Fibulin-2 expression marks transformed mesenchymal cells in developing cardiac valves, aortic arch vessels, and coronary vessels

Previous studies showed that extracellular matrix protein, fibulin-2, is ex pressed during epithelial-mesenchymal transformation in the endocardial cus hion matrix during embryonic heart development. Our current study revealed that, in addition to the cardiac valvuloseptal formation, fibulin-2 is synt hesized by the smooth muscle precursor cells of developing aortic arch vess els and the coronary endothelial cells that are originated from neural cres t cells and epicardial cells, respectively. In the cardiac valves and the a ortic arch vessels, fibulin-2 expression shows robust up-regulation when th e transformed mesenchymal cells migrate into the existing extracellular mat rix. In the epicardium, epicardial cells produce fibulin-2 upon their migra tion over the myocardial surface and its expression persists throughout cor onary vasculogenesis and angiogenesis. Fibulin-2 is produced by the endothe lial cells of coronary arteries and veins but not by the capillary endothel ial cells in the myocardium. Thus, fibulin-2 not only uniquely marks the tr ansformed mesenchymal cells during mouse embryonic cardiovascular developme nt, but also indicates vascular endothelial cells of coronary arteries and veins in postnatal life. (C) 2001 Wiley-Liss, Inc.