Bilayered scaffold for engineering cellularized blood vessels.

Vascular scaffolds fabricated by electrospinning poly(epsilon-caprolactone) (PCL) and collagen have been designed to provide adequate structural support as well as a favorable adhesion substrate for vascular cells. However, the presence of small-sized pores limits the efficacy of smooth muscle cells (SMC) seeding, as these cells could not adequately infiltrate into the scaffolds. To overcome this challenge, we developed a bilayered scaffolding system that provides different pore sizes to facilitate adequate cellular interactions. Based on the fact that pore size increases with the increase in fiber diameter, four different fiber diameters (ranging 0.27-4.45 mum) were fabricated by electrospinning with controlled parameters. The fabricated scaffolds were examined by evaluating cellular interactions, and the mechanical properties were measured. Endothelial cells (EC) seeded on nanoscaled fibers showed enhanced cellular orientation and focal adhesion. Conversely, fabrication of a larger fiber diameter improved SMC infiltration into the scaffolds. To incorporate both of these properties into a scaffold, bilayered vascular scaffolds were produced. The inner layer yielded small diameter fibers and the outer layer provided large diameter fibers. We show that the bilayered scaffolds permit EC adhesion on the lumen and SMC infiltration into the outer layer. This study suggests that the use of bilayered scaffolds may lead to improved vessel formation.