Impact of delayed type hypersensitivity arthritis on development of heart failure by aortic constriction in mice.

AIMS: Patients with rheumatoid arthritis (RA) have increased risk of heart failure (HF). The mechanisms and cardiac prerequisites explaining this association remain unresolved. In this study, we sought to determine the potential cardiac impact of an experimental model of RA in mice subjected to HF by constriction of the ascending aorta. METHODS: Aorta was constricted via thoracotomy and placement of o-rings with inner diameter 0.55 mm or 0.66 mm, or sham operated. RA-like phenotype was instigated by delayed-type hypersensitivity arthritis (DTHA) two weeks after surgery and re-iterated after additional 18 days. Cardiac magnetic resonance imaging (MRI) was performed before surgery and at successive time points throughout the study. Six weeks after surgery the mice were euthanized, blood and tissue were collected, organ weights were documented, and expression levels of cardiac foetal genes were analysed. In a supplemental study, DTHA-mice were euthanized throughout 14 days after induction of arthritis, and blood was analysed for important markers and mediators of RA (SAP, TNF-α and IL-6). In order to put the latter findings into clinical context, the same molecules were analysed in serum from untreated RA patients and compared to healthy controls. RESULTS: Significant elevations of inflammatory markers were found in both patient- and murine blood. Furthermore, the DTHA model appeared clinically relevant when compared to the inflammatory responses observed in three prespecified RA severity disease states. Two distinct trajectories of cardiac dysfunction and HF development were found using the two o-ring sizes. These differences were consistent by both MRI, organ weights and cardiac foetal gene expression levels. Still, no difference within the HF groups, nor within the sham groups, could be found when DTHA was induced. CONCLUSION: DTHA mediated systemic inflammation did not cause, nor modify HF caused by aortic constriction. This indicates other prerequisites for RA-induced cardiac dysfunction.

Pharmacological Value of Murine Delayed-type Hypersensitivity Arthritis: A Robust Mouse Model of Rheumatoid Arthritis in C57BL/6 Mice.

In this MiniReview, we summarize the body of knowledge on the delayed-type hypersensitivity arthritis (DTHA) model, a recently developed arthritis model with 100% incidence, low variation and synchronized onset in C57BL/6 (B6) mice, and compare it to other murine arthritis models. It is desirable to have robust arthritis models in B6 mice, as many transgene strains are bred on this background. However, several of the most widely used mouse model of arthritis cannot be induced in B6 mice without the drawback of lower incidence, reduced severity and higher variation, if at all. DTHA is induced by modifying a classical methylated bovine serum albumin (mBSA)-induced DTH response by administering a cocktail of anti-type II collagen antibodies (anti-CII) between immunization and challenge. Arthritis affects one, predefined paw in which acute inflammation and severe arthritis rapidly develop and peak after 4-7 days. Disease is self-resolving over the course of around 3 weeks. Disease manifestations resemble those seen in other arthritis models and include bone erosion, cartilage destruction, oedema, pannus and new bone formation. Induction of DTHA is dependent on CD4+ T cells while B cells are dispensable. The DTHA model is set apart from other murine arthritis models in that it can be induced in B6 mice with 100% incidence and with high and consistent severity. This is the clearest advantage of the model, as the mechanisms of disease and clinical manifestations can be found in other arthritis models. The model holds potential for future modifications that may improve the lack of chronicity.

Depletion of regulatory T cells leads to an exacerbation of delayed-type hypersensitivity arthritis in C57BL/6 mice that can be counteracted by IL-17 blockade.

Rodent models of arthritis have been extensively used in the elucidation of rheumatoid arthritis (RA) pathogenesis and are instrumental in the development of therapeutic strategies. Here we utilise delayed-type hypersensitivity arthritis (DTHA), a model in C57BL/6 mice affecting one paw with synchronised onset, 100% penetrance and low variation. We investigate the role of regulatory T cells (Tregs) in DTHA through selective depletion of Tregsand the role of IL-17 in connection with Tregdepletion. Given the relevance of Tregsin RA, and the possibility of developing Treg-directed therapies, this approach could be relevant for advancing the understanding of Tregsin inflammatory arthritis. Selective depletion of Tregswas achieved using aFoxp3-DTR-eGFPmouse, which expresses the diphtheria toxin receptor (DTR) and enhanced green fluorescent protein (eGFP) under control of theFoxp3gene. Anti-IL-17 monoclonal antibody (mAb) was used for IL-17 blockade. Numbers and activation of Tregsincreased in the paw and its draining lymph node in DTHA, and depletion of Tregsresulted in exacerbation of disease as shown by increased paw swelling, increased infiltration of inflammatory cells, increased bone remodelling and increased production of inflammatory mediators, as well as increased production of anti-citrullinated protein antibodies. Anti-IL-17 mAb treatment demonstrated that IL-17 is important for disease severity in both the presence and absence of Tregs, and that IL-17 blockade is able to rescue mice from the exacerbated disease caused by Tregdepletion and caused a reduction in RANKL, IL-6 and the number of neutrophils. We show that Tregsare important for the containment of inflammation and bone remodelling in DTHA. To our knowledge, this is the first study using theFoxp3-DTR-eGFPmouse on a C57BL/6 background for Tregdepletion in an arthritis model, and we here demonstrate the usefulness of the approach to study the role of Tregsand IL-17 in arthritis.

Anti-RANKL treatment inhibits erosive joint destruction and lowers inflammation but has no effect on bone formation in the delayed-type hypersensitivity arthritis (DTHA) model.

BACKGROUND: The aims of the present study were to determine the relationship between bone destruction and bone formation in the delayed-type hypersensitivity arthritis (DTHA) model and to evaluate the effect of receptor activator of nuclear factor κB ligand (RANKL) blockade on severity of arthritis, bone destruction, and bone formation. METHODS: DTHA was induced in C57BL/6 mice. Inflammation, erosive joint damage, and new bone formation were semiquantitatively scored by histology. Osteoclast activity was assessed in vivo, and messenger RNA (mRNA) expression of mediators of bone destruction and bone formation were analyzed by mRNA deep sequencing. Serum concentrations of tartrate-resistant acid phosphatase 5b, carboxy-terminal telopeptide I (CTX-I), matrix metalloproteinase 3 (MMP3), and serum amyloid P component (SAP) were determined by enzyme-linked immunosorbent assay. Anti-RANKL monoclonal antibody treatment was initiated at the time of immunization. RESULTS: Bone destruction (MMP3 serum levels, cathepsin B activity, and RANKL mRNA) peaked at day 3 after arthritis induction, followed by a peak in cartilage destruction and bone erosion on day 5 after arthritis induction. Periarticular bone formation was observed from day 10. Induction of new bone formation indicated by enhanced Runx2, collagen X, osteocalcin, MMP2, MMP9, and MMP13 mRNA expression was observed only between days 8 and 11. Anti-RANKL treatment resulted in a modest reduction in paw and ankle swelling and a reduction of serum levels of SAP, MMP3, and CTX-I. Destruction of the subchondral bone was significantly reduced, while no effect on bone formation was seen. CONCLUSIONS: Anti-RANKL treatment prevents joint destruction but does not prevent new bone formation in the DTHA model. Thus, although occurring sequentially during the course of DTHA, bone destruction and bone formation are apparently not linked in this model.