ObjectiveLupus nephritis (LN) is one of the most severe organ manifestations of systemic lupus erythematosus (SLE). Early identification of renal disease in SLE is important. Renal biopsy is currently recognized as the gold standard for diagnosing LN, however, it is invasive and inconvenient for dynamic monitoring. Urine has been considered more promising and valuable than blood in identifying inflamed kidney tissue. Here, we determine whether the signatures of tRNA-derived small noncoding RNA (tsRNA) in urinary exosomes can serve as novel biomarkers for the diagnosis of LN.MethodstsRNA sequencing was performed in exosome extracted from pooled urine of 20 LN patients and 20 SLE without LN, and the top 10 upregulated tsRNAs were screened as candidate markers of LN. The candidate urinary exosomal tsRNAs were primarily elected by TaqMan probe-based quantitative reverse transcription-PCR (RT-PCR) in 40 samples (20 LN and 20 SLE without LN) in the training phase. In the validation phase, selected tsRNAs from the training phase were further confirmed in a larger cohort (54 LN patients and 39 SLE without LN). Receiver operating characteristic curve (ROC) analysis was conducted to evaluate the diagnostic efficacy.ResultsUpregulated levels of tRF3-Ile-AAT-1 and tiRNA5-Lys-CTT-1 in the urinary exosomes were observed in LN compared with SLE without LN (P < 0.0001 and P < 0.001) and healthy controls (P < 0.01 and P < 0.01), with the area under the curve (AUC) of 0.777 (95% CI: 0.681-0.874, sensitivity 79.63%, specificity 66.69%) and 0.715 (95% CI: 0.610-0.820, sensitivity 66.96%, specificity 76.92%) for discriminating LN from SLE without LN patients. SLE patients with mild activity and moderate to severe activity had higher levels of urinary exosome derived tRF3-Ile AAT-1 (P = 0.035 and P < 0.001) and tiRNA5-Lys-CTT-1 (P = 0.021 and P < 0.001) compared with patients with no activity. Moreover, bioinformatics analysis revealed that both of the tsRNAs regulate the immune process by modulating metabolism and signal pathway.ConclusionIn this study, we demonstrated that urinary exosome tsRNAs can be served as noninvasive biomarkers for the efficient diagnosis and prediction of nephritis in SLE.

Although various studies have been performed on the function of polymorphonuclear myeloid‐derived suppressor cells (PMN‐MDSCs) in RA, the results were conflicting. Here we were trying to clarify the role of PMN‐MDSCs in the pathogenesis of RA and its specific mechanisms. We detected the frequencies and counts of PMN‐MDSCs, TNF‐α+ B cells and Ki67+ B cells in spleen and inflamed joints of collagen‐induced arthritis (CIA) mice using flow cytometry. The pathological role of PMN‐MDSCs was examined by anti‐Ly6G neutralizing antibodies against PMN‐MDSCs or adoptive transfer of PMN‐MDSCs. And the modulation of PMN‐MDSCs on B cells was conducted by coculture assays, RNA‐Seq, RT‐qPCR, and so on. The mechanism of BAFF regulating B cells was verified through western blot and flow cytometry. PMN‐MDSCs accumulated in the spleen and joints of CIA mice. PMN‐MDSCs depletion could alleviate the arthritis severity, which was accompanied by decreased TNF‐α secretion and proliferation of B cells. And its adoptive transfer also facilitated disease progress. Furthermore, PMN‐MDSCs from CIA mice had higher expression level of BAFF, which regulated TNF‐α expression, proliferation and apoptosis of B cells in vitro. What's more, BAFF promoted phosphorylation of BTK/NF‐κB signalling pathway. And Ibrutinib (BTK inhibitor) could reverse the effect of BAFF on TNF‐α expression of B cells. Our study suggested that PMN‐MDSCs enhanced disease severity of CIA and manipulated TNF‐α expression, proliferation and apoptosis of B cells via BAFF, furthermore, BAFF promoted TNF‐α expression through BTK/NF‐κB signalling pathway, which demonstrated a novel pathogenesis of PMN‐MDSCs in CIA.