Objective: Primary Sjögren’s syndrome (pSS) is a systemic autoimmune disease, and its pathogenetic mechanism is far from being understood. In this study, we aimed to explore the cellular and molecular mechanisms that lead to pathogenesis of this disease.Methods: We applied single-cell RNA sequencing (scRNA-seq) to 57,288 peripheral blood mononuclear cells (PBMCs) from five patients with pSS and five healthy controls. The immune cell subsets and susceptibility genes involved in the pathogenesis of pSS were analyzed. Flow cytometry was preformed to verify the result of scRNA-seq.Results: We identified two subpopulations significantly expand in pSS patients. The one highly expressing cytotoxicity genes is named as CD4⁺ CTLs cytotoxic T lymphocyte, and another highly expressing T cell receptor (TCR) variable gene is named as CD4⁺ TRAV13-2+ T cell. Flow cytometry results showed the percentages of CD4⁺ CTLs, which were profiled with CD4⁺ and GZMB⁺ staining; the total T cells of 10 patients with pSS were significantly higher than those of 10 healthy controls (P= 0.008). The expression level of IL-1β in macrophages, TCL1A in B cells, as well as interferon (IFN) response genes in most cell subsets was upregulated in the patients with pSS. Susceptibility genes including HLA-DRB5, CTLA4, and AQP3 were highly expressed in patients with pSS.Conclusions: Our data revealed disease-specific immune cell subsets and provided some potential new targets of pSS. Specific expansion of CD4⁺ CTLs may be involved in the pathogenesis of pSS, which might give valuable insights for therapeutic interventions of pSS.

Background/Aims: Circular RNAs (circRNAs) compose a large class of RNAs that can be used as biomarkers in clinical blood samples. This study aimed to determine the expression of circRNAs in peripheral blood mononuclear cells (PBMCs) from rheumatoid arthritis (RA) patients to identify novel biomarkers for RA screening. Methods: We started with a microarray screening of circRNA changes in PBMCs from 5 RA patients and 5 healthy controls. We then confirmed the selected circRNA changes in PBMCs from 30 RA patients and 25 age- and sex-matched controls using the real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Spearman correlation test was performed to assess the correlation of circRNAs and clinical variables. Receiver operating characteristic (ROC) curve was calculated to evaluate the diagnostic value. Results: We identified and verified five circRNAs (092516, 003524, 103047, 104871, 101873) that were significantly elevated in PBMCs from RA patients. Among these RA patients, we detected no significant correlation between the five circRNAs and the disease severity, including disease activity score (DAS28), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and health assessment questionnaire (HAQ). Yet, ROC curve analysis suggested that circRNA_104871 has significant value of RA diagnosis (AUC=0.833, P<0.001), followed by circRNA_003524 (AUC = 0.683, P = 0.020), circRNA_101873 (AUC = 0.676, P = 0.026), and circRNA_103047 (AUC = 0.671, P = 0.030). Conclusions: This study suggests that increased expression of circRNAs circRNA_104871, circRNA_003524, circRNA_101873 and circRNA_103047 in PBMC from RA patients may serve as potential biomarkers for RA patient diagnosis.

Dysregulation of circular RNAs (circRNAs) is involved in various human diseases. Fibroblast-like synoviocytes (FLSs), which form the lining of the joint, are epigenetically imprinted with an aggressive phenotype and contribute to joint destruction in rheumatoid arthritis (RA). In the present study, we identified a novel circRNA, Circ_0088194, which was upregulated in RA fibroblast-like synoviocytes (RA-FLSs) and correlated with the disease activity score in 28 joints. Overexpression of Circ_0088194 promoted RA-FLS migration and invasion, while inhibition of Circ_0088194 had the opposite effect. Mechanistically, Circ_0088194 acted as a miR-766-3p sponge to relieve the repressive effect of miR-766-3p on its target, MMP2 (encoding matrix metalloproteinase 2), thereby promoting migration and invasion. The expression level of Circ_0088194 was inversely correlated with that of miR-766-3p in RA-FLSs. Importantly, overexpression of miR-766-3p partially blocked the migration and invasion induced by Circ_0088194 overexpression. Collectively, this study identified a novel circRNA Circ_0088194 that promotes RA-FLS invasion and migration via the miR-766-3p/MMP2 axis. Circ_0088194 might represent a novel therapeutic target to prevent and treat RA.

The culture of synovial fibroblasts (SFs) is one of the most effective tools for investigating the pathology and physiology of synovial tissues and should prove useful for identifying the importance of SFs in disease as well as for the development of novel therapeutic approaches for several chronic joint diseases, such as rheumatoid arthritis. However, thus far, a detailed protocol for the primary culture and isolation of murine SFs has not been established. Therefore, the present study describes an easy and convenient method for isolating and culturing SFs from C57BL/6 mice. This protocol can be divided into 4 stages: Isolation of synovial tissues, isolation of SFs, seeding of SFs for growth in culture and purity analysis of SFs using the four cell markers, vimentin, cluster of differentiation 90.2 (CD90.2; Thy‑1.2), intracellular adhesion molecule 1 (CD54) and vascular cell adhesion molecule 1 (CD106). This method is efficient and a purified population of SFs can be obtained 10 days after the initiation of culture.