Background and ObjectiveBone erosion is common in patients with gout. The role of neutrophil-derived exosomes in gouty bone erosion remains elusive. This study aimed to investigate the functions of the neutrophil-derived exosomes in the development of bone erosion in gout.MethodsNeutrophil-derived exosomes were collected and assessed by transmission electron microscopy and nanoparticle tracking analysis. Cell counting kit-8 assay was applied to evaluate cell viability, and cell apoptosis was assessed by flow cytometry. In addition, quantitative Real-time PCR and Western blotting were used to determine the expression levels of alkaline phosphatase (ALP), osteoprotegerin (OPG), and receptor activator of nuclear factor-κB ligand (RANKL). Neutrophil-derived exosomes were tagged with PKH67. The miRNA expression profiles of exosomes and human fetal osteoblasts (hFOB) were compared using high-throughput sequencing. Functional miRNAs transfected into hFOB after co-incubation with exosomes were selected and validated by preliminary qPCR.ResultsNeutrophil-derived exosomes were stimulated by monosodium urate (MSU). The exosomes could inhibit the viability of the hFOB, and the expression levels of ALP and OPG were down-regulated, while the expression level of RANKL was up-regulated. However, there was no significant difference in the viability of osteoclasts and the expression of nuclear factor of activated T cells 1. Exosomes were observed in the cytoplasm under a confocal microscopy, confirming that exosomes could be taken up by hFOB. In total, 2590 miRNAs were found, of which 47 miRNAs were differentially expressed. Among the delivered miRNAs, miR-1246 exhibited the highest level of differential expression. The viability of hFOB was reduced by miR-1246 mimics and increased by miR-1246 inhibitors. There was no significant difference in hFOB apoptosis rate between the miR-1246 mimic and miR-1246 inhibitor group. MiR-1246 overexpression decreased the expression levels of ALP and OPG, whereas increasing the expression level of RANKL. In contrast, miR-1246 inhibitor increased the expression levels of ALP and OPG, while decreasing the expression level of RANKL. Neutrophil-derived exosomes stimulated by MSU could increase the expression of miR-1246. ConclusionNeutrophil-derived exosomes stimulated by MSU could inhibit the viability of osteoblasts.

Microscopic polyangiitis (MPA) is a systemic small-vessel vasculitis associated with anti-neutrophil cytoplasmic antibody (ANCA) and predominantly causes kidney and pulmonary injuries. Subarachnoid hemorrhage, a life-threatening manifestation of the central nervous system (CNS), rarely occurs in patients with ANCA-associated vasculitis (AAV). We report the case of a young man with spontaneous SAH recurrence and active nephritis. The patient was treated with a glucocorticoid pulse and intravenous cyclophosphamide (CTX) in combination with decreasing cerebral perfusion pressure and analgesic therapy. All the patients’ symptoms except the proteinuria resolved. We reviewed the clinical characteristics of 34 previously reported cases of SAH with AAV, comprising six cases of MPA, eight cases of granulomatosis with polyangiitis (GPA), and 19 cases of eosinophilic granulomatosis with polyangiitis (EGPA), and one case of unclassified AAV. All the cases showed features of active vasculitis. Concomitant nephritis and peripheral neuropathy were found in the MPA and EGPA cases with SAH, respectively. Renal and pulmonary manifestations were predominant in the patients with GPA and SAH. Ten patients had aneurysmal abnormalities, and six patients had cardiac abnormalities. Thirty-one patients were treated with glucocorticoids, and 18 patients received concurrent immunosuppressants. Patients with SAH had a mortality rate of 38.2%. The presence of cerebrovascular events or cardiac involvement in patients with AAV and SAH is associated with increased mortality of 64.3%. Our study indicates that SAH should be cautioned as a disease occurring in patients with AAV. Early diagnosis with aggressive immunosuppressive therapy can help improve the prognosis of patients with SAH.