IntroductionInterleukin (IL)-21 is a member of type I cytokine family. Recent studies indicate that IL-21 can promote T follicular helper (Tfh) cell differentiation and survival, a specialized T cell subset which provides help for B cell. It can also regulate the activation, proliferation and differentiation of human B cell and immunoglobulin (Ig) production as well as isotype switching of plasma cell. Rheumatoid arthritis (RA) is characterized by auto-antibodies overproduction such as rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibody, suggesting a pivotal role of Tfh cell and B cell in the pathogenesis of RA. This study aimed to investigate whether IL-21 had a regulatory effect on Tfh cell and B cell in RA.MethodsSerum IL-21 concentrations were measured by ELISA. The correlations between serum IL-21 levels and clinical features of RA patients were analyzed by Spearman's rank test. The percentages of Tfh-like cells, IL-21 receptor (R) expression on Tfh-like cells and B cells in peripheral blood (PB) were analyzed by flow cytometry. Peripheral blood mononuclear cells (PBMC) were stimulated by rIL-21 (100 ng/ml) in the presence or absence of anti-CD40 and/or anti-IgM, and changes of IL-21R, activation-associated surface markers (CD25, CD69 and CD40), the proliferation, apoptosis and differentiation of B cells were analyzed by flow cytometry. Production of IgG and IgM in the culture supernatants was determined by ELISA.ResultsThe results showed that the serum IL-21 levels in RA patients were significantly higher than that of healthy controls (HC). IL-21 concentrations were positively correlated with 28-joint count disease activity score (DAS28) and anti-CCP antibody in RA patients with high IL-21 levels. Furthermore, the frequencies of peripheral CXCR5+PD-1+CD4+ Tfh-like cells markedly increased in RA patients and the percentages of Tfh-like cells were positively correlated with DAS28 and anti-CCP antibody levels. Moreover, elevated IL-21 levels were also correlated with the frequencies of Tfh-like cells. IL-21R expression on both Tfh-like cells and B cells were significantly enhanced in RA patients. In cultures vitro, exogenous IL-21 upregulated IL-21R expression and activation-associated surface markers on B cells and promoted more B cell proliferation in RA than in HC. This IL-21-mediated effect could be reversed by IL-21R-specific neutralizing antibody. Importantly, IL-21 promoted more differentiation of B cell into plasmablast and higher levels of IgG and IgM production in RA than in HC.ConclusionsIncreased serum IL-21 levels in RA patients correlate with DAS28, anti-CCP antibody and frequencies of Tfh-like cells. IL-21 supports B cell activation, proliferation and antibody secretion via IL-21R pathway. Thus, IL-21 may be involved in the pathogenesis of RA and antagonizing IL-21 could be a novel strategy for the therapy of RA.

Mesenchymal stem cells (MSCs) are critical for immune regulation. Although several microRNAs (miRNAs) have been shown to participate in autoimmune pathogenesis by affecting lymphocyte development and function, the roles of miRNAs in MSC dysfunction in autoimmune diseases remain unclear. Here, we show that patients with systemic lupus erythematosus (SLE) display a unique miRNA signature in bone marrow-derived MSCs (BMSCs) compared with normal controls, among which miR-663 is closely associated with SLE disease activity. MiR-663 inhibits the proliferation and migration of BMSCs and impairs BMSC-mediated downregulation of follicular T helper (T) cells and upregulation of regulatory T (T) cells by targeting transforming growth factor β1 (TGF-β1). MiR-663 overexpression weakens the therapeutic effect of BMSCs, while miR-663 inhibition improves the remission of lupus disease in MRL/lpr mice. Thus, miR-663 is a key mediator of SLE BMSC regulation and may serve as a new therapeutic target for the treatment of lupus.Cellular and Molecular Immunology advance online publication, 26 March 2018; doi:10.1038/cmi.2018.1.

Osteoporosis in patients with systemic lupus erythematosus (SLE) is thought to be the result of accelerated osteoclastogenesis induced by pro-inflammatory cytokines such as tumor necrosis factor (TNF). However, the molecular mechanisms involved in the osteoblastogenesis in SLE patients are not fully understood. We investigated the bone morphogenetic protein-2 (BMP-2)-induced osteoblastic capacity of bone marrow-derived mesenchymal stem cells (BMMSCs) from SLE patients and the TNF signaling system in determining BMP-2-induced regulatory pathways. It showed that the capacity of osteogenic differentiation of BMMSCs from SLE patients was reduced compared with that from healthy controls. The nuclear factor kB (NF-kB) signaling was activated while the BMP/Smad pathway was repressed in BMMSCs from SLE patients. TNF activated NF-kB pathway and inhibited the phosphorylation of Smad 1/5/8 and BMP-2-induced osteoblastic differentiation in BMMSCs from normal controls, while addition of pyrollidine dithiocarbamate (PDTC), an NF-kB inhibitor, to SLE-BMMSCs could partially reverse these effects. Thus, our findings have shown that the activated NF-kB pathway in SLE-BMMSCs inhibits the BMP-2-induced osteoblastic differentiation through BMP/Smad signaling pathway, suggesting that the impaired osteoblastic differentiation may participate in the pathology of osteoporosis in SLE patients.

Objective. Mesenchymal stem cells (MSCs) derived from patients with systemic lupus erythematosus (SLE) exhibit enhanced senescence. Cellular senescence has been reported to be induced by several inflammatory cytokines, including interferon-a (IFNa) and IFNg, that are involved in the pathogenesis of SLE. We undertook this study to investigate whether the inflammatory environment in SLE could affect MSC senescence.Methods. Cellular senescence was measured by staining of senescence-associated b-galactosidase and by expression of the cell cycle inhibitors p53 and p21. Eighty cytokines and chemokines in serum from healthy controls and patients with SLE were identified by cytokine antibody array.Results. SLE serum promoted senescence of MSCs, which was reversed by the phosphatidylinositol 3-kinase (PI3K)/Akt signaling inhibitor LY294002 but not by the JAK/STAT inhibitor AG490 and not by the MEK/ERK inhibitor PD98059. Cytokine antibody array analysis revealed that leptin and neutrophil-activating peptide 2 (NAP-2) were the 2 factors most significantly elevated in SLE serum compared with normal serum. Blockade of leptin or NAP-2 in MSC cultures abolished SLE seruminduced senescence, while direct addition of these 2 factors could promote senescence in cultures of normal MSCs. Inhibition of PI3K/Akt signaling with LY294002 reduced leptin-and NAP-2-induced senescence in MSCs.Conclusion. Taken together, our data show that leptin and NAP-2 act synergistically to promote MSC senescence through enhancement of the PI3K/Akt signaling pathway in SLE patients.

Aberrant autophagy played an important role in the pathogenesis of autoimmune diseases, especially in systemic lupus erythematosus (SLE). In this study, we showed that T cells from SLE patients had higher autophagic activity than that from healthy controls. A correlation between autophagic activity and apoptotic rate was observed in activated T cells. Moreover, activation of autophagy with rapamycin increased T cell apoptosis, whereas inhibition of autophagy with 3-MA decreased T cell apoptosis. Umbilical cord-derived mesenchymal stem cells (UC-MSCs) could inhibit respiratory mitochondrial biogenesis in activated T cells to downregulate autophagy and consequently decrease T cell apoptosis through mitochondrial transfer and thus may play an important role in SLE treatment.