Tendons: Engineering of Functional Tissues

Modern advances in medical care have greatly improved survival rate and life expectancy following trauma or degenerative conditions, indirectly leading to an ever-increasing need for functional tissue substitutes to improve quality of life. As tendons have limited regeneration capacity, suitable substitutes are required for reconstruction. The current gold standards in tendon reconstruction are autografts, allografts, or even xenografts. However, the injury of a healthy tissue to obtain the graft and to partially repair the damaged side, the lack of donors and the risk of transmitting disease and/or induce an immunogenic reaction have significantly discouraged their use. Tissue engineering was pioneered as the solely valuable alternative. Advancements in the field allow us to fabricate facsimile that closely imitate the native architecture, remedy a deficit and restore functionality in the living tissue or organ. Indeed, numerous biocompatible and biodegradable constructs of various physical forms have been introduced aiming to provide mechanical stability and a three dimensional template for neotissue formation and organisation. Bioactive materials, materials designed to interact with the body to encourage tissue repair, have also been introduced. Strategies to encourage construct interactions with extracellular matrix components, growth factors and cell surface receptors are being explored. However, for a successful tissue reconstruction, it is of paramount importance to understand how the tissue forms and behaves in vivo. Following that, we need to evaluate how closely we can imitate nature. Only then we will be able to engineer constructs with clinical relevance. This chapter discusses the structural composition of the native tendon and summarises approaches in engineering tendon substitutes.