<p>The knee joints were harvested from control (A, C, E and G) and α5 CKO (B, D, F and H) 4 weeks after OA surgery. The sagittal sections were subjected to hematoxylin-eosin staining (HE, A-D), CD31 immunostaining (E and F) and Safranin O staining (G and H). C and D are magnified images of the box of A and B, respectively. Double headed arrows indicate thickening of synovium (C and D). Arrows indicate CD31-positive vessels (E). Bar, 250 μm for A, B, G and H; 125 μm for C-F.</p
