Microvesicles are small, right-side out cell-secreted vesicles of about 30-100 nm, derived from fusion of multivesicular bodies to plasma membranes. Beyond their characteristic repertoire of surface markers, they feature a wide range of surface and internal proteins specific to their source, and recent studies found that they can also transport mRNA and microRNA (miRNA). We developed and optimized protocols for the routine isolation of microvesicles (most of them being exosomes, based on surface markers and electromicroscopy) from both whole and glandular saliva and we showed that microvesicles can be readily isolated from saliva, and that they contain miRNAs in quantities adequate for both qPCR and microarray hybridization. We also successfully hybridized microRNA microarrays with microRNAs isolated from salivary microvesicles from a healthy volunteer and a Sjogren's syndrome patient as a proof of concept. We are currently in the process of further and more extensively characterizing the small nucleic acid content of microvesicles since salivary microvesicular miRNAs may be valuable not only as a diagnostic tool but may also provide an insight in the role miRNAs play in the underlying pathophysiologic processes of various salivary gland diseases. Among others they may help understanding if specific miRNAs are involved abnormalities in saliva production or regulation of the peripheral inflammatory response in the salivary gland and oral characteristic of Sjogren's syndome. Exosomal miRNA analysis may also be valuable in understanding the pathogenesis of salivary gland tumors as a number of studies have identified miRNA dysregulation as a characteristic marker in cancer cell proliferation in vivo have found distinctive exosomal miRNA profiles in blood plasma, urine, and other fluids. In summary, isolation of salivary gland derived microvesicle miRNAs holds the promise of focused biomarker discovery for pathologies that directly or indirectly affect the salivary glands.
