Landmarks in chondrocyte differentiation and maturation as envisaged by changes in the distribution of calcium complexes: an ultrastructural histochemical study.

Organ cultures of fetal condylar cartilages have been examined using the K-pyroantimonate-osmium fixation method to follow alterations in cellular calcium distribution in maturing cartilage. Special attention has been given to analyzing the temporal and spatial relationships among intracellular calcium accumulation, cell maturation, and matrix mineralization. The findings of this study suggest that concomitant with the change in cellular metabolism from aerobic respiration to glycolysis there is a distinctive change in the distribution of cellular and matrical calcium complexes. This ultrastructural histochemical method can thus be used to evaluate the maturational state of chondrocytes actively involved in endochondral ossification.