The annexin A5 protective shield model revisited: inherited carriage of the M2/ANXA5 haplotype in placenta as a predisposing factor for the development of obstetric antiphospholipid antibodies

Research progress on ANXA5 in recurrent pregnancy loss

The incidence of recurrent pregnancy loss (RPL) in fertile women ranges from 1% to 5%, of which about 50% of them are due to unknown causes. The possible pathogenesis of RPL is an urgent problem to be solved in the clinical. Mutations or polymorphisms of certain genes in the coagulation mechanism are associated with susceptibility to thrombotic diseases and are one of the main reasons for the occurrence of RPL. Among them, the ANXA5 gene was newly studied and some single nucleotide polymorphisms (SNPs) in the promoter region of ANXA5 have been reported to be associated with RPL in multiple races. In this review, we summarized the research progress on the correlation between the SNPs in ANXA5 and RPL, hoping to provide some valuable guidance for the future studies.

Maternal and paternal carriage of the annexin A5 M2 haplotype: a possible risk factor for recurrent implantation failure (RIF)

OBJECTIVE

This study was carried out to determine the potential role of the M2/ANXA5 haplotype as a risk factor for recurrent implantation failure (RIF). Carriage of the M2/ANXA5 haplotype that induces prothrombotic changes has been implicated in failure of early pregnancies and placenta-mediated complications (preeclampsia, IUGR, preterm birth).

MATERIAL AND METHODS

In the present case control study, 63 couples (females and males) with RIF presenting for IVF/ICSI to the Fertility Center of [masked] were analyzed. RIF was defined as ≥ 4 consecutive failed ART-transfers of ≥ 4 blastocysts or ≥ 8 cleavage-stage embryos of optimal quality and maternal age ≤ 41. Fertile female controls (n = 90) were recruited from the same center. Population controls (n = 533) were drafted from the PopGen biobank, UKSH Kiel.

RESULTS

Couples carrying the M2/ANXA5 haplotype turned out to have a significantly increased relative risk (RR) for RIF. Compared with female fertile controls, RR was 1.81 with p = 0.037 (OR 2.1, 95%CI 1.0-4.3) and RR was 1.70, with p = 0.004 (OR 2.0, 95%CI 1.2-3.1) compared with population controls (15.4% M2 carriers). Male partners were comparable with RIF females for M2/ANXA5 haplotypes (28.6% vs. 23.8%, p = 0.54). RIF females compared with population controls had a RR of 1.55 (p = 0.09) and RIF males compared with population controls had a RR of 1.9 (p = 0.01). Couples with ≥ 7 failed transfers showed a RR of 1.82 (p = 0.02) compared with population controls.

CONCLUSION

Our findings suggest that maternal as well as paternal M2/ANXA5 haplotype carriages are risk factors for RIF. These results allow new insights into the pathogenesis of RIF and might help to identify relevant risk groups.

Association between M2/ANXA5 haplotype and repeated pregnancy loss: a meta-analysis

OBJECTIVE

To ascertain the magnitude and precision of the association between M2/ANXA5 haplotype and repeated pregnancy loss (RPL).

DESIGN

Meta-analysis of odds ratios.

SETTING

Not applicable.

PATIENT(S)

Subjects were women with RPL and their partners.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

The association between M2/ANXA5 haplotype and RPL was evaluated in a meta-analysis of odds ratios. We further scrutinized this association according to [1] the sequence of miscarriages, [2] the number of consecutive losses, [3] the extent of excluding other pathologies of RPL, and [4] the timing of fetal loss.

RESULT(S)

Fourteen individual studies (n = 4,664 subjects) were included in this meta-analysis. The results show that women with the M2/ANXA5 haplotype have 1.54 times (95% confidence interval, 1.08-2.20) the odds of having associated RPL compared with women with the normal haplotype, regardless of consecutive or nonconsecutive pregnancy losses. Acknowledging the clinical heterogeneity among the studies, this significant association comes with a caveat that the lower bound of the confidence interval is close to unity. In couple populations (n = 2,449), M2/ANXA5 haplotype subjects have an odds ratio of 1.48 (95% confidence interval, 1.14-1.91) of experiencing RPL, which suggests contributions from paternal M2/ANXA5 carriers in RPL.

CONCLUSION(S)

This meta-analysis ascertains that women with the M2/ANXA5 haplotype have a higher risk of experiencing RPL, especially consecutive early idiopathic RPL. Male partners with the M2/ANXA5 haplotype partly contribute to this risk. Hence, screening for the M2/ANXA5 haplotype as a panel of laboratory investigations for RPL is recommended.

Investigation of the Annexin A5 M2 haplotype in 500 white European couples who have experienced recurrent spontaneous abortion

Annexin A5 is a placental anti-coagulant protein that contains four nucleotide substitutions (M2 haplotype) in its promoter. This haplotype is a risk factor for recurrent spontaneous abortion (RSA). The influence of the M2 haplotype in the gestational timing of spontaneous abortions, paternal risk and relationships with known risk factors were investigated. European couples (n = 500) who had experienced three or more consecutive spontaneous abortions, and two fertile control groups, were selected for this study. The allele frequency of M2 was significantly higher among patients who had experienced early RSA than among controls (P = 0.002). No difference was found between controls and patients who had undergone late spontaneous abortions. No difference was found between patients who had experienced RSA who had a live birth or no live births, or between patients who were positive or negative for known risk factors. Male and female partners in each group had similar allele frequencies of M2. The M2 haplotype is a risk factor for early spontaneous abortions, before the 12th week of gestation, and confers about the same relative risk to carriers of both sexes. Having one or more M2 allele(s) in combination with other risk factors further increases the RSA risk.

Multicentre study of the clinical relevance of screening IVF patients for carrier status of the annexin A5 M2 haplotype

Thrombophilia and impaired placental vasculature are a major cause of adverse pregnancy outcome. In 2007, a new hereditary factor for obstetric complications and recurrent pregnancy loss (RPL) was identified as a sequence variation in the core promoter of the annexin A5 gene, ANXA5, called the M2 haplotype. M2 carriership has been demonstrated in couples with recurrent miscarriage and its origin is embryonic rather than specifically maternal, confirmed by subsequent papers. The M2 haplotype is the first report of a hereditary factor related to pregnancy pathology caused by embryonic-induced anticoagulation. It has been demonstrated that couples with RPL had equal and significantly increased M2 carriership and that maternal and paternal carriership confers equal risk. Given its importance for patients with RPL, and potentially implantation failure, this study assessed the incidence of carrier status for the M2 ANXA5 haplotype in both the male and female of couples attending five CARE IVF centres. In 314 patients (157 couples), 44% of couples (one or both partners), 24% of females, 26% of males and 37% of couples with unexplained infertility were M2 carriers. This high incidence has provoked further urgent studies on specific patient populations and on the value of post embryo-transfer therapy.

Further insights into the role of the annexin A5 M2 haplotype as recurrent pregnancy loss factor, assessing timing of miscarriage and partner risk

OBJECTIVE

To study the influence of M2/ANXA5 for recurrent pregnancy loss (RPL), according to the timing of miscarriages and assess the male partner risk.

DESIGN

Genetic association study.

SETTING

Academic research center.

PATIENT(S)

Female patients from two academic centers in Germany and Bulgaria with two or more unexplained miscarriages were selected for this study. Male partners were available for a part of the German sample. Population controls were recruited from healthy individuals of respective populations.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Incidence of M2 carriage and odds ratios were calculated between patient and control groups, and RPL risk was evaluated.

RESULT(S)

The M2 haplotype in ANXA5 was associated with greater overall RPL risk in German and in Bulgarian women, and a trend of higher prevalence was seen for male partners of German RPL patients. The highest relative risk of M2 carriage was observed in women of both populations with "early" fetal losses between the 10th and 15th gestational weeks, which was significant in the meta-analysis.

CONCLUSION(S)

M2 carriage seems to have an RPL risk role mostly for early abortions, gestational weeks 10-15. In the first phase of pregnancy this correlates with vascular remodeling to accomplish the transition from high- to low-resistance blood vessels.

The haplotype M2 of the ANXA5 gene is not associated with antitrophoblast antibodies

PURPOSE

The M2 haplotype in ANXA5 as well as antitrophoblast antibodies predispose to recurrent pregnancy loss (RPL). Since M2/ANXA5 can be a factor for development of antiphospholipid antibodies (aPL), this study aimed to trace a possible association of M2 with antitrophoblast antibodies.

METHODS

One hundred patients with two or more consecutive, idiopathic RPLs were divided in two subgroups, JEG-3(+) (n = 42) and JEG-3(-) (n = 58), according to the anti-JEG-3 reactivity measured in subjects' sera. Both subgroups were genotyped for ANXA5 promoter haplotypes and genetic frequencies were compared to available fertile and control populations, as well as within the subgroups.

RESULTS

M2/ANXA5 was generally enriched in the JEG-3 screened cohort of RPL patients in comparison to fertile and population controls. Despite the relatively higher abundance of the haplotype in the JEG-3(-) sample as compared to JEG-3(+) patients and in the JEG-3(-) primary RPL subset in particular, compared to the rest of patients, there was no statistically significant difference between both, JEG-3(-) and JEG-3(+) subgroups.

CONCLUSION

It appears that the haplotype M2/ANXA5 is not associated with the presence of anti-trophoblast antibodies. Our finding indicates that anti-trophoblast antibodies are a class of molecules that differ from aPL and from anti-b2-GPI antibodies, apparently not directed to same or similar epitopes that aPL and anti-b2-GPI would recognize.