Stereological studies on the epiphyseal growth cartilage and characterization of costal cartilage proteoglycans in the achondroplastic (cn/cn) mouse.

The achondroplastic mouse is a dwarf mouse in which the endochondral growth of the skeleton is disturbed. The main morphological characteristic of the affected growth cartilage is an underdeveloped hypertrophic zone. The pattern of matrix mineralization seems to be unaffected, even in areas where hypertrophic chondrocytes are completely absent. The present stereological results indicate a disturbance of the cn/cn cartilage already in the proliferative zone. At the electron microscopical level a clearly abnormal spatial distribution of matrix vesicles was observed in the affected growth cartilage. The vesicle concentration of the cn/cn cartilage was increased, but the mineralizing cartilage showed a decrease of vesicles similar to that in the normal tissue. Parallel biochemical characterization of the proteoglycans and glycosaminoglycans of the cn/cn costal cartilage revealed normal conditions, also in the growth region, which was sampled as a separate tissue fraction. Thus the biochemical results provide no evidence of disturbed glycosaminoglycan metabolism.