title: Fimbriae of Porphyromonas gingivalis are important for initial invasion of osteoblasts, but not for inhibition of their differentiation and mineralization.
abstract: BACKGROUND
  Porphyromonas gingivalis is etiologically associated with chronic periodontitis. The major fimbriae of this periodontal pathogen mediate binding to host gingival epithelial cells and fibroblasts, a critical function in the initiation of periodontitis. However, the role of fimbriae in P. gingivalis-osteoblast interactions remains unknown. In the present study, the involvement of major fimbriae in the initial and long-term interactions between P. gingivalis and osteoblasts is investigated.
  
  
  METHODS
  Primary mouse calvarial osteoblast cultures were established and inoculated with P. gingivalis ATCC 33277 or YPF1, a major fimbriae-deficient mutant of P. gingivalis. Confocal microscopy images were acquired to assess bacterial invasion. DNA content measurement, real-time polymerase chain reaction, and alizarin red S staining and calcium content analysis were used to study the impact of bacteria on the proliferation, differentiation, and mineralization of osteoblasts, respectively.
  
  
  RESULTS
  Compared to the parent strain, YPF1 was significantly reduced in invasion of osteoblasts after 3 hours interaction. However, extended culture of infected osteoblasts did not reveal significant differences in persistence between the two strains. Proliferation of osteoblasts was not affected by either strain, and differentiation and mineralization of osteoblasts were inhibited by both strains to comparable levels.
  
  
  CONCLUSIONS
  This study reveals that major fimbriae are involved in the initial invasion of osteoblasts by P. gingivalis, but are not essential for the subsequent inhibition of osteoblast differentiation and mineralization in long-term culture.
authors.affiliation: Department of Diagnostic Sciences, University of Texas Dental Branch at Houston, Houston, TX, USA. Wenjian.Zhang@uth.tmc.edu
authors.forename: Wenjian
authors.initials: W
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Ju
authors.forename: Todd
authors.initials: T
authors.lastname: Rigney
authors.forename: Gena D
authors.initials: GD
authors.lastname: Tribble
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion / Q000502:physiology; D002113:Calcification, Physiologic; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D036781:Fimbriae Proteins / Q000235:genetics; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000502:physiology*; D055786:Gene Knockout Techniques; D051379:Mice; D008815:Mice, Inbred Strains; D010006:Osteoblasts / Q000382:microbiology*; D016966:Porphyromonas gingivalis / Q000502:physiology*; D013045:Species Specificity
chemical_list: C063055:fimbrillin; D036781:Fimbriae Proteins