THE CELL BIOLOGY OF THE CARDIAC INTERSTITIUM

The cardiac interstitium represents a system of diverse extracellular matrix (ECM) components organized into a complex, three-dimensional ne twork that surrounds the cellular components of the heart (Borg and Ca ulfield 1981, Weber et al. 1994, Comper 1995). The interaction of the cellular components with the interstitium is dynamic and occurs in res ponse to physiological signals during development, normal homeostasis, and disease (Borg and Caulfield 1981, Weber et al 1994). Both the qua ntitative and qualitative expression of ECM components play an importa nt role in cardiac function; however the mechanisms that regulate the expression and function are not well understood. The manner in which t he terminally differentiated myocyte perceives its external environmen t is of critical importance to the function of the heart. These extern al signals ave delivered via the other two major components of the hea rt: the vascular system and the surrounding interstitium or ECM. Altho ugh it is obvious that the vascular system provides the transport of a variety of regulatory components that influence the contractile abili ty of the myocyte, the role of the interstitium in relation to cardiac function is less understood and is the focus of this review.