Osteoarthritis (OA), a disease with whole-joint damage and dysfunction, is the leading cause of disability worldwide. The progressive loss of hyaline cartilage extracellular matrix (ECM) is considered as its hallmark, but its exact pathogenesis needs to be further clarified. MicroRNA(miRNA) contributes to OA pathology and may help to identify novel biomarkers and therapies against OA. Here we identified miR-214-3p as an important regulator of OA. qRT-PCR and in situ hybridization were used to detect the expression level of miR-214-3p. The function of miR-214-3p in OA, as well as the interaction between miR-214-3p and its downstream mRNA target (IKBKB), was evaluated by western blotting, immunofluorescence, qRT-PCR and luciferase assay. Mice models were introduced to examine the function and mechanism of miR-214-3p in OA in vivo. In our study, we found that miR-214-3p, while being down-regulated in inflamed chondrocytes and OA cartilage, regulated ECM metabolism and cell apoptosis in the cartilage. Mechanically, the protective effect of miR-214-3p downregulated the IKK-β expression and led to the dysfunction of NF-κB signaling pathway. Furthermore, intra-articular injection of miR-214-3p antagomir in mice joints triggered spontaneous cartilage loss while miRNA-214-3p agomir alleviated OA in the experimental mouse models. Decreased miR-214-3p activates the NF-κB signaling pathway and aggravates OA development through targeting IKKβ, suggesting miR-214-3p may be a novel therapeutic target for OA. This study was financially supported by grants from the National Natural Science Foundation of China (81,773,532, 81,974,342).

Inflammatory cytokines-induced activation of the nuclear factor κB (NF-κB) pathway plays a critical role in the pathogenesis of osteoarthritis (OA). Circular RNA (circRNA) has been identified as important epigenetic factor in numerous diseases. However, the biological roles of inflammation-related circRNAs in regulating OA pathogenesis remain elusive. Here, we revealed circRNA expression profiles in human primary chondrocytes with interleukin-1β (IL-1β) stimulation by circRNA sequencing. We identified a highly upregulated circRNA, termed as circNFKB1 in inflamed chondrocytes and osteoarthritic cartilage. As a circRNA derived from exon 2–5 of NFKB1, circNFKB1 is located in both cytoplasm and nucleus of chondrocytes. Furthermore, knockdown of circNFKB1 inhibited extracellular matrix (ECM) catabolism and rescued IL-1β impaired ECM anabolism whereas ectopic expression of circNFKB1 significantly promoted chondrocytes degradation in vitro. Moreover, intraarticular injection of adenovirus-circNFKB1 in mouse joints triggered spontaneous cartilage loss and OA development. Mechanistically, circNFKB1 interacted with α-enolase (ENO1), regulated the expression of its parental geneNFKB1and sustained the activation of NF-κB signaling pathway in chondrocytes. Therefore, this study highlights a novel ENO1-interacting circNFKB1 in OA pathogenesis, and provides valuable insights into understanding the regulatory mechanism of NF-κB signaling in chondrocytes and a promising therapeutic target for the treatment of OA.

Osteoarthritis (OA) progression is closely related to dysregulated glycolysis. As the primary metabolite of glycolysis, lactate plays a detrimental role in OA. However, how lactate exacerbates OA process remains unclear. Here, this study revealed that lactate levels are elevated in the synovial fluid of OA patients and IL‐1β‐treated human primary chondrocytes, promoting protein pan‐lactylation. Functionally, hyper‐lactylation exacerbates chondrocytes extracellular matrix (ECM) degradation and cell apoptosis in vitro and in vivo. Moreover, UDP‐glucose dehydrogenase (UGDH) is proven to be the key lactylated protein in lactate‐treated chondrocytes, which undergoes lactylation at lysine 6 (K6). Lactylated UGDH repressed its enzymatic activity, reducing glycosaminoglycan synthesis and disregulating its nuclear‐cytoplasmic distribution. Mechanistically, K6 lactylation of UGDH impedes the interaction of UGDH and signal transducer and activator of transcription 1 (STAT1), thus promoting the transcription of mitogen‐activated protein kinase kinase kinase 8 (MAP3K8) and activating the MAPK signaling pathway. Importantly, in vitro and in vivo treatment with A485, a specific acyltransferase P300 inhibitor, suppressed UGDH lactylation and rescued chondrocytes ECM degradation and OA progression. These findings uncover a new mechanism underlying OA pathogenesis and highlight the potential of targeting UGDH lactylation as a novel therapeutic strategy for OA.

Infrapatellar fat pad (IPFP) is closely associated with the development and progression of knee osteoarthritis (OA), but the underlying mechanism remains unclear. Here, it is find that IPFP from OA patients can secret small extracellular vesicles (sEVs) and deliver them into articular chondrocytes. Inhibition the release of endogenous osteoarthritic IPFP‐sEVs by GW4869 significantly alleviated IPFP‐sEVs‐induced cartilage destruction. Functional assays in vitro demonstrated that IPFP‐sEVs significantly promoted chondrocyte extracellular matrix (ECM) catabolism and induced cellular senescence. It is further demonstrated that IPFP‐sEVs induced ECM degradation in human and mice cartilage explants and aggravated the progression of experimental OA in mice. Mechanistically, highly enriched let‐7b‐5p and let‐7c‐5p in IPFP‐sEVs are essential to mediate detrimental effects by directly decreasing senescence negative regulator, lamin B receptor (LBR). Notably, intra‐articular injection of antagomirs inhibiting let‐7b‐5p and let‐7c‐5p in mice increased LBR expression, suppressed chondrocyte senescence and ameliorated the progression of experimental OA model. This study uncovers the function and mechanism of the IPFP‐sEVs in the progression of OA. Targeting IPFP‐sEVs cargoes of let‐7b‐5p and let‐7c‐5p can provide a potential strategy for OA therapy.