Circulating miR-126-3p is a mechanistic biomarker for knee osteoarthritis

As a chronic joint disease, osteoarthritis (OA) is a major contributor to pain and disability worldwide, and yet there are currently no validated soluble biomarkers or disease-modifying treatments. Since microRNAs are promising mechanistic biomarkers that can be therapeutically targeted, we aimed to prioritize reproducible circulating microRNAs in knee OA. We performed secondary analysis on two microRNA-sequencing datasets and found circulating miR-126-3p to be elevated in radiographic knee OA compared to non-OA individuals. This finding was validated in an independent cohort (N=145), where miR-126-3p showed an area under the receiver operating characteristic curve of 0.91 for distinguishing knee OA. Measuring miR-126-3p in six primary human knee OA tissues, subchondral bone, fat pad and synovium exhibited the highest levels, and cartilage the lowest. Following systemic miR-126-3p mimic treatment in a surgical mouse model of knee OA, we found reduced disease severity. Following miR-126-3p mimic treatment in human knee OA tissue explants, we found direct inhibition of genes associated with angiogenesis and indirect inhibition of genes associated with osteogenesis, adipogenesis, and synovitis. These findings suggest miR-126-3p becomes elevated during knee OA and mitigates disease processes to attenuate severity.