Antiphospholid antibodies regulate the expression of trophoblast cell adhesion molecules

Anti-phospholipid autoantibodies in human diseases

Anti-phospholipid autoantibodies are a group of antibodies that can specifically bind to anionic phospholipids and phospholipid protein complexes. Recent studies have reported elevated serum anti-phospholipid autoantibody levels in patients with antiphospholipid syndrome, systemic lupus erythematosus, rheumatoid arthritis, metabolic disorders, malaria, SARS-CoV-2 infection, obstetric diseases and cardiovascular diseases. However, the underlying mechanisms of anti-phospholipid autoantibodies in disease pathogenesis remain largely unclear. Emerging evidence indicate that anti-phospholipid autoantibodies modulate NETs formation, monocyte activation, blockade of apoptotic cell phagocytosis in macrophages, complement activation, dendritic cell activation and vascular endothelial cell activation. Herein, we provide an update on recent advances in elucidating the effector mechanisms of anti-phospholipid autoantibodies in the pathogenesis of various diseases, which may facilitate the development of potential therapeutic targets for the treatment of anti-phospholipid autoantibody-related disorders.

Trophoblast Cell Function in the Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a complex thrombo-inflammatory autoimmune disease characterized by the presence of antiphospholipid antibodies (aPL). Women with APS are at high risk of recurrent early pregnancy loss as well as late obstetrical complications-premature birth due to placental insufficiency or severe preeclampsia. Accumulating evidence implies that vascular thrombosis is not the only pathogenic mechanism in obstetric APS, and that the direct negative effect of aPL on the placental cells, trophoblast, plays a major role. In this review, we summarize the current findings regarding the potential mechanisms involved in aPL-induced trophoblast dysfunction. Introduction on the APS and aPL is followed by an overview of the effects of aPL on trophoblast-survival, cell function and aPL internalization. Finally, the implication of several non-coding RNAs in pathogenesis of obstetric APS is discussed, with special emphasis of their possible role in trophoblast dysfunction and the associated mechanisms.

Treatment with low-dose prednisone in refractory obstetric antiphospholipid syndrome: A retrospective cohort study and meta-analysis

BACKGROUND

Glucocorticoids have been suggested as a potential therapy in refractory obstetric antiphospholipid syndrome (oAPS). Our aims were to describe a cohort of patients with oAPS treated with low-dose glucocorticoids and to perform a systematic review and meta-analysis evaluating the effects of additional glucocorticoids on the pregnancy outcomes in oAPS patients.

METHODS

Retrospective study that included 11 women diagnosed with primary antiphospholipid syndrome. The meta-analysis was conducted by fitting random effects models and was checked for heterogeneity.

RESULTS

All women had suffered from early pregnancy losses and two also had a history of fetal deaths. We studied 47 pregnancies that resulted in 32 abortions (68.1%) and 3 fetal deaths (6.4%). Twenty-six pregnancies were under treatment, mainly LDA and LMWH. Low-dose glucocorticoids were indicated in 13 pregnancies (always in association with LDA and LMWH). There was a decrease in pregnancy loss in those patients treated with LDA and LMWH. Treatment with glucocorticoids significantly increased the rate of successful pregnancy (38.5% abortions in treated vs 85.3% abortions in non-treated pregnancies; p=0.003). After multivariate GEE analysis, only glucocorticoids remained inversely associated with pregnancy loss (OR=0.157, (CI 0.025-0.968, p=0.046)). The meta-analysis showed that glucocorticoids tended to improve the frequency of successful pregnancy (OR= 0.509 (0.252-1.028), p=0.06). Three cases of gestational diabetes and one of preeclampsia were observed in our cohort. The meta-analysis, which mostly included studies using high-dose steroids, showed that glucocorticoids increased not only the frequency of preeclampsia and gestational diabetes, but also the rate of pre-term birth.

CONCLUSIONS

The efficacy of low-dose glucocorticoids in addition to the standard therapy in patients with refractory oAPS should be confirmed in well-designed clinical trials. However, high doses of steroids significantly increase the frequency of maternal and fetal morbidities, making their use strongly inadvisable.

Long-term pituitary downregulation before frozen embryo transfer improves clinical outcomes in women positive for serum autoantibodies

OBJECTIVE

Autoantibodies are associated with worse outcomes in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI), including increasing miscarriage rate, lowering pregnancy rate, and lowering delivery rate. However, little is known about improving IVF/ICSI outcomes for autoantibody-positive women, especially in frozen-thawed embryo transfer (FET) cycles. This study aimed to investigate whether pituitary suppression before FET improves the clinical pregnancy rate (CPR) and live birth rate (LBR) for IVF/ICSI women positive for serum autoantibodies.

STUDY DESIGN

A total of 181 infertile women positive for serum autoantibodies were recruited, including 65 women receiving GnRHa and hormone replacement therapy protocols (G-HRT group) and 116 women using modified natural cycles (MNC)/mild stimulated cycles (MSC) as FET protocols (MNC/MSC group). The outcomes were compared between two groups, including CPR, implantation rate (IR), miscarriage rate (MR), ongoing pregnancy rate (OPR), LBR, and gestational age (GA). The primary outcome of the study was CPR.

RESULTS

CPR, OPR, and LBR per embryo transferred in the G-HRT groups were significantly higher than those in the MNC/MSC group. No statistically significant differences were observed in the IR and MR. The CPR, IR, MR, OPR, and LBR was 72.23%, 64.00%, 12.77%, 63.07%, and 63.07% in the G-HRT group, respectively, while that was 56.90%, 53.07%, 10.60%, 50.00%, and 50.00% in the MNC/MSC group, respectively. After adjusting for partial potential confounding factors using multiple logistic regression, the type of endometrial preparation is the factor independently associated with enhanced CPR (OR = 0.48, 95%CI: 0.24-0.96, P = 0.039).

CONCLUSIONS

The current study showed that prior long-term GnRHa suppression could benefit patients with high serum autoantibody levels during IVF/ICSI FET cycles.

Obstetric anti-phospholipid syndrome: from pathogenesis to treatment

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by clinical manifestations such as thrombosis and obstetric complications with documented persistence of antiphospholipid antibodies (aPLs). Recent studies have revealed that the cause of aPL-related obstetric complications is dysfunction of placental trophoblasts and inflammation of the maternal-fetal interface induced by aPLs, not thrombosis. Although aPLs are associated with recurrence of serious complications during pregnancy, appropriate combination therapy with heparin and low-dose aspirin can improve the course of 70-80% of subsequent pregnancies. Preconception counseling and patient-tailored treatment are fundamental to improving maternal and fetal outcomes. Non-anticoagulant treatments such as hydroxychloroquine and statins are being developed for cases refractory to conventional treatment. Risk factors for thrombosis after pregnancy complications were identified based on the analysis of large databases of obstetric APS.

Comparison of treatments for the prevention of fetal growth restriction in obstetric antiphospholipid syndrome: a systematic review and network meta-analysis

Women with criteria and non-criteria obstetric antiphospholipid syndrome (APS) carry an increased risk of pregnancy complications, including fetal growth restriction (FGR). The management of obstetric APS traditionally involves clinicians, obstetricians and gynaecologists; however, the most appropriate prophylactic treatment strategy for FGR prevention in APS is still debated. We performed a systematic review and network meta-analysis (NetMA) to summarize current evidence on pharmacological treatments for the prevention of FGR in APS. We searched PubMed and Embase from inception until July 2020, for randomized controlled trials and prospective studies on pregnant women with criteria or non-criteria obstetric APS. NetMA using a frequentist framework were conducted for the primary outcome (FGR) and for secondary outcomes (fetal or neonatal death and preterm birth). Adverse events were narratively summarised. Out of 1124 citations, we included eight studies on 395 pregnant patients with obstetric APS treated with low-dose aspirin (LDA) + unfractionated heparin (UFH) (n = 132 patients), LDA (n = 115), LDA + low molecular weight heparin (n = 100), LDA + corticosteroids (n = 29), LDA + UFH + intravenous immunoglobulin (n = 7), or untreated (n = 12). No difference among treatments emerged in terms of FGR prevention, but estimates were largely imprecise, and most studies were at high/unclear risk of bias. An increased risk of fetal or neonatal death was found for LDA monotherapy as compared to LDA + heparin, and for no treatment as compared to LDA + corticosteroids. The risk of preterm birth was higher for LDA + UFH + IVIg as compared to LDA or LDA + heparin, and for LDA + corticosteroids as compared to LDA or LDA + LMWH. No treatment was associated with an increased risk of bleeding, thrombocytopenia or osteopenia.

Antiphospholipid antibodies and pregnancy outcome of assisted reproductive treatment: A systematic review and meta-analysis

PROBLEM

Antiphospholipid antibodies (aPLs) are a group of autoantibodies associated with a variety of pregnancy complications, but the impact of aPL on the outcomes of assisted fertility treatment (ART) is controversial. This systematic review and meta-analysis were designed to explore the association between aPL and ART outcomes and to explore in which stages does aPL play a role.

METHOD OF STUDY

PubMed and Cochrane database were systematically retrieved, and odds ratios (ORs) or risk ratios (RRs) with 95% confidence intervals (CIs) were calculated in a random-effect model or fixed-effect model according to the heterogenicity assessed by the Cochran Q and I²  statistic test. Of 246 records identified by the search, 10 case-control studies and 13 cohort studies that explored the association between aPL and in vitro fertilization (IVF) and/or intracytoplasmic sperm injection (ICSI) were analyzed.

RESULTS

The results showed that aPL positive rate was higher in females who failed in IVF/ICSI than those who succeeded in IVF/ICSI (OR: 3.62, 95% CI: 1.95-6.74). This study also indicated that females positive for aPL have a higher miscarriage rate (RR: 1.68, 95% CI: 1.24-2.28) than those negative for aPL, but live birth rate, biochemical pregnancy rate, and clinical pregnancy rate were similar between two groups (RR: 1.01, 95% CI: 0.91-1.12; RR: 1.18, 95% CI: 0.57-2.43 and RR: 0.95, 95% CI: 0.80-1.13).

CONCLUSIONS

There was higher aPL prevalence in females with adverse IVF/ICSI outcomes. It seems that aPL mainly affects the miscarriage rate, but has little effect on live birth rate, biochemical pregnancy rate, and clinical pregnancy rate. Routine detection of aPL before IVF/ICSI treatment is meaningful.

Amniotic fluid antiphospholipid antibodies: potential role in antiphospholipid syndrome-independent aberrant implantation process

BACKGROUND

The direct role of antiphospholipid antibodies (aPL) at maternal-fetal interface has not been fully investigated, especially whether they are involved in physiological and pathological implantation conditions, in an antiphospholipid syndrome (APS)-independent manner. In fact, trophoblast cells and placental endothelial cells at the implantation site express potential aPL targeted-phospholipid antigens (PL Ags); thus, the local production and presence of their specific antibodies, not related to APS (characterized by aPL presence in the peripheral blood), could be a potential marker of aberrant invasion, implantation and fetal-maternal immune tolerance processes.

METHODS

Anti-Beta₂glycoprotein I (anti-β₂GPI) and anticardiolipin (aCL Ab) antibodies (the most clinically relevant aPL) were detected by immunoenzymatic assay (ELISA), in the amniotic fluid (AF) of 167 women with physiological and complicated common pregnancy conditions, sharing an aberrant implantation process, such as recurrent pregnancy loss (RPL), autoimmune hypothyroidism (ahT) and smoking. All women included in the study were negative to peripheral blood aPL.

RESULTS

aCL and anti-β₂GPI antibodies were detectable in all the AF samples. RPL, ahT and smoking patients had higher level of anti-β₂GPI Abs (IgM) compared to women with physiological pregnancies (p < 0.0001). Since IgM cannot cross the placenta, their local production in response to maternal-fetal interface stimuli, could be hypothesized.

CONCLUSIONS

The presence of aPL in the AF (not related to APS) could reveal a potential clinical significance at maternal-fetal interface in selected pregnancy complications, in which an aberrant implantation process, and in turn an impaired fetal-maternal immune tolerance cross-talk, could occur.

Immunoglobulins from sera of antiphospholipid syndrome patients are internalized in the HTR-8/SVneo cell line and cytotrophoblast in culture

Women with antiphospholipid syndrome (APS) experience pregnancy complications mostly due to impaired trophoblast cell functions. Antiphospholipid antibodies (aPL) affect extravillous trophoblast in vivo and in culture, but the mechanisms are still poorly understood. Previously, syncytiotrophoblast was shown to bind and internalize aPL, which was not replicated for extravillous cytotrophoblast in short term culture. Here, aPL binding and time dependent internalization was demonstrated with exposure to aPL in the extravillous cell line HTR-8/SVneo and isolated first trimester of pregnancy cytotrophoblast (CT) using immunocytochemistry and flow cytometry. Intracellular aPL were detectable from 2 h of culture, reaching 30.7 ± 3.1% (p < 0.001) positive cells in CT and 24.8 ± 7% (p < 0.01) in HTR-8/SVneo cells at 24 h and 33 ± 4.2% (p < 0.01) at 48 h. The data presented show that extravillous trophoblast cells internalize aPL in a time-dependent manner significantly more than control immunoglobulins after 24 h of exposure.

Cellular and Molecular Mechanisms of Anti-Phospholipid Syndrome

The primary anti-phospholipid syndrome (APS) is characterized by the production of antibodies that bind the phospholipid-binding protein β2 glycoprotein I (β2GPI) or that directly recognize negatively charged membrane phospholipids in a manner that may contribute to arterial or venous thrombosis. Clinically, the binding of antibodies to β2GPI could contribute to pathogenesis by formation of immune complexes or modification of coagulation steps that operate along cell surfaces. However, additional events are likely to play a role in pathogenesis, including platelet and endothelial cell activation. Recent studies focus on neutrophil release of chromatin in the form of neutrophil extracellular traps as an important disease contributor. Jointly, the participation of both the innate and adaptive arms of the immune system in aspects of the APS make the complete understanding of crucial steps in pathogenesis extremely difficult. Only coordinated and comprehensive analyses, carried out in different clinical and research settings, are likely to advance the understanding of this complex disease condition.

Immunoglobulins from sera of APS patients bind HTR-8/SVneo trophoblast cell line and reduce additional mediators of cell invasion

Immunoglobulins from sera of patients with antiphospholipid syndrome (APS) decrease trophoblast cell invasion in vitro. This study aimed to extend understanding of cellular effects of immunoglobulins from APS (aPL+) in HTR-8/SVneo cells. aPL+ IgG induced change in effector molecules important for cell invasion was investigated further. After 1h of culture 21% cells bound aPL+ IgG, as opposed to 6% in control (aPL-). This was accompanied by increase in phospho-p38 at 30min. After 24h treatment aPL+IgG decreased protein levels of integrin subunits α1 (78% of control; p<0.01), α4 (65% of control, p<0.01), α5 (76% of control; p<0.01) and β1 (80% of control; p<0.01), and secreted gal-1 (68% of control; p<0.05). ProMMP-9 was reduced to 70% of control (p<0.001). Treatment with inhibitor of p38 MAPK signaling SB202190 reversed inhibition in integrin β1 and secreted gal-1. Involvement of p38 MAPK signaling and decrease in integrin subunit α4_, proMMP-9, and secreted gal-1 in HTR-8/SVneo cells are novel and extend the list of mediators of trophoblast invasion affected by aPL.

Pathogenesis and management of antiphospholipid syndrome

Antiphospholipid antibodies are a heterogeneous group of autoantibodies that have clear associations with thrombosis and pregnancy morbidity, and which together constitute the 'antiphospholipid syndrome' (APS). However, the pathophysiology of these complications is not well understood and their heterogeneity suggests that more than one pathogenic process may be involved. Diagnosis remains a combination of laboratory analysis and clinical observation but there have been significant advances in identifying specific pathogenic features, such as domain I-specific anti-β2-glycoprotein-I antibodies. This in turn has pointed to endothelial and complement activation as important factors in the pathogenesis of APS. Consequently, although anticoagulation remains the standard treatment for thrombotic APS and during pregnancy, the realisation that these additional pathways are involved in the pathogenesis of APS has significant implications for treatment: agents acting outside the coagulation system, such as hydroxychloroquine for pregnancy complications and sirolimus as an inhibitor of the mammalian target of rapamycin (mTOR) pathway, are now under evaluation and represent a radical change in thinking for haematologists. Conventional anticoagulation is also under challenge from new, direct acting anticoagulants. This review will provide a comprehensive overview of the evolving understanding of APS pathogenesis and how this and novel therapeutics will alter diagnosis and management.

Placental Oxidative Stress: From Miscarriage to Preeclampsia

OBJECTIVE

To review the role of oxidative stress in two common placental-related disorders of pregnancy, miscarriage and preeclampsia.

METHODS

Review of published literature.

RESULTS

Miscarriage and preeclampsia manifest at contrasting stages of pregnancy, yet both have their roots in deficient trophoblast invasion during early gestation. Early after implantation, endovascular trophoblast cells migrate down the lumens of spiral arteries, and are associated with their physiological conversion into flaccid conduits. Initially these cells occlude the arteries, limiting maternal blood flow into the placenta. The embryo therefore develops in a low oxygen environment, protecting differentiating cells from damaging free radicals. Once embryogenesis is complete, the maternal intervillous circulation becomes fully established, and intraplacental oxygen concentration rises threefold. Onset of the circulation is normally a progressive periphery-center phenomenon, and high levels of oxidative stress in the periphery may induce formation of the chorion laeve. If trophoblast invasion is severely impaired, plugging of the spiral arteries is incomplete, and onset of the maternal intervillous circulation is premature and widespread throughout the placenta. Syncytiotrophoblastic oxidative damage is extensive, and likely a major contributory factor to miscarriage. Between these two extremes will be found differing degrees of trophoblast invasion compatible with ongoing pregnancy but resulting in deficient conversion of the spiral arteries and an ischemia-reperfusion-type phenomenon. Placental perfusion will be impaired to a greater or lesser extent, generating commensurate placental oxidative stress that is a major contributory factor to preeclampsia.

CONCLUSION

Miscarriage, missed miscarriage, and early- and late-onset preeclampsia represent a spectrum of disorders secondary to deficient trophoblast invasion.

Antiphospholipid antibodies as cause of pregnancy loss

Antiphospholipid antibodies detected by lupus anticoagulant, anticardiolipin or anti-beta2 glycoprotein I assays were associated with fetal loss. Rather than being diagnostic tools only, antiphospholipid antibodies are thought to be pathogenic. The strongest demonstration of their pathogenic role lies in the ability to induce fetal resorptions - the experimental equivalents of the human fetal losses - when passively infused in pregnant naive animals. However, still debated is how the antibodies might induce the obstetrical manifestations. Thrombotic events at the placental levels might be related to endothelial cell activation, inhibition of protein C/S system and fibrinolysis as well as to Annexin V displacement. However, the thrombophilic state apparently cannot explain all the miscarriages and a direct antibody-mediated damage on the trophoblast has been suggested. During differentiation to syncytium, trophoblasts express cell membrane anionic phospholipids that can bind beta2 glycoprotein I, the main cationic phospholipid binding protein recognized by the antiphospholipid antibodies. Adhered b2-glycoprotein I might be recognized by the antibodies that, once bound, strongly interfere with in vitro trophoblast cell maturation so resulting in a defective placentation. These mechanisms have been suggested to play a role in early fetal loss, while thrombotic events would be responsible for miscarriages late in the pregnancy.

The role of anti-phospholipid antibodies in autoimmune reproductive failure

Anti-phospholipid antibodies (aPL) are autoantibodies that are associated with thrombosis and a range of pregnancy complications including recurrent pregnancy loss and pre-eclampsia. The three clinically relevant, well-characterized aPL are anti-cardiolipin antibodies, lupus anticoagulant and anti-beta-2-glycoprotein I (β2GPI) antibodies. aPL do not bind directly to phospholipids but instead bind to a plasma-binding ‘cofactor’. The most extensively studied cofactor is β2GPI, whose role in pregnancy is not fully elucidated. Although the pathogenicity of aPL in recurrent pregnancy loss is well established in humans and animal models, the association of aPL with infertility does not appear to be causative. aPL may exert their detrimental effects during pregnancy by directly binding trophoblast cells of the placenta, altering trophoblast signalling, proliferation, invasion and secretion of hormones and cytokines, and by increasing apoptosis. Heparin is commonly used to treat pregnant women with aPL; however, as thrombotic events do not occur in the placentae of all women with aPL, it may exert a protective effect by preventing the binding of aPL to β2GPI or by acting through non-thrombotic pathways. The aim of this review is to present evidence summarizing the current understanding of this field.

Antiphospholipid antibodies and the placenta: a systematic review of their in vitro effects and modulation by treatment

BACKGROUND

Antiphospholipid antibodies (aPL) are a family of auto-antibodies that are associated with an increased risk of recurrent miscarriage, intrauterine growth restriction and preterm birth. The placenta is a major target of aPL and it is likely that these antibodies promote pregnancy morbidity by affecting trophoblast function. Numerous studies have investigated the effect of aPL on trophoblast function in vitro. However, different trophoblast models and a variety of culture conditions have been employed, resulting in a myriad of different reported findings. This review systematically summarized those published studies that have investigated the effect of aPL on trophoblast function in vitro. In addition, the reported effects of pharmacological treatment on trophoblast function in the presence of aPL were also systematically reviewed.

METHODS

PubMed, Scopus, Embase and Web of Science databases were searched using the keywords 'placenta OR trophoblast' AND 'antiphospholipid antibody OR antiphospholipid syndrome' up to 25 April 2014. Studies were excluded based on the absence of appropriate controls. The effects of aPL on trophoblast proliferation, death, syncytialization, invasion, hormone production, cytokine production, coagulation and complement activation were recorded. The effects of different treatments on the function of trophoblasts in the presence of aPL were also recorded.

RESULTS

A total of 1071 records were retrieved from the four databases. After removing duplicates, the titles and abstracts of 529 articles were reviewed. Of those, 48 articles were read and relevant experimental results were extracted from 47 articles.

CONCLUSIONS

This systematic review provides an overview of all the studies performed to date on the effects of aPL on trophoblast function in vitro. There is considerable support for aPL decreasing trophoblast viability, syncytialization and invasion in vitro. Some work has also suggested that aPL may affect the production of hormones and signalling molecules by trophoblasts, and may stimulate coagulation and complement activation in vitro. Current reports of the in vitro effects of therapeutic treatments on trophoblast function in the presence of aPL are inconclusive. This systematic review has highlighted many gaps in our knowledge of how aPL work and may direct future research in this area.

Hydroxychloroquine restores trophoblast fusion affected by antiphospholipid antibodies

BACKGROUND

Obstetric antiphospholipid syndrome (APS) is defined by pregnancy complications associated with antiphospholipid antibodies (aPL). The mechanisms of the pathogenic effects of aPL in pregnancy are poorly understood. Toll-like receptors (TLR) have been implicated previously in APS.

OBJECTIVES

The aims of our study were (1) to determine aPL effects on trophoblastic cell fusion and differentiation, (2) to identify which TLR is involved in this process, and (3) to evaluate the efficacy of hydroxychloroquine (HCQ) to counteract the effects of aPL.

METHODS

BeWo cells are a model for trophoblast fusion and differentiation. Fusion index was assessed by immunocytochemical examination, and biochemical differentiation by using ELISA-measured β-human choronic gonadotropin hormone (β-hCG) secretion. We used three types of aPL to study their effect on cell fusion and differentiation: aPL derived from obstetric APS patients and affinity purified and polyclonal rabbit anti-β2-glycoprotein-1 (anti-β2GP1) antibodies. Experiments on fusion were confirmed using primary cytotrophoblastic cells.

RESULTS

All of the types of aPL used decreased the fusion index in BeWo and primary trophoblastic cells (64%, 52%, and 41% for BeWo cells and 67% and 62% for primary cells, respectively), and anti-β2GP1 antibodies decreased hCG secretion in BeWo cells (41%). To block TLR4 antibodies or to abolish TLR4 cell surface expression restored fusion index in both cell types and β-human choronic gonadotropin hormone excretion in BeWo cells. HCQ treatment induced the same effect and decreased TLR4 mRNA (40% and 35%, respectively) and protein expressions (62% and 42%, respectively) in BeWo cells.

CONCLUSION

Anti-β2GP1 antibodies decrease trophoblastic differentiation via TLR4. This effect is restored by HCQ, suggesting its therapeutic interest in APS pregnancies.

Obstetric antiphospholipid syndrome: a recent classification for an old defined disorder

Obstetric antiphospholipid syndrome (APS) is now being recognized as a distinct entity from vascular APS. Pregnancy morbidity includes >3 consecutive and spontaneous early miscarriages before 10weeks of gestation; at least one unexplained fetal death after the 10th week of gestation of a morphologically normal fetus; a premature birth before the 34th week of gestation of a normal neonate due to eclampsia or severe pre-eclampsia or placental insufficiency. It is not well understood how antiphospholipid antibodies (aPLs), beyond their diagnostic and prognostic role, contribute to pregnancy manifestations. Indeed aPL-mediated thrombotic events cannot explain the obstetric manifestations and additional pathogenic mechanisms, such as a placental aPL mediated complement activation and a direct effect of aPLs on placental development, have been reported. Still debated is the possible association between aPLs and infertility and the effect of maternal autoantibodies on non-vascular manifestations in the babies. Combination of low dose aspirin and unfractionated or low molecular weight heparin is the effective treatment in most of the cases. However, pregnancy complications, in spite of this therapy, can occur in up to 20% of the patients. Novel alternative therapies able to abrogate the aPL pathogenic action either by interfering with aPL binding at the placental level or by inhibiting the aPL-mediated detrimental effect are under active investigation.

Pathophysiology of the antiphospholipid antibody syndrome

Antiphospholipid antibodies (aPL) are associated with the recurrent pregnancy loss and thrombosis that characterizes the antiphospholipid antibody syndrome (APS). Although the ontogeny of these pathogenic antibodies has not been fully elucidated, there is evidence that indicates the involvement of both genetic and environmental factors. The ability of aPL to induce a procoagulant phenotype in APS patients plays a central role in the development of arterial and venous thrombotic manifestations typical of the disease. Inflammation serves as a necessary link between this procoagulant phenotype and actual thrombus development and is an important mediator of the placental injury seen in APS patients with obstetric complications. Recent evidence has indicated a role for abnormal cellular proliferation and differentiation in the pathophysiology of APS, especially in those patients with pregnancy morbidity and other more atypical manifestations that have no identifiable thrombotic cause. The interplay of genetic and environmental factors responsible for aPL development and the mechanisms by which these antibodies produce disease in APS patients is the focus of this review.

Mechanisms of antiphospholipid antibody-associated pregnancy complications

Women with antiphospholipid syndrome (APS) and antiphospholipid antibodies (aPL) are at high risk for recurrent spontaneous miscarriage and late pregnancy complications, such as preeclampsia and preterm labor. Recent clinical and experimental observations suggest that the pathophysiology of pregnancy failure in patients with APS may involve inflammation at the maternal-fetal interface and disruption of normal trophoblast function and survival, rather than a pro-thrombotic event. While treatment with heparin and aspirin from early pregnancy has been shown to significantly increase the live birth rate in recurrent miscarriage patients with APS, the incidence of severe late pregnancy complications still remains high. This review will discuss what is currently known about the mechanisms by which aPL may compromise pregnancy outcome.

Antiphospholipid antibodies induce a pro-inflammatory response in first trimester trophoblast via the TLR4/MyD88 pathway

PROBLEM

Women with antiphospholipid antibodies (aPL) are at risk for recurrent miscarriage, pre-eclampsia, and pre-term labor. aPL target the placenta directly by binding to beta(2)-glycoprotein I (beta(2)GPI) expressed on the surface of trophoblast cells. The objective of this study was to determine the effects of aPL on trophoblast function and the mechanisms involved.

METHOD OF STUDY

First trimester trophoblast cells were treated with anti-beta(2)GPI monoclonal antibodies and patient-derived aPL, after which cell survival and function was evaluated.

RESULTS

We report that anti-beta(2)GPI antibodies trigger an inflammatory response in trophoblast, characterized by increased secretion of interleukin (IL)-8, MCP-1, GRO-alpha, and IL-1beta, and that this occurs in a TLR-4/MyD88-dependent manner. At high concentrations, these antibodies also induce caspase-mediated cell death. This was attenuated upon disabling of the MyD88 pathway, suggesting that anti-beta(2)GPI-induced inflammatory mediators compromise trophoblast survival by acting in an autocrine/paracrine manner. Enhanced IL-8, GRO-alpha, and IL-1beta secretion also occurred when trophoblast cells were incubated with antibodies from patients with antiphospholipid syndrome. Heparin, which acts as a pro-survival factor in human trophoblast, attenuated the anti-beta(2)GPI antibody-mediated cell death, and also the pro-inflammatory response, but only at high concentrations.

CONCLUSION

These findings demonstrate that aPL triggers a placental inflammatory response via the TLR-4/MyD88 pathway, which in turn compromises trophoblast survival. Thus, the TLR-4/MyD88 pathway may provide a new therapeutic target to improve pregnancy outcome in antiphospholipid syndrome patients.

Anti-phospholipid antibodies increase non-apoptotic trophoblast shedding: a contribution to the pathogenesis of pre-eclampsia in affected women?

Pre-eclampsia is associated with trophoblast shedding-deportation and endothelial cell dysfunction. Anti-phospholipid autoantibodies increase a women's risk factor of developing pre-eclampsia. In this study we examined the hypothesis that anti-phospholipid antibodies alter the number and nature of trophoblasts shed from the placenta, and that phagocytosis of these altered trophoblasts results in endothelial cell activation. To investigate this we used a placental explant model in which explants were treated with anti-phospholipid antibodies. This treatment resulted in a doubling of the amount of trophoblast shed from the explants. Furthermore, the trophoblasts shed from anti-phospholipid antibody-treated explants were more readily phagocytosed by endothelial cells and subsequently caused the activation of the endothelial cells, as indicated by increased expression of endothelial cell surface ICAM-1 determined by cell-based ELISA, and monocyte adhesion as determined by flow cytometry. Confocal microscopy analysis of trophoblasts shed from anti-phospholipid antibody-treated or control explants demonstrated that anti-phospholipid antibodies, but not control antibodies, were internalised within trophoblasts shed from the explants, and this was accompanied by a reduction in the activity of caspases 3 and 7 in the shed trophoblasts as indicated by FLICA. These results suggest that anti-phospholipid antibodies are selectively transported into trophoblasts where they affect the regulation of the cell cycle leading to excess and aberrant death (necrotic or aponecrotic) and shedding of trophoblasts. If reflected in vivo this might explain, at least in part, how anti-phospholipid antibodies contribute to the pathogenesis of pre-eclampsia.

Updating on the pathogenic mechanisms 5 of the antiphospholipid antibodies-associated pregnancy loss

Anti-phospholipid antibodies (aPL) are risk factor for recurrent pregnancy loss and obstetrical complications. The mechanisms of aPL-mediated pregnancy failure are still a matter of research. Although aPL are associated with thrombosis, thrombotic events cannot explain all the miscarriages. There is evidence for a direct in vitro aPL effect on the trophoblast as shown by their binding; reduction of proliferation, human chorionic gonadotrophin release, in vitro invasiveness, adhesion molecule expression; and increased apoptosis. Such a direct reactivity is supported by the expression of beta2 glycoprotein (beta 2GP) I on trophoblast cell membranes. aPL/anti-beta 2GPI antibodies also bind to human decidual/endometrial cells in vitro and induce a pro-inflammatory phenotype. APL-mediated inflammatory processes at the placental level are apparently responsible for fetal loss at least in animal models. Both complement activation and pro-inflammatory cytokine/chemokine secretion have been shown to play a role. More recently, complement-induced tissue factor expression on infiltrating neutrophils was described as an additional pathogenic mechanisms mediated by aPL. As a whole, these findings do suggest that aPL may induce a defective placentation by acting at different levels without involving necessarily thrombotic events.

Effects of anti-phospholipid antibodies on a human trophoblast cell line (HTR-8/SVneo)

Antibodies to phospholipids (aPL) have been shown to adversely affect trophoblast invasion in vivo and in vitro. HTR-8/SVneo cells derived from first trimester of pregnancy extravillous trophoblast were studied. Matrigel invasion assay, cytochemistry and cell-based enzyme-linked immunosorbant assay (ELISA) with aPL or normal IgG was used. Our data show that aPL at 100 microg/ml decrease invasiveness of HTR-8/SVneo cells to 60% of control (p<0.01), and this was also shown for primary cytotrophoblast (to 15.5% of control, p<0.001). aPL treatment caused a significant decrease in integrin alpha(1), alpha(5), and beta(1) proteins (86%, 84%, and 87%, respectively). We conclude that HTR-8/SVneo cell culture is a suitable model to study mechanisms of action of aPL on trophoblast, which in HTR-8/SVneo cells inhibit invasion by decreasing integrins alpha(5), alpha(1), and beta(1).

Controversies and unresolved issues in antiphospholipid syndrome pathogenesis and management

While much is understood concerning the clinical features of patients with antiphospholipid syndrome (APS), many issues remain. The proper designation of patients with "definite" APS and the correct categorization of patients by both laboratory and clinical features are matters of ongoing debate. Recent proposals have identified new subsets of patients who have many typical features of APS but either do not fit the criteria for a "definite" diagnosis or have initially negative laboratory tests for antiphospholipid antibodies. Meanwhile, decisions about laboratory tests are based on expert opinion, rather than the results of controlled trials. As for treatment, many guidelines are offered, but few are backed by data from strong clinical trials. This article summarizes the clinical questions remaining to be answered and debates concerning pathogenesis, diagnosis, and management.

Role of anti-β2 glycoprotein I antibodies in antiphospholipid syndromeglycoprotein I antibodies in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is characterized by the presence of recurrent venous/ arterial thrombosis and fetal losses associated with a family of auto-antibodies directed against phospholipid (PL)-binding proteins. Among them, beta2 glycoprotein I (beta2GPI) is the most important. As a plasma cationic protein, beta2GPI binds to anionic PLs involved in several fluid-phase coagulation steps, and more importantly, it can be expressed on the surface of different cell types. Anti-beta2GPI antibodies recognize the molecule expressed on endothelial cells, platelets, monocytes, and trophoblast cells. Once bound, the antibodies trigger in vitro cell signaling that modulates biological responses potentially responsible for pathogenic mechanisms. Experimental animal models have supported the in vivo pathogenic role of anti-beta2GPI antibodies in both thrombosis and fetal loss models.

Pathogenic role of anti-β2-glycoprotein I antibodies on human placenta: functional effects related to implantation and roles of heparin

Most of the clinical manifestations of the antiphospholipid syndrome (APS) can be related to thrombotic events; however, placental thrombosis cannot explain all of the pregnancy complications that occur in women with this syndrome. In this regard, it has been hypothesized that antiphospholipid (aPL) antibodies can directly attack trophoblasts, but it is still unclear what pathogenetic mechanisms play a role and which aPL antibodies subpopulations are involved. Although it has been assumed that aPL antibodies are directed against anionic phospholipids (PLs), current advances in the field suggest that antibodies to PL-binding plasma protein such as beta2-glycoprotein-I (beta2-GPI) are the clinically relevant aPL antibodies. It appears that following the attachment of beta2-GPI to PLs, both molecules undergo conformational changes that result in the exposure of cryptic epitopes within the structure of beta2-GPI allowing the subsequent binding of antibodies. aPL antibodies detected by anti-beta2-GPI assays are associated with fetal loss. However, there is still debate on how the antibodies might induce the obstetrical manifestations. The significantly improved outcome of pregnancies treated with heparin has stimulated interest in the drug's mechanisms of action. Several mechanisms could explain its beneficial effects, because in addition to a direct effect of heparin on the coagulation cascade, it might protect pregnancies by reducing the binding of aPL antibodies, reducing inflammation, facilitating implantation and/or inhibiting complement activation. Further investigations are needed to better understand how aPL antibodies induce obstetric complications and to better clarify the functional role of heparin in the human placenta leading to more successful therapeutic options.

Anti-beta-2 glycoprotein I antibodies affect Bcl-2 and Bax trophoblast expression without evidence of apoptosis

Antiphospholipid antibodies (aPLs) reacting with beta-2 glycoprotein I (beta2GPI) have been associated with recurrent fetal loss and pregnancy complications. The aim of the study was to investigate whether aPLs with anti-beta2GPI specificity induce apoptosis of human trophoblasts in vitro. To this end, human anti-beta2GPI monoclonal IgM derived from a patient with antiphospholipid syndrome and a human irrelevant monoclonal IgM were incubated with human trophoblast cell cultures for 24, 48, and 72 h. In all the cultures we evaluated: (i) Bcl-2 and Bax mRNA and protein expression by Western blot and reverse transcription polymerase chain reaction (RT-PCR), respectively; (ii) DNA fragmentation by a commercial ELISA kit and by agarose gel electrophoresis; and (iii) the percentage of cells reactive with the monoclonal antibody (MAb) M30 by indirect immunofluorescence. The results were: Bcl-2/Bax ratio increased in untreated trophoblast cells during the time of culture, showing the highest values detectable after 72 h (2.68 and 2.28 at protein and mRNA levels, respectively). Cell incubation with anti-beta2GPI MAbs induced a significant Bcl-2/Bax ratio reduction in comparison with untreated cells (1.22 and 1.28 at protein and mRNA levels, respectively, after 72 h incubation). No significant difference was detected after cell exposure to irrelevant MAbs. However, neither DNA fragmentation nor increase in cells positive for the caspase-cleaved epitope of cytokeratin 18 cytoskeletal protein (M30) was found. In Conclusion, anti-beta2GPI antibodies react with trophoblast cells and reduce the Bcl-2/Bax ratio, but without any clear apoptotic effect.

Recurrent miscarriage

Many human conceptions are genetically abnormal and end in miscarriage, which is the commonest complication of pregnancy. Recurrent miscarriage, the loss of three or more consecutive pregnancies, affects 1% of couples trying to conceive. It is associated with psychological morbidity, and has often proven to be frustrating for both patient and clinician. A third of women attending specialist clinics are clinically depressed, and one in five have levels of anxiety that are similar to those in psychiatric outpatient populations. Many conventional beliefs about the cause and treatment of women with recurrent miscarriage have not withstood scrutiny, but progress has been made. Research has emphasised the importance of recurrent miscarriage in the range of reproductive failure linking subfertility and late pregnancy complications and has allowed us to reject practice based on anecdotal evidence in favour of evidence-based management.

Disturbances in placental immunology: ready for therapeutic interventions?

Recent studies have provided new insight into aberrations in the immunological interplay between mother and fetus and their potential role in the development of recurrent fetal loss and preeclampsia. The action of anti-phospholipid antibodies in recurrent fetal loss is now proposed to involve the complement system, neutrophil activation and the production of TNFalpha by immune bystander cells. A clear involvement of the immune system is emerging in preeclampsia, involving mainly the innate arm, especially neutrophils. The activation of peripheral neutrophils by placentally released inflammatory debris triggers the induction of neutrophil extracellular traps (NETs), which may lead to an occlusion of the intervillous space, thereby further promoting a condition of placental hypoxia. It has, hence, been suggested that new therapeutic strategies be developed, including the possible use of TNFalpha antagonists in cases of recurrent miscarriage. These strategies need to be addressed with caution due to the possible induction of fetal congenital abnormalities.

Heparin prevents programmed cell death in human trophoblast

Heparin is used clinically for the prevention of pregnancy complications associated with prothrombotic disorders, especially antiphospholipid antibody syndrome. Recent studies have suggested that heparin may exert direct effects on placental trophoblast, independently of its anticoagulant activity. We now demonstrate that heparin abrogates apoptosis of primary first trimester villous trophoblast in response to treatment with the pro-inflammatory cytokines interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha. This multifunctional glycosaminoglycan also inhibited apoptosis induced by other agents, including staurosporin, broad-spectrum kinase inhibitor and thrombin. Furthermore, heparin attenuated caspase-3 activity, a hallmark of apoptosis, in human first trimester villous and extravillous trophoblast cell lines treated with peptidoglycan, a Toll-like receptor-2 agonist isolated from Staphylococcus aureus. The ability of heparin to antagonize cell death induced by such diverse apoptotic signals suggested that it acts as a survival factor for human trophoblast. We demonstrate that heparin, like epidermal growth factor (EGF) and heparin-binding EGF (HB-EGF), elicits phosphorylation of the EGF receptor and activation of the phosphatidyl inositol 3-kinase (PI3K)-, the extracellular signal-related kinase 1/2 (ERK1/2)- and the c-Jun NH2 terminal kinase (JNK)-signal transduction pathways in primary villous trophoblast. In summary, we have demonstrated that heparin activates multiple anti-apoptotic pathways in human trophoblast. Our results suggest that heparin may be useful in the management of at-risk patients, even in the absence of an identifiable thrombophilic disorder.

[Hormone therapy, fertility and pregnancy in antiphospholipid syndrome]

Antiphospholipid syndrome (APS) carries a risk of thrombosis and infertility. Consequently the use of any type of hormone therapy and pregnancy in APS requires special considerations. The present article provides a broad review of all these issues. The use of contraception, hormone replacement therapy and selective estrogen receptor modulators in APS are described. In vitro fertilization/embryo transfer and ovarian induction in these patients are reviewed. Lastly, the possible fetal and maternal complications that can occur during pregnancy are described and, based on the literature, recommendations for the management of pregnancy in women with APS are provided.

Antiphospholipid antibodies in serum and follicular fluid--is there a correlation with IVF implantation failure?

BACKGROUND

Antiphospholipid antibodies (aPLs) are associated with infertility, but the mechanism underlying this statistical association is currently obscure. We aimed to investigate the finding that aPLs are concentrated in follicular fluid and to establish if this is associated with a poorer outcome from IVF.

METHODS AND RESULTS

In 19.2% of 99 women undergoing IVF, at least one aPL was detected in their serum and/or follicular fluids, but the antibody levels in follicular fluid were not higher than in serum. Women with aPLs had a lower implantation rate (14%) than women without these antibodies (24.1%), but this difference was not significant (P=0.127). There was also a non-significant reduction in the live birth rate for women with aPLs. In a parallel investigation, 10 sheep immunized with beta2 glycoprotein I (beta2GPI) or irrelevant control antigens showed strong immune responses, but there were no significant differences between the levels of antibodies in the follicular fluid or serum from beta2GPI or control immunized sheep.

CONCLUSION

aPLs do not appear to be selectively concentrated in follicular fluids and, when present, do not adversely affect the reproductive outcome of women undergoing IVF.

Pathophysiology of histological changes in early pregnancy loss

An early pregnancy loss (EPL) or first-trimester miscarriage is the most common complication of human reproduction, with an incidence ranging between 50 and 70% of all conceptions. Two-thirds of EPL cases present with a thinner and fragmented trophoblastic shell, and reduced cytotrophoblast invasion of the tips of the spiral arteries. This leads to incomplete plugging during early pregnancy, and premature onset of the maternal circulation throughout the placenta. The excessive entry of maternal blood into the intervillous space has a direct mechanical effect on the villous tissue, and an indirect oxidative stress effect that contributes to cellular dysfunction and/or damage. Correlation of in vivo and in vitro data suggests that overwhelming oxidative stress of the placental tissues represents a common pathophysiological mechanism for the different etiologies of EPL. Autosomal trisomies are the most frequent karyotypic abnormalities found in EPL, but the comparison of data from different cytogenetic studies is difficult because of the lack of clinical information in many cases on maternal age, gestational age, time of fetal demise and the cytogenetic methodology employed. The majority of authors did find a weak association between villous morphologic features and chromosomal abnormalities, with the exception of partial mole triploidy. The comparison of ultrasound findings and placental histological data indicates that villous changes following fetal demise in utero could explain the overall low predictive value of placental histology alone in identifying an aneuploidy or another non-chromosomal etiology. By contrast, the histological features of complete and partial hydatidiform molar EPL are so distinctive that most cases of molar EPL are correctly diagnosed by histological examination alone. Overall, histopathology when correlated with in vivo ultrasound/Doppler has provided novel clues to the pathophysiology of EPL. Prospective studies are needed to evaluate the impact of these findings on routine histopathologic examination in first-trimester miscarriages.

Current debates in antiphospholipid syndrome: the acquired antibody-mediated thrombophilia

Antiphospholipid (APL) syndrome is the most common form of acquired thrombophilia. It can cause significant morbidity and even mortality. The term "APL antibodies" represents a heterogeneous group of antibodies associated with this disorder. Currently no single assay can identify every APL antibody. Clinically relevant APL antibodies are mainly anticardiolipin antibodies (ACA) detected by solid phase enzyme-linked immunosorbent assay (ELISA) and lupus anticoagulants (LA) demonstrated by in vitro coagulation assay. However, there are some other antibodies associated with the APL syndrome (i.e., subgroup APL antibodies). ACAs, LAs, and subgroup APL antibodies represent intersecting, but non-identical, subsets of autoantibodies. Thus, those autoantibodies may coexist or may occur independently. Any organ system and any size of vessel can be affected during the clinical course of the disease. Therefore, the APL syndrome can manifest itself in a wide variety of clinical thrombotic features. Fetal loss and pregnancy morbidity represent a specific challenge. Despite tremendous advances in the understanding of the pathogenesis of APL syndrome during the past decade, the mainstay of management is still anticoagulation. However, there is no general agreement regarding the duration and intensity of anti-coagulant therapy. In this review, we focused on the current dilemmas and their present clarifications in the wide clinicopathologic spectrum of APL syndrome and APL antibody-related distinct pathologic conditions.

Autoimmune disease as a cause of reproductive failure

High-risk pregnancy is the most common clinical association with antiphospholipid antibodies; the principal manifestations are pregnancy loss and early preeclampsia. Membership in this family of antibodies is continually growing and includes antibodies against a variety of phospholipids, phospholipid-protein complexes, and phospholipid-binding proteins. The current information in the literature is inadequate to clearly implicate a subgroup of antiphospholipid antibodies or a particular pathophysiologic mechanism as being responsible for poor pregnancy outcomes. It is clear, however, that prevalent diagnostic tests for LA and aCL are extremely useful to identify many of these patients, but are inadequate for diagnosis of all patients with autoimmune pregnancy loss or to elucidate the pathophysiology. Many patients who present clinically with autoimmune-like pregnancy complications currently are negative in tests for LA or aCL, but have antibodies against annexin V, phosphatidylserine, or other relevant antigens. The greatest risk for a complicated pregnancy is conveyed by a subgroup of antibodies that affect the normal function of placental trophoblast. As clinical laboratory tests designed to detect more members of the antiphospholipid antibody family become available, understanding of this complicated disease (APS) will increase.

Antiphospholipid antibodies in implantation failures

PROBLEM

The amino phospholipids (PL), phosphatidylserine (PS) and phosphatidylethanolamine (PE) are distributed asymmetrically in the plasma membranes of eucaryotic cells. This arrangement involves active transport of PS and PE from the outer to inner membrane leaflet by an aminophospholipid translocase (flipase). Cell activation, injury and programmed cell death (apoptosis) cause collapse of the PS/PE asymmetry by activation of another enzyme system, scramblase. Unlike other cells, the developing trophoblast exteriorizes PS during its differentiation.

METHODS OF STUDY

An analysis of published and unpublished data.

RESULTS

The trophoblast is targeted by antiphospholipid antibodies (aPL), especially to PS (aPS). Cardiolipin is not present in the trophoblast plasma membrane, nonetheless, anticardiolipin (aCL) has been implicated in trophoblast pathology. The aPS and aCL are often crossreactive. Both animal and in vitro experimental models have shown monoclonal and polyclonal aPS and aCL to specifically destroy trophoblast, inhibit syncytium formation, halt human chorionic gonadatropin (hCG) production, and limit trophoblast invasion. Antibodies to PE (aPE) have not been well characterized, however, recent reports from several independent laboratories document that aPE are associated significantly with very early (embryonic) recurrent pregnancy loss (RPL). Umeda and coworkers have shown that during cytokinesis (late telophase) of Chinese hamster ovary (CHO) cells, formation of PE rafts in cleavage furrows is required for completion of cell division and formation of daughter cells. This raises the question whether aPE might interfere with implantation and cell division during embryogenesis.

CONCLUSIONS

A role for aPL in implantation failure and occult pregnancy loss constitutes the basis of this overview.