Intra-articular inflammation and cartilage degradation are the major pathological characteristics of osteoarthritis (OA). Mounting studies have revealed that circular RNAs (circRNAs) act as an important regulatory role in inflammatory diseases and are frequently dys-expressed in OA cartilage tissues. Here, a dys-regulated cicrRNA (has_circ_0017636, termed circSFMBT2-OA) was identified, and its role in regulating lipopolysaccharide (LPS)-induced chondrocyte injury was next investigated. CHON-001 chondrocytes were treated with LPS, and then the levels of circSFMBT2-OA, cartilage-related genes, and pro-inflammatory cytokines were measured using quantitative real-time PCR (qRT-PCR) and Western blot analysis. CHON-001 cell viability, proliferation, and apoptosis were assayed using Cell Counting Kit-8 (CCK-8), 5-Ethynyl-2′-deoxyuridine (EDU), and terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) assay, respectively. CircSFMBT2-OA level was significantly down-regulated in OA cartilage tissues and LPS-treated CHON-001 cells. Functionally, circSFMBT2-OA overexpression accelerated cell proliferation, and suppressed cell apoptosis, pro-inflammatory cytokines production, matrix-degrading enzymes expression, and ECM degradation in CHON-001 cells. Inversely, circSFMBT2-OA depletion decreased cell viability and increased matrix-degrading enzymes expression and ECM degradation. Mechanistically, circSFMBT2-OA inhibited LPS-induced NF-κB/NOD-like receptor family pyrin domain containing protein 3 (NLRP3) inflammasome activation in CHON-001 cells. Consequently, NLRP3 activator reversed the effect of circSFMBT2-OA on repressing LPS-induced CHON-001 cell injury. These data reveal a vital effect of a novel circSFMBT2-OA on repressing OA progression and provide a promising target to treat OA.

Background: The lower limb mechanical axis was used to assess the severity of knee osteoarthritis (KOA) with varus/valgus deformity and the accuracy of targeted lower limb alignment correction after operation by conventional X-rays. There are lots of parameters to assess the gait in elder patients such as velocity, stride length, step width and swing/stance ratio by knee joint movement analysis system. However, the correlation between the lower limb mechanical axis and gait parameters is not clear. This study is aimed at obtaining the accuracy of the lower limb mechanical axis by the knee joint movement analysis system and the correlation between the lower limb mechanical axis and gait parameters. Methods: We analysed 3D knee kinematics during ground gait of 99 patients with KOA and 80 patients 6 months after the operations with the vivo infrared navigation 3D portable knee joint movement analysis system (Opti-Knee®, Innomotion Inc, Shanghai, China). The HKA (Hip-Knee-Ankle) value was calculated and compared to X-ray findings. Results: HKA absolute variation after the operation was 0.83 ± 3.76°, which is lower than that before the operation (5.41 ± 6.20°, p = 0.001) and also lower than the entire cohort (3.36 ± 5.72). Throughout the cohort, a significant correlation with low coefficients (r = -0.19, p = 0.01) between HKA value and anterior-posterior displacement was found. In comparing the HKA values measured on the full-length alignment radiographs and 3D knee joint movement analysis system (Opti-Knee), there was a significant correlation with moderate to high coefficients (r = 0.784 to 0.976). The linear correlation analysis showed that there was a significant correlation between the values of HKA measured by X-ray and movement analysis system (R² = 0.90, p < 0.01). Conclusions: Data with equivalent results as HKA, the 6DOF of the knee and ground gait data could be provided by infrared navigation based 3D portable knee joint movement analysis system comparing with the conventional X-rays. There is no significant effect of HKA on the kinematics of the partial knee joint.