Current Methods in Synovial Fluid Microbiota Characterization: A Systematic Review.

Area of Science:

• Microbiology
• Immunology
• Rheumatology

Background:

• The gut-joint axis highlights the gut microbiota's influence on joint health.
• Microorganisms are increasingly implicated in arthritis pathogenesis within synovial joints.
• Synovial fluid was historically considered sterile, but recent evidence suggests microbial presence.

Purpose of the Study:

• To systematically review methodologies for characterizing the human synovial fluid (SF) microbiome.
• To identify current techniques and their limitations in SF microbiota analysis.
• To emphasize the need for standardized approaches in SF microbiome research.

Main Methods:

• Systematic literature search of PubMed, Embase, and Web of Science up to February 5, 2025.
• Included studies focused on characterizing the SF microbiome using next-generation sequencing or polymerase chain reaction.
• Analysis of nine studies that investigated microbial presence in human SF.

Main Results:

• Eight of the nine reviewed studies detected bacterial DNA in human synovial fluid.
• Significant heterogeneity was observed in methodologies across studies.
• Incomplete reporting of sample collection, preparation, contamination control, DNA extraction, amplification, sequencing, and bioinformatics processing was common.

Conclusions:

• Current methods for synovial fluid microbiome characterization lack standardization, limiting comparability and reproducibility.
• Standardized protocols are crucial for accurate SF microbiota analysis in arthritis research.
• Improved methodologies will enhance understanding of arthritis mechanisms and inform targeted therapeutic strategies.