The study of representative populations of native aggrecan aggregates synthesized by human chondrocytes in vitro

Abstract

Chondrocytes were cultured in gelified agarose. Aggrecans, accumulated during culture, were liberated by agarase digestion of the artificial agarose matrix and studied by electron microscopy. The culture system and the specific method used to liberate the extracellular macromolecules enabled us to study the whole population of de novo synthesized, native aggrecan aggregates. The average length of the aggrecans was 188 nm. Aggrecans were observed as free molecules or attached on hyaluronan chains. In these aggregates no free binding sites on the hyaluronan chain were observed, and the average distance between the aggrecans was 27 nm. Consequently, the length of the hyaluronan chain defines the molecular size of the aggregate. Mature human articular cartilage cells were found to synthesize a relatively small proportion of very large aggrecan aggregates with over 100 aggrecans attached to a single hyaluronan chain. However, the average aggrecan aggregate carried about 12 aggrecans. © 1993, Tissue Culture Association. All rights reserved.