人TFPI基因转染对兔移植静脉血栓形成和近期通畅率的影响

目的： 为减少冠状动脉旁路移植术后血栓形成，探讨人组织因子途径抑制因子(TFPI)基因转染对兔移植静脉血栓生成的影响。方法：构建真核表达质粒pCMV-(Kozak)TFPI。采用阳离子脂质体和腔内加压灌注法，转染移植静脉内皮细胞。RT-PCR、Western blotting和免疫组化法检测外源基因在兔移植静脉中的表达。病理标本、扫描电镜观察移植静脉血栓形成情况，血管多普勒观测其通畅率。结果：移植静脉中有人TFPI基因和蛋白表达。静脉移植术后3 d，基因转染组、空载体和空白对照组分别有1条、8条和7条移植静脉发生血栓，术后30 d，以上各组分别有0条、5条和5条移植静脉完全闭塞，前者静脉血栓发生率和闭塞率均低于后两者(P<0.05)。扫描电镜显示两对照组内皮表面有红细胞和血小板黏附、聚集，而转染组基本正常。结论：人TFPI基因干预，减少了兔移植静脉血栓形成，提高了近期通畅率。     

儿童过敏性紫癜不同时期凝血功能状态检测及分析

目的　研究儿童过敏性紫癜 (HSP)发作期及缓解期凝血状态的改变情况及其机制。方法　 2 0 0 1～2 0 0 3年深圳市儿童医院收治的HSP患儿共 6 0例 ,根据发病期和缓解期的不同 ,相应分为HSP发作组 (30例 )和HSP缓解组 (30例 ) ,检测凝血酶原时间比 (PTR)、血浆D 二聚体 (D dimer)及组织因子途径抑制物 (TFPI)水平 ,并与对照组 35例健康体检儿童比较。结果　两组HSP患儿的PTR与对照组比较差异无显著性 (均P >0 0 5 ) ;HSP发作组血浆D dimer明显升高 (P <0 0 5 ) ,而HSP缓解组血浆D dimer浓度下降 ,与对照组差异无显著性(P >0 0 5 ) ;HSP发作组血浆TFPI含量高于对照组 (P <0 0 5 ) ,HSP缓解组降至正常水平 ,和对照组比较差异无显著性 (P >0 0 5 )。结论　HSP患儿发作期凝血解溶状态处于高活动状态 ,随着病情进入缓解期高凝状态可恢复正常 ;TFPI在HSP患儿发作期可能具有防止血管内凝血活动过度和扩散的重要作用。     

The V264M polymorphism of tissue factor pathway inhibitor gene in patients with acute coronary syndrome

Objective： To investigate V264M polymorphism of tissue factor pathway inhibitor （TFPI） in patients with acute coronary syndrome （ACS） in Chinese. Methods ： The genotypes of V264M were detected by polymerase chain reaction （PCR） and restriction fragment length polymorphism （PCR-RFLP） in 136 patients with ACS and 106 healthy controls with their plasmal f-TFPI tested by enzyme linked immunosorbent assay （ELISA）. Results： Two genotypes were found in V264M： GG and GA. The distribution frequencies of alleles and genotypes were in accordance with those predicted by Hardy Weinberg equilibrium in the present study （χ2 = 0.437, P 〉 0.05）. Plasma f-TFPI level was lower in A allele bearer than that in non-A allele carriers and higher in ACS than control subjects （P〈0.05）. No relationship was found between ACS and V264M polymorphism （P〉0.05）. Conclusion： The V264M polymorphism may have an impact on the plasma level of free TFPI（f-TFPI）, but it has no relationship with ACS.     

Increased tissue factor pathway inhibitor activity is associated with myocardial infarction in young women: results from the RATIO study

Summary. Background: The tissue factor pathway inhibitor (TFPI)/protein S anticoagulant system is a potent inhibitor of blood coagulation. TFPI and protein S are major determinants of thrombin generation (TG) tests determined at low tissue factor (TF) and at high TF concentrations in the presence of activated protein C (APC). Both TFPI and protein S protect against venous thrombosis, but the importance of the TFPI/protein S system in arterial thrombosis remains unclear. Objectives: To investigate the influence of the TFPI/protein S anticoagulant system on the risk of myocardial infarction (MI) in young women. Methods: The RATIO study is a case–control study in women under 50 years of age, including 205 patients and 638 controls. TFPI and protein S were quantified using ELISA. The TFPI/protein S activity (nTFPIr) and the APC sensitivity ratio (nAPCsr) were determined using TG tests. Odds ratios (ORs) adjusted for putative confounders and corresponding 95% confidence intervals (95% CI) were determined. Results: Women with MI had higher TFPI levels than controls (135.9 ± 40% vs. 124.2 ± 41%), resulting in increased TFPI/protein S activities and increased APC sensitivity. Furthermore, an increased TFPI activity was associated with MI [nTFPIr: adjusted OR Q1 vs. Q4 = 2.1 (95%CI 1.1–4.1)]. Additionally, an increased APC sensitivity was associated with MI [nAPCsr: adjusted OR Q1 vs. Q4 = 1.7 (95% CI 0.9–3.2)] Conclusion: Women with MI had increased TFPI levels compared with controls. Consequently, the TFPI/protein S activity and APC sensitivity are increased in women with MI. Whether this increase in TFPI activity acts as a compensating mechanism for an increased procoagulant state or is a marker of endothelial damage remains to be investigated.     

Anti-tissue factor pathway inhibitor activity in patients with primary antiphospholipid syndrome

The association between antiphospholipid antibodies and an increased risk of thrombosis in antiphospholipid syndrome (aPS) patients is probably caused by numerous mechanisms, including the effects of antibodies to phospholipid-binding proteins such as beta(2)-glycoprotein I and prothrombin. In this study, we investigated the inhibition of tissue factor pathway inhibitor (TFPI) in 33 patients with primary antiphospholipid syndrome (PAPS). TFPI was measured in PAPS patients using an amidolytic assay, dependent on the generation of activated factor X (Fxa), and this was compared with 55 healthy subjects. Functional levels of TFPI (mean +/- SD) were significantly lower in PAPS patients (0.89 +/- 0.37 U/ml) than the control group (1.05 +/- 0.15 U/ml) (P = 0.02). The difference was caused by a subset of five patients who had TFPI levels below the lower 99% confidence interval of the normal reference range, representing increased FXa generation in the assay system. IgG fractions were isolated from these five patients and five control subjects, then incorporated into normal plasma to measure FXa generation in the TFPI assay system. FXa generation was increased when polyclonal rabbit anti-human TFPI IgG (P < 0.0001) or PAPS IgG (P = 0.0001) were added to normal plasma, demonstrating inhibition of TFPI. The apparent anti-TFPI activity demonstrated in the five subjects with PAPS in this study may represent a significant new mechanism for thrombosis in patients with aPS, as it implies that increased tissue factor FVIIa-mediated thrombin generation might occur.     

Hypermethylation of TFPI2 correlates with cervical cancer incidence in the Uygur and Han populations of Xinjiang,China

Tissue factor pathway inhibitor 2 (TFPI2) is a Kunitz-type serine proteinase inhibitor, which plays an important role in the etiology of human malignancies. DNA methylation is a common epigenetic modification of the genome that is involved in regulating many cellular processes. In addition to human papilloma virus (HPV) infection, DNA methylation may play a role in the carcinogenesis of cervical cancer. Methylation of 22 CpG sites in the promoter region of the TFPI2 gene was detected by MassARRAY spectrometry and a gene mass spectrogram was drawn using MALDI-TOF MS. HPV16 was detected by PCR. We show that aberrant methylation of TFPI2 is present in a higher proportion of invasive cervical carcinoma (ICC) clinical samples as compared to normal cervical samples in Uygur and Han. Across the four pathologic lesions of the progression of cervical cancer, ICC showed the highest level of aberrant methylation, and with a stronger correlation between CpG site and lesion grade in Uygur than in Han. Moreover, a difference in TFPI2 methylation between Uygur patients positive and negative for HPV16 infection was observed at CpG_6 (P = 0.028) and CpG_15 (P = 0.007). Altogether, these results indicate that DNA methylation of TFPI2 may play an important role in the carcinogenesis of cervical cancer and that the differential methylation of TFPI2 may at least partially explain the disparity in cervical cancer incidence between Uygur and Han women.     

Target-mediated clearance and bio-distribution of a monoclonal antibody against the Kunitz–type protease inhibitor 2 domain of Tissue Factor Pathway Inhibitor

Introduction

A humanised monoclonal antibody, concizumab, that binds with high affinity to the Kunitz-type protease inhibitor (KPI) 2 domain of human tissue factor pathway inhibitor (TFPI) is in clinical development. It promotes coagulation by neutralising the inhibitory function of TFPI and may provide a subcutaneous prophylaxis option for patients with haemophilia. We aimed to study biodistribution and pharmacokinetics (PK) of concizumab.

Materials and Methods

Blockage of cellular TFPI by concizumab was measured by tissue factor/Factor VIIa-mediated Factor X activation on human EA.hy926 cells. Biodistribution of concizumab was analysed in rabbits by immunohistology, and the PK was measured in rabbits and rats.

Results and Conclusions

Concizumab bound to cell surface TFPI on EA.hy926 cells and neutralised TFPI inhibition of Factor X activation. The antibody cross-reacted with rabbit TFPI, but not with rat TFPI, allowing for comparative PK studies. PK data in rats described a log-linear profile typical for a non-binding antibody, whereas PK data in rabbits revealed a non-linear, dose-dependent profile, consistent with a target-mediated clearance mechanism. Immunohistology in rabbits during target-saturation showed localisation of the antibody on the endothelium of the microvasculature in several organs. We observed a marked co-localisation with endogenous rabbit TFPI, but a negligible sub-endothelial build-up. Concizumab binds and neutralises the inhibitory effect of cell surface-bound TFPI. The PK profile observed in rabbits is consistent with a TFPI-mediated drug disposition. Double immunofluorescence shows co-localisation of the antibody with TFPI on the endothelium of the microvasculature and points to this TFPI as a putative target involved in the clearance mechanism.     

Measurement of thrombin generation intra-operatively and its association with bleeding tendency after cardiac surgery

Introduction

Patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) are susceptible to haemostatic disturbances. Monitoring the haemostatic capacity by conventional clotting tests is challenging.

Materials and Methods

Thrombin generation (TG) by Calibrated Automated Thrombography, clotting tests and tissue factor pathway inhibitor (TFPI) measurements were performed to describe the relationship between haemostatic changes and alterations in these tests. Blood samples were collected before, during and after CPB. Furthermore, it was investigated whether TG measured intraoperatively, is associated with increased risk of bleeding postoperatively.

Results

TG diminished significantly (p < 0.01) after heparinization in the presence and absence of platelets (37% and 50%) compared to baseline. After the start of CPB, TG elevated and persisted till the end of surgery but remained lower than preoperatively. Activated clotting time increased after heparinization and after the start of bypass compared to baseline (400% and 500%). Anti-FXa activity reduced on the start of CPB compared to the level after heparinization, to almost the baseline value following protamine reversal of heparin. The plasma levels of total and free TFPI elevated 9 and 14 fold during bypass and remained after protamine administration higher than preoperatively. Plasma D-dimer levels reduced (p < 0.01) when bypass started. However, a marked elevation was observed in the following time points. TG in platelet-rich plasma measured after heparinization and after the start of CPB associated (p < 0.05) with postoperative blood loss.

Conclusions

TG can be determined during CPB despite the high heparinization level, it reflects the haemostatic capacity better than clotting-based assays and might better predict bleeding when performed intraoperatively.     

Tamoxifen induces resistance to activated protein C

Introduction

The estrogen antagonist tamoxifen (TAM) increases the thrombotic risk similar to estrogen containing oral contraceptives (OC). In OC users this risk is attributed to alterations of hemostasis resulting in acquired resistance to activated protein C (APC). TAM-induced APC resistance has not been reported yet.

Materials and Methods

Blood samples were collected prospectively from women with breast cancer before (n = 25) and monthly after start of adjuvant TAM treatment (n = 75). APC resistance was evaluated on basis of the effect of APC on the endogenous thrombin generation potential. To detect increased in vivo APC generation APC plasma levels were measured using a highly sensitive oligonucleotide-based enzyme capture assay. Routine hemostasis parameters were measured additionally.

Results

APC sensitivity decreased by 41% (p = 0.001) compared to baseline after one month of TAM application and remained significantly decreased during the study period. Free protein S increased (p = 0.008) while other analyzed procoagulant factors, inhibitors, and activation markers of coagulation decreased or did not change significantly. In five patients the APC concentration increased to non-physiological levels but an overall significant increase of APC was not observed.

Conclusions

This is the first study showing acquired APC resistance under TAM therapy. Acquired APC resistance might explain the increased thrombotic risk during TAM treatment. Observed changes of hemostasis parameters suggest different determinants of TAM-induced APC resistance than in OC-induced APC resistance. The presence of acquired APC resistance in TAM patients warrants further evaluation if these patients may benefit from antithrombotic prophylaxis in the presence of additional thrombotic risk factors.     

Tissue factor pathway inhibitor and thrombin-activatable carboxypeptidase B for prediction of early atherosclerosis in gouty arthritis

Background

Gouty arthritis (GA) is a chronic inflammatory arthritis in which both clinical and subclinical atherosclerosis are more frequent. The dynamic equilibrium between coagulation and fibrinolysis is impaired in inflammatory diseases. We determined TFPI and TAFI antigen levels in GA patients and evaluated their association with subclinical atherosclerosis.

Methods

We included 45 GA patients (41 males, 4 females; mean age: 51.6 years) and 25 asymptomatic hyperuricemic (AHU) subjects (19 males, 6 females; mean age: 48.1 years). Cardiovascular risk factors were determined. TAFI and TFPI levels were determined by ELISA. B-mode ultrasonography was used to detect subclinical atherosclerosis.

Results

Cardiovascular risk factors were similar in both groups. The carotid IMT was significantly higher in GA group than in AHU group (0.74 ± 0.23 mm vs. 0.61 ± 0.13 mm, p = 0.009). TFPI level was significantly higher in GA group than in AHU group (86.2 ± 48.9 ng/mL vs. 25.8 ± 21.4 ng/mL, p < 0.001); TAFI antigen was significantly higher in AHU group (22.6 ± 3.6 ng/mL vs. 25.7 ± 5.3 ng/mL, p = 0.006) than in GA patients. Atherosclerotic plaque formation was more frequent in GA group (p = 0.041). When GA patients with and without plaques were compared, the first group had significantly higher mean age (p = 0.01) and TFPI level (p = 0.028). TFPI level correlated with carotid IMT (r = 0.302; p = 0.028). Logistic regression analysis showed that age (OR: 1.236, 95%CI: 1.059-1.443, p = 0.007) and TFPI (OR: 1.031, 95%CI: 1.008-1.054, p = 0.008) were independent risk factors for the presence of plaques.

Conclusions

GA patients had more frequent subclinical atherosclerosis than subjects with AHU. Higher TFPI levels in GA patients –probably associated with enhanced endothelial damage- were related to subclinical atherosclerosis. Lower TAFI levels in GA pointed to impaired fibrinolysis.