Mechanics of Aortic Smooth Muscle Cells in Tissue Constructs: Effects of Matrix Composition

Remodeling of arteries in response to altered loads is an area of intense interest to cardio-vascular clinicians and researchers. In humans, changes due to cardiovascular diseases (e.g. aortic dilatation) may occur slowly over many years, and mathematical models that describe the remodeling response are needed for predicting the course, and possible treatment, of these diseases. Recently, Humphrey and coworkers have proposed constrained mixture models [1] that can describe these acute and chronic changes[2, 3]. These models consider local stresses in the arterial wall to be the sum of individual contributions from collagen, elastic fibers, and vascular smooth muscle cells (VSMCs) Therefore, the mechanical behavior of VSMCs (presumed to be mechanically in parallel) should be independent of the exact composition of the extracellular matrix (ECM) at any specified stage of tissue remodeling. Previously we have studied the mechanics of VSMCs in 3-D bio-artificial tissue constructs made with collagen [4]. In this study, we made 3-D constructs using fibrin, and investigated whether VSMC morphology and mechanics are dependent on the ECM composition. Because previous studies have shown that VSMCs respond to cyclic stretch by increasing alignment and extra-cellular matrix production[5], we measured the mechanical responses of the VSMCs under continuous cyclic stretch.