LIGHT AND ELECTRON-MICROSCOPIC IMMUNOHISTOCHEMICAL LOCALIZATION OF THE SMALL PROTEOGLYCAN CORE PROTEINS DECORIN AND BIGLYCAN IN HUMAN KNEE-JOINT CARTILAGE

The distribution of decorin and biglycan was investigated at the light and electron microscopical level in adult human articular cartilage. In general, the amount of decorin and biglycan was found to decrease w ith the depth of the layer of the cartilage. Decorin was found in the interterritorial matrix where most of the collagen is located. This fi ts in well with the assumption that decorin may modulate collagen meta bolism. Biglycan was found next to the chondrocytes in the pericellula r matrix and is assumed to be responsible for cellular activities. At the ultrastructural level, decorin was localized in the interterritori al matrix and in vesicles in chondrocytes. Biglycan was found, usually though not exclusively in the pericellular matrix. Both small proteog lycans were detected close to and on the collagen fibres and also asso ciated with the more globular structures of the matrix between the fib rils. A double-staining approach revealed that the two molecules could be located along the same collagen fibril. However, staining for bigl ycan and decorin was not observed simultaneously within the same regio n of the fibre.