Structural analysis of cartilage proteoglycans and glycoproteins using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Cartilage extracellular matrix molecules synthesized and maintained by chondrocytes form a strong, elastic tissue functioning to cushion and protect the subchondral bone. Osteoarthritis is characterized by degradation of cartilage extracellular matrix molecules resulting in fibrillation, irreversible erosion, and eventual failure of the tissue. With recent interest in the degradation of cartilage extracellular matrix molecules, a need for more detailed structural information exists. Posttranslational modifications are believed to play a role in determining the susceptibility of these molecules to proteolytic degradation during the development of osteoarthritis. The purpose of this paper is to show how the application of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry to extracellular matrix protein and proteoglycan structure will help elucidate problems in extracellular matrix biochemistry. Methodological issues relating to the high molecular weight, polydispersity, and high degree of posttranslational modification of these molecules are discussed. MALDI-TOF mass spectrometry provides an improved level of detail for extracellular matrix protein and proteoglycan structure and is useful in addressing issues surrounding the causes of degradation during osteoarthritis.