Proteoglycans Quantification in Tissue Engineered Cartilage using Sodium MRI at 11.7 T

Musculoskeletal disorders affect nearly 33% Americans annually, with injuries to cartilage due to osteoarthritis and sports injuries, accounting for a large fraction of these afflictions. There are currently no effective long-term treatments and cartilage tissue engineering is expected to play a leading role in cartilage treatment. Cartilage tissue engineering relies on the production of collagen and proteoglycans (PG), the two major extracellular matrix components of cartilage, as biomarkers for success. The current characterization and quantification methods for these biomarkers, such as histology and biochemical analyses, are invasive and cannot be performed in vivo. As sodium is known to bind with negatively charged PG, sodium MRI has potential to be used for PG quantification in tissue engineered cartilage. In this study, we present preliminary results of sodium MRI using a) Phantoms with 150 mM, 300 mM, and 500 mM sodium concentration prepared in 1% agarose gel and b) Scaffold free bovine chondrocyte pellets grown in culture medium for four weeks. Sodium MRI experiments were performed at room temperature on an 11.7 T Bruker Avance spectrometer (23Na freq = 132.30 MHz) using a 5 mm proton-sodium double tuned rf coil. Our preliminary results show that the sodium concentration changes correlate with sodium image intensity, which suggests a potential use of sodium MRI for PG quantification for tissue engineered cartilage.