Isolation and characterization of proteoglycans synthesized in ovo by embryonic chick cartilage and new bone

Cartilage proteoglycans have been well characterized in a number of developing systems, both in vitro and in vivo, but the newly synthesized molecules have been analyzed only from culture material. Because of potential culture artifacts, an attempt was made to characterize the proteoglycans newly synthesized in ovo in chick embryo sternum, tibial epiphysis, and tibial shaft. These in ovo synthesized proteoglycans share many structural features with chick proteoglycans synthesized by chondrocytes in culture including average monomer size, chondroitin sulfate chain size, keratan sulfate chain size, and the ability to aggregate with hyaluronic acid. Moreover, the newly synthesized in ovo proteoglycans, notably those of the tibial epiphysis, display reproducible changes in their structure as a function of embryonic age. These changes correlate with similar changes documented for chick cartilage proteoglycans synthesized in culture. Finally, the proteoglycans synthesized in ovo in the day 17 tibial shaft include, in addition to cartilage proteoglycans, one proteoglycan which seems to be characteristic of bone.