[Morphological study of the epiphyseal cartilage in cartilage matrix deficiency (CMD) mouse--a consideration on the roles and functions of cartilage-specific proteoglycan].

Epiphyseal cartilages in mouse with cartilage matrix deficiency due to genetic failure to synthesize cartilage-characteristic proteoglycan were examined under light and electron microscope. Chondrogenesis and proliferation of chondrocytes seemed to occur, though extracellular matrix was small in amount and chondrocytes were packed closely without consistent orientation. In diaphysis, hypertrophic change of chondrocytes and perichondral ossification were observed. In the epiphysis, there was neither zone formation nor column formation, but hypertrophic chondrocytes and calcification in matrix were observed in the area adjacent to the bone shaft. Electron microscopy showed dilatation of rough endoplasmic reticulum, swelling of mitochondria and a large amount of lipid deposition in the chondrocyte. In the cartilage matrix, it was characteristic that a large number of thick collagen fibrils was arranged in parallel and few matrix granule was seen. These findings suggested that cartilage-characteristic proteoglycan was not essential for chondrogenesis, proliferation of chondrocytes and ossification, but were important for cytodifferentiation and chondrocyte activity.