Fig 2: CKLF1 knockdown alleviates extracellular matrix degradation in IL-1β-treated chondrocytes via the suppression of CCR5. (A) RT-qPCR and (B) western blotting were performed to examine MMP3, MMP13 and type II collagen expression in IL-1β-exposed ATDC5 cells. (C) RT-qPCR and (D) western blotting were performed to examine ADAMTS-4, ADAMTS-5 and aggrecan expression in IL-1β-exposed ATDC5 cells. (E) sGAG content was examined using the dimethylmethylene blue method. **P<0.01 and ***P<0.001. CKLF1, chemokine-like factor 1; CCR5, CC chemokine receptor 5; ADAMTS-4, a disintegrin and metalloproteinase with thrombospondin motifs type 4; ADAMTS-5, a disintegrin and metalloproteinase with thrombospondin motifs type 5; Ov-CCR5, CCR5 overexpression vector; Ov-NC, empty overexpression vector; RT-qPCR, reverse transcription-quantitative PCR; sGAG, soluble glycosamine sulfate additive; siRNA, small interfering RNA.

Fig 3: Silencing CKLF1 reverses the IL-1β-stimulated viability decrease and inflammatory response in chondrocytes by downregulating CCR5 expression. (A) Transfection efficiency of the Ov-CCR5 plasmid was examined by RT-qPCR. (B) Viability of IL-1β-treated ATDC5 cells was assessed by Cell Counting Kit-8 assays. (C) ELISA was performed to determine the levels TNF-α and IL-6 in IL-1β-exposed ATDC5 cells. (D) RT-qPCR was performed to determine the expression levels of TNF-α and IL-6 in IL-1β-exposed ATDC5 cells. **P<0.01 and ***P<0.001. CKLF1, chemokine-like factor 1; CCR5, CC chemokine receptor 5; Ov-CCR5, CCR5 overexpression vector; Ov-NC, empty overexpression vector; RT-qPCR, reverse transcription-quantitative PCR; siRNA, small interfering RNA.

Fig 4: Proposed mechanism of CKLF1/CCR5 in osetoarthritis. The main finding of the present study was that CKLF1 silencing alleviated the IL-1ß-induced inflammation, apoptosis and degradation of the ECM in chondrocytes via binding to its receptor CCR5. CKLF1, chemokine-like factor 1; ECM, extracellular matrix; CCR5, CC chemokine receptor 5.

Fig 5: CKLF1 knockdown mitigates the IL-1ß-evoked apoptosis in chondrocytes by inhibiting CCR5 expression. (A) TUNEL assays estimated the apoptosis of IL-1ß-stimulated ATDC5 cells. (B) Protein levels of apoptosis-related factors were analyzed by western blotting. ***P<0.001. CKLF1, chemokine-like factor 1; CCR5, CC chemokine receptor 5; Ov-CCR5, CCR5 overexpression vector; Ov-NC, empty overexpression vector; siRNA, small interfering RNA.