ORIGINAL ARTICLE: Decreased Factor XII Activity is Associated with Recurrent IVF-ET Failure

Antibody inhibition of contact factor XII reduces platelet deposition in a model of extracorporeal membrane oxygenator perfusion in nonhuman primates

BACKGROUND

The contact factor XII (FXII) activates upon contact with a variety of charged surfaces. Activated FXII (FXIIa) activates factor XI, which activates factor IX, resulting in thrombin generation, platelet activation, and fibrin formation. In both in vitro and in vivo rabbit models, components of medical devices, including extracorporeal oxygenators, are known to incite fibrin formation in a FXII-dependent manner. Since FXII has no known role in hemostasis and its inhibition is therefore likely a safe antithrombotic approach, we investigated whether FXII inhibition also reduces accumulation of platelets in extracorporeal oxygenators.

OBJECTIVES

We aimed to determine the effect of FXII inhibition on platelet deposition in perfused extracorporeal membrane oxygenators in nonhuman primates.

METHODS

A potent FXII neutralizing monoclonal antibody, 5C12, was administered intravenously to block contact activation in baboons. Extracorporeal membrane oxygenators were temporarily deployed into chronic arteriovenous access shunts. Radiolabeled platelet deposition in oxygenators was quantified in real time using gamma camera imaging. Biochemical assays were performed to characterize the method of action of 5C12.

RESULTS

The anti-FXII monoclonal antibody 5C12 recognized both the alpha and beta forms of human and baboon FXII by binding to the protease-containing domain, and inhibited FXIIa activity. Administration of 5C12 to baboons reduced platelet deposition and fibrin formation in the extracorporeal membrane oxygenators, in both the presence and absence of systemic low-dose unfractionated heparin. The antiplatelet dose of 5C12 did not cause measurable increases in template bleeding times in baboons.

CONCLUSIONS

FXII represents a possible therapeutic and safe target for reducing platelet deposition and fibrin formation during medical interventions including extracorporeal membrane oxygenation.

Uneventful delivery of two pregnancies in a woman with severe factor XII deficiency: case report and systematic review

Background

Deficiency of factor XII (FXII) is widely considered to have a detrimental effect on pregnancy. Several reports underline the increased risk for antenatal complications with few published case reports of uncomplicated deliveries. The main objective of our article is to perform a systematic review to highlight pregnancies with severe deficiency of FXII that have been delivered uneventfully, along with presenting our relative case of a woman with severe deficiency of FXII.

Materials and methods

A systematic review was performed in the Pubmed database. Inclusion criteria were considered to be case reports and case series presenting delivery of uncomplicated pregnancies in women with severe FXII deficiency. Medical records of our patient were also reviewed in terms of signs and symptoms, laboratory and imaging examinations and neonatal outcomes.

Results

There were 62 abstracts derived while 44 were assessed for eligibility. There were finally three case reports of women with FXII deficiency delivering live newborns and one case series of 12 women with a final outcome of 19 deliveries. Regarding our case presentation, the woman with FXII levels <12%, after a neonatal death because of extreme prematurity (24 weeks + 4 days), was set in regular follow-up and treatment with bemiparin natriate, 3.5 mg/kg and acetylsalicylic acid, 100 mg/day. She finally managed to have her second pregnancy delivered at 38 weeks + 3 days, her third pregnancy ended up as a miscarriage and her fourth pregnancy was also delivered at 37 weeks + 4 days.

Conclusion

Despite the increased risk for antenatal complications, appropriate follow-up of pregnancies with severe FXII pregnancy may finally lead to an uneventful delivery.

Factor XII (Hageman) levels in women with recurrent pregnancy loss

Objective. To evaluate factor XII levels in women with recurrent pregnancy loss (RPL) in a tertiary referral hospital. Methods. Women who were referred to our hospital for two consecutive abortions or three abortions in between 2007 and 2013 were included in this retrospective observational study. Women were further grouped according to factor XII levels, as <60% and ≥60%. Results. Mean factor XII level was 109.1 ± 35.7% (range: 9–200). Ninety-three (7.4%) women had factor XII levels < 60%. Mean factor XII level was 44.8 ± 13.1, and levels ranged between 9 and 60 in this group. Only one woman had factor XII level < 10 %. Remaining 1164 (92.6%) women had factor XII levels ≥ 60%. Mean factor XII level was 114.3 ± 31.7, and levels ranged between 60.3 and 200 in this group, while 1015 (72.4%) women had factor XII levels within the normal range (60%–150% [100% = 30 μg/mL]). Conclusion. Decreased activity of F-XII was diagnosed in 7.4% of women with RPL. We concluded factor XII deficiency that might be a rare but significant factor for RPL, and should be evaluated in women who are investigated for recurrent pregnancy loss.

Bibliography. Current world literature

This bibliography is compiled by clinicians from the journals listed at the end of this publication. It is based on literature entered into our database between 1 February 2008 and 31 January 2009 (articles are generally added to the database about two and a half months after publication). In addition, the bibliography contains every paper annotated by reviewers; these references were obtained from a variety of bibliographic databases and published between the beginning of the review period and the time of going to press. The bibliography has been grouped into topics that relate to the reviews in this issue.

Autoantibodies and coagulation in reproductive medicine

Management of recurrent pregnancy loss (RPL) is considered to be difficult, in part because of cunfusion between autoantibodies and coagulation disorders. Autoantibodies and coagulation are related; two groups of multicenter studies concerning autoantibodies and coagulation reported that factor XII deficiency, hypofibrinolysis, anti-phosphatidylethanolamine (aPE), anti-beta2-glycoprotein I, anti-annexin A5, and lupus anticoagulant (LA) were found to be frequent risk factors in RPL women. Therefore, discrimination of autoantibodies and coagulation is important in understanding RPL well. We propose three types of pathways regarding reproduction, which are different and independent: (1) Negatively charged-phospholipid related antibodies (anti-phosphatidylserine; aPS, anti-cardiolipin; aCL, lupus anticoagulant; LA, anti-annexin A5; aANX), (2) factor XII-aPE-fibrinolysis: suppression of fibrinolysis, (3) protein C-protein S-factor V: loss of inactivation against activated factor V. Women with RPL and infertility showed similar findings in terms of the above clinical tests. Available data, however, is not enough to conclude whether these are pathogenic to infertile women.

Factor XII gene expression in endometrial stromal cells during decidualisation

Decidualisation of endometrial stromal cells (ESC) is a prerequisite for the implantation of human embryos. Identification of genes that are upregulated or downregulated during decidualisation could lead to a better understanding of the molecular mechanisms involved in this process. In the present study, we examined differences in gene expression between decidualised and non-decidualised cells using microarray analysis and found that Factor XII (FXII) gene expression was upregulated during decidualisation. Furthermore, we also examined the expression of FXII by human ESC before and during pregnancy, as well as its expression by cells that had undergone decidualisation in vitro. Weak expression of FXII mRNA was detected in the non-pregnant endometrium that increased gradually from the proliferative to the secretory endometrium. During pregnancy, FXII mRNA expression was markedly increased in decidualised endometrium. When sex steroids (200 pg mL–1 of 17β-oestradiol and 100 ng mL–1 of progesterone) were used to induce in vitro decidualisation of ESC, the expression of FXII mRNA increased by approximately 25.3-fold compared with that in non-decidualised ESC. Using western blotting, we confirmed the presence of FXII protein (80 kDa) in ESC after in vitro decidualisation. Increased expression of FXII in ESC during decidualisation suggests that the kallikrein–kininogen–kinin system may be activated during the implantation of human embryos.