ABSTRACT
Mammalian tissues are composed of cells and a more or less abundant extracellular matrix (ECM). In order to understand aging of the ECM one has to take into consideration the following three aspects of the problem: age-related modifications of the biosynthesis of ECM components, postsynthetic modifications of ECM macromolecules, and modifications with age of cell-matrix interactions. Heparin has a similar structure to heparan sulfate chains of a special class of proteoglycans present on cell membranes and also in the ECM. Other domains recognize ECM macromolecules present on collagens, proteoglycans, or on elastin. They also play important "structural" roles in specialized ECM constructions as for instance basement membranes. As many of the ECM macromolecules on the genomic level are known and specific antibodies are also available, their biosynthesis could be studied at both these levels of regulation. The nature of the ECM at these sites is specifically adapted to the physiological role they have to perform.
