A novel interpretation of the role of von Willebrand factor in thrombotic microangiopathies based on platelet adhesion studies at high shear rate flow

Adenoviral-mediated gene transfer restores plasma ADAMTS13 antigen and activity in ADAMTS13 knockout mice

ADAMTS13 is a plasma metalloprotease that regulates the size of the von Willebrand factor (VWF) multimers. Genetic or acquired deficiency of ADAMTS13 causes thrombotic thrombocytopenic purpura (TTP) in humans. Plasma infusion is the treatment of choice for patients with congenital ADAMTS13 deficiency. However, this practice exposes patients to the risk of infections, allergies and fluid volume overload. The search for alternative treatments is required. Here, we tested the ability of systemically administered adenovirus encoding human ADAMTS13 to restore the deficient protein in the circulation of Adamts13(-/-) mice. Injection of the adenovirus efficiently transduced the liver, kidney, lung, heart and spleen, resulting in the secretion of ADAMTS13 into plasma. A reduced area of thrombi was observed when blood from Ad-ADAMTS13-treated mice was perfused over a collagen-coated surface in a parallel plate flow chamber compared with blood of Ad-betaGal-treated controls. The secreted ADAMTS13 protein was functionally active even after 2 months from injection. The data provide the proof of principle for developing a novel therapy for the correction of ADAMTS13 deficiency in patients with hereditary TTP.

New aspects in the pathogenesis and treatment of thrombotic thrombocytopenic purpura and hemolytic uremic syndrome

The thrombotic microangiopathy (TM) syndromes, thrombotic thrombocytopenic purpura and the hemolytic uremic syndrome, are a rare and heterogeneous group of disorders characterized by widespread microvascular thrombosis and end organ injury. Decades of descriptive studies have defined clinical subsets of TM syndromes by clinical and laboratory features. Despite many advances, however, progress towards understanding of the etiology and pathogenesis of TM disorders remains limited. The rarity of occurrence and lack of natural animal models of TM syndromes have hampered progress in experimental and clinical studies. Treatment remains essentially empirical and options are limited. However, recent advances in the genetic and molecular understanding of subsets of TM disorders and the development of relevant animal models offer new resources to explore the pathogenic mechanisms. With these new advances more effective and individualized treatments for TM syndromes can be developed.