Tissue-Engineering Strategies for the Tendon/Ligament-to-Bone Insertion

Abstract

Injuries to connective tissues are painful and disabling and result in costly medical expenses. These injuries often require reattachment of an unmineralized connective tissue to bone. The uninjured tendon/ligament-to-bone insertion (enthesis) is a functionally graded material that exhibits a gradual transition from soft tissue (i.e., tendon or ligament) to hard tissue (i.e., mineralized bone) through a fibrocartilaginous transition region. This transition is believed to facilitate force transmission between the two dissimilar tissues by ameliorating potentially damaging interfacial stress concentrations. The transition region is impaired or lost upon tendon/ligament injury and is not regenerated following surgical repair or natural healing, exposing the tissue to risk of reinjury. The need to regenerate a robust tendon-to-bone insertion has led a number of tissue engineering repair strategies. This review treats the tendon-to-bone insertion site as a tissue structure whose primary role is mechanical and discusses current and emerging strategies for engineering the tendon/ligament-to-bone insertion in this context. The focus lies on strategies for producing mechanical structures that can guide and subsequently sustain a graded tissue structure and the associated cell populations.

• engineering of graded tissues
• tendon-to-bone insertion site
• fibrocartilage
• mineralized fibrocartilage
• enthesis
• mechanical conditioning of engineered tissues

ACKNOWLEDGMENT

This work was supported by the National Institutes of Health (AR055184 and AR060820) and the National Science Foundation (CAREER 844607).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.