Fig. 4.

Evaluation of histology score using Toluidine blue and Alcian blue staining. a Toluidine blue staining of the 5 different groups at 3 months after cell (or PBS + coacervate) injection. Upper panel showed entire tibia plateau at the condyle axial level, scale bar = 500 μm. Lower panel showed high magnification, scale bar = 100 μm. The PBS + coacervate group showed that the knee joint cartilage layer was almost completely destroyed. Very limited chondrocytes were left at the joint cartilage. All other groups showed cartilage regeneration at cartilage surface to different extent. b OARSI histology scores based on Toluidine blue staining in each of the 5 groups. All groups that were injected with hMDSCs had lower scores compared to the PBS + coacervate control group. *P < 0.05, **P < 0.01. Wilcoxon rank-sum test. c Alcian blue staining showed similar results as Toluidine blue staining. Upper panel showed the morphology of cartilage of entire knee at condyle axial level. Scale bar = 1000 μm. Lower panel showed chondrocytes morphology at the articular surface of each group, scale bar = 100 μm