Micropatterning of three-dimensional electrospun polyurethane vascular grafts

The uniform alignment of endothelial cells inside small-diameter synthetic grafts can be directed by surface topographies such as microgrooves and microfibers to recapitulate the flow-induced elongation and alignment of natural endothelium. These surface micropatterns may also promote directional migration and potentially improve anastomotic ingrowth of endothelial cells inside the synthetic grafts. In this paper, we developed electrospinning and spin casting techniques to pattern the luminal surface of small-diameter polyurethane (PU) grafts with microfibers and microgrooves, respectively, and evaluated endothelial cell orientation on these surface micropatterns. Tracks of circumferentially oriented microfibers were generated by electrospinning PU onto a mandrel rotated at high velocity, whereas longitudinal tracks of microgrooves were generated by spin casting PU over a rotating poly(dimethylsiloxane) mold. We found that both PU grafts possessed longitudinal Young's moduli in the range of 0.43 ± 0.04 to 2.00 ± 0.40 MPa, comparable with values obtained from native artery. Endothelial cells seeded onto the grafts formed confluent monolayers with individual cells exhibiting elongated morphology parallel to the micropatterns. The cells were phenotypically similar to natural endothelium as assessed by the expression of the endothelial cell-specific marker, vascular endothelial cell cadherin. In addition, the cells were also responsive to stimulation with the pro-inflammatory cytokine tumor necrosis factor-α as assessed by the inducible expression of intercellular adhesion molecule-1. These results demonstrate that our micropatterned PU grafts possessed longitudinal Young's moduli in the same range as native vascular tissue and were capable of promoting the formation of aligned and cytokine-responsive endothelial monolayers.