Electron microscopic study of proteoglycan aggregates synthesized by embryonic chick sternal chondrocytes in vitro

Proteoglycan(PG)-aggregates are known to play an important role in the inhibition of matrix calcification. PG extracted from future calcifying cartilage are smaller than those extracted from non-calcifying cartilage. The present study investigates if alterations in aggregate size are also observed in chrondrocyte cultures. Agarose cultures from chondrocytes derived from the non-calcifying (caudalic) and the future calcifying (cephalic) region of embryonic chick sterna are used. An average aggregate of the caudalic culture contained 27 monomers, an average aggregate of the cephalic culture 20. These data are in accordance with in vivo observation. Since the agarose culture creates the possibility to observe the whole population of de novo synthesized PG, this culture system can be helpful to investigate the role of PG-aggregates in matrix calcification.