Animal models: importance in research on hemorrhage and thrombosis

Despite some sentiments against animal research, animal models continue to be important in studying hemorrhage and thrombosis. Examples of genetic models are dogs and pigs with von Willebrand's disease. The homozygous von Willebrand pig appears to be resistant to arteriosclerosis, presumably due to impairment of the platelet aggregating function. Among acquired models, pigs are gaining in favor, perhaps because their clotting and platelet characteristics resemble those in humans. Species vary markedly in their normal plasma levels of platelet aggregating factor/von Willebrand factor (PAF/vWF). One promising approach to the study of thrombosis is using platelet anti-aggregating drugs to inhibit PAF/vWF dependent platelet thrombus formation; a drug-induced von Willebrand state seems feasible.