Figure 3.

Toluidine blue stained histology section of the defect at 8 weeks postinjury. (A) Low-power view to show structure of the edge (red arrows) and base of the defect (black defect). Large rounded cells that are stained more intensely with the toluidine blue can be seen lining the edges and base of the defect (white arrows). Bar = 500 µm. (B) Higher power view of box region of A to show the appearance of the large rounded cells. Bar = 750 µm. (C) Higher power view of box region of B stained with anti-type C collagen antibody with a FITC-labelled secondary antibody. Type X collagen is shown in green, confirming the identity of these large rounded cells adjacent to the edge and base of the defect as hypertrophic chondrocytes. Bar = 750 µm. c = cartilage edge; f = fibrous tissue in defect; b = bone; s = surface of tissue infill in defect; hc = hypertrophic chondrocytes; bv = blood vessel.