TAFI deficiency causes maladaptive vascular remodeling after hemophilic joint bleeding

Aberrant methylation and expression of TNXB promote chondrocyte apoptosis and extracullar matrix degradation in hemophilic arthropathy via AKT signaling

Recurrent joint bleeding in hemophilia patients frequently causes hemophilic arthropathy (HA). Drastic degradation of cartilage is a major characteristic of HA, but its pathological mechanisms has not yet been clarified. In HA cartilages, we found server matrix degradation and increased expression of DNA methyltransferase proteins. We thus performed genome-wide DNA methylation analysis on human HA (N=5) and osteoarthritis (OA) (N=5) articular cartilages, and identified 1228 differentially methylated regions (DMRs) associated with HA. Functional enrichment analyses revealed the association between DMR genes (DMGs) and extracellular matrix (ECM) organization. Among these DMGs, Tenascin XB (TNXB) expression was down-regulated in human and mouse HA cartilages. The loss of Tnxb in F8-/- mouse cartilage provided a disease-promoting role in HA by augmenting cartilage degeneration and subchondral bone loss. Tnxb knockdown also promoted chondrocyte apoptosis and inhibited phosphorylation of AKT. Importantly, AKT agonist showed chondroprotective effects following Tnxb knockdown. Together, our findings indicate that exposure of cartilage to blood leads to alterations in DNA methylation, which is functionally related to ECM homeostasis, and further demonstrate a critical role of TNXB in HA cartilage degeneration by activating AKT signaling. These mechanistic insights allow development of potentially new strategies for HA cartilage protection.

Brain Expression of CPB2 and Effects of Cpb2 Deficiency in Mouse Models of Behavior

BACKGROUND

 Procarboxypeptidase B2 (proCPB2 or TAFI) is a zymogen that after activation cleaves C-terminal basic residues from peptides or proteins with many identified targets. A splice variant of CPB2 has been found in the brain lacking essential residues for its carboxypeptidase function. The aim was to determine CPB2 expression in the brain and effects of CPB2 deficiency (Cpb2 -/-) on behavior.

MATERIALS AND METHODS

 Behavioral effects were tested by comparing Cpb2 -/- mice in short-term (open field and elevated zero maze tests) and long-term (Phenotyper) observations with wild-type (WT) controls.

RESULTS

 Long-term observation compared day 1 (acclimatizing to novel environment) to day 4 (fully acclimatized) with the inactive (day) and active (night) periods analyzed separately. Brain expression of CPB2 mRNA and protein was interrogated in publicly available databases. Long-term observation demonstrated differences between WT and Cpb2 -/- mice in several parameters. For example, Cpb2 -/- mice moved more frequently on both days 1 and 4, especially in the normally inactive periods. Cpb2 -/- mice spent more time on the shelter and less time in it. Differences were more pronounced on day 4 after the mice had fully acclimatized. In short-term observations, no differences were observed between Cpb2 -/- mice and WT mice. Brain expression of CBP2 was not detectable in the human protein atlas. Databases of single-cell RNAseq did not show expression of CPB2 mRNA in either human or mouse brain.

CONCLUSION

 Continuous observation of home-cage behavior suggests that Cpb2 -/- mice are more active than WT mice, show different day-night activity levels, and might have a different way of processing information.

The value of radiosynoviorthesis for treatment of chronic synovitis in hemophilic joint disease

Chronic synovitis is contributing to the development of arthropathy in hemophilia A and B. In most patients with severe and moderate hemophilia, during lifetime, joint damage progresses despite early prophylaxis and intense treatment with coagulation factor concentrates. Recurrent hemorrhages into the joints and subclinical bleeding lead to chronic inflammation of the synovium, neoangiogenesis and remodeling, sustaining a vicious circle of bleeding-remodeling-bleeding and progression of osteochondral damage. Imaging techniques including ultrasound and MRI are able to early visualize synovitis and osteochondral changes. Early detection and sustained therapy of synovitis are important preconditions to prevent further deterioration of joint status. Chronic synovitis requires intensified substitution of coagulation factors and concomitant analgetic, antiphlogistic and physical therapy. The value of early radiosynoviorthesis (RSO) as effective method to control ongoing synovitis is discussed here. RSO is recommended as first choice therapy in case of persistant chronic synovitis, recorded in both national and international guidelines.

Fibrinogen and Antifibrinolytic Proteins: Interactions and Future Therapeutics

Thrombus formation remains a major cause of morbidity and mortality worldwide. Current antiplatelet and anticoagulant therapies have been effective at reducing vascular events, but at the expense of increased bleeding risk. Targeting proteins that interact with fibrinogen and which are involved in hypofibrinolysis represents a more specific approach for the development of effective and safe therapeutic agents. The antifibrinolytic proteins alpha-2 antiplasmin (α2AP), thrombin activatable fibrinolysis inhibitor (TAFI), complement C3 and plasminogen activator inhibitor-2 (PAI-2), can be incorporated into the fibrin clot by FXIIIa and affect fibrinolysis by different mechanisms. Therefore, these antifibrinolytic proteins are attractive targets for the development of novel therapeutics, both for the modulation of thrombosis risk, but also for potentially improving clot instability in bleeding disorders. This review summarises the main properties of fibrinogen-bound antifibrinolytic proteins, their effect on clot lysis and association with thrombotic or bleeding conditions. The role of these proteins in therapeutic strategies targeting the fibrinolytic system for thrombotic diseases or bleeding disorders is also discussed.

Systemic vascular basement membrane markers linked to synovial vascular remodeling are biomarkers of hemarthrosis in patients with hemophilia

INTRODUCTION

Interstitial, cartilage, and bone collagens have been proposed as biomarkers of joint deterioration in hemophilic arthropathy. The role of basement membrane (type IV and VIII) collagens as biomarkers of endothelial turnover in relation to acute joint bleeding is not understood.

METHODS

Thirty-one adult patients with hemophilia were studied prospectively for 3 years with musculoskeletal ultrasound/power Doppler (MSKUS/PD) during pain-free intervals and painful events for joint bleed status, synovial vascular flow, and 10 plasma markers of collagen turnover. Joint health was determined using Hemophilia Joint Health Scores and Pettersson scores. In animal studies, bleeding was induced in factor VIII-/- mice by knee joint injury. Synovial vascular remodeling was assessed using MSKUS/PD and histology. Murine plasma samples were analyzed for type IV collagen turnover markers.

RESULTS

Ninety-one patient visits were compiled. Twenty-five were due to acute painful episodes, with 16 confirmed hemarthroses. Type IV collagen turnover markers (PRO-C4 and C4M), and a type VIII collagen synthesis marker (PRO-C8), were transiently elevated during acute hemarthrosis. Hemarthrosis was accompanied by increased synovial microvascular flow (MSKUS/PD), and levels of type IV collagen markers correlated with PD signals in the joint. In factor VIII-deficient mice, plasma levels of type IV collagen turnover markers correlated negatively with synovial αSMA staining, indicating that reduced type IV collagen turnover was associated with thicker vessels.

CONCLUSIONS

Our findings suggest that basement membrane turnover markers, closely linked to synovial vascular remodeling, may be systemic biomarkers of acute hemarthrosis. Vascular instability during neovascularization may be involved in the dynamics of hemarthrosis.

Illustrated State-of-the-Art Capsules of the ISTH 2020 Congress

The 2020 Congress of the International Society of Thrombosis and Haemostasis (ISTH) was held virtually July 12-15, 2019, due to the coronavirus disease 2019 pandemic. The congress convenes annually to discuss clinical and basic topics in hemostasis and thrombosis. Each year, the program includes State of Art (SOA) lectures given by prominent scientists. Presenters are asked to create Illustrated Capsules of their talks, which are concise illustrations with minimal explanatory text. Capsules cover major themes of the presentation, and these undergo formal peer review for inclusion in this article. Owing to the shift to a virtual congress this year, organizers reduced the program size. There were 39 SOA lectures virtually presented, and 29 capsules (9 from talks omitted from the virtual congress) were both submitted and successful in peer review, and are included in this article. Topics include the roles of the hemostatic system in inflammation, infection, immunity, and cancer, platelet function and signaling, platelet function disorders, megakaryocyte biology, hemophilia including gene therapy, phenotype tests in hemostasis, von Willebrand factor, anticoagulant factor V, computational driven discovery, endothelium, clinical and basic aspects of thrombotic microangiopathies, fibrinolysis and thrombolysis, antithrombotics in pediatrics, direct oral anticoagulant management, and thrombosis and hemostasis in pregnancy. Capsule authors invite virtual congress attendees to refer to these capsules during the live presentations and participate on Twitter in discussion. Research and Practice in Haemostasis and Thrombosis will release 2 tweets from @RPTHJournal during each presentation, using #IllustratedReview, #CoagCapsule and #ISTH2020. Readers are also welcome to utilize capsules for teaching and ongoing education.