Fig. 6: EP4 antagonist HL-43 enhanced cartilage repair and regeneration in three different CD animal models.

a–c EP4 antagonist HL-43 induced cartilage regeneration in MF surgery-induced CD rat model. Macroscopic appearance of the articular cartilage, H&E staining and S.O. staining of the sham and defect cartilage 6 weeks after MF surgery were shown (a). Black dotted boxes indicate the defect region. The International Cartilage Repair Society (ICRS) macroscopic score and ICRS Visual Histological Score of regenerated tissues analysis was analyzed (b, c). n = 4 for each group, scale bar = 500 μm. Error bars are means ± s.d., *P < 0.05, **P < 0.01 by ANOVA and LSD post hoc test. ns, not significant. d EP4 antagonists induced the mature cartilage formation in MF surgery-induced CD rat model. Joint sections from Sham, Vehicle (Veh), Grapiprant and HL-43-treated rats were stained with antibodies against Col2, Acan, Col1, and ColX. Nucleus were shown by DAPI staining. Scale bars are 100 μm. Dotted lines indicated the surface of articular cartilage. e EP4 antagonist HL-43 alleviated OA in the DMM surgery-induced CD mouse model. The corresponding Osteoarthritis Research Society International (OARSI) scores were compared. Error bars are means ± s.d., n = 8 for each group, **P < 0.01, ***P < 0.001, ****P < 0.0001 by ordinary one-way ANOVA with multiple comparison using Tukey method. ns, not significant. f, g The relief of the pain by treatment of HL-43 in the DMM surgery-induced CD mouse model. Von Frey assay (f) and radiant heat paw-withdrawal test (g) were measured in each group 6 weeks after DMM surgery. n = 8 for each group in Von Frey assay, n ≥ 6 for radiant heat paw-withdrawal test, *P < 0.05, **P < 0.01, ***P < 0.001 by ANOVA and LSD post hoc test. h EP4 antagonist HL-43 induced cartilage regeneration in the aging-induced CD mouse model. Articular cartilage thickness of the tibia plateau at same position was measured. Error bars are means ± s.d., n = 9 for the vehicle and HL-43-treated groups, n = 6 for Celecoxib treated group, *P < 0.05, ***P < 0.001 by one-way ANOVA with multiple comparison using Tukey method. i EP4 antagonist HL-43 induced cartilage regeneration in the aging-induced CD mouse model. Representative images of S.O. staining of knee joint sections in aged mice (21-month-old), which treated with 30 mg/kg vehicle, Celecoxib, and HL-43 daily from 19 to 21 months by gavage. Scale bar, 200 μm. Immunostaining of knee joint sections from each group with indicated antibodies. Scale bar, 100 μm. Dotted lines indicated the surface of articular cartilage.