Cardiovascular diseases are increasingly becoming the main cause of death all over the world, which has led to an increase in the economic and social burden of such diseases. Vascular tissue engineering (VTE) is providing a route towards interesting applications, mainly focussing on the in vitro, in vivo, or combined in vitro/in vivo regeneration of small-diameter blood vessels (<6 mm) for coronary or peripheral vascular substitutions. Although different approaches have been investigated in the past two decades to achieve this aim, the most common method uses a macromolecular-based structure to scaffold cells during the regeneration process. Therefore, the aim of this work is to comprehensively review macromolecular biomaterials that were designed, developed, fabricated, and tested for scaffolding VTE. In an effort to provide a comprehensive overview, this review will mainly focus on the mechanical properties of the construct and its biological performance that results from the scaffold colonization during cell growth.

The objective of this work was to design a bioreactor to stimulate the three-dimensional regeneration of arterial tissue on a cylindrical scaffold with a methodological approach. Once seeded, the scaffold is perfused internally and the externally with culture medium with two independent perfusion systems at different flow rates. The horizontal position and the rotation of the construct ensure the uniformity of the arterial growth and of the endothelial cell spreading. During cell culture, the parameters, such as internal flow and stretching of the vessel, can evolve gradually from the fetal stage to the adult stage. The bioreactor will also be useful for investigating the influence of mechanical stresses and strains on the properties of mature arteries (rigidity, burst strength, adhesion of endothelial cells, etc.).

Vascular tissue engineering focuses on the replacement of diseased small-diameter blood vessels with a diameter less than 6 mm for which adequate substitutes still do not exist. One approach to vascular tissue engineering is to culture vascular cells on a scaffold in a bioreactor. The bioreactor establishes pseudophysiological conditions for culture (medium culture, 37°C, mechanical stimulation). Collagen gels are widely used as scaffolds for tissue regeneration due to their biological properties; however, they exhibit low mechanical properties. Mechanical characterization of these scaffolds requires establishing the conditions of testing in regard to the conditions set in the bioreactor. The effects of different parameters used during mechanical testing on the collagen gels were evaluated in terms of mechanical and viscoelastic properties. Thus, a factorial experiment was adopted, and three relevant factors were considered: temperature (23°C or 37°C), hydration (aqueous saline solution or air), and mechanical preconditioning (with or without). Statistical analyses showed significant effects of these factors on the mechanical properties which were assessed by tensile tests as well as stress relaxation tests. The last tests provide a more consistent understanding of the gels' viscoelastic properties. Therefore, performing mechanical analyses on hydrogels requires setting an adequate environment in terms of temperature and aqueous saline solution as well as choosing the adequate test.

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Cardiovascular diseases are increasingly becoming the main cause of death all over the world, leading to an increase in the economical and social burden. Vascular tissue engineering (VTE) is paving its routes toward challenging applications, focused mainly on substitutions of small-diameter blood vessels (\6 mm). Native collagen, a natural biological material which possesses extraordinary properties in terms of biocompatibility, has been extensively investigated as a scaffold for VTE. However, collagen is mainly extracted from collagen-rich native natural tissues by different harsh chemical and physical treatments, resulting in a solution susceptible to be processed for the fabrication of supports. These treatments imply the destruction of the native organization of the collagen microstructure, thus resulting in a collagen-based support less resistant in terms of mechanical properties than the native one. Therefore, different approaches have been investigated to increase these mechanical properties. Although UV irradiation present a strong potential for efficient crosslinking collagen macromolecules, the undesirable effects of UV on cell activity still remain the main challenge to be overpassed. The aim of this study was to investigate the potential of UV radiation and glycation for the crosslinking of collagen gels, with particular concern to the cells and capacity of the cells to remodel the collagen structure.