Developmental expression of dermatan sulfate proteoglycans in the elastic bovine nuchal ligament

The nuchal ligament of bovines is a useful system in which to study elastic fibre formation since it contains up to 83% elastin and undergoes a period of rapid elastinogenesis during the last trimester of fetal development an d in the first four post-natal months. To identify proteoglycans (PGs) whic h may be involved in this process we initially investigated changes in the glycosaminoglycan (GAG) profiles during nuchal ligament development. In con trast to the collagenous Achilles tendon, nuchal ligament exhibited: (a) el evated hyaluronan (HA) levels in the peak period of elastin-associated micr ofibril (fibrillin) synthesis (130-200 days) which precedes elastinogenesis ; and (b) markedly increased synthesis of a glucuronate-rich copolymeric fo rm of dermatan sulfate (DS) in the period corresponding to elastin formatio n (200-270 days). Analysis of DSPGs isolated from 230-day nuchal ligament s howed that this copolymer was predominantly associated with a glycoform of biglycan which was specifically elevated at this stage in development. This finding was consistent with Northern blot analysis which showed that stead y-state biglycan mRNA levels increased significantly during the elastinogen ic period. In contrast, the mRNA levels for decorin, the only other DSPG de tected in this tissue, declined rapidly after 140 days of fetal development . In conclusion, the results suggest that HA may play a role in microfibril assembly and that a specific glycoform of biglycan may be associated with the elastinogenic phase of elastic fibre formation. (C) 2000 Published by E lsevier Science B.V. /International Society of Matrix Biology. All rights r eserved.