K. Roepstorff

Antibody-Mediated Targeting of the Orai1 Calcium Channel Inhibits T Cell Function

Despite the attractiveness of ion channels as therapeutic targets, there are no examples of monoclonal antibodies directed against ion channels in clinical development. Antibody-mediated inhibition of ion channels could offer a directed, specific therapeutic approach. To investigate the potential of inhibiting ion channel function with an antibody, we focused on Orai1, the pore subunit of the calcium channel responsible for store-operated calcium entry (SOCE) in T cells. Effector T cells are key drivers of autoimmune disease pathogenesis and calcium signaling is essential for T cell activation, proliferation, and cytokine production. We show here the generation of a specific anti-human Orai1 monoclonal antibody (mAb) against an extracellular loop of the plasma membrane-spanning protein. The anti-Orai1 mAb binds native Orai1 on lymphocytes and leads to cellular internalization of the channel. As a result, T cell proliferation, and cytokine production is inhibited in vitro. In vivo, anti-Orai1 mAb is efficacious in a human T cell-mediated graft-versus host disease (GvHD) mouse model. This study demonstrates the feasibility of antibody-mediated inhibition of Orai1 function and, more broadly, reveals the possibility of targeting ion channels with biologics for the treatment of autoimmunity and other diseases.

A novel F8 -/- rat as a translational model of human hemophilia A.

In preclinical hemophilia research, an animal model that reflects both the phenotype and the pathology of the disease is needed.

The F8‐/‐ rat as a model of hemophilic arthropathy

Essentials Validating the F8 rat as a new intermediate‐size animal model of hemophilic arthropathy. Factor VIII (FVIII) treated F8−/− rats suffered induced hemarthrosis analyzed by histopathology. F8 −/− animals develop hemophilic arthropathy upon hemarthrosis, preventable by FVIII treatment. The F8 −/− rat presents as a new pharmacologic model of hemophilic arthropathy.

Altered collagen turnover in factor VIII-deficient rats with hemophilic arthropathy identifies potential novel serological biomarkers in hemophilia

Essentials Joint bleeding in hemophilia may induce significant remodeling of the extracellular matrix. Biomarkers of collagen turnover were investigated in a F8−/− rat model of hemophilic arthropathy. Biomarkers of cartilage degradation increased significantly during development of arthropathy. Basement membrane and interstitial matrix turnover changed significantly following hemarthrosis.

Serological biomarkers detect active joint destruction and inflammation in patients with haemophilic arthropathy

Progressive arthropathy caused by recurrent joint bleeds is a severe complication in haemophilia.

Visualization of haemophilic arthropathy in F8(-/-) rats by ultrasonography and micro-computed tomography.

A major complication of haemophilia is haemophilic arthropathy (HA), a debilitating disorder with an incompletely defined pathobiology. High‐resolution imaging may provide new knowledge about onset and progression of HA, and thereby support identification of new treatment opportunities. Recently, a F8−/− rat model of HA was developed. The size of the rat allows for convenient and high resolution imaging of the joints, which could enable in vivo studies of HA development.

Increased basement membrane turnover and strongly attenuated interstitial matrix turnover is a key pathological feature of haemophilia

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Rapid inflammation and early degeneration of bone and cartilage revealed in a time-course study of induced haemarthrosis in haemophilic rats

OBJECTIVES Detailed knowledge of the sequential cell and tissue responses following haemarthrosis is important for a deep understanding of the pathological process initiated upon extensive bleeding into the joint causing haemophilic arthropathy (HA). The underlying pathobiology driving haemarthrosis towards HA has been difficult to establish in detail, although animal models have shed light on some processes. Previous studies have focused on a single or a few distant time points and often only characterizing one tissue type of the joint. The objective of this study was, therefore, to carefully map early onset of synovitis and HA following induced haemarthrosis. METHODS One hundred and thirty haemophilia A rats were subjected to induced haemarthrosis or a sham procedure in full anaesthesia and euthanized from 30 min to 7 days after the procedure. Pathological changes of the joints were visualized using micro-computed tomography, histology and immunohistochemistry. RESULTS Synovitis developed within 24 h and was dominated by myeloid cell infiltrations. Cartilage and bone pathology were evident as early as 48-96 h after haemarthrosis, and the pathology rapidly progressed with extensive periosteal bone formation and formation of subchondral cysts. CONCLUSION Fast, extensive and simultaneous cartilage and bone degeneration developed shortly after haemarthrosis, as shown by the detailed mapping of the early pathogenesis of HA. The almost immediate loss of cartilage and the pathological bone turnover suggest a direct influence of blood on these processes and are unlikely to be attributed simply to an indirect effect of inflammation.

High‐affinity von Willebrand factor binding does not affect the anatomical or hepatocellular distribution of factor VIII in rats

Essentials Von Willebrand factor (VWF) stabilizes factor VIII (FVIII) and prevents its premature clearance. Rat anatomical and hepatocellular distribution studies assessed the VWF effect on FVIII clearance. Hepatocytes and liver sinusoidal endothelial cells play a key role in FVIII clearance. Anatomical and hepatocellular distribution of FVIII is independent of high‐affinity VWF binding.