GSE173808
The transcriptome of paired major and minor salivary gland tissue in patients with primary Sjögren's syndrome
While all salivary glands (SGs) can be involved in primary Sjögren's syndrome (pSS), their respective role in pathogenesis remains unclear. To assess immunopathway activation in paired parotid and labial gland tissue from biopsy-positive and biopsy-negative pSS and non-SS sicca patients, paraffin-embedded, paired parotid and labial salivary gland tissue and peripheral blood mononuclear cells were obtained from 39 pSS and 20 non-SS sicca patients. The patients were subdivided based on fulfillment of ACR-EULAR criteria and histopathology and the samples were analyzed for differentially expressed genes (DEGs).  The principal component analysis of SG gene expression could only separate biopsy-positive pSS from non-SS sicca patients. However, when comparing the transcriptome of biopsy-positive pSS and biopsy-negative non-SS sicca patients, 1235 and 624 DEGs (FDR<-1 or >1) were identified for parotid and labial glands, respectively. The number of DEGs between biopsy negative pSS and non-SS sicca patients was scarce. The overall, transcript expression levels correlated strongly between parotid and labial glands (R2=0.86, p-value<0.0001). Gene signatures present in both glands of biopsy-positive pSS patients included IFN-a signaling, IL-12/IL-18 signaling, CD3/CD28 T-cell activation, CD40 signaling in B-cells, DN2 B-cells, and FcRL4+ B-cells. Signature scores varied considerably amongst pSS patients. In conclusion, the transcriptomes of paired major and minor SGs in pSS were overall comparable, although significant inter-individual heterogeneity in immunopathway activation existed. The SG transcriptome of biopsy-negative pSS was indistinguishable from non-SS sicca patients. The different patterns of SG immunopathway activation in pSS argue for personalized treatment approaches. Overall design: Differential expression analysis of a cohort of 39 patients with primary Sjogren's syndrome and 20 non-SS sicca patients.