Figure 5: Section through a RT of a cartilage defect treated with chondrocytes on a hyaluronan web (detail of Figure 1C) showing hyaline-like tissue in the lower half and fibrous tissue in the upper half. A: The toluidine blue stained light microscopic image shows homogeneously and densely stained ECM in the lower half and a fibrous, less dense matrix in the upper half of the column. The cells are regularly distributed, either singularly or in pairs (circles). The cellularity is higher in the deeper than in the superficial regions. B-H: TEM images show the alteration of chondrocytes from the surface to the depth of the RT. B: Superficial chondrocytes of different shape, separated by a matrix layer from the joint surface. Note the thin dark sheath locally covering the matrix (arrow). C: Polygonal chondrocytes extending several cell processes into a dense but fibrous matrix. D: Similar polygonal cell as in C but with fewer and thicker cell processes and with a small bundle of intermediate filaments around the nucleus. E, F: Cells in the upper, hyaline-like tissue are by tendency (E) or totally (F) spherical. The matrix is very dense and homogeneous. G: In the deepest region of the hyaline-like RT, many chondrocytes are ovoid and arranged as double hondrons. Note the bundle of intermediar filaments around the nucleus(arrow) and the Pericellular Matrix (pm) between the cells; im= interterritoreal matrix; H: hondrocyte close to the tide mark surrounded by a dark Pericellular Matrix (pm) and matrix vesicles (arrowhead) in the Interterritoreal Matrix (im). Scale bars: (A) 50 µm, (B-G) 5µm, (H) 2 µm.