Heterogeneity of proteoglycan particles in thin sections and replicas of human articular cartilage

Proteoglycans were studied in articular cartilage of human femoral condyles. On the basis of the histochemical data obtained by means of light microscopy (AB + CEC MgCl2; pre-incubation with hyaluronidase or with chondroitinase ABC), the proteoglycan concentration as well as the keratan sulfate-chondroitin sulfate ratio seemed to increase proportionally to the articular cartilage depth. AB-proteoglycan particles of various shapes (filament-like or leaf-like) and sizes (10 nm or 16-18 nm), depending on the articular cartilage depth and on the histochemical conditions (as above), were visualized in thin sections. Similar heterogeneity of elongated non-collagen particles was shown in replicas of fresh freeze-fractured and deep-etched specimens. An interpretation of the distribution and nature of articular cartilage proteoglycans was made by comparing the obtained morphological findings.