Pulsed electromagnetic field alleviates synovitis and inhibits the NLRP3/Caspase-1/GSDMD signaling pathway in osteoarthritis rats

Low-grade inflammation is a key mediator of the pathogenesis of Osteoarthritis (OA). Pulsed electromagnetic field (PEMF) can improve the symptoms of OA and potentially acts as an anti-inflammatory. The aim of this study was to investigate the effect of the PEMF on OA and its relationship with the NLRP3/Caspase-1/GSDMD signaling pathway.18 Three-month-old Sprague-Dawley (SD) rats were randomly divided into three groups (n = 6 per group): 1) OA group, 2) OA+PEMF group (OA with PEMF exposure), 3) Control group (sham operation with placebo PEMF). Rats in the OA and OA+PEMF groups were subjected to bilateral anterior cruciate ligament transection and ovariectomy. PEMF scheme: Pulse waveform, 3.82 mT, 8 Hz, 40 min/day, 5 days a week, for 12 weeks. The expression levels of NLRP3, Caspase-1, GSDMD, IL-1 beta, and MMP-13 were detected by qRT-PCR and Western blot. The pathological structures of OA were monitored with Safranin O/fast green staining and hematoxylin eosin staining. Our results showed that PEMF alleviated the degree of inflammation and degeneration of cartilage in rats with OA, based on the histopathological changes and decline of the expression of IL-1 beta and MMP-13. Moreover, the over-expression of NLRP3, Caspase-1, and GSDMD in the cartilage of the OA rats decreased after PEMF treatment. These results suggested that PEMF could be a highly promising noninvasive strategy to slow down the progression of OA and inhibition of the NLRP3/Caspase-1/GSDMD signaling pathway might be involved in the beneficial effect of PEMF.