Proteomic analysis for the identification of serum diagnostic markers for joint hypermobility syndrome

Joint hypermobility syndrome (JHS) (also termed Ehlers-Danlos syndrome, hypermobility type) is a heritable connective tissue disorder which is characterized by generalized joint hypermobility, chronic pain, dizziness, fatigue, and minor skin changes. However, it has yet to be determined in patients with JHS whether specific genetic factors are involved in the risk of developing the disorder. Therefore, interventions have been limited to symptomatic treatments, and biomarkers for diagnosis and therapy have not yet been identified. In the present study, to identify potential serum biomarkers for JHS, we examined proteins with differential levels in sera from patients with JHS and in sera from control individuals using isobaric tags for relative and absolute quantitation (iTRAQ) labeling in combination with nano LC-MALDI-TOF/TOF-MS/MS followed by ProteinPilot analysis. In the sera of patients with JHS, a total of 106 proteins with differential levels were identified, and they were further narrowed down to 6 proteins (p<0.05, patient vs. control). Of the 6 proteins, proteins involved in the complement system including complement C1r subcomponent (C1R), vitronectin (VTN), complement component C9 (C9), and C4b-binding protein alpha chain (C4BPA) were identified as increased proteins in sera from patients with JHS compared with those in sera from controls. We confirmed increased levels of C1R and VTN in sera from patients with JHS by western blot analyses. The results indicate the possibility of a locally occurring inflammatory process in patients with JHS.