This is the first report that oral delivery of BMEVs ameliorates experimental arthritis and this warrants further research to determine whether this beneficial effect can be seen in rheumatoid arthritis patients.

ScopeExtracellular vesicles, including exosomes, have been identified in all biological fluids and rediscovered as an important part of the intercellular communication. Breast milk also contains extracellular vesicles and the proposed biological function is to enhance the antimicrobial defense in newborns. It is, however, unknown whether extracellular vesicles are still present in commercial milk and, more importantly, whether they retained their bioactivity. Here, we characterize the extracellular vesicles present in semi-skimmed cow milk available for consumers and study their effect on T cells.Methods and ResultsExtracellular vesicles from commercial milk were isolated and characterized. Milk-derived extracellular vesicles contained several immunomodulating miRNAs and membrane protein CD63, characteristics of exosomes. In contrast to RAW 267.4 derived extracellular vesicles the milk-derived extracellular vesicles were extremely stable under degrading conditions, including low pH, boiling and freezing. Milk-derived extracellular vesicles were easily taken up by murine macrophages in vitro. Furthermore, we found that they can facilitate T cell differentiation towards the pathogenic Th17 lineage. Using a (CAGA)12-luc reporter assay we showed that these extracellular vesicles carried bioactive TGF-β, and that anti-TGF-β antibodies blocked Th17 differentiation.ConclusionOur findings show that commercial milk contains stable extracellular vesicles, including exosomes, and carry immunoregulatory cargo. These data suggest that the extracellular vesicles present in commercial cow milk remains intact in the gastrointestinal tract and exert an immunoregulatory effect.

ObjectiveRheumatoid arthritis (RA) is a chronic and progressive joint disease. It appears that anti-inflammatory feedback mechanisms that could restrain joint inflammation and restore homeostasis are insufficient to perform this control. In this study, we investigated the contribution of the MER tyrosine kinase-mediated anti-inflammatory response on arthritis and whether targeting MER could be a valid approach to treat RA.MethodsKRN serum transfer arthritis (KRN STA) was induced in either Mertk-deficient mice or in mice that adenovirally overexpressed Pros1. Human synovial micromasses were treated with MER-specific antibodies or PROS1. Collagen-induced arthritis (CIA) mice were treated with MER-specific agonistic antibodies or by viral overexpression of Pros1.ResultsMertk−/− mice showed exacerbated arthritis pathology, whereas Pros1 overexpression diminished joint pathology in KRN STA. Human synovial micromasses challenged with MER-specific antibodies enhanced the secretion of inflammatory cytokines, whereas stimulating MER with PROS1 reduced the secretion of these cytokines, confirming the protective role of MER. Next, we treated CIA mice with MER-specific agonistic antibodies, and this unexpectedly resulted in exacerbated arthritis pathology. This was associated with increased numbers of apoptotic cells in their knee joints and higher serum levels of interleukin (IL)-16C, a cytokine released by secondary necrotic neutrophils. Apoptotic cell numbers and IL-16C levels were enhanced during arthritis in Mertk−/− mice and reduced in Pros1-overexpressing mice.ConclusionMER plays a protective role during joint inflammation and activating MER by its ligand PROS1 ameliorates disease. Treatment of mice with MER receptor agonistic antibodies is deleterious due to its counterproductive effect of blocking efferocytosis in the arthritic joint.

Disease-inducible promoters for the treatment of rheumatoid arthritis (RA) have the potential to provide regulated expression of therapeutic proteins in arthritic joints. In this study, we set out to identify promoters of human genes that are upregulated during RA and are suitable to drive the expression of relevant amounts of anti-inflammatory interleukin (IL)-10. Microarray analysis of RA synovial biopsies compared with healthy controls yielded a list of 22 genes upregulated during RA. Of these genes, CXCL10 showed the highest induction in lipopolysaccharide-stimulated synovial cells. The CXCL10 promoter was obtained from human cDNA and cloned into a lentiviral vector carrying firefly luciferase to determine the promoter inducibility in primary synovial cells and in THP-1 cells. The promoter activation was strongest 8-12 hr after stimulation with the proinflammatory cytokine tumor necrosis factor (TNF)-α and was reinducible after 96 hr. In addition, the CXCL10 promoter showed a significant response to RA patient serum, compared with sera from healthy individuals. The luciferase gene was replaced with IL-10 to determine the therapeutic properties of the CXCL10p-IL10 lentiviral vector. Primary synovial cells transduced with CXCL10p-IL10 showed a great increase in IL-10 production after stimulation, which reduced the release of proinflammatory cytokines TNF-α and IL-1β. We conclude that the selected proximal promoter of the CXCL10 gene responds to inflammatory mediators present in the serum of patients with RA and that transduction with the lentiviral CXCL10p-IL10 vector reduces inflammatory cytokine production by primary synovial cells from patients with RA. CXCL10 promoter-regulated IL-10 overexpression can thus provide disease-inducible local gene therapy suitable for RA.

Gabalawy, 2011). The cells in the synovium can produce several pro-inflammatory cytokines and matrix-degrading enzymes. At the interface of the synovium, cartilage and bone, pannus tissue is formed, which contributes to bone destruction. An important mediator of these processes is tumor necrosis factor alpha (TNF-α) (Vasanthi et al., 2007). Specific inhibitors of TNF-α are the most widely used biological therapeutics and can successfully inhibit the progress of RA in the majority of patients (Mewar and Wilson, 2011). Synovial pathology is also described for OA. Although OA has traditionally been described as a wear-and-tear disease of the articular cartilage, synovitis is observed in up to 50% of the OA patients and may contribute to the disease process (Scanzello and Goldring, 2012). A second factor that contributes to the synovial thickening in OA is tissue fibrosis (Wenham and Conaghan, 2010). Synovial fibrosis is also associated with joint pain and stiffness (Remst et al., 2015). Although the pathogenesis of OA