Affiliation: Department of Orthopaedic and Trauma Surgery, Campus Bio-Medico University, Via Alvaro del Portillo, 200, 00128 Trigoria, Rome, Italy.
Background: Fibronectin, a large dimeric plasma glycoprotein found only in vertebrates, is a core component of several extracellular matrices. Integrin receptors regulate different cell activities. Fibronectin expression patterns in intervertebral disc have not been extensively studied. The aim of this study was to evaluate the distribution of fibronectin in the different regions of the intervertebral disc, and in intervertebral discs of different levels of monkeys. Methods: Spines of nine 3-4 year-old cynomolgus monkeys (Macaca fascicularis) were studied. From every spine, 5 vertebral motion segments were sectioned (C5-C6, T3-T4, T9-T10, L2-L3, L4-L5) producing forty-five vertebral motion segments. These were bisected in the sagittal plane. Immunohistochemical studies were performed using specific antibodies to detect fibronectin. Results: A positive immunoreaction for fibronectin was found in the endplates, in the peripheral annulus fibrosus, and in the longitudinal ligaments. There was no fibronectin immunoreactivity in the nucleus pulposus and in the central annular region close to the nucleus pulposus. There were no differences in immunoreactivity to fibronectin among discs of different levels and discs of different monkeys. Conclusions: Fibronectin may exert a role in the organization of the extracellular matrix of the intervertebral discs. Identifying the structural features of the intervertebral disc extracellular matrix may help to understand the mechanisms of intervertebral disc pathology.