Fig. 4

Therapeutic effect of WPV-CuO NPs in an ACLT rat model. a Schematic diagram of surgical and different treatments. NPs or PBS were intraarticularly injected into the knee joint 4 weeks after establishment of the ACLT model following a q7dx4 course. A sham treatment group was used as the control. b Cartilage erosion evaluation of knee joint sections based on OARSI score. c Ratio of hyaline cartilage and calcified cartilage (HC/CC). d The number of chondrocytes in the cartilage lesion area. Chondrocytes were calculated from the H&E-stained sections shown in panel f. The WPV-CuO NP group presented the lowest OARSI score but highest HC/CC ratio among all treatment groups, indicating that WPV-CuO NPs reduce cartilage damage via generation of hyaline cartilage. Representative safranin O-fast green- (e) and H&E-stained (f) sections subjected to different treatments. Cartilage erosion is highlighted with black arrows in d. Scale bar = 500 μm in d, and = 100 μm in e. Immunofluorescent staining of COL2 (g) and MMP-13 (h) in cartilage. Bars represent mean ± SEM (n = 6). *p < 0.05, **p < 0.01, #p < 0.05, ##p < 0.01