miR-146a and Smad4 are expressed reciprocally in surgically induced osteoarthritis in rats. (A) The level of miR-146a increases in cartilage from the osteoarthritis (OA) group compared with the sham group. Values are the mean ± standard deviation of 10 animals per group. *P < 0.05. Femoral condyles from OA and Sham rats were stained with safranin O and subjected to immunohistochemistry for Smad4 and vascular endothelial growth factor (VEGF). (B), (C) Femoral condyles from OA rats exhibited reduced safranin O staining. (D), (E) Cartilage from normal and osteoarthritic rats were immunostained for Smad4 protein. (F), (G) Cartilage from normal and osteoarthritic rats were immunostained for VEGF protein. Original magnification: (B), (C) ×40; (D) to (G) ×400.