title: Direct contact between enamel matrix derivative (EMD) and osteoblasts is not required for EMD-induced cell proliferation.
abstract: OBJECTIVE
  The purpose of this study was to determine whether the effect of enamel matrix derivative (EMD) on osteoblast proliferation is dependent on direct contact between EMD and the cells.
  
  
  METHODS
  MC3T3-E1 cells were seeded onto 6-well culture plates at an initial density of 5000/cm(2) in Dulbecco's modified eagle medium (DMEM) with 10% fetal bovine serum (FBS). Serum was removed from the culture medium after 24 hours with or without the addition of EMD. Four groups were evaluated: group 1, DMEM only; group 2, DMEM with 100 microg/mL EMD directly added to the culture medium; group 3, DMEM with a culture plate insert (30-mm diameter; 0.4-microm pore size) only; group 4, DMEM with 100 microg/mL EMD added onto a culture plate insert. The porous membrane of the insert prevented direct contact between EMD and the cells. After 3-day incubation, cell morphology was examined and the total cell number per well was counted and analyzed using 1-way ANOVA.
  
  
  RESULTS
  EMD formed precipitated aggregates on the membrane of the culture insert with the same appearance as when it was added directly to the medium. The culture plate insert alone did not cause any changes in cell morphology or proliferation. The addition of EMD significantly increased cell number regardless the presence of the culture plate insert.
  
  
  CONCLUSIONS
  This study suggests that direct contact between EMD and osteoblasts is not required to induce cell proliferation. Soluble peptides released from EMD may contribute to the stimulating effects of EMD on cell proliferation.
authors.affiliation: Department of Endodontics, Baylor College of Dentistry, Dallas, Tex, USA.
authors.forename: Jianing
authors.initials: J
authors.lastname: He
authors.forename: Jin
authors.initials: J
authors.lastname: Jiang
authors.forename: Kamran E
authors.initials: KE
authors.lastname: Safavi
authors.forename: Larz S W
authors.initials: LS
authors.lastname: Spångberg
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhu
mesh_terms: D016475:3T3 Cells; D000704:Analysis of Variance; D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods; D002455:Cell Division / Q000187:drug effects; D003470:Culture Media; D003746:Dental Enamel Proteins / Q000494:pharmacology*; D006133:Growth Substances / Q000494:pharmacology; D008567:Membranes, Artificial; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects*
chemical_list: D003470:Culture Media; D003746:Dental Enamel Proteins; D006133:Growth Substances; D008567:Membranes, Artificial; C109069:enamel matrix proteins