Extracellular matrix

Abstract

In this survey of the advances in the understanding of the extracellular matrix during the past 25 years, the findings of relevance to cell and developmental biology are emphasized. The first paragraph deals with collagen: starting from the first electron-microscopy and physical-chemistry studies, the discovery of the quarter-stagger model of the native collagen fibrils, the identification of the three polypeptides (α-chains) comprising tropocollagen, the definition of procursors and of enzymes that posttranslate, cross-link and degrade the molecules, the examination of the cell pathways and cell types involved in biosynthesis, the immunological specificity and the genetic diversity of the molecules related to epigenetic differentation are successively reviewed. The next paragraph takes into consideration the ground substance surrounding the collagen fibrils: from the initial concept of neutral and acid mucopolysaccharides to the subsequent identification of glycosaminoglycans (free as hyaluronic acid or linked covalently to proteins as proteoglycans), the advances in biochemical analysis and in electron microscopy (mainly applying ruthenium-red fixation) in correlation with morphogenetic studies led to the present understanding of the supramolecular organization. Other matrix proteins such as elastin, fibronectin and laminin are mentioned for their biochemical and immunohistochemical characterisation. A final paragraph deals especially with embryology and the morphogenetic role of matrix molecules: It shows how the studies on connective tissues, basement membrane, tissue interaction, cell attachment in-vitro have been of value to solve problem of developmental biology (245 references). (Gerzeli - Pavia)