Figure 4: Effects of pterosin B on osteoarthritis development in DMM-operated knees.

(a–c) Eight-week-old mice with DMM were treated with pterosin B for 8 weeks. (a) Histology of articular cartilage of DMM-operated knees injected with pterosin B or vehicle. Safranin O-fast green-iron haematoxylin staining. Boxed regions in the top panels are shown in the bottom panels. OARSI scores of articular cartilage in DMM-operated knees injected with pterosin B or vehicle (black dots) are shown to the right. OARSI scoring was also done on non-operated knees injected with pterosin B or vehicle (black triangles). Two blinded scorers gave consistent results. Representative data are shown; Mann–Whitney test. (b) Immunohistochemistry for Col10 in knees. Boxed regions in the top panels are shown in the bottom panels. The percentage of lacunae surrounded by Col10-positive matrix per total number of lacunae is indicated. Tukey–Kramer post hoc test. (c) Histology of synovium; haematoxylin–eosin staining. Boxed regions in the top panels are shown in the bottom panels. Synovitis scores in DMM-operated knees injected with pterosin B or vehicle (black dots) and in non-operated knees injected with pterosin B or vehicle (black triangles); Mann–Whitney test. (d,e) Thirteen-week-old mice with DMM were treated with pterosin B for 12 weeks. (d) Histology of articular cartilage of DMM-operated knees injected with pterosin B or vehicle. Safranin O-fast green-iron haematoxylin staining. Boxed regions in the top panels are shown in the bottom panels. OARSI scores of articular cartilage in DMM-operated knees injected with pterosin B or vehicle are shown to the right. Two blinded scorers gave consistent results. Representative data are shown; Mann–Whitney test. (e) Immunohistochemistry for Col10 in articular cartilage in DMM-operated knees injected with pterosin B or vehicle. White dotted lines indicate tidemarks. White arrow represents Col10 expression above the tidemark. The images are representative of two independent experiments. Number of mice examined is indicated at the bottom of the graphs. *P<0.05 and **P<0.01. NS, not significantly different. Scale bars, 100 μm.