Tailoring biomaterial scaffolds for osteochondral repair
Articular cartilage is a mechanically and structurally complex, lubricious tissue that permits load-bearing and frictionless movement of our joints upon articulation. Unfortunately, cartilage is unable to properly self-heal as a result of acute trauma or damage, resulting in many cases in significant pain, reduction in physical activity and quality of life for the patient. Due to the inability of resident cells to repair damaged osteochondral tissue, researchers have focused on utilizing endogenously or exogenously sourced cells (chondrocytes or tissue-derived mesenchymal stem cells), with or without scaffolds, to encourage the secretion of extracellular matrix (ECM) that replicates this highly anisotropic osteochondral tissue, in which the phenotype of the cells and the composition and orientation of the ECM varies along its depth. Important advances have been achieved towards the development of scaffolds with macroscopically relevant structures, however, articular cartilage and bone tissue contain complex, hierarchical structures that provide cells with biophysical and biochemical cues spanning multiple length scales, presenting researchers with some substantial challenges. This review summarizes the latest advances in mechanical, biochemical and topographical engineering of biomaterials to drive requisite biological responses, such as cell differentiation and matrix deposition, in an effort to achieve functional repair of osteochondral defects.