Proteomic Signature of the Murine Intervertebral Disc
Low back pain is the most common musculoskeletal problem, with a lifetime prevalence of 84% in North America. A significant proportion of low back pain is attributed to degeneration of the intervertebral disc. The lack of effective treatment for this widespread problem is directly related to our limited understanding of the biological pathways responsible for maintaining disc tissue health. While transcriptional analysis has permitted some initial insights into the pathways responsible for maintaining disc health, a more complete characterization is required for the development of targeted treatments for disc degeneration. We therefore employed liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) protein/peptide separation and mass spectrometric analyses to identify the total protein content of intervertebral discs from skeletally mature wild-type mice.
A total of 786 proteins were identified and categorized using PANTHER. The proteins identified were primarily intracellular (64%), extracellular (24%) and plasma membrane (5%). Most proteins categorized by molecular function were grouped into three categories: protein binding (29%), catalytic activity (27%) or structural activity (13%). To validate the list of identified proteins, 20 previously identified IVD-associated markers, including matrix proteins, transcriptional regulators, and secreted proteins were queried for. We identified 14 of 20 IVD-associated markers and further confirmed localization of select proteins within the disc by immunohistochemistry. The characterization of the protein composition of healthy intervertebral disc tissue is an important first step in identifying cellular processes and pathways disrupted during aging or disease progression.