Increasing evidence has shown that macrophage pyroptosis in different tissues participates in chronic aseptic inflammation and is related to tissue fibrosis. Our last studies also revealed the vital role of synovial fibroblast pyroptosis in the onset and development of knee osteoarthritis (KOA). In this study, we aimed to investigate whether synovial macrophage pyroptosis did occur and whether this form of cell death should be related to synovitis and fibrosis of KOA. In the synovial tissue of KOA model rats, we observed a decrease of caspase1, NLRP3, ASC, and GSDMD caused by macrophage depletion in both the mRNA and protein expressions. Besides, rats treated with the specific caspase1 inhibitor Ac-YVAD-CMK showed less inflammatory reaction and fibrosis, not only in the expression of proinflammatory factors IL-1β, IL-18, and HMGB1 and fibrosis markers TGF-β, PLOD2, COL1A1, and TIMP1 but also in the observation of HE staining, Sirius Red staining, and the transverse diameters of the right knees. Subsequently, we established an LPS+ATP-induced model in macrophages mimicking the inflammatory environment of KOA and inducing macrophage pyroptosis. Macrophages transfected with caspase1 siRNA showed reduced cell death; meanwhile, the relative expression of pyroptosis-related proteins were also downregulated. In addition, the level of fibrotic markers in synovial fibroblasts were significantly decreased after coculture with siRNA GSDMD-transfected macrophages. To conclude, synovial macrophage pyroptosis may occur in the pathological processes of KOA and inhibition of synovial macrophage pyroptosis alleviates synovitis and fibrosis in KOA model rats.

Fibroblast-like synoviocytes (FLSs) are the main effector cells of knee osteoarthritis (KOA) synovial fibrosis. Our last report showed that NLRP1 and NLRP3 inflammasomes may mediate LPS/ATP-induced FLSs pyroptosis in KOA. In the present study, we found an elevated hypoxia-inducible factor-1α (HIF-1α) level in the synovial tissue of KOA model rats, and inhibiting the increase of HIF-1α could improve synovial fibrosis in rats. Subsequently, we established LPS/ATP-induced model in FLSs mimicking the inflammatory environment of KOA. FLSs transfected with siRNA HIF-1α showed a reduced cell death; meanwhile, the relative expression of pyroptosis-related proteins was also downregulated. Additionally, FLSs transfected with or without siRNA GSDMD were exposed to hypoxia. GSDMD silencing can significantly reduce both gene and protein levels of fibrogenic markers transforming growth factor-β (TGF-β), procollagen-lysine, 2-oxoglutarate 5-dioxygenase2 (PLOD2), collagen type I α1 chain (COL1A1), and tissue inhibitor of metalloproteinases 1 (TIMP1). Taken together, our findings indicate that increased HIF-1α is highly involved in the KOA synovial fibrosis. Moreover, elevated HIF-1α may aggravate synovial fibrosis via FLS pyroptosis.

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Background To evaluate the effect of intramedullary nail and locking plate in the treatment of proximal humerus fracture (PHF). Methods China National Knowledge Infrastructure (CNKI), Chinese Scientific Journals Database (VIP), Wan-fang database, Chinese Biomedicine Database (CBM), PubMed, EMBASE, Web of Science, and Cochrane Library were searched until July 2018. The eligible references all show that the control group uses locking plates to treat PHF, while the experimental group uses intramedullary nails to do that. Two reviewers independently retrieved and extracted the data. Reviewer Manager 5.3 was used for statistical analysis. Results Thirty-eight retrospective studies were referred in this study which involves 2699 patients. Meta-analysis results show that the intramedullary nails in the treatment of proximal humeral fractures are superior to locking plates in terms of intraoperative blood loss, operative time, fracture healing time, postoperative complications, and postoperative infection. But there is no significance in constant, neck angle, VAS, external rotation, antexion, intorsion pronation, abduction, NEER, osteonecrosis, additional surgery, impingement syndrome, delayed union, screw penetration, and screw back-out. Conclusions The intramedullary nail is superior to locking plate in reducing the total complication, intraoperative blood loss, operative time, postoperative fracture healing time and postoperative humeral head necrosis rate of PHF. Due to the limitations in this meta-analysis, more large-scale, multicenter, and rigorous designed RCTs should be conducted to confirm our findings. Trial registration PROSPERO CRD42019120508