Proteomic analysis of human saliva: An approach to find the marker protein for ovulation

Human saliva contains numerous molecules that play a variety of roles. Among them there are proteins which serve as biomarkers of various physiological and/or pathological conditions. Compared to other body fluids, saliva is the most convenient material for investigations, and especially for monitoring the disease conditions. Presently, there is an increasing need to develop a noninvasive method to identify the time of ovulation in humans to ensure successful fertilization, and for evolving strategies for family planning. The present investigation has been an attempt to identify one or more proteins in the human saliva that would be an indicator(s) of ovulation. SDS-PAGE of salivary proteins showed seven prominent bands during the different phases of the menstrual cycle. Particularly, the 14.5kDa band was highly expressed during the ovulatory phase. Eleven proteins were identified in this band of which ten were highly specific to the ovulatory phase. Among those proteins the intense expression of Cystatin-S was validated using immunoblot analysis (p<0.05). The functional annotation of salivary proteins revealed a high percentage of proteins that engage in binding and regulatory activities. The present results indicate that salivary proteins, particularly those present during the ovulatory phase, might be used as biomarkers for impending ovulation.