Identification of novel salivary biomarkers for chronic periodontitis

Objectives: This study aimed to compare selected protein profiles of whole saliva from patients with chronic periodontitis and healthy subjects, to identify and characterize novel salivary biomarkers for chronic periodontitis.
Methods: Salivary levels of 102 cytokines and 34 proteases were measured using Proteome Profiler Arrays (PPA, R&D Systems). PPA assays were performed on saliva from 12 patients with untreated chronic periodontitis and 12 healthy volunteers. Protein expression on PPA membranes was quantified using image analyser software. PPA data was confirmed by enzyme-linked immunoassay (ELISA).
Results: Overall analysis of salivary PPA revealed that; 75 of 102 cytokines were positively expressed in both groups (63 were higher in the patients, compared to 12 highly expressed cytokines in the healthy volunteers). Similarly, 24 proteases were higher in the patient group and 10 higher in the healthy volunteers. Interleukins and matrix metalloproteases such as IL-1β, MMP-8 and MMP-9, which are previously identified biomarkers associated with periodontal diseases, were detected along with several novel proteins. Urokinase plasminogen activator (uPA) which is a serine protease enzyme involved in MMP activation, extracellular matrix proteins degradation, inflammation and tissue repair, was identified as a candidate salivary biomarker. ELISA results revealed that salivary uPA levels in the patients ranged between 360.03-4196.88 pg/ml, which were significantly higher than in saliva from the healthy subjects (31.65-632.48 pg/ml, p < 0.001).
Conclusions: PPA assays can be used to identify salivary biomarkers, an approach that may contribute positively to the diagnosis of periodontal diseases. Salivary uPA is a candidate biomarker for chronic periodontitis.