(337b) Collagen-Elastin Scaffolds for Heart Valve Tissue Engineering

Since most of the body’s extracellular matrix (ECM) is composed of collagen and elastin, we believe the choice of these materials is key for the future and promise of tissue engineering. Of particular interest in the cardiovascular system are the elastic properties of elastin. Once it is known how the elastin content of ECM guides cellular behavior (in 2D or 3D), one will be able to harness the power of collagen-elastin microenvironments to design and engineer stimuli-responsive tissues. Moreover, the implementation of such matrices to promote endothelial-mesenchymal transition of primary endothelial cells constitutes a powerful tool to engineer 3D tissues.

Here, we design a 3D collagen-elastin scaffold to mimic the native ECM of heart valves, by providing the strength of collagen layers as well as elasticity. Valve interstitial cells (VICs) were encapsulated in the collagen-elastin gels while valve endothelial cells (VECs) were cultured onto the surface to create an in vitro 3D VEC-VIC co-culture. Cell numbers were counted every other day up to 7 days after seeding and proliferation rates were calculated based on cell counts. In an experimental period of 7 days, VICs continuously proliferated while cell morphology changed to more elongated and aligned. VICs had stable expression levels of integrin β1 and F-actin during the entire culture period. The expression of integrin β1 remained low in VECs as expected. VECs maintained endothelial phenotype up to day 5, as indicated by low expression of F-actin while transformed VECs accounted for less than 7% of the total VECs in culture. On day 7, over 20% VECs were transformed to mesenchymal phenotype indicated by increased actin filaments and higher expression of integrin β1. These findings demonstrate that our 3D collagen-elastin scaffolds provided a novel tool to study cell-cell or cell-matrix interactions in vitro, promoting advances in the current knowledge of valvular endothelial cell mesenchymal transition.