In vivo effect of rFVIII and rFVIIa in hemophilia A rats evaluated by the Tail Vein Transection Bleeding Model.

Background: Preclinical bleeding models increase current hemophilia A (HA) knowledge and aid the development of new pharmacological treatments. There are several well-established mouse bleeding models, but limited options are available for rat models despite their high resemblance to human disease process.

Objective: To provide a comprehensive description of the tail vein transection (TVT) bleeding model in HA rats and examine the correlation between in vivo pharmacological efficacy and global hemostatic assays.

CTLA4-Ig prevents development of neutralizing antibody formation after continuous treatment with human FVIII in HA rats.

Introduction: Immunogenicity causing development of anti-drug antibodies (ADAs) are major challenges in the treatment of haemophilia, as well as other diseases where proteins are used for treatment. Furthermore, it is a complication for preclinical testing of such therapies in animal models.

Aim: To investigate if the immunosuppressive drug CTLA4 immunoglobulin (CTLA4-Ig) can induce tolerance in haemophilia A (HA) rats receiving recombinant human coagulation factor VIII (rhFVIII) treatment.

Initial joint bleed volume in a delayed on-demand treatment setup correlates with subsequent synovial changes in hemophilic mice.

Background: Hemophilic arthropathy is a debilitating morbidity of hemophilia caused by recurrent joint bleeds. We investigated if the joint bleed volume, before initiation of treatment, was linked to the subsequent degree of histopathological changes and the development of bone pathology in a mouse model of hemophilic arthropathy.

Methods: FVIII knock-out (F8-KO) mice were dosed with a micro-CT blood pool agent prior to induction of hemarthrosis.

Bleed volume of experimental knee haemarthrosis correlates with the subsequent degree of haemophilic arthropathy.

Background: Haemophilic arthropathy is the main morbidity of haemophilia. The individual pathological response to the same number of clinically evident joint bleeds is highly variable; thus, it remains unknown if certain joint bleeding characteristics are critical for the development of arthropathy.

Aim: To study the relation between bleed volume and subsequent development of arthropathy, we aimed to develop quantitative in vivo imaging of active joint bleeds in a mouse model of haemophilia.

Absence of functional compensation between coagulation factor VIII and plasminogen in double-knockout mice.

Plasminogen deficiency is associated with severely compromised fibrinolysis and extravascular deposition of fibrin. In contrast, coagulation factor VIII (FVIII) deficiency leads to prolonged and excessive bleeding. Based on opposing biological functions of plasminogen and FVIII deficiencies, we hypothesized that genetic elimination of FVIII would alleviate the systemic formation of fibrin deposits associated with plasminogen deficiency and, in turn, elimination of plasminogen would limit bleeding symptoms associated with FVIII deficiency.

Engineering of a membrane-triggered activity switch in coagulation factor VIIa.

Recombinant factor VIIa (FVIIa) variants with increased activity offer the promise to improve the treatment of bleeding episodes in patients with inhibitor-complicated hemophilia. Here, an approach was adopted to enhance the activity of FVIIa by selectively optimizing substrate turnover at the membrane surface. Under physiological conditions, endogenous FVIIa engages its cell-localized cofactor tissue factor (TF), which stimulates activity through membrane-dependent substrate recognition and allosteric effects.