Fig 1: Macrophage–chondrocyte crosstalk enhanced the production of metalloproteinases in PsE-stimulated cultures. THP-1–derived macrophages, chondrocytes, and macrophage–chondrocyte cocultures were stimulated with P. semirufa bristle extract (PsE; 60 µg/mL) or buffer (control) for 24 and 48 h. The concentrations of MMP-1 (A–D), MMP-3 (E–H) and MMP-13 (I–L) in culture supernatants were quantified by ELISA. Data are presented as dot plots showing the mean ± SEM of biological replicates from three independent experiments. Each data point represents an individual biological replicate, and symbol shape identifies the independent experiment (circles, Experiment A; triangles, Experiment B; squares, Experiment C). Data were assessed for normality prior to statistical analysis. Statistical analyses were performed within each culture system using one-way ANOVA followed by Tukey’s post hoc test for parametric data, or Kruskal–Wallis followed by Dunn’s post hoc test for nonparametric data (*p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001 and ****p ≤ 0.0001). For comparisons between culture systems, data were log-transformed to meet parametric assumptions and analyzed using two-way ANOVA, where “a” indicates statistically significant differences between cocultures and macrophage monocultures, and “b” indicates differences between cocultures and chondrocyte monocultures. The dotted line represents the limit of detection for each analyte.