrix metalloproteinases; periodontal ligament; tetracycline