THE ROLE OF PROTEOGLYCANS IN MAINTAINING COLLAGEN FIBRIL MORPHOLOGY

The aortic wall contains various heterogeneous proteoglycan population s which interact in different ways with other components of extracellu lar matrix. Proteoglycans (PGs) are known to provide structural suppor t to the vessel wall as well as to influence specific physiological fu nctions of the tissues. The aim of the present study was to investigat e the effects of Chondroitinase AC (Chase), Streptococcal Hyaluronidas e (Hyase) and Heparanase on human aortic wall collagen which had been treated previously with 4M GuHCl, in order to verify the effects of se lective glycanolytic treatment on type I collagen fibril ultrastructur e. Following 4M GuHCl treatment, collagen fibrils are seen to have a c learly visible period. Subsequent to GuHCl and Streptococcal Hyase tre atment all collagen fibrils appear to be completely swollen in thin ap eriodic filaments; the typical 64 nm collagen period is completely und etectable. After GuHCl and Chase treatment a small number of collagen fibrils are seen to be swollen in thin fibrils which are mainly locali zed at some distance from elastic fibres. Following GuHCl and Heparana se/Heparitinase III treatment a considerable number of collagen fibril s appear to be swollen in thin fibrils; the majority of which are situ ated in the vicinity of elastic fibrils. The swelling of collagen fibr ils underlines the fundamental role of proteoglycans in maintaining co llagen fibril integrity and periodicity. It is as yet impossible to pr ecisely map interactions between these proteoglycans and collagen fibr es. The role of Hyaluronic acid requires further investigation, althou gh the nature of this interaction is undoubtedly a matter of considera ble interest.