Regulation and Function of Tenascin-C in Heart Valve Homeostasis

Tenascin-C (TN-C) interacts with extracellular molecules and plays a role in cell adhesion, signaling, and differentiation. There is evidence that TN-C is regulated by mechanical forces and since the heart valve is a highly dynamic structure, it is possible that TN-C is expressed within specific sites within the aortic valve, as these sites are subject to unique mechanical forces. It is also reasonable to expect differences in TN-C expression between the pulmonary and the aortic valve because these two locations experience different levels of mechanical force. Here we compare TN-C expression levels in adult pulmonary versus aortic valves and determine if different cell types within aortic valves express different amounts of TNC. Our results indicate that TN-C is expressed in normal post-natal heart valves and expression is higher on the aortic versus ventricular side of the aortic valve. TN-C expression may be higher in aortic versus pulmonary valve. SMC, fibroblasts or myofibroblasts may produce TN-C, but endothelial cells appear not to produce TN-C. These studies will help us in determining the role TN-C plays in normal heart valve tissue homeostasis and how different cell types react to different mechanical forces.