Western Society of Periodontics

Laboratory Studies

Volume Number 4, 1995

Attachment of Fusobactenum nucleatum to fibronectin immobilized on gingival epithelial cells or glass coverslips

This article investigated the possibility that fibronectin may serve as a receptor for the attachment of F. nucleatum to gingival epithelial cells. Researchers first took three strains of F. nucleatum ATCC 109552 and UTFn2 and UTFn5 from patients with periodontitis, then took gingival epithelial cell suspensions and grown-on-glass coverslips. For control the epithelial cells were coated with PBDS/BSA. The researchers then tested the effects of the proteins by incubating the coverslips with whole human saliva, or human saliva depleted of fibronectin. This was incubated with 0.5 ml of F. nucleatum and then evaluated for bacterial adhesion. The researchers also did indirect immunofluorescence, incubating the coverslips with antibodies. They also wanted to find out the effect of protein-specific antibodies on the adhesion of F. nucleatum. The results show that all three strains of F. nucleatum adhered poorly to buffer-coated epithelial cells. But when the cells were coated with exogenously added plasma fibronectin, adhesion was enhanced three times. Saliva that was depleted of fibronectin did not have the same adhesion as the whole human saliva. However, when fibronectin was added to the fibronectin-depleted saliva, there was an increase in F. nucleatum adhesion. The researchers further investigated the interaction between fibronectin and F. nucleatum minus the surface of the epithelial cells. They coated the coverslips with the test proteins and showed that the three strains adhered in larger numbers to the ones coated with fibronectin and to a lesser degree to the whole human saliva. The control and the fibronectin-depleted saliva were similar in the amount of F. nucleatum adhesion. Incubation at 4šC and 25šC for 60 minutes showed a decrease in attachment of F. nucleatum compared to 37šC. Pretreatment of the bacteria with soluble fibronectin resulted in 92% inhibition of the adhesion of F. nucleatum. When the fibronectin coverslips were incubated with antifibronectin antibodies, the attachment of F. nucleatum was inhibited by 93%. The authors therefore conclude that fibronectin may play an important role in promoting colonization of F. nucleatum in the oral cavity. [M.C.R.]