Fig. 5

Myeloid differentiation factor 88 (MyD88)-dependent Toll-like receptor (TLR)-2 signaling pathway regulates 29-kDa amino-terminal fibronectin fragment (29-kDa FN-f)-induced matrix metalloproteinase (MMP) production in normal and osteoarthritis (OA) chondrocytes. To determine the involvement of the MyD88-dependent TLR-2 signaling pathway in 29-kDa FN-f-triggered catabolic responses, human chondrocytes were transfected using control small interfering RNA (siRNA) or small interfering MyD88 (siMyD88). After 48 h, the cells were stimulated using 29-kDa FN-f for 6 or 24 h. a Inhibition of MyD88 expression by siMyD88. b Effect of siMyD88 on mRNA expression of 29-kDa FN-f-induced MMPs was determined using SYBR Green real-time reverse transcription polymerase chain reaction. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was used as an internal control. In normal and OA chondrocytes, the expression of MMP-1, MMP-3, and MMP-13 mRNA were reduced significantly by siMyD88 treatment. The mRNA expression level in untreated control siRNA transfected chondrocytes was set as 1. Data represent the mean ± SD for triplicate experiments from three different donors. *P < 0.05, **P < 0.01, and ***P < 0.001 vs. control. c MMP-1 and MMP-3 protein levels in culture supernatants were determined using Western blot analysis. d Enzyme-linked immunosorbent assay showed that 29-kDa FN-f-triggered MMP-13 production was suppressed significantly in siMyD88-transfected cells compared with siRNA-transfected control cells. Values represent the mean ± SD of triplicate samples from three different donors. *P < 0.05 and **P < 0.01 vs. control siRNA-transfected chondrocytes