Synovial joints: Mechanobiology and tissue engineering of articular cartilage and synovial fluid

This chapter provides an overview of the components of synovial joints including articular cartilage, synovium, and synovial fluid. Focus is placed on the biomechanical properties of these tissues and models of their behavior. Further insight is given into the influence of mechanical loading on the development of these joint components and changes during pathology. Finally, perspectives on engineering articular cartilage and synovial fluid are provided.\ud \ud Synovial joints allow for the articulation of long bones within a fluid-filled cavity. Articular cartilage (AC) is a connective tissue covering the ends of bones that functions as a load-bearing, low-friction, and wear-resistant surface to facilitate joint movement. Synovial fluid (SF) is the viscous liquid found inside synovial joints that functions as a biomechanical lubricant. The SF is encapsulated within the joint space by the synovium (SYN), a thin membrane-like tissue consisting of cells and extracellular matrix. The extracellular matrix of cartilage allows for load-bearing during joint motion, while the viscous and lubricating properties of SF reduce cartilage wear. The homeostasis of these tissues is dependent on mechanobiology – cell populations receiving mechanical cues to guide biosynthesis and thereby alter their microenvironment and tissue-scale mechanical properties. This chapter includes Tissue engineering (TE) and regenerative medicine (RM) approaches to the in vitro and in vivo development of articular cartilage and SF for the treatment and study of damaged synovial joints. First, the composition, structure, and function of cartilage and SF are discussed, followed by the mechanical properties of these tissues and the theoretical models that have been used to describe them. Next, the effects of mechanical stimuli on chondrocyte biosynthesis and pathological changes in SF composition are covered. Finally, advances in the fields of TE and RM applied to cartilaginous tissue and SF are reviewed, focusing on the mechanobiology of chondrocytes in Tissue engineered constructs