Biomechanical Properties of Articular Cartilage Pericellular Matrix Measured in situ via Atomic Force Microscopy

INTRODUCTION: Articular cartilage is the connective tissue lining the articulating surfaces of diarthrodial joints, providing a low-friction, load bearing surface during joint motion. Articular cartilage consists of a single cell type, chondrocytes, embedded within an extensive extracellular matrix (ECM). The chondrocytes are surrounded by a narrow region called the pericellular matrix (PCM) that together with the cell is termed a chondron. While multiple techniques have been used to determine the mechanical properties of isolated chondrons, including micropipette aspiration [1], few studies have measured the biomechanical properties of chondrons in situ. Atomic force microscopy (AFM) provides a high resolution form of nanoand microindentation approaches that can be used to measure local mechanical properties in situ [2,3]. The objective of this study was to use AFM to generate elasticity maps of articular cartilage and measure the biomechanical properties of extracellular and pericellular matrices in situ.