Salivary Protein Profile in Patients with Recurrent Aphthous Stomatitis: A Pilot Proteomic Study

Recurrent aphthous stomatitis (RAS) is the most common ulcerative disorder of the oral cavity, although its etiology is still unknown. The present study aimed to identify the proteomic profile associated with the RAS inflammatory process, thereby enhancing our understanding of its etiopathogenesis. We compared salivary protein profiles of RAS patients during an active episode of oral ulceration (30 patients, mean age 36.9) to those from healthy donors without a history of RAS (30 healthy subjects, mean age 37.9). Using 2D-electrophoresis and mass spectrometry (MALDI-TOF) analysis, we identified 17 proteins that were differentially expressed in the two groups. Notably, Cystatin SN (CST1) appeared to be significantly downregulated in RAS patients. These findings were validated by Western blot analysis: CST1 was detected in only 3 of the 30 RAS cases, while it was strongly expressed in all the healthy subjects. Although preliminary, our results suggest a potential role for CST1 in the etiopathogenesis of RAS. Interestingly, the relative absence of CST1 in RAS patients seems to align with some clinical and molecular features of this disease.