ACP5 and osteoarthritis: Since we found that the number of Tartrate-resistant acid phosphatase (TRAP)-positive cells (osteoclasts) in the subchondral bone of OA mice was significantly higher than that of the corresponding sham group at 30 and 60 days after the model was established (Figure 3A), and previous studies including ours [25] also confirmed that the number of osteoclasts in the subchondral bone of OA mice was significantly increased at the early stage of osteoarthritis.