A full spectrum of functional tissue-engineered blood vessels : from macroscopic to microscopic

Tissue engineering has created several original and new avenues of investigation in biology (Auger et al., 2000). This new domain of research in biotechnology was introduced in the l980$ as a life-saving procedure for burn patients. The successful engrai‘tment of autologous living epidermis was the first proof of concept of this powerful approach. From the efforts in this field, two schools of thought emerged. A first one is the seeding of cells into various gels or scatTolds in which the cells secrete and/or reorganize the surrounding extracellular matrix (ECM), and a second one, the coaxing of cells onto the secretion of an abundant autologous ECM, thus creating their own environment in the absence of any exogenous material. This latter methodology, which we called the “self assembly approach,” takes advantage of the ability of cells to recreate in vitro tissue-like structures when appropriately cultured (Auger et al., 2000). The conditions entail particular media composition and adapted mechanical straining ol‘ these three-dimensional structures. Our own experience with the culture of autologous epidermal sheets gave us some insight in the property of cells to recreate such in rim: tissue-like structures. This expertise led us to develoP tissue-engineered structures on the basis ol‘ the following two concepts: the living substitutes that we created have no artificial biomaterial, and the ECM is either a biological one repopulated by the ceiis or an ECM neosynthesized by the cells themselves. Such living substitutes have distinct advantages because of their cellular composition that confer to them superior physiologicai characteristics when implanted into the human body, that is, their ability to renew themselves over time and their healing property if they are damaged. Moreover, the presence of autologous cells in the living reconstructed tissue should facilitate its interactions with the surrounding host environment. Here, we describe our own experience in the reconstruction of a full spectrum of blood vessels by tissue engineering: macroscopic and microscopic. We applied the self-assembly approach with some impressive results to the reconstruction of a small-diameter blood vessel and the use of a cell-seeded scaffold leading to the formation of capillary-like structures in a full-thickness skin. The following highlights the major points for the generation of these organs