Animal models of hemophilia and related bleeding disorders.

Animal models of hemophilia and related diseases are important for the development of novel treatments and to understand the pathophysiology of bleeding disorders in humans. Testing in animals with the equivalent human disorder provides informed estimates of doses and measures of efficacy, which aids in design of human trials. Many models of hemophilia A, hemophilia B, and von Willebrand disease (VWD) have been developed from animals with spontaneous mutations (hemophilia A dogs, rats, sheep; hemophilia B dogs; and VWD pigs and dogs), or by targeted gene disruption in mice to create hemophilia A, B, or VWD models. Animal models have been used to generate new insights into the pathophysiology of each bleeding disorder and also to perform preclinical assessments of standard protein replacement therapies, as well as novel gene transfer technology. The differences both between species and in underlying causative mutations must be considered in choosing the best animal for a specific scientific study.

Health status and health-related quality of life associated with von Willebrand disease.

Von Willebrand disease (VWD) is the commonest inherited disorder of hemostasis and the majority of women with this disorder experience excessive uterine bleeding. Yet very little information is available on the health-related quality of life (HRQL) in individuals with VWD. To test the a priori hypotheses that these individuals will have poorer HRQL than members of the general population, and that this burden of morbidity will correlate with the severity of VWD, a cross-sectional study was undertaken of a population-based cohort in a regional hemophilia program in Ontario, Canada. A survey was made of individuals over 13 years of age with VWD who self-reported their health status using a standard 15 item questionnaire. The responses were converted to levels in the Health Utilities Index Mark 2 (HUI2) and Mark 3 (HUI3) health status classification systems to form multi-element vectors from which single attribute morbidity and overall HRQL utility scores were determined. As a group, individuals with VWD were shown to have poorer HRQL than members of the general population and those with Type 2 disease carried a greater burden of overall morbidity than those with Type 1 disorder. Morbidity was evident mainly in the attributes of emotion, cognition with pain. A striking difference was observed between males and females, with the latter having overall HRQL utility scores similar to those reported previously for HIV positive, severe hemophiliacs. It is possible that this remarkable burden of morbidity reflects chronic iron deficiency associated with menorrhagia. A national study has been proposed to address this likelihood as it offers an opportunity for effective therapeutic intervention (iron supplementation) with a concomitant gain in health status and HRQL.

Comparative response of plasma VWF in dogs to up-regulation of VWF mRNA by interleukin-11 versus Weibel-Palade body release by desmopressin (DDAVP).

Recombinant human interleukin-11 (rhIL-11), a glycoprotein 130 (gp130)-signaling cytokine approved for treatment of thrombocytopenia, also raises von Willebrand factor (VWF) and factor VIII (FVIII) by an unknown mechanism. Desmopressin (1-deamino-8-d-arginine vasopressin [DDAVP]) releases stored VWF and FVIII and is used for treatment of VWF and FVIII deficiencies. To compare the effect of these 2 agents, heterozygous von Willebrand disease (VWD) and normal dogs were treated with either rhIL-11 (50 microg/kg/d subcutaneously x 7 days) or DDAVP (5 microg/kg/d intravenously x 7 days). The rhIL-11 produced a gradual and sustained elevation of VWF and FVIII levels in both heterozygous VWD and normal dogs while DDAVP produced a rapid and unsustained increase. Importantly, rhIL-11 treatment produced a 2.5- to 11-fold increase in VWF mRNA in normal canine heart, aorta, and spleen but not in homozygous VWD dogs, thus identifying a mechanism for elevation of plasma VWF in vivo. Moreover, dogs pretreated with rhIL-11 retain a DDAVP-releasable pool of VWF and FVIII, suggesting that rhIL-11 does not significantly alter trafficking of these proteins to or from storage pools. The half-life of infused VWF is unchanged by rhIL-11 in homozygous VWD dogs. These results show that rhIL-11 and DDAVP raise plasma VWF by different mechanisms. Treatment with rhIL-11 with or without DDAVP may provide an alternative to plasma-derived products for some VWD and hemophilia A patients if it is shown safe in clinical trials.