Differential expression of miR-17-92 cluster among varying histological stages of minor salivary gland in patients with primary Sjögren's syndrome.

OBJECTIVES

To investigate the differential expression of miR-17-92 cluster, which encodes 6 microRNAs (miR-NAs) including miR-17, miR-18a, miR-19a, miR-19b, miR-20a and miR-92a, among varying histological stages of labial minor salivary gland (MSG) tis- sues in patients with primary Sjögren's syndrome (pSS).

METHODS

Fifty-seven pSS patients and 13 healthy volunteers were enrolled in this study. The pSS patients were allocated to 3 subgroups of advanced clinical stages according to the histological findings of the MSG biopsies. Salivary flow rate, Schirmer test and some laboratory indexes were also tested. The expression levels of the 6 miRNAs in MSG were evaluated using quantitative real-time polymerase chain reaction with TaqMan miRNA assay.

RESULTS

The differences between the healthy individuals and the 3 pSS subgroups were statistically significant for positive findings of salivary flow rate, Schirmer test and laboratory indexes. In the labial MSG tissues, we observed that the expression level of miR-18a was significantly up-regulated in patients of the 3 pSS subgroups compared to healthy individuals, while the expression level of miR-92a was significantly down-regulated. We also observed that there was no notable difference in the expression levels of miR-17, miR-19a, miR-19b, and miR-20a. Furthermore, we distinguished that miR-18a was progressively up-regulated along the advanced histological stages of the 3 pSS subgroups, while the miR-92a was progressively down-regulated.

CONCLUDIONS: This is the first study on the expression of the miR-17-92 cluster in MSG of pSS patients. The association of increased expression levels of miR-18a and reduced expression levels of miR-92a with advanced clinical stages of pSS could significantly reduce the substantial subjectivity of scoring inflammatory infiltrates and may aid in the diagnosis of pSS.