MALDI-TOF MS profiling in the discovery and identification of salivary proteomic patterns of temporomandibular joint disorders

This research aimed to identify differences in polypeptide/protein profiles of the unstimulated whole saliva between patients with temporomandibular joint disorders (TMDs) and healthy individuals. A fraction of the polypeptides/proteins (<30 kDa) was analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The spectra were recovered from methanoic acid/acetonitrile salivary samples overlaid with an alpha-cyano-4-hydroxy-cinnamic acid matrix in positive linear mode at an interval of 1,500-20,000 m/z mass acquisition range. The data were analyzed for the selection of characteristic peaks by using the ClinProTools 3.0 software. Discriminative classification models were generated by using a quick classifier, supervised neural network, and genetic algorithms. From the 23 peaks exhibiting the highest discriminatory power, the ten top-scored peaks with the area under the receiver operating characteristic >0.8 were selected. A panel of salivary markers that predicted the patients with TMDs was selected (2728.0, 4530.2, 5174.2, 5193.3, 6303.4, 6886.7, 8141.7, 8948.7, 10663.2, 10823.7 and 11009.0 m/z). Although carried out on relatively small datasets, the classification algorithm used in this study allows the differentiation between salivary samples from subjects with TMDs and healthy individuals and confirms the usefulness of a proteomic profiling approach in the monitoring of the disease.