Defining a scaffold for ligament tissue engineering: What has been done, and what still needs to be done

Tissue engineering is a promising alternative to current surgical methods for ligament repair. However, despite a large variety of reported scaffolds for ligament, tissue-engineered solutions struggle to reach the clinics. The issue of proposing a scaffold meeting the key requirements for ligament tissue engineering is still largely open. In this article, a brief up-to-date review is proposed concerning what has been done and what still needs to be done in order to propose a suitable scaffold structure and material for ligament tissue engineering. A particularly focus is made on the selection of and structures, biomaterials and their functionalization, on the characterization of the initial and evolutive scaffold properties, and on the challenge of anchoring it within bone tunnels. The interest of computational approaches in the definition of suited scaffolds is also presented. We thus propose to list the remaining steps that should permit in the forthcoming years to propose a bioactive composite bone-ligament-bone scaffold to regenerate ligaments. Keywords: Ligament tissue engineering, Scaffold design, Bone-ligament interface, Composite scaffold, Ligament anchorage