Hans-Ulrich Pauer

Defective thrombus formation in mice lacking coagulation factor XII

Blood coagulation is thought to be initiated by plasma protease factor VIIa in complex with the membrane protein tissue factor. In contrast, coagulation factor XII (FXII)–mediated fibrin formation is not believed to play an important role for coagulation in vivo. We used FXII-deficient mice to study the contributions of FXII to thrombus formation in vivo. Intravital fluorescence microscopy and blood flow measurements in three distinct arterial beds revealed a severe defect in the formation and stabilization of platelet-rich occlusive thrombi. Although FXII-deficient mice do not experience spontaneous or excessive injury-related bleeding, they are protected against collagen- and epinephrine-induced thromboembolism. Infusion of human FXII into FXII-null mice restored injury-induced thrombus formation. These unexpected findings change the long-standing concept that the FXII-induced intrinsic coagulation pathway is not important for clotting in vivo. The results establish FXII as essential for thrombus formation, and identify FXII as a novel target for antithrombotic therapy.

Targeting coagulation factor XII provides protection from pathological thrombosis in cerebral ischemia without interfering with hemostasis

Formation of fibrin is critical for limiting blood loss at a site of blood vessel injury (hemostasis), but may also contribute to vascular thrombosis. Hereditary deficiency of factor XII (FXII), the protease that triggers the intrinsic pathway of coagulation in vitro, is not associated with spontaneous or excessive injury-related bleeding, indicating FXII is not required for hemostasis. We demonstrate that deficiency or inhibition of FXII protects mice from ischemic brain injury. After transient middle cerebral artery occlusion, the volume of infarcted brain in FXII-deficient and FXII inhibitor–treated mice was substantially less than in wild-type controls, without an increase in infarct-associated hemorrhage. Targeting FXII reduced fibrin formation in ischemic vessels, and reconstitution of FXII-deficient mice with human FXII restored fibrin deposition. Mice deficient in the FXII substrate factor XI were similarly protected from vessel-occluding fibrin formation, suggesting that FXII contributes to pathologic clotting through the intrinsic pathway. These data demonstrate that some processes involved in pathologic thrombus formation are distinct from those required for normal hemostasis. As FXII appears to be instrumental in pathologic fibrin formation but dispensable for hemostasis, FXII inhibition may offer a selective and safe strategy for preventing stroke and other thromboembolic diseases.

Targeted deletion of murine coagulation factor XII gene-a model for contact phase activation in vivo

To analyze the biological role of factor XII (FXII, Hageman Factor) in vivo, we generated mice deficient for FXII using a gene targeting approach on two distinct genetic backgrounds, i.e. mixed C57Bl/6J X 129X1/SvJ and inbred 129X1/SvJ. Homozygous FXII knockout (FXII(-)/(-)) mice showed no FXII plasma activity and had a markedly prolonged activated partial thromboplastin time (aPTT). In contrast, coagulation factors XI, VIII, IX, X,VII, V, II and fibrinogen did not differ between FXII(-/-) mice and their wild-type littermates. Heterozygous matings segregated according to the Mendelian inheritance indicating that FXII deficiency does not increase fetal loss. Furthermore, matings of FXII(-/-) males and FXII(-/-) females resulted in normal litter sizes demonstrating that total FXII deficiency in FXII(-/-) females does not affect pregnancy outcome. Also, gross and histological anatomy of FXII(-/-) mice was indistinguishable from that of their wild-type littermates on both genetic backgrounds. Thus it appears that deficiency of murine FXII does not cause thrombophilia or impaired fibrinolysis in vivo. These results indicate that FXII deficiency does not affect hemostasis in vivo and we anticipate that the FXII(-/-) mice will be helpful to elucidate the biological role(s) of FXII in health and disease.

Factor XII deficiency is strongly associated with primary recurrent abortions

OBJECTIVE To evaluate factor XII deficiency in women with primary and secondary recurrent abortion. DESIGN Prospective case-control study. SETTING University hospital. PATIENT(S) Sixty-seven women with primary and 33 women with secondary recurrent abortion of unexplained nature and 49 healthy controls with no history of thrombotic disease or adverse pregnancy outcomes. MAIL OUTCOME MEASURE(S): Plasma factor XII activity, activated protein C resistance, factor V Leiden mutation analysis, protein C, protein S, antithrombin III, karyotyping, and anticardiolipin antibodies. RESULT(S) Ten of 67 women with primary recurrent abortion (14.9%) and 4 of 33 women (12.1%) with secondary recurrent abortion had reduced factor XII activity (<60%). These results are highly significant in the former group and showed a tendency toward significance in the latter group. All controls had normal factor XII activity. CONCLUSION(S) Factor XII deficiency is strongly associated with primary recurrent abortion, and women with secondary recurrent abortion show a tendency toward factor XII deficiency.

Analyzes of three common thrombophilic gene mutations in German women with recurrent abortions

Background.  Several etiological factors have been proposed as a cause for recurrent fetal abortions. Changes in blood coagulation during pregnancy may play an important role in the occurrence of recurrent abortions (RA).

Introital ultrasound of the lower genital tract before and after colposuspension: a 4-year objective follow-up

To assess the topography of the bladder neck by introital ultrasound before and after open colposuspension.

Uterine Cervical Metastasis of Breast Cancer: A Rare Complication that May be Overlooked

Background: Metastasis of distant malignancies to the cervix uteri is a rare occurrence and the frequency is approximately 4% for all tumours. However, the frequency of cervical metastasis of breast cancer is much lower and is estimated to range between 0.8 and 1.7%. With the exception of ovarian metastases, secondary tumours of the female genital tract are rather uncommon. Therefore, these conditions pose diagnostic problems for the clinician. Patient: A 40-year-old woman with the diagnosis of invasive ductal cell carcinoma of the right breast underwent mastectomy with dissection of axillary lymph nodes in 1998. Subsequently, the patient received 6 cycles of chemotherapy with cyclophosphamide, methotrexate and fluorouracil. The initial tumour stage was pT2, pN0 (0/13), M0, G2. The oestrogen and progesterone receptors were positive and expression of the C-erb-B2 coding oncogene was negative. Gynaecological and ultrasonographic examination revealed a normal cervix without evident lesions. Exfoliative cytology was negative. 14 months after treatment the patient presented with an axillary relapse and surgery, second-line chemotherapy with doxorubicine and radiation therapy of the chest wall and the axilla were performed. The patient developed liver metastases 14 months later and at this time ultrasonographic pelvic examination revealed a 2.2 cm tumour of the cervix with good vascularisation. The patient had no clinical symptoms, i.e. no vaginal bleeding or discharge. Sonomorphologically this tumour appeared as a leiomyoma of the cervix. Cervical biopsies and curettage, however, revealed metastatic carcinoma expressing oestrogen and progesterone receptors consistent with the primary breast cancer. Under palliative chemotherapy with docetaxel progression of liver metastases and cervical metastasis occurred and the patient died 9 months later. Conclusion: Metastatic involvement of the cervix should be considered in women with a history of breast cancer who present with vaginal bleeding or suspicious changes of the cervix on transvaginal ultrasound. Therefore, gynaecological and ultrasonographic examination of the pelvis represent an important part of the follow- up investigations in women with primary breast cancer.

Homozygous factor V Leiden mutation in a woman with multiple adverse pregnancy outcomes

Abstract We report a case with one intrauterine fetal death (IUFD) at 32 weeks of gestation, one premature delivery at the same week, and one abortion of unknown etiology at 12 weeks of gestation. We discuss that the presence of homozygosity for Factor V Leiden may be associated with placental insufficiency in this woman. Application of anticoagulant therapy may have been beneficial in her current pregnancy.