Once it became possible to knock out genes in mice, mouse models of haemophilia were created. click here Mouse models have an advantage in that mice are smaller so that less material is needed than that in dog studies. Also the costs associated with mouse studies are lower than those for dog studies. However, while the general pattern of

haemostatic response in mice may be the same as in dogs or patients, it is clear that dosing requirements can be very different in mice and this limitation should be considered when evaluating the results in mice. In general, there are two types of models for assessing immediate haemostasis in mice: vessel transection models and intravascular injury models. The initial mouse haemostasis model assessed the amount of blood lost following removal Palbociclib mw of the tip of the tail [19]. Decreased blood loss following therapy was considered evidence of haemostatic efficacy. Other models have been developed which may have somewhat less variability than the tail snip models. One such model involves a vessel transection model in the saphenous vein; wild-type animals have multiple bleeding stops while haemophilic animals do not stop

bleeding within the 30 min evaluation period. In both the tail snip and the vessel transection model, administration of bypassing agent gives a dose-dependent change in the readout making it possible to generate a dose response medchemexpress curve. The dose responses of different therapeutic agents can be compared to give an assessment of relative efficacy [20]. Another type of model involves an injury to a vessel that leaves it intact. An example is a ferric chloride injury in which

the endpoint is vessel occlusion [21,22]. While sometimes dismissed as a thrombosis model, if properly done this type of model shows a completely different response in wild-type and haemophilic animals; in wild-type animals the injured vessel occludes while in haemophilia animals the injured vessel does not occlude in a defined period of time. Time to occlusion has been shown to be sensitive to factor levels in a dose dependent fashion; time to occlusion should also be sensitive to bypassing agent levels. There is a suggestion that these models may have less variability than models where vessels are cut and therefore might have value in determining dose responses. Beyond assessing the immediate haemostatic effect of bypassing agents or novel therapeutics it may prove important to assess longer term effects. In dogs, long-term expression of a bypassing agent by gene therapy can be monitored by following the natural history of bleeding as well as monitoring the whole blood clotting time [23]. In mice there are at least two models that may be useful for assessing long-term efficacy. One is a dermal wound healing model [24]; haemophilic mice have poor wound healing compared to wild-type animals.