Fibronectin (FN, FN1) is an extracellular matrix glycoprotein forming a dimer (~250 kD). Two isoforms exist: plasma fibronectin from hepatocytes and cellular fibronectin made by fibroblasts, endothelial and mesangial cells (3). The FN1 gene belongs to the ECM protein family (3). Fibronectin is ubiquitous, especially in fibroblast and endothelial rich tissues, hepatocytes and renal glomerular mesangial cells (1). During embryogenesis it lines basement membranes of developing vessels and kidneys and is essential for angiogenesis; FN null mice die embryonically with severe vascular defects (2,4). In adults it participates in wound healing. By binding integrins (e.g., α5β1) and growth factors, fibronectin provides a scaffold for cell adhesion, migration and proliferation, regulating morphogenesis and angiogenesis. Clinically, elevated cellular fibronectin occurs in diabetic nephropathy and mesangial expansion (1). After cerebral ischemia it rises sharply, and an imbalance with MMP mediated degradation predicts hemorrhagic transformation (3). Altered fibronectin matrices also promote fibrosis.
