Proteomics study on biomarkers for heterotopic ossification secondary to traumatic brain injuries.

Objective: To identify differentially expressed serum proteins that could serve as sensitive biomarkers of heterotopic ossification in patients with traumatic brain injury. Methods: From August 2014 to December 2015, 18 patients with traumatic brain injury were enrolled in the study, and blood samples were collected. Patients with traumatic brain injury were divided based on the presence (n = 9 patients, heterotopic ossification group) or absence (n =9 patients, traumatic brain injury group or control group) of heterotopic ossification. Protein expression profiles were compared using 2-dimensional electrophoresis. Differentially expressed proteins were examined using matrix-assisted laser desorption/ionization and time-of-flight tandem mass spectrometry (MALDI-TOF/TOF). The differentially expressed proteins identified were further confirmed by Western blotting. Results: Seven protein spots were differentially expressed between heterotopic ossification and traumatic brain injury groups in 2-dimensional electrophoresis analysis. Vitamin D binding protein (Gc protein), retinol binding protein 4 (RBP4) and haptoglobin expression decreased significantly in the heterotopic ossification group compared with the control group (p < 0.05), and this was further confirmed by Western blotting. Conclusion: Lower levels of expression of Gc protein, RBP4 and haptoglobin may be closely related to heterotopic ossification after traumatic brain injury. These proteins may be potential biomarkers of heterotopic ossification secondary to traumatic brain injury.