T1–T2 Correlation and Biopolymer Diffusion Within Human Osteoarthritic Cartilage Measured with Nuclear Magnetic Resonance

Abstract

Cartilage is a load-bearing tissue that provides smooth articulation during motion of human joints like the knee and hip. Cartilage deterioration in the form of osteoarthritis (OA) causes painful joint motion in more than 100 million patients worldwide, and thus there is great interest in improving our understanding of cartilage to further clinical treatment. Previous studies have examined many aspects of cartilage mechanics, including the flow of interstitial water and repulsion of neighboring glycosaminoglycan chains. However, the contributions of specific molecules to overall tissue properties remain unclear. In this study, we use nuclear magnetic resonance (NMR) diffusometry and relaxometry to examine the molecular dynamics of water and cartilage polymers in OA human articular cartilage. To our knowledge, this is the first identification of two macromolecular populations corresponding to collagen and proteoglycan in human cartilage through their diffusive properties. Further, we performed NMR T₁–T₂ correlation studies on human cartilage and observed two populations of water distinguished by differing NMR relaxation corresponding to a solid-like component and a liquid-like component. These results provide fundamental insight on the water behavior and polymeric interactions that drive the functional mechanics of cartilage. This study provides a basis to both expand our understanding of basic cartilage mechanics and provide molecular dynamics data for design of novel biomaterials to improve joint health.