Macromolecules of the extracellular compartment of embryonic and mature hearts.

THE FORM and function of the heart are the final result of an integration of cells, tissues, and extracellular material. The structure of many extracellular macromolecules is known, but studies of the cardiac extracellular matrix are still inadequate to provide a comprehensive understanding of it. The purpose of this review is to summarize the present knowledge of the cardiac extracellular matrix and to focus specific attention on this physiologically important compartment. It does not purport to be a detailed review of extracellular molecules; several excellent recent reviews exist." The three general types of macromolecules—collagen, glycosaminoglycan, and glycoprotein—which are characteristic of extracellular matrices probably differ qualitatively and quantitatively between different matrices and as a function of different ages, both preand postnatal, in the life of an animal. These three general classes of macromolecules will be described briefly after a review of some structural characteristics of the extracellular matrix.