PRG4 and osteoarthritis: Gene expression analyses on human articular chondrocytes exposed to the RPM for 24 h showed significant upregulations of IL6, RUNX2, RUNX3, SPP1, SOX6, SOX9, and MMP13. At the same time, IL8, ACAN, PRG4, ITGB1, TGFB1, COL1A1, COL2A1, COL10A1, SOD3, SOX5, MMP1, and MMP2 remained unchanged, indicating that the chondrocytes experienced stress, as evidenced by the expression of markers for osteoarthritis and cartilage damage [154].