Association Between Gut Microbiota Dysbiosis and Synovial Inflammation in Carpal Osteoarthritis of Ili Racehorses: A Preliminary Study Integrating Imaging, Synovial Fluid Analysis, and Fecal 16S rRNA Sequencing

Osteoarthritis (OA) is a leading cause of lameness and premature retirement in racehorses. Gut microbiota may contribute to OA pathogenesis through the gut–joint axis, but this relationship remains unclear in racehorses. This study focused on six OA-affected Ili racehorses and six healthy Ili racehorses from the same region; the Ili horse originated from Yili, Xinjiang, China. OA severity was assessed by clinical examination, lameness grading, radiography, arthroscopy, synovial fluid biomarker analysis, and fecal 16S rRNA gene sequencing. Associations between differential gut microbiota and synovial inflammatory markers were evaluated by Spearman correlation analysis. OA horses exhibited higher lameness scores and typical radiographic findings. Compared with healthy controls, OA horses exhibited significantly higher synovial concentrations of IL-1β, IL-6, TNF-α, total protein, COMP, and MMP-3. Gut microbiota analysis revealed reduced microbial diversity and significant compositional alterations in OA horses. Spearman correlation analysis demonstrated significant associations between these microbial changes and synovial inflammatory mediators as well as cartilage degradation markers. Overall, gut microbiota dysbiosis in Ili racehorses with carpal OA may be associated with synovial inflammation and abnormal cartilage metabolism via the gut–joint axis. However, the experimental scale and the number of animals will be increased as needed for further validation.