In vitro engineering of pressure-resistant vascular networks and proof-of-concept anastomosis in a rabbit model

One of the major challenges for tissue-engineered constructs is the lack of complex, functional vascular networks. In this study, we developed compression-resistant, heparin-loaded vascular structures using 3D printing and dip-coating. Maltitol, chosen for its notable molding properties and compatibility with fused deposition modeling (FDM), served as a sacrificial material to create complex, interconnected 3D vascular templates. The maltitol templates were coated with three layers: two layers of poly(butylene succinate)/poly(lactic acid) (PBS/PLA) blends containing ammonium bicarbonate as a porogen, and a heparin-loaded fibroin/agarose hydrogel layer sandwiched between them. After removing maltitol, the constructs showed mechanical properties comparable to native vessels, with Young's modulus ranging from 6.7 ± 1.1 to 12.6 ± 0.4 MPa and flexural modulus from 0.4 ± 0.1 to 2.3 ± 0.9 MPa. Heparin provided anticoagulant effects by increasing clotting time and platelet adhesion. The grafts were cytocompatible and supported in vitro cell proliferation. In vivo, artificial vessels with a length of 6 mm and an inner diameter of 1.5 mm were bridged between severed femoral arteries in rabbits via end-to-end anastomosis. Color Doppler ultrasound and histology confirmed sustained patency and continuous blood flow. These engineered vascular networks demonstrate potential for supporting perfusion in large-scale tissue-engineered constructs, advancing the development of viable organ substitutes. STATEMENT OF SIGNIFICANCE: We developed a multilayered, heparin-loaded vascular network using a 3D printing and dip-coating strategy to endow tissue-engineered constructs with functional vascular networks. By employing maltitol as a sacrificial template and coating with two porous PBS/PLA layers with a middle heparin-loaded fibroin/agarose hydrogel layer, the engineered vascular network attained notable mechanical properties and anticoagulant activity. The prepared grafts exhibited successful functionality in vivo rabbit model, highlighting their translational potential in constructing perfusable complex organ tissue-engineered scaffolds.