Histological analyses. (a) Observation 1 day after cell transplantation. Sagittal sections stained with Toluidine blue (TB) and the serial sections under fluorescence for the 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) label are shown. Higher magnifications of the framed areas are shown in images e, f, i, and j. The nuclei were counterstained by 4',6-diamidino-2-phenylindole dihydrochloride in images f and j. Bars (a to d, g, h) = 1 mm; bars (e, f, i, j) = 100 μm. (b) Sagittal sections stained with TB. The distal side is shown on the right side of the image. Bars = 1 mm. (c) Histological score for the cartilage defect after cell transplantation. Histological findings were quantitated using the scoring system (Table 1), in which a full score was 15 and a higher score indicates cartilage repair. The scores of the local adherent group improved continuously through 24 weeks and were better than those of other groups at each point. Data expressed as the mean ± standard deviation (n = 3; P < 0.05 by Kruskal–Wallis test).