Fig. 6

Histological changes in the chondral defect model after injection of MSCs cultured at low and high density. A Macroscopic appearance of the defect lesions of the only-defect group and the treatment groups which injected either naïve hES-MSCs or hES-MSCs cultured under low- or high-density conditions at 4, 8, and 12 weeks. B and C Safranin-O staining of the only-defect group and the treatment groups which injected either naïve hES-MSCs or hES-MSCs cultured under low- or high-density conditions at 4, 8, and 12 weeks (40 × , low magnification and 200 × , high magnification, respectively). D Scoring of cartilage regeneration parameters using the O’Driscoll scoring system after injection (n = 8 per group) ****p < 0.0001