Abstract
In this report an autoradiographic approach is used to compare synthetic activities of cells within differentiated cartilage colonies. While amino acid incorporation is uniform throughout the colony, H^3^βuridine is incorporated more actively by cells having little matrix, cells which are typically in the peripheral regions of a colony. On the other hand S^35^O~4~ is incorporated most actively by cells in the colony centers. This difference in sulfation appears to occur independently of the mitotic state of the cells, since it is apparent in both growing and nearβstationary cultures. Instead, there is a correlation between the accumulation of extracellular matrix and more active levels of sulfation. In support of the idea that matrix creates a microenvironment more favorable to chondrogenesis is the observation that a brief treatment with hyaluronidase, which removes about 60% of the S^35^O~4~ from prelabeled cultures, depresses sulfation, as determined both autoradiographically and biochemically by the isolation of labeled glycosaminoglycans. The possible role of extracellular matrices in altering the expression of differentiated functions by creating a more favorable microenvironment is considered.