Effect of Porphyromonas gingivalis-induced inflammation on the development of rheumatoid arthritis

Periodontitis is an extra-synovial chronic inflammatory condition, which has been proposed to be inter-related with rheumatoid arthritis.

We investigated the effect of an established extra-synovial chronic inflammatory lesion on the induction and severity of experimental arthritis.

Chronic inflammatory lesions were induced by the implantation of polyurethane sponges impregnated with heat-killed Porphyromonas gingivalis into the backs of DA rats. Thirty-five days later, adjuvant arthritis (AA) was induced in the rats by injecting a mycobacterium cell wall in complete Freund's adjuvant. The development of arthritis was then monitored for 2 weeks.

Histological assessment of the implanted sponges confirmed that a chronic inflammatory lesion had been established after 21 days. Following induction of adjuvant arthritis, the severity of disease was scored and paw swelling was measured. Severe arthritis developed more rapidly in animals with a pre-existing P. gingivalis-induced inflammatory lesion elsewhere.

The results show that a pre-existing extra-synovial chronic inflammatory lesion induced by P. gingivalis promotes the development of arthritis in an animal model. These findings provide further evidence for a relationship between the presence of periodontal pathogen-associated inflammation and the development of rheumatoid arthritis.