The structure and abundance of cartilage proteoglycans during early development of the human fetus.

Proteoglycan was isolated from the epiphyseal cartilage of the knee joint from human fetuses, ranging in age from 11 to 19 wk of gestation. The content of proteoglycan, per wet weight of cartilage, increased with gestational age, and structural changes were observed in the proteoglycan subunits, particularly with respect to hydrodynamic size and the position of sulfation of the chondroitin sulfate chains. While 6-sulfation remained fairly constant on about half the disaccharide residues during the age period examined, the proportion of nonsulfated residues decreased with gestational age and there was a corresponding increase in the proportion of 4-sulfated residues. Other structural parameters showed little change, and after 11 wk of gestation the majority of proteoglycan subunits were able to interact with hyaluronic acid to form aggregates. Link proteins were detected in the cartilage at all ages and their abundance increased with age relative to other cartilage proteins. They showed little change in structural heterogeneity, with the two larger molecular forms predominating. In contrast to the proteoglycans, cartilage proteins were in high abundance at 11 wk of gestation, but decreased considerably with time, although there was little change in the relative proportion of the majority of the components.