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. 2022 Oct 28;13:1012508. doi: 10.3389/fendo.2022.1012508

Figure 1.

Figure 1

OPN regulates inflammatory activity in OA and OP. OPN plays a controversial role in the inflammation response in OA. Overexpression of OPN in chondrocytes, synoviocytes and subchondral bone stimulates the secretion of proinflammation cytokines and enhances the inflammation activity in OA. OPN-deficiency in chondrocytes leads to chondrocyte senescence and the secretion of cytokines and proteins degraded the articular cartilage. A high level of OPN suppresses the secretion of proinflammation cytokines and matrix-degrading enzymes, alleviates bone mass reduction, and promotes bone formation as well as matrix calcification in OP. The proinflammation cytokines include IL-1β, TNF-ɑ, IL-6, IL-8, NO, iNOS, COX-2, and CRP, while the articular cartilage matrix-degrading enzymes mainly refer to MMP-9, MMP-13, ADAMTS-4, ADAMTS-5 in this review.