FIBRONECTIN EXPRESSION IN THE CARDIOVASCULAR-SYSTEM

Fibronectin (FN) is a dimeric glycoprotein found in the extracellular matrix (ECM) of most tissues and serves as a bridge between cells and the interstitial collagen meshwork. It also influences diverse process es including cell growth, adhesion, migration, and wound repair. Multi ple FN forms arise by the alternative splicing of a primary transcript originating from a single gene. The spatial and temporal alterations in FN expression in the cardiovascular system have been studied in vit ro in cell culture and in vivo during fetal development, hypertrophy, infarction, arterial injury and aging. This review describes character istics of FN expression in cardiovascular system: 1. the FN phenotype is regulated during development. A high FN mRNA level is related to an early cardiac organogenesis and a progressive decrease that begins at the fetal stage and continues through senescence. During cardiac onto geny, there is a linear correlation between total FN mRNA accumulation and the relative amounts of FN-EIIIA and EIIIB RNA. This correlation is absent during cardiac growth in the adult. 2. A differential reexpr ession of the FN isoforms is observed in both myocardium and aorta in different models of hypertension or infarction but with different thre shold and time course. Changes in total FN mRNA levels in hypertensive models vary depending on the authors. Nevertheless the differences in the expression of the fetal forms of FN mRNA observed among the vario us models of hypertension-induced hypertrophy indicate that the proces s of FN pre-mRNA splicing in the adult myocardium is specifically regu lated and depends on the pathological situations and the type of cell. Although the mechanisms of regulation are poorly understood their imp ortance cannot be underestimated since they control cell phenotype and behavior. Some possible mechanisms of regulation of the expression of fibronectin within the myocardium are proposed using more advanced st udies performed in other tissues and with other experimental models.