Tissue engineering of skeletal muscle, tendons and nerves: A review of manufacturing strategies to meet structural and functional requirements

Additive manufacturing technologies have become at the forefront in tissue engineering, enabling the fabrication of complex tissues with intricate geometries that were not feasible using conventional manufacturing techniques. Due to the rapid progress in this field, it has become difficult not only to choose the most appropriate method, but also the optimal material, biological model (i.e., cells and bioactive compounds), and processing technique to fulfill the macro-and microstructural architecture and functions of biological tissues. The aim of this review is to describe recent advances in tissue engineering fabrication methods, from established electrospinning to emerging additive manufacturing technologies, with particular emphasis on tissues that exhibit hierarchically organized anisotropic architecture (skeletal muscle, tendons, and peripheral nerves). One of the current challenges is that the designs are usually dictated by the constraints imposed by the methods, rather than by criteria based on mechanical and biological requirements. Therefore, the review focuses on describing how the anatomical structure and function of muscles, tendons, and nerves should serve as the basis for an efficient three-dimensional design that considers both micro and macro aspects of the tissue. In addition, the individual factors that influence the fabrication strategy are discussed and related to the mechanical and biological properties of the three tissue types. The review highlights the advantages and limitations of each fabrication strategy and provides an over-view of critical aspects relevant to future research strategies in this area.