CCL2 and osteoarthritis: In osteoarthritis, the CCL2/CCR2 signaling axis can induce monocytes to be recruited to inflammatory areas, worsening inflammation and tissue damage.37 Our results showed that inflammatory responses in the supernatant of hDPCs were inhibited by BMP9, reducing the migration ability of monocytes-macrophages and suggesting that the inhibition of inflammation by BMP9 may be harmful to the chemotaxis of immune cells.