Development of a Novel Hierarchically Biofabricated Blood Vessel Mimic Decorated with Three Vascular Cell Populations for the Reconstruction of Small-Diameter Arteries
Lichele Carrabba, Marco Fagnano, Mohamed T Ghorbel, Filippo Rapetto, Bo Su, Carmelo De Maria, Giovanni Vozzi, Giovanni Biglino, Adam W. Perriman, Massimo Caputo, Paolo Madeddu.

The availability of grafts to replace small-diameter arteries remains an unmet clinical need. Here, the validated methodology is reported for a novel hybrid tissue-engineered vascular graft that aims to match the natural structure of small-size arteries. The blood vessel mimic (BVM) comprises an internal conduit of co-electrospun gelatin and polycaprolactone (PCL) nanofibers  (corresponding to the tunica intima of an artery), reinforced by an additional layer of PCL aligned fibers (the internal elastic membrane). Endothelial cells are deposited onto the luminal surface using a rotative bioreactor. A bioprinting system extrudes two concentric cell-laden hydrogel layers containing respectively vascular smooth muscle cells and pericytes to create the tunica media and adventitia. The semi-automated cellularization process reduces the production and maturation time to 6 days. After the evaluation of  mechanical properties, cellular viability, hemocompatibility, and suturability, the BVM is successfully implanted in the left pulmonary artery of swine. Here, the BVM showed good hemostatic properties, capability to withstand blood pressure, and patency at 5 weeks post-implantation. These promising data open a new avenue to developing an artery-like product for reconstructing small-diameter blood vessels.

5. Experimental Section

R-GL consists of a polymeric conduit entirely formed of GL nanofibers. Before electrospinning, a solution of GL 15% (w v−1) (Type A gelatin from porcine skin, Sigma-Aldrich) was prepared by dissolving GL powder in a liquid solution of 60/40 (v v−1) acetic acid/deionized water. A crosslinking agent GPTMS (Sigma-Aldrich) was added at the concentration of 3% (v v−1) and stirred for 1 h before using the solution. The GL solution was electrospun on the 5-mm diameter mandrel rotating at 1000 rpm for 3 h, and the electrospinning device (Electrospinning Station, Nadetech, Navarra, Spain) was set as 20 kV (Voltage), 15 cm (distance from the collector) and
0.2 mL hour−1 (flow rate). After the deposition. The conduit was dried at 37 0C for 48 h to allow the GL crosslinking.