Figure 2: TLR-4, MMP-3, IL-1β, and TNF-α expression was induced during osteoarthritis induction. Chondrocytes were collected and assayed for gene expression by real-time RT-PCR. The relative expression levels were normalized to the expression of the housekeeping GAPDH gene expression and presented as the -fold difference. (a) TLR-2 and TLR-1 showed a similar pattern of expression during OA induction, whereas TLR-6 was only expressed during the acute stage of OA. TLR-4 showed a remarkable increase in expression with respect to the CTL group throughout OA induction, with a significant linear trend ( ; ). (b) The relative expression levels of MMP-3, MMP-9, and MMP-13, normalized to GAPDH gene expression, are shown. MMP-3 expression increased during OA induction ( , ) and was highest on days 8 (1.8-fold; 95% CI 0.005241 to 3.609) and 10 (2.1-fold; 95% CI 0.3375 to 3.941). (c) The relative expression of IL-1β, IL-6, and TNF-α, normalized to GAPDH gene expression, is shown. IL-1β gene expression increased during OA induction ( ), while TNF-α gene expression changed modestly ( ), with the highest increase on day 10 (1.6-fold). The results are pooled data from five independent experiments with 50 total rats. The asterisks indicate , , and , which were determined using a 2-way ANOVA followed by Tukey’s post hoc test to compare the experimental groups with the CTL group. The error bars indicate the SEM.