Characterizing the Native Microbiome Using Next-Generation Sequencing of Bilateral 'Aseptic' Knees

Current Methods in Synovial Fluid Microbiota Characterization: A Systematic Review

Evidence suggests that a cross-talk between the gut microbiota and joint health exists in a paradigm known as the gut-joint axis. Recent studies have also reported the presence of microorganisms potentially involved in the pathogenesis and progression of arthritis in synovial joints, previously believed to be sterile. This systematic review describes in detail the methodologies employed to characterize the microbiota in human synovial fluid (SF). A literature search was conducted in PubMed, Embase, and Web of Science up to 5 February 2025. Nine studies aimed to characterize the SF microbiome using next-generation sequencing or polymerase chain reaction. Eight studies detected bacterial DNA in SF. However, significant heterogeneity and incomplete reporting in methodologies, including sample collection and preparation, contamination management, DNA extraction and amplification, sequencing technology, targeted 16S rRNA or ITS regions, and bioinformatics processing, limit the comparability and significance of findings. Given the potential implications for understanding arthritis mechanisms and developing targeted treatments, a standardized methodological and reporting approach in SF microbiota characterization is needed to enhance the reproducibility and the relevance of results.

Gut and Joint Microbiomes: Implications in Osteoarthritis

This review summarizes and discusses key recent findings suggesting that microbiomes can play a role in the development and progression of osteoarthritis. Evidence supporting a gut microbiome-joint connection derived from human and animal studies is enumerated and discussed, with particular attention on the microbial and molecular basis for the development of therapeutic interventions that involve targeting the gut. Additionally, clinical data supporting the concept of a living microbiome within a diarthrodial joint are summarized. A discussion of key limitations in the current data and important technical considerations for firmly establishing the existence of a synovial joint microbial community is included.

The Interaction Between Microbiota and Stem Cells on Progression of Osteoarthritis and Engineered Stem Cell for Enhancing Osteoarthritis Treatment

Osteoarthritis (OA) is characterized by the degeneration of articular cartilage caused by several factors of which novel most trends include microbiota. Specific microbiota and the role in the development of OA is less clear. The microbiota is presumed to influence OA occurrence and progression mainly via immune modulation. In recent years, bone marrow mesenchymal stem cells (MSCs) have shown great potential for the treatment of OA, however, the therapeutic efficiency has been seriously affected by the harsh microenvironment in the joint cavity. At present, many strategies have been used to enhance the function of MSCs, among them, engineering are a promising method. Therefore, this review mainly focuses on the latest research on how the microbiota affects the development of OA, stem cell repair, and the use of engineered MSCs in the treatment of OA. In addition, engineered MSCs can enhance the therapeutic potential of exosomes as a novel strategy for treating OA. Our review provides a comprehensive perspective on the role of microbiota in OA and the influence of MSCs therapy and engineered MSCs on the treatment of OA.

Inflammaging contributes to osteoarthritis development and human microbiota variations and vice versa: A systematic review

OBJECTIVE

To report evidence on microbiota and its relationship with inflammaging, the innate immune system and osteoarthritis (OA) in human patients.

DESIGN

A systematic review was performed in accordance with PRISMA and following the PICO model. Web of Science, Scopus, Cochrane Library for clinical trials and PubMed were searched. The analysis was focused on human OA patients, and the outcome was mainly microbiota identification, improvement or deterioration of OA pain, stiffness or inflammation.

RESULTS

After screening, 24 studies fulfilled the inclusion criteria. There is not a standardised procedure yet, as microbiota analysis in OA is relatively new. The 16S rRNA gene is the most used in bacterial phylogeny and taxonomy studies as it is highly conserved. Selected articles hypothesise about the correlation between the altered composition of the gut microbiota and OA severity, which seems to affect the immune composition by disrupting gut permeability and releasing pro-inflammatory factors. Five preliminary clinical trials used pro-prebiotics to treat OA patients, and although their results are not conclusive and the methodology needs to be improved, it might indicate a favourable approach for further studies in the prevention of OA.

CONCLUSIONS

Several hypotheses have been made on the associations between microbiota changes and inflammation. They mainly advocate that those changes in the gastrointestinal tract affect gut permeability, which alters the immune system, leading to OA progression. Research advances, along with the continual growth and improvement of technology, mark this 'microbiota-inflammaging-OA' axis as a promising line of investigation.