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Objectives To explore the immunosuppressive effect and mechanism of action of intraperitoneal (ip) and intra-articular (ia) mesenchymal stem cell (MSC) injection in proteoglycan induced arthritis (PGIA). Methods MSC were administered ip or ia after establishment of arthritis. We used seria bioluminescence imaging (BLI) to trace luciferase-transfected MSC. Mice were sacrificed at different time points to examine immunomodulatory changes in blood and secondary lymphoid organs. Results Both ip and local ia MSC injection resulted in a beneficial clinical and histological effect on established PGIA. BLI showed that MSC ip and ia in arthritic mice are largely retained for several weeks in the peritoneal cavity or injected joint respectively, without signs of migration. Following MSC treatment pathogenic PG-specific IgG2a antibodies in serum decreased. The Th2 cytokine IL-4 was only upregulated in PG-stimulated lymphocytes from spleens in ip treated mice and in lymphocytes from draining lymph nodes in ia treated mice. An increase in production of IL-10 was seen with equal distribution. Although IFN-γ was also elevated, the IFN-γ/IL-4 ratio in MSC treated mice was opposite to the ratio in (untreated) active PGIA. Conclusions MSC treatment, both ip and ia, suppresses PGIA, a non-collagen induced arthritis model. MSC are largely retained for weeks in the injection region. MSC treatment induced at the region of injection a deviation of PG-specific immune responses, suggesting a more regulatory phenotype with production of IL-4 and IL-10, but also of IFN-γ, and a systemic decrease of pathogenic PG-specific IgG2a antibodies. These findings underpin the potential of MSC treatment in resistant arthritis. [ABSTRACT FROM AUTHOR]

Background and objectives Juvenile dermatomyositis (JDM) is a childhood disease characterised by inflammation in the muscle and the skin. In several human chronic inflammatory diseases CD4 T cell responses to epitopes of heat shock proteins (hsp) have been found to play a role, both pathogenic and regulatory. In JDM hsp70 is highly up regulated in the inflamed muscle. Therefore, hsp70 could be a target in the inflammatory process in JDM. Responses to hsp70 epitopes in JDM have not yet been characterised. In HLA elution studies it has become clear that epitopes from self-hsp70 are abundantly bound to HLA. In this study the authors tested whether peripheral blood CD4 T cell responses to hsp70-epitopes can be detected and whether they are different in JDM patients compared to healthy controls (HC). Materials and methods Hsp70-epitopes were selected based on (1) literature on HLA-elution studies, (2) HLA-class II binding capacity tested with computer models and (3) in vitro responses by CD4 T cells from healthy donors. Proliferation of PBMC from healthy controls (HC, age 2–18) and JDM patients and juvenile idiopathic arthritis patients as disease controls was tested using 3H-thymidine assays and CFSE-staining. Cytokine production was tested by Luminex analysis, flow cytometry and PCR. Results The following epitopes were selected: aa 38–52, aa 161–175, aa 290–304 and aa 443–457. These peptides were immunogenic in humans, inducing proliferation or cytokine production. The proliferation of CD4 T cells towards aa 443–457 is increased in JDM. Conclusion The authors identified novel epitopes of hsp70 that are immunogenic in healthy donors and JDM and they found indications that the CD4 T cell response towards H443 is increased in JDM. [ABSTRACT FROM PUBLISHER]