Fatal thrombosis of antithrombin deficient mice is rescued differently in the heart and liver by intercrossing with low tissue factor mice

点击翻译按钮获取中文摘要

We previously reported that targeted disruption of murine antithrombin (AT) gene resulted in embryonic lethality before 16.5gd because of severe cardiac and hepatic thrombosis. To investigate influences of lowered tissue factor (TF) activity upon hypercoagulation of AT^<-/-> embryos, we crossed AT^<+/-> with low TF (mTF^<-/->hTF^+) mice to yield homozygous AT deficient mice with extremely low TF activity, that is expressed from the inserted human TF mini gene. AT^<-/-> embryos either with 50% TF (AT^<-/->mTF^<+/->hTF^+) or with low (〜1% TF, AT^<-/->mTF^<-/->hTF^+) were not born, although the survival was prolonged until 18.5gd. In both genotypes, histological examination showed disseminated thrombosis in hepatic sinusoidal space or in the portal veins, suggesting that thrombogenesis caused loss of hepatic blood flow. As in original AT^<-/->, AT^<-/->mTF^<+/->hTF^+ showed subcutaneous bleeding and also suffered from myocardial degeneration apparently due to coronary thrombus formation. However, AT^<-/->mTF^<-/->hTF^+ had no skin hemorrhage and the thrombosis and degeneration was completely abolished in the heart. Myocardium of adult low TF mice had exhibited fibrosis secondary to hemorrhage, however, it was significantly decreased in low TF mice with AT^<+/->. Our current model suggest that in the heart, TF plays an important role in the thrombogenesis and it counterbalances AT-dependent anticoagulation. AT may be a potent anticoagulant during mice development and the activation and subsequent regulation of TF-procoagulant activity take place differently between the liver and the heart. These differences appear to point to local regulatory mechanisms in murine hemostasis.