Detection and characterization of bacterial nucleic acids in culture-negative synovial tissue and fluid samples from rheumatoid arthritis or osteoarthritis patients

Yan Zhao,Ye Wang,Junjie Yang,Zhongtao Gai,Bin Chen,Dequan Zhu,Lei Zhang,Haiying Wang,Xueyuan Heng,Lanxiu Yang,Bin Shi,Jun Yang,Tao Wang,Shufeng Li

doi:10.1038/s41598-018-32675-w

Abstract

Human intestinal microbes can mediate development of arthritis – Studies indicate that certain bacterial nucleic acids may exist in synovial fluid (SF) and could be involved in arthritis, although the underlying mechanism remains unclear. To characterize potential SF bacterial nucleic acids, we used 16S rRNA gene amplicon sequencing to assess bacterial nucleic acid communities in 15 synovial tissue (ST) and 110 SF samples from 125 patients with rheumatoid arthritis (RA) and 16 ST and 42 SF samples from 58 patients with osteoarthritis (OA). Our results showed an abundant diversity of bacterial nucleic acids in these clinical samples, including presence of Porphyromonas and Bacteroides in all 183 samples. Agrobacterium, Comamonas, Kocuria, Meiothermus, and Rhodoplanes were more abundant in synovial tissues of rheumatoid arthritis (STRA). Atopobium, Phascolarctobacterium, Rhodotorula mucilaginosa, Bacteroides uniformis, Rothia, Megasphaera, Turicibacter, Leptotrichia, Haemophilus parainfluenzae, Bacteroides fragilis, Porphyromonas, and Streptococcus were more abundant in synovial tissues of osteoarthritis (STOA). Veillonella dispar, Haemophilus parainfluenzae, Prevotella copri and Treponema amylovorum were more abundant in synovial fluid of rheumatoid arthritis (SFRA), while Bacteroides caccae was more abundant in the synovial fluid of osteoarthritis (SFOA). Overall, this study confirms existence of bacterial nucleic acids in SF and ST samples of RA and OA lesions and reveals potential correlations with degree of disease.

Highlights

rheumatoid arthritis (RA) is a synovitis-based systemic autoimmune disease whose etiology remains elusive both genetic and environmental factors play an important role in disease pathogenesis[1,2]
We aseptically collected synovial tissue (ST) and synovial fluid (SF) samples from patients with RA (n=125) and OA (n=58) and used 16S rRNA V1-V2 sequencing to analyze microbiome profiles. We found that both ST and SF possess microbial DNA amplicons belonging to various microflora, confirming that bacterial nucleic acids are present in the articular cavity of RA and OA
Our results indicate that phagocytosis mediated by the Fcγ receptor – which plays a crucial role in RA pathogenesis43–45 – and the GnRH signaling pathway, are negatively correlated with IL-17, IL-1α, and IL-6 expression

Summary

Introduction

RA is a synovitis-based systemic autoimmune disease whose etiology remains elusive both genetic and environmental factors play an important role in disease pathogenesis[1,2]. Recent data indicate a role for human microbiota in the pathology of inflammatory arthritis, as mucosa exposed to high loads of bacterial antigens (such as in intestines) may break through the first immune resistance of rheumatoid arthritis, psoriatic arthritis, and related diseases. Injection of filamentous bacteria induces murine autoimmune responses and affects the role of T17 cells, with bacteria influencing IL17 secretion and increasing production of antibodies, resulting in arthritis. Zhang et al used shotgun metagenomic sequencing of saliva, dental plaque and fecal samples to show that RA patients lack Haemophilus species, and that their abundance is inversely proportional to RA autoimmune antibody titers[9]. Lactobacillus salivarius is significantly enriched in dental plaque, saliva, and fecal samples of RA patients, especially those with highly active disease. IL-1 and TNF-α prompt white blood cells to accumulate in the articular cavity and stimulate production of small molecule inflammatory mediators, thereby leading to cartilage damage and changes in bone

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