Tendon introduction

Tendon is one of the important components of the musculoskeletal system, which links muscles to bones, so that the tensile force created by muscles can be transmitted to bone for body movement. Tendon injury and defects are common diseases of the musculoskeletal system. Nevertheless, the treatment of tendon defects remains a major challenge to reconstructive surgery, partly because there is limited availability of autologous tendon grafts.

Regenerative medicine represents the future direction for tendon repair and functional recovery, in which stem cell therapy, tissue engineering, and regenerative materials will play important roles in tendon regeneration. Actually, engineered tendon repair might be the major contributor to tendon regeneration, because it can also integrate stem cells and biomaterials into tendon regeneration, although we are a long way from its ultimate translation to clinical therapy.

Scaffold materials

General requirements on tendon scaffold materials

As the major contributor to tissue regeneration, biomaterial plays a key role in engineered tendon regeneration, because it provides an essential scaffold for extracellular matrix (ECM) production and tissue formation. The main tendon extracellular matrix is type I collagen, which is highly organized in a hierarchy of bundles that are aligned in a parallel fashion. In addition, there are small amounts of other collagens and proteoglycans, such as collagens type III, V, XII, and XIV, decorin, and tenascin. In particular, the small linking proteins play important roles in enabling the structural integrity of tendon and affording it mechanical strength. This unique structure provides the unique biomechanical properties of tendon tissues. Therefore, the parallel alignment structure and mechanical strength should be considered for tendon scaffold design.