BackgroundAntiphospholipid syndrome (APS) is a systemic autoimmune disease that can lead to thrombosis and/or pregnancy complications. Exosomes, membrane-encapsulated vesicles that are released into the extracellular environment by many types of cells, can carry signals to recipient cells to affect angiogenesis, apoptosis, and inflammation. There is increasing evidence suggesting that exosomes play critical roles in pregnancy. However, the contribution of exosomes to APS is still unknown.MethodsPeripheral plasma was collected from healthy early pregnancy patients (NC-exos) and early pregnancy patients with APS (APS-exos) for exosome extraction and characterization. The effect of exosomes from different sources on pregnancy outcomes was determined by establishing a mouse pregnancy model. Following the coincubation of exosomes and human umbilical vein endothelial cells (HUVECs), functional tests examined the features of APS-exos. The APS-exos and NC-exos were analyzed by quantitative proteomics of whole protein tandem mass tag (TMT) markers to explore the different compositions and identify key proteins. After incubation with HUVECs, functional tests investigated the characteristics of key exosomal proteins. Western blot analysis was used to identify the key pathways.ResultsIn the mouse model, APS-exos caused an APS-like birth outcome. In vitro experiments showed that APS-exos inhibited the migration and tube formation of HUVECs. Quantitative proteomics analysis identified 27 upregulated proteins and 9 downregulated proteins in APS-exos versus NC-exos. We hypothesized that apolipoprotein H (APOH) may be a core protein, and the analysis of clinical samples was consistent with finding from the proteomic TMT analysis. APOH-exos led to APS-like birth outcomes. APOH-exos directly enter HUVECs and may play a role through the phospho-extracellular signal-regulated kinase pathway.ConclusionsOur study suggests that both APS-exos and APOH-exos impair vascular development and lead to pregnancy complications. APOH-exos may be key actors in the pathogenesis of APS. This study provides new insights into the pathogenesis of APS and potential new targets for therapeutic intervention.

BackgroundExosomes are small membrane vesicles (40–150 nm) of endocytic origin secreted by many types of cells and engage in cell-to-cell communication by transferring proteins, microRNAs, mRNA, and lipid to recipient cells. Exosomes are also identified in various biological fluids including blood, urine, amniotic fluid, saliva, malignant ascites, and synovial fluid. Until now, the role of exosomes from synovial fluid (SF) on human osteoclastogenesis is unknown.ObjectivesWe aimed to identify the characteristics of synovial exosomes and evaluate the effects on human osteoclastogenesis.MethodsSynovial exosomes were isolated from SF of rheumatoid arthritis (RA), osteoarthritis (OA), ankylosing spondylitis (AS), and gout patients using ExoQuick (System Biosciences, USA). Monocytes were isolated from human peripheral blood mononuclear cell and were differentiated into macrophages by treatment of 20 ng/ml recombinant human macrophage colony-stimulating factor (M-CSF) for 3–4 days. Then, macrophages were incubated with synovial exosomes in alpha-MEM supplemented with 10% FBS and 1% penicillin/streptomycin for 9–10 days. Osteoclast differentiation was evaluated by tartrate resistant acid phosphatase stain. Exosomes from RA (n=11), OA (n=5), AS (n=6), and gout (n=6) patients were quantified by measuring acetylcholinesterase activity in colorimetric assay.ResultsThe number of synovial exosomes isolated from same volume of SF from RA, OA, AS, and gout patients was assessed. We found that exosomes are abundant in SF of RA, AS, and gout patients compared to OA patients. (mean ± SEM 7.36×107±1.35×107, 9.91×107±2.50×107, 7.50×107±2.17×107 vs. 2.66×107±0.42×107). Interestingly, the number of exosomes from AS SF was significantly higher (by 3.72 fold, p=0.0476) than exosomes from OA SF. Exosomes from RA, OA, AS, and gout patients induced proliferation and osteoclast formation without M-CSF and receptor activator of nuclear factor kappa-B ligand (RANKL) (Figure 1), which is essential to proliferation and differentiation of osteoclast. Noticeably, exosomes from RA SF had higher potential on osteoclast differentiation than other three diseases. (20.28±14.28 fold vs. 2.38±0.42 fold).ConclusionsOur results suggest that exosomes from SF of various inflammatory diseases might have differential functional roles in osteoclast differentiation and the number of exosomes may be associated with inflammatory conditions.ReferencesL. Raimondi et al. Oncotarget 2015 May 30; 6(15): 13772–13789C Théry et al. Nat Rev Immunol 2002 Aug; 2(8): 569–579RJ Simpson J et al. Proteomics 2008 Oct; 8(19): 4083–4099Disclosure of InterestNone declared