Ex vivo analysis of human synovial mesenchymal stem cell attachment to human cartilage defect. The cartilage defect at 2.5 mm diameter was faced upward, filled with 800 × 103 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)-labeled human synovial mesenchymal stem cells (MSCs) in 8 μl PBS, and held stationary for 5, 10, 20, and 30 minutes. (a) Macroscopic features of cartilage defects filled with DiI-labeled human synovial MSCs for the indicated time. Bar = 2.5 mm. (b) Cell number attached to the cartilage defects. Data expressed as the mean ± standard deviation (n = 3). (c) Adhesion molecule expressions in cartilage defects filled with synovial MSC suspension for 10 minutes. Bars = 50 μm. Ab, antibody; ICAM-1, intercellular adhesion molecule 1; VCAM-1, vascular adhesion molecule 1. (d) Effects of neutralizing antibodies for adhesion molecules on attachment of human synovial MSCs on human cartilage defects. The cartilage defect was filled with DiI-labeled human synovial MSC suspension with control or neutralizing antibodies. After 10 minutes, the attached cell number was measured. Data expressed as the mean ± standard deviation (n = 3; P < 0.05 by Kruskal–Wallis test). ALCAM, activated leukocyte-cell adhesion molecule.