Localization and Distribution of Cartilage Oligometric Matrix Protein in Spine

Introduction: Cartilage oligomeric matrix protein (COMP) is an important structural component of extracellular matrix [1]. Previous reports have shown that it is primarily localized to articular cartilage, with presence also found in tendon, ligament, and synovium. Its importance is suggested by its association with several pathological conditions. COMP distribution and degradation rates are altered in human rheumatoid and osteoarthritic cartilage [2]. Altered levels of COMP and its degradation products in serum and synovial fluid have been proposed to be used as markers for cartilage destruction in osteoarthritis and rheumatoid arthritis [2,3]. The importance of COMP to cartilage structure and function is further underscored by findings that COMP mutations lead to human skeletal dysplasias, pseudoachondroplasia, and multiple epiphyseal dysplasia, including Fairbanks and Ribbing types [4,5]. These dysplasias are due to mutations in residues in the type 3 calcium-binding repeats and COOHterminal globular region of COMP which lead to the misfolding of the protein [6]. Patient's spine also show characteristic platyspondyly [4,5], especially in childhood, suggesting that COMP plays a role in maintaining normal spine structure and function. However, the distribution and role of COMP in spine has not been investigated. The purpose of this study is to investigate the distribution of COMP in normal spine with emphasis on intervertebral disc localization.