Immunohistochemical expression of Annexin A5 in preeclamptic placentas

Annexin A1, A2, A5, and A6 involvement in human pathologies

The human genome codes for 12 annexins with highly homologous membrane-binding cores and unique amino termini, which endow each protein with its specific biological properties. Not unique to vertebrate biology, multiple annexin orthologs are present in almost all eukaryotes. Their ability to combine either dynamically or constitutively with membrane lipid bilayers is hypothetically the key property that has led to their retention and multiple adaptation in eukaryotic molecular cell biology. Annexin genes are differentially expressed in many cell types but their disparate functions are still being discovered after more than 40 years of international research. A picture is emerging from gene knock down and knock out studies of individual annexins that these are important supporters rather than critical players in organism development and normal cell and tissue function. However, they appear to be highly significant "early responders" toward challenges arising from cell and tissue abiotic or biotic stress. In humans, recent focus has been on involvement of the annexin family for its involvement in diverse pathologies, especially cancer. From what has become an exceedingly broad field of investigation, we have selected four annexins in particular: AnxA1, 2, 5, and 6. Present both within and external to cells, these annexins are currently under intensive investigation in translational research as biomarkers of cellular dysfunction and as potential therapeutic targets for inflammatory conditions, neoplasia, and tissue repair. Annexin expression and release in response to biotic stress appears to be a balancing act. Under- or over-expression in different circumstances appears to damage rather than restore a healthy homeostasis. This review reflects briefly on what is already known of the structures and molecular cell biology of these selected annexins and considers their actual and potential roles in human health and disease.

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.

Clinicopathological study and immunohistochemical analysis of expression of annexin A5 and apelin in human placentae of gestational diabetes mellitus

BACKGROUND AND AIMS

Gestational diabetes mellitus (GDM) is one of the commonest medical complications of pregnancy. Annexin A5 (ANXA5) is a protein, found in apical surfaces of syncytiotrophoblasts, which prevents fetal and placental vascular thrombosis in GDM. Apelin is a bioactive peptide which has been linked to GDM. The aim of the present study was to correlate macroscopic as well as microscopic changes and immunohistochemical expression of ANXA5 and apelin in placentae of GDM with maternal and neonatal clinical features and also to compare the results with those in matched controls.

METHODS

This prospective observational study was undertaken for a period of one year from April 2020 to March 2021. It comprised of 42 patients of GDM. Gross features, microscopic features and intensity and grade of expression of ANXA5 and Apelin were analyzed in placentae of GDM.

RESULTS

Morphological changes detected in GDM placentae included increased immature villi (16 cases, 38%), increased syncytial knots (36, 86%), perivillous fibrin deposition (20, 48%), fibrosis of villous stroma (20, 48%), presence of nucleated red blood cells (12, 28.5%) and hypervascularity (34, 81%). The extent of histopathological changes noted in GDM placentae was significantly higher than that in matched controls. GDM placentae showed significantly reduced expression of ANXA5 and Apelin in terms of grade and intensity when compared with matched controls. Reduced expression (mild intensity) of ANXA5 was noted in 22 GDM cases (52.3%) whereas apelin expression was of weak intensity in 26 (61.9%) cases. Among GDM patients, statistically significant association was noted between ANXA5 intensity and neonatal resuscitation, apelin grade and preterm birth as well as low birth weight and apelin intensity and requirement of treatment in sick neonatal care unit.

CONCLUSION

The placental expression of the proteins, ANXA5 and Apelin, is altered in GDM though their exact pathogenetic mechanisms are yet to be understood. They can be targets for development of prophylactic and therapeutic agents in future.

Unveiling molecular signatures of preeclampsia and gestational diabetes mellitus with multi-omics and innovative cheminformatics visualization tools

To fully enable the development of diagnostic tools and progressive pharmaceutical drugs, it is imperative to understand the molecular changes occurring before and during disease onset and progression. Systems biology assessments utilizing multi-omic analyses (e.g. the combination of proteomics, lipidomics, genomics, etc.) have shown enormous value in determining molecules prevalent in diseases and their associated mechanisms. Herein, we utilized multi-omic evaluations, multi-dimensional analysis methods, and new cheminformatics-based visualization tools to provide an in depth understanding of the molecular changes taking place in preeclampsia (PRE) and gestational diabetes mellitus (GDM) patients. Since PRE and GDM are two prevalent pregnancy complications that result in adverse health effects for both the mother and fetus during pregnancy and later in life, a better understanding of each is essential. The multi-omic evaluations performed here provide new insight into the end-stage molecular profiles of each disease, thereby supplying information potentially crucial for earlier diagnosis and treatments.

Reduced ANXA5 mRNA and protein expression in pregnancies complicated by preeclampsia

INTRODUCTION

The placental anticoagulant protein Annexin A5 (ANXA5) is a multifunctional protein that is highly expressed on the apical surfaces of syncytiotrophoblasts, and plays an important role in haemostatic regulations, maintaining blood fluidity of the placenta. The aim of this study was to investigate the expression of ANXA5 in pregnancies complicated by preeclampsia (PE).

MATERIALS AND METHODS

Placental tissue samples were collected from 23 pregnancies with PE and 34 normal pregnancies. ANXA5 mRNA levels were measured by quantitative Real-Time PCR (qPCR), while ANXA5 protein expression was measured by Western Blot (WB) and immunohistochemistry.

RESULTS

ANXA5 mRNA expression in PE samples was lower than 1% of its expression in normal samples (mean ± SD: 0.002 ± 0.004 vs. 0.55 ± 0.38, p < 0.001), while ANXA5 protein levels in PE samples were approximately at 65% of the average normal expression (mean ± SD: 0.53 ± 0.30 vs. 0.81 ± 0.25, p=0.001). Immunohistochemical analysis also verified the above results, since PE placentas tended to have low labelling indexes (LIs), in contrast to controls which demonstrated high LIs (p=0.020). Statistical analysis of the WB data revealed that ANXA5 protein expression was increased in PE smokers vs. PE non-smokers (mean ± SD: 0.64 ± 0.23 vs. 0.41 ± 0.33, p=0.027).

CONCLUSIONS

These results suggest that ANXA5 downregulation could be part of the pathophysiology of PE and the possible impairment in coagulation processes, which are seen in pregnancies that demonstrate PE. Further studies may investigate whether ANXA5 could be used as a biomarker for the early detection of PE and for the prediction of its severity.

Effects of embryo culture media do not persist after implantation: a histological study in mice

STUDY QUESTION

Is post-implantation embryonic development after blastocyst transfer affected by exposure to different assisted reproduction technology (ART) culture media?

SUMMARY ANSWER

Fetal development and placental histology of ART embryos cultured in vitro in different ART media was not impaired compared with embryos grown in vivo.

WHAT IS KNOWN ALREADY

The application of different in vitro culture (IVC) media for human ART has an effect on birthweight of newborns. In the mouse model, differences in blastocyst formation were reported after culture in different ART media. Moreover, abnormalities in the liver and heart have been detected as a result of suboptimal IVC conditions.

STUDY DESIGN, SIZE, DURATION

Fertilized oocytes from inbred and outbred breeding schemes were retrieved and either immediately transferred to foster mothers or incubated in control or human ART culture media up to the blastocyst stage prior to transfer. Placental and fetal anatomy and particularly bone development were evaluated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

B6C3F1 female mice were used as oocyte donors after ovulation induction. C57Bl/6 and CD1 males were used for mating and CD1 females as foster mothers for embryo transfer. Fertilized oocytes were recovered from mated females and incubated in sequential human ART media (ISM1/ISM2 and HTF/Multiblast), in control media [KSOM(aa) and Whitten's medium] or grown in utero without IVC (zygote control). As in vivo, control B6C3F1 females were superovulated and left untreated. Fetuses and placentae were isolated by Caesarean section and analysed at 18.5 days post-coitum (dpc) for placenta composition and at 15.5 dpc for body weight, crown-rump length (CRL), fetal organ development, morphological development, total bone length and extent of bone ossification.

MAIN RESULTS AND THE ROLE OF CHANCE

No major differences in the number of implantation sites or in histological appearance of the placentae were detected. CRL of KSOM(aa) fetuses was higher compared with zygote control and Whitten's medium. Histological analysis of tissue sections revealed no gross morphological differences compared with the in vitro groups or in vivo controls. Furthermore, no changes in skeletal development and degree of ossification were observed. However, fibula and tibia of ISM1/ISM2 fetuses were longer than the respective ones from in vivo fetuses.

LIMITATIONS, REASONS FOR CAUTION

Findings in the mouse embryo and fetus may not be fully transferable to humans. In addition to skeletal development and placentation, there may be other parameters, e.g. on the molecular level which respond to IVC in ART media. Some comparisons have limited statistical power.

WIDER IMPLICATIONS OF THE FINDINGS

Our data suggest that once implantation is achieved, subsequent post-implantation development unfolds normally, resulting in healthy fetuses. With mouse models, we gather information for the safety of human ART culture media. Our mouse study is reassuring for the safety of ART conditions on human embryonic development, given the lack of bold detrimental effects observed in the mouse model.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Deutsche Forschungsgemeinschaft (BO 2540/4-1 and SCHL 394/9-1) and by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (S.L.G.); Bilateral grant NWO-DFG 63-258. None of the authors has any conflict of interest to declare.

TRIAL REGISTRATION NUMBER

Not applicable.

Contribution of fetal ANXA5 gene promoter polymorphisms to the onset of pre-eclampsia

OBJECTIVE

A common haplotype M2 consisting of minor SNP alleles located in the ANXA5 gene promoter region has been described as a risk factor for various obstetric complications such as recurrent pregnancy loss, pre-eclampsia and pregnancy-related thrombophilic disorder. However, the question of whether it is the maternal or fetal genotype that contributes to the onset of these disorders remains to be resolved.

METHODS

We analyzed ANXA5 gene variants in the blood and placental tissues from pre-eclampsia patients and normotensive controls. ANXA5 expression was examined by qRT-PCR, Western blotting and immunostaining. Results were compared between M2 and non-M2 carriers.

RESULTS

The M2 haplotype was found to be significantly frequent in placentas from pre-eclamptic patients relative to the controls (25.5% versus 10%, P = 0.044), In contrast, no significant differences were observed in maternal blood (13.0% versus 11.3%, P = 0.597). The placental expression of ANXA5 mRNA was found to be lower in M2 carriers. When examined by Western blot and immunostaining, the ANXA5 protein levels were found to be affected more by the placental than the maternal genotype. Histological examination of the placentas from the pre-eclamptic patients demonstrated that a placental M2 haplotype correlated more closely than maternal M2 with the severity of perivillous fibrin deposition.

CONCLUSIONS

Although preliminary, these results suggest that hypomorphic M2 alleles in the in placental ANXA5 promoter, whether transmitted maternally or paternally, might be an essential determinant of an increased risk of pre-eclampsia via local thrombophilia at the feto-maternal interface.

Identification of differential gene expression profiles in placentas from preeclamptic pregnancies versus normal pregnancies by DNA microarrays

The purpose of this study was to perform a comprehensive analysis of gene expression profiles in placentas from preeclamptic pregnancies versus normal placentas. Placental tissues were obtained immediately after delivery from women with normal pregnancies (n=6) and patients with preeclampsia (n=6). The gene expression profile was assessed by oligonucleotide-based DNA microarrays and validated by quantitative real-time RT-PCR. Functional relationships and canonical pathways/networks of differentially-expressed genes were evaluated by GeneSpring™ GX 11.0 software, and ingenuity pathways analysis (IPA). A total of 939 genes were identified that differed significantly in expression: 483 genes were upregulated and 456 genes were downregulated in preeclamptic placentas compared with normal placentas (fold change ≥ 2 and p<0.05 by unpaired t-test corrected with Bonferroni multiple testing). The IPA revealed that the primary molecular functions of these genes are involved in cellular function and maintenance, cellular development, cell signaling, and lipid metabolism. Pathway analysis provided evidence that a number of biological pathways, including Notch, Wnt, NF-κB, and transforming growth factor-β (TGF-β) signaling pathways, were aberrantly regulated in preeclampsia. In conclusion, our microarray analysis represents a comprehensive list of placental gene expression profiles and various dysregulated signaling pathways that are altered in preeclampsia. These observations may provide the basis for developing novel predictive, diagnostic, and prognostic biomarkers of preeclampsia to improve reproductive outcomes and reduce the risk for subsequent cardiovascular disease.

The M2 haplotype in the ANXA5 gene is an independent risk factor for idiopathic small-for-gestational age newborns

Hereditary thrombophilias can impair vascular placental functions and predispose to the birth of small-for-gestational age (SGA) babies. The placental anticoagulant protein annexin A5 (ANXA5) may contribute to this process. A functional haplotype (M2) within the ANXA5 gene is associated with fetal loss and venous thrombosis. This study investigated the prevalence of the M2 haplotype in a group of women with idiopathic SGA newborn babies. Seventy-eight women with at least one previous unexplained SGA birth and 195 controls all from Southern Italy were investigated. Hereditary thrombophilia was found in 13 (16.5%) cases and 21 (11%) controls (P < 0.05.). The M2 haplotype was found in 29% of cases (n = 23) and 15% of controls [n = 30; P = 0.001; OR = 2.3, 95% CI (1.17-4.48)]. Within the case group, 82.5% of the M2 haplotype carriers gave birth to babies with a birthweight below the 3rd percentile [P = 0.01; OR = 2.4, 95% CI (1.26-4.73)]. A logistic regression, corrected for age, parity and gravity showed that the M2 haplotype was independently associated with the delivery of an SGA new born [P = 0.029; OR = 2.6, 95% CI (1.1-6.0)]. In conclusion, the M2 haplotype of the ANXA5 gene confers a risk of delivering SGA babies.

Hydroxychloroquine reduces binding of antiphospholipid antibodies to syncytiotrophoblasts and restores annexin A5 expression

OBJECTIVE

Antibody-mediated disruption of the annexin A5 anticoagulant shield has been posited to be a thrombogenic mechanism in the antiphospholipid syndrome. We recently showed that the antimalarial drug, hydroxychloroquine, dissociates antiphospholipid immune complexes and restores annexin A5 binding to planar phospholipid bilayer. Using quantitative immunoassays, we demonstrated similar effects on BeWo trophoblasts. We therefore, investigated the effects of the drug on localization of annexin A5 in primary cultures of human placental syncytiotrophoblasts.

STUDY DESIGN

Laser confocal microscopy with computer-based morphometric analysis was used to localize annexin A5 and antiphospholipid antibodies on syncytiotrophoblasts exposed to polyclonal and monoclonal antiphospholipid and control immunoglobulin-Gs.

RESULTS

Hydroxychloroquine reversed the effects of the antiphospholipid antibodies on the syncytiotrophoblasts by markedly reducing immunoglobulin-G binding and restoring annexin A5 expression.

CONCLUSION

These results provide the first morphologic evidence for this effect of hydroxychloroquine on human placental syncytiotrophoblasts and support the possibility of novel treatments that target antiphospholipid antibody binding.

Macrophage migration inhibitory factor in fetoplacental tissues from preeclamptic pregnancies with or without fetal growth restriction

The proinflammatory cytokine MIF (macrophage migration inhibitory factor) is involved in physiological and pathological processes in pregnancy. MIF maternal serum levels are increased in preeclampsia (PE). We hypothesize that pregnancy tissues are the source of MIF overexpression in PE. MIF protein was studied in maternal sera, placental tissues, fetal membranes, and umbilical cord of 8 control and 20 PE pregnancies: 10 with normal fetal growth (PE-AGA) and 10 with fetal growth restriction (PE-FGR). MIF levels were significantly higher in PE-AGA membranes than in controls and PE-FGR. In PE-FGR, MIF cord concentrations were higher than in PE-AGA while MIF placental levels were lower than in controls. MIF maternal serum levels were higher in PE, compared to controls, and the difference was mainly due to PE-FGR samples. These data support MIF involvement in PE pathogenesis and suggest that different pregnancy tissues contribute to MIF production in PE with and without fetoplacental compromise.