Abstract: BACKGROUND: Cervical spondylotic myelopathy is the most severe type of cervical spondylosis, yet its specific serum biomarkers that can distinguish it from healthy individuals remain unclear.  
OBJECTIVE: To analyze the differential expression of serum proteins between patients with cervical spondylotic myelopathy of Qi deficiency and blood stasis type and healthy individuals using isobaric tags for relative and absolute quantification (iTRAQ), and to screen and identify potential serum biomarkers for this condition.  
METHODS: Serum samples were collected from 13 patients with cervical spondylotic myelopathy of Qi deficiency and blood stasis type and 8 healthy individuals. Proteomic analysis was performed using iTRAQ with liquid chromatography-tandem mass spectrometry. Functional annotation and pathway enrichment analysis of differentially expressed proteins were conducted using bioinformatics methods to reveal their potential biological significance and involved signaling pathways.  
RESULTS AND CONCLUSION: (1) Mass spectrometry analysis identified a total of 78 differentially expressed proteins (P < 0.05). Compared with healthy individuals, 12 differential proteins, including vasodilator-stimulated phosphoprotein, multiple epidermal growth factor-like domains protein 9, complement factor H-related protein 3, and mitogenin A, were significantly upregulated, while 66 differential proteins, including transferrin, cartilage intermediate layer protein 2, fibronectin, and fibrinogen beta chain, were significantly downregulated. (2) These differentially expressed proteins were primarily involved in various biological processes such as nucleic acid transport and protein activation cascade, and exhibited molecular functions including protein kinase B binding, immunoglobulin receptor binding, and translation elongation factor activity. They were associated with seven signaling pathways, including mineral absorption, oxidative phosphorylation, and platelet activation. (3) Among the differentially expressed proteins in the serum of patients with cervical spondylotic myelopathy of Qi deficiency and blood stasis type compared with healthy individuals, IGLC2, IGLC7, IGLL5, IGLV2-8, IGLV3-25, and IGKV3D-11 showed extensive interactions with other proteins in the functional network. (4) Validation of the differentially expressed protein IGLC2 using western blot yielded results consistent with the proteomics analysis. To conclude, these findings indicate that iTRAQ combined with liquid chromatography-tandem mass spectrometry successfully screened differentially expressed proteins between patients with cervical spondylotic myelopathy of Qi deficiency and blood stasis type and healthy individuals, and preliminarily suggest that seven proteins, including IGLC2, IGLL5, and IGLV3-25, may serve as specific serum biomarkers for this population.  

Key words: cervical spondylotic myelopathy, proteomics, isobaric tags for relative and absolute quantification, serum biomarkers, Qi deficiency and blood stasis