Design and Assembly Considerations in the Engineering of Vascular Tissue

Abstract

Native vascular tissue functions are highly dependent on structural organization at the super-cellular, cellular, and sub-cellular spatial scales. We hypothesized that the structure-function relationship of vascular tissues in vivo can be leveraged to engineer vascular tissues in vitro by prescribing the shape of constituent cells and their assembly into organized three-dimensional structures. To this end, we first asked if vascular smooth muscle cell shape influences cellular contractility. We engineered human vascular smooth muscle cells to assume similar shapes to those in elastic and muscular arteries and then measured their contraction while stimulating with endothelin-1. We found that vascular smooth muscle cells with elongated shapes exhibited lower contractile strength but a greater percentage increase in contraction after endothelin-1 stimulation, suggesting that elongated vascular smooth muscle cell shape endows the muscular artery with greater dynamic contractile range. Next, we sought to assemble cells into tissues by employing a three-dimensional cellular patterning strategy based on the folding of porous, thin polymer films. We assembled different three-dimensional endothelial and vascular smooth muscle organizations by patterning two-dimensional poly(lactic-co-glycolic) acid and collagen thin films with cell suspensions at prescribed locations. The films were subsequently folded following Miura-ori geometry guidelines and the matrices were embedded subcutaneously in immunodeficient mice in order to assess the vascularization of the implanted constructs. We found that spatial organization that allowed endothelial and vascular smooth muscle cells to interact adjacent to each other laterally in the same folding plane created the densest vascularized network, suggesting that three-dimensional structural organization of vascular cells can influence the formation of vascularized networks. Taken together, our result shows that functional vascular tissues in vitro can be engineered by encoding structure cues in their design and assembly.