Fusobacterium nucleatum enters normal human oral fibroblasts in vitro.
BACKGROUND
Fusobacterium nucleatum, a commensal opportunistic oral bacterium, is capable of invading gingival epithelial cells, but the entrance into human primary oral fibroblast cells has not been documented. This study evaluated the ability of three strains of F. nucleatum (F. nucleatum ssp. nucleatum, F. nucleatum ssp. polymorphum, and F. nucleatum ssp. vincentii) to enter gingival fibroblasts (GFs) and periodontal ligament fibroblasts (PLFs).


METHODS
GFs and PLFs were cocultured for various periods of time with different strains of F. nucleatum. Scanning and transmission electron microscopy, together with confocal laser scanning microscopy, were used to visualize the entrance and presence of bacteria in host cells. Flow cytometry was performed to compare the load of internalized bacteria in GFs and PLFs exposed for 3 and 5 hours to live F. nucleatum labeled with fluorescein isothiocyanate.


RESULTS
All three strains of F. nucleatum were found entering and located in the cytoplasm of GFs and PLFs after 1 hour of exposure. Flow cytometry tests revealed a significant increase in the fluorescent signal, compared to baseline, derived from bacteria internalized in fibroblasts exposed for 3 hours (P <0.001); a further increase was found at 5 hours. The greatest bacterial mass in exposed fibroblasts of both types was of F. nucleatum ssp. polymorphum; the smallest was of F. nucleatum ssp. vincentii. Although not statistically significant, PLFs had a higher bacterial load than corresponding GFs.


CONCLUSIONS
F. nucleatum was capable of entering GFs and PLFs in a manner that is dependent on the cell type and the bacterial strain.
Dabija-Wolter
Gabriela
G
Faculty of Medicine and Dentistry, The Gade Institute, University of Bergen, Bergen, Norway.
Cimpan
Mihaela-Roxana
MR
Costea
Daniela E
DE
Johannessen
Anne Christine
AC
Sørnes
Steinar
S
Neppelberg
Evelyn
E
Al-Haroni
Mohammed
M
Skaug
Nils
N
Bakken
Vidar
V
D001422:Bacterial Adhesion / Q000502:physiology; D002478:Cells, Cultured; D018920:Coculture Techniques; D005347:Fibroblasts / Q000382:microbiology* / Q000502:physiology; D045825:Fusobacteriaceae Infections / Q000382:microbiology; D016967:Fusobacterium nucleatum / Q000472:pathogenicity / Q000502:physiology*; D005881:Gingiva / Q000166:cytology; D054884:Host-Pathogen Interactions / Q000502:physiology*; D006801:Humans; D012016:Reference Values; D013045:Species Specificity; D014774:Virulence