INVERSE RELATIONSHIP BETWEEN HYALURONAN AND COLLAGENS IN DEVELOPMENT AND ANGIOGENESIS

The extracellular matrix plays a vital role in regulating normal tissu e development and function - largely via the specific arrangement of m acromolecules such as collagens, proteoglycans, glycosaminoglycans and glycoproteins. Previous reports have concentrated on associations bet ween combinations of collagens/proteoglycans, collagens/glycoproteins and proteoglycans/glycosaminoglycans whilst little information is avai lable on associations between collagens and free glycosaminoglycans. I n this review, we discuss possible associations between collagens and the glycosaminoglycan hyaluronan; macromolecules which are known to ex hibit changes in amount and composition during development and under p athological conditions. We demonstrate two types of collagen/hyalurona n association in vivo: the first, during the formation of extracellula r matrix structures where neither collagens nor hyaluronan are degrade d, resulting in the regulation of collagen fibrillogenesis, and the se cond, involving an inverse correlation between collagen synthesis and hyaluronan degradation and vice versa. We suggest that associations be tween collagens and hyaluronan play an important role in the initiatio n and maintenance of angiogenesis and put forward a model of cartilage vascularisation which relies on these associations.