Proteomics Differentiate Between Thyroid-Associated Orbitopathy and Dry Eye Syndrome

Purpose: In patients with thyroid-associated orbitopathy (TAO), the dry eye syndrome occurs frequently, and symptoms and signs of both disorders overlap making early and accurate differential diagnosis difficult. A differentiation via specific markers is warranted.

Methods: Tear fluid samples of 120 subjects with TAO, TAO + dry eye, dry eye, and controls were collected. The samples were measured using matrix-assisted laser desorption ionization mass spectrometry. The identified proteins were tested with antibody microarrays.

Results: Proteomics identified deregulated proteins in TAO and dry eye. Compared with dry eye, proline-rich protein 1 (PROL1, P = 0.002); uridine diphosphate (UDP)-glucose-dehydrogenase (UGDH, P = 0.017); calgranulin A (S10A8, P < 0.0001); transcription-activator BRG1 (SMCA4, P < 0.0001); annexin A1 (P = 0.007); cystatin (P = 0.009); heat shock protein 27 (P = 0.03); and galectin (P = 0.04) were markedly downregulated in TAO. Compared with healthy controls, PROL1 (P < 0.05.); proline-rich protein 4 (PRP4, P < 0.05), S10A8 (P = 0.004) and SMCA4 (P = 0.002) were downregulated in TAO. In contrast, the proteins midasin and POTE-ankyrin-domain family-member I were upregulated in TAO versus healthy controls (P < 0.05). Protein dysregulation was associated with inflammatory response and cell death. Antibody microarray confirmed significant changes of PRP4, PROL1, and UGDH between TAO and dry eye or healthy controls (P < 0.01). The presence of these three proteins was negatively correlated with smoking (P < 0.05).

Conclusions: Proteomics of tear fluid demonstrated an upregulation of inflammatory proteins versus a downregulation of protective proteins in TAO, and a significantly different protein panel in TAO versus dry eye and/or controls. The spectrum of inflammatory and protective proteins might be a useful indicator for disease activity and ocular surface disease in patients with TAO.