Figure 3: Matrix organisation of the differentiated RT of a defect treated with chondrocytes on a hyaluronan web (A – D, F, G) and collagen fleece (E) in comparison to the control (H). A, E, G and H: Immunohistochemical reaction with collagen type II antibodies and B, C, D and F: Polarized light microscopy. A: The RT shows the same intense staining for collagen type II antibody but a more fibrous appearance than the NC. The fibres are wavy and vertically arranged (large arrows) and occasionally cross each other (small arrows). Note that the cellularity in the RT is higher than in the NC. The circles in A & B indicate the same areas to show that the images were taken from the same section. The squares in A & B label the areas shown in high magnification in C & D. B: In olarized light the vertical fibre arrangement (arrows) is especially well discernible because only fibres with the same orientation appear bright. In addition, lique and horizontal fibres are visible (appear dark) in between the vertical strands. C, D: Detail images of the matrix in polarized light in two different ientations showing either the vertical or oblique fibres. The arrows correspond to those in (A). E: RT area with weak collagen type II positive staining forming a network-like feature around the cells (curved arrows). In the left of the image, collagen type II stained fibres are vertically and more densely arranged. F, G: pper margin of the hyaline-like RT in transition to the fibrous RT, showing vertically arranged, wavy collagen type II-positive fibres (bent arrows) extending to an area of unstained, three-dimensionally arranged fibres (horizontal lines). H: Periphery of a control defect. Locally, fibre-bunches extend from residual cartilage into the defect area. Scale bars: (A, B) 100 µm, (C, D) 20 µm, (E-H) 50 µm.