Collagen Cross-Linking in Tendons: The Role of Lysyl Oxidase and Posttranslational Modifications in Injury, Aging, and Congenital Disorders

Tendons enable movements by transmitting forces from muscle to bone, requiring highly specialized material properties for their mechanically demanding functions. Unfortunately, tendon material properties are frequently compromised by physical overuse or genetic aberrations. Lysyl oxidase (LOX)-mediated collagen cross-linking, which is governed by collagen posttranslational modifications (PTMs), is a critical regulator of tendon material properties. Despite studies implicating roles for LOX-mediated cross-linking and underlying PTMs in tendon material properties, these mechanisms are not well understood in tendons in birth disorders, aging, or healing from injury. Here, we review what is known regarding collagen PTMs that influence LOX-mediated collagen cross-linking in tendon and their known contributions to tendon material properties, and we highlight critical gaps in our understanding of these mechanisms. With a more thorough understanding of mechanisms responsible for LOX-mediated collagen cross-linking in tendons, we could exploit these mechanisms to improve the material properties of tendons affected by injury, aging, or congenital disorders.