Abstract
IntroductionWe evaluated the presence of Porphyromonas gingivalis (Pg) DNA in the synovial tissue through synovial biopsy and in other compartments of rheumatoid arthritis (RA) patients in comparison with patients affected by other arthritides. Possible links with clinical, immunologic and genetic features were assessed.MethodsPeripheral blood (PB), sub-gingival dental plaque, synovial fluid (SF) and synovial tissue samples were collected from 69 patients with active knee arthritis (32 with RA and 37 with other arthritides, of which 14 had undifferentiated peripheral inflammatory arthritis - UPIA). Demographic, clinical, laboratory and immunological data were recorded. The presence of Pg DNA was evaluated through PCR. The HLA-DR haplotype was assessed for 45 patients with RA and UPIA.ResultsNo differences arose in the positivity for Pg DNA in the sub-gingival plaque, PB and SF samples between RA and the cohort of other arthritides. Full PB samples showed a higher positivity for Pg DNA than plasma samples (11.8% vs. 1.5%, P = 0.04). Patients with RA showed a higher positivity for Pg DNA in the synovial tissue compared to controls (33.3% vs. 5.9%, P <0.01). UPIA and RA patients carrying the HLA DRB1*04 allele showed a higher positivity for Pg DNA in the synovial tissue compared to patients negative for the allele (57.1% vs. 16.7%, P = 0.04). RA patients positive for Pg DNA in the sub-gingival plaque had a lower disease duration and a higher peripheral blood leucocyte and neutrophil count. The presence of Pg DNA did not influence disease activity, disease disability or positivity for autoantibodies.ConclusionsThe presence of Pg DNA in the synovial tissue of RA patients suggests a pathogenic role of the bacterium. The higher positivity of Pg DNA in full peripheral blood and synovial tissue samples compared to plasma and synovial fluid suggests a possible intracellular localization of Pg, in particular in patients positive for HLA-DR4.
Highlights
We evaluated the presence of Porphyromonas gingivalis (Pg) DNA in the synovial tissue through synovial biopsy and in other compartments of rheumatoid arthritis (RA) patients in comparison with patients affected by other arthritides
The aims of the study were to see whether Pg DNA could be found in the synovial tissue of RA patients and compare it to patients affected by other arthritides, to determine whether the prevalence of DNA positivity in other compartments, such as dental plaque and peripheral blood of RA patients, could differ from that of patients with other arthritides, and to assess the possible links between the presence of Pg DNA and clinical, immunological and genetic features
Disease activity and disability were higher in RA patients than in patients affected by undifferentiated peripheral inflammatory arthritis (UPIA) (P
Summary
We evaluated the presence of Porphyromonas gingivalis (Pg) DNA in the synovial tissue through synovial biopsy and in other compartments of rheumatoid arthritis (RA) patients in comparison with patients affected by other arthritides. HLA alleles DRB1*01 and *04, the main genetic risk factors for RA, are primarily involved in the antigen presentation positive results, mainly in the synovial tissue compared to the synovial fluid [7], supporting the idea of a prevalence of intracellular bacteria. Live bacteria have never been isolated, to date, in the joint compartment of RA patients. The role of these bacterial structures is unknown; they can be bystanders related to the recruitment of inflammatory cells, or they may play a specific part in the etiology of the disease
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