Antiphosphatidylserine antibody removes annexin-V and facilitates the binding of prothrombin at the surface of a choriocarcinoma model of trophoblast differentiation

The Relevance, Predictability, and Utility of Annexin A5 for Human Physiopathology

As an important functional protein molecule in the human body, human annexin A5 (hAnxA5) is widely found in human cells and body fluids. hAnxA5, the smallest type of annexin, performs a variety of biological functions by reversibly and specifically binding phosphatidylserine (PS) in a calcium-dependent manner and plays an important role in many human physiological and pathological processes. The free state hAnxA5 exists in the form of monomers and usually forms a polymer in a specific self-assembly manner when exerting biological activity. This review systematically discusses the current knowledge and understanding of hAnxA5 from three perspectives: physiopathological relevance, diagnostic value, and therapeutic utility. hAnxA5 affects the occurrence and development of many physiopathological processes. Moreover, hAnxA5 can be used independently or in combination as a biomarker of physiopathological phenomena for the diagnosis of certain diseases. Importantly, based on the properties of hAnxA5, many novel drug candidates have been designed and prepared for application in actual medical practice. However, there are also some gaps and shortcomings in hAnxA5 research. This in-depth study will not only expand the understanding of structural and functional relationships but also promote the application of hAnxA5 in the field of biomedicine.

The Weight of IgA Anti-β2glycoprotein I in the Antiphospholipid Syndrome Pathogenesis: Closing the Gap of Seronegative Antiphospholipid Syndrome

The specific value of IgA Anti-β2glycoprotein I antibodies (aB2GP1) in the diagnosis and management of antiphospholipid syndrome (APS) is still controversial and a matter of active debate. The relevance of the IgA aB2GP1 isotype in the pathophysiology of APS has been increasingly studied in the last years. There is well know that subjects with multiple positive APS tests are at increased risk of thrombosis and/or miscarriage. However, these antibodies are not included in the 2006 APS classification criteria. Since 2010 the task force of the Galveston International Congress on APS recommends testing IgA aB2GP1 isotype in patients with APS clinical criteria in the absence of criteria antibodies. In this review, we summarize the molecular and clinical “state of the art” of the IgA aB2GP in the context of APS. We also discuss some of the characteristics that may help to evaluate the real value of the IgA aB2GP1 determination in basic research and clinical practice. The scientific community should be aware of the importance of clarifying the role of IgA aB2GP1 in the APS diagnosis.

Reimagining the antiphospholipid syndrome, an enigmatic thrombophilic disorder, through the looking glass of microscopic imaging

The antiphospholipid syndrome (APS) is an autoimmune thrombophilic disorder that was described as a diagnostic entity over 30 years ago. And yet the pathogenic mechanisms that are responsible for its clinical manifestations remain to be definitively established. The syndrome is defined by (1) the concurrence of vascular thrombosis and/or pregnancy complications together with (2) positivity for immunoassays and coagulation tests that were derived from clinical observations of two anomalous laboratory test results-specifically, false positivity for syphilis infection in uninfected individuals and the finding of inhibitors of blood coagulation in patients who lacked any bleeding tendencies. Over the years, these were standardized into immunoassays and coagulation assays for APS. Here, we describe how prior knowledge of the immunologic and coagulation aspects of the disorder led to research involving a range of imaging modalities including light microscopy, immunohistochemistry, confocal scanning laser microscopy, transmission and scanning electron microscopy, and atomic force microscopy. In turn, the results from those studies led to a "reimagining" of APS that has advanced the understanding of pathogenic mechanisms of the disorder and has led to the development of novel mechanistically based diagnostics along with potential new treatment approaches that target disease mechanisms.

Antiphosphatidylserine antibodies and reproductive failure

Some cases of reproductive failure with autoimmune background are characterized by the involvement of autoantibodies. This occurs mainly in patients having systemic lupus erythematosus or antiphospholipid syndrome. The autoantibodies associated with reproductive failure include: a) antibodies which directly bind phospholipid (e.g., cardiolipin, phosphatidylserine, phosphatidylethanolamine); b) antiphospholipid Abs which bind the phospholipid via phospholipid-binding glycoproteins such as b2glycoprotein-I, annexin V and prothrombin; c) autoantibodies directed to laminin-I, actin, thromboplastin, the corpus luteum, prolactin, poly (ADP-ribose), thyroglobulin and mitochondrial antibodies of the M5 type. This paper will focus on the association of antiphosphatidylserine autoantibodies and reproductive failure. Future studies are likely to help to identify peptides resembling the epitope specificities associated with the specific clinical manifestations.

Recurrent Miscarriage Syndrome and Infertility Due to Blood Coagulation Protein/Platelet Defects: A Review and Update

Three-hundred fifty-one women were referred for thrombosis and hemostasis evaluation after suffering recurrent miscarriages. All patients were referred by a high-risk obstetrician or reproductive medicine specialist after anatomic, hormonal or chromosomal defects had been ruled out. These patients were assessed over a three year period. The mean patient age at referral was 34 years and the mean number of miscarriages was 2.9 (2-9). All patients underwent a thorough evaluation for thrombophilia and, when indicated, a hemorrhagic disorder. Of the 351 patients, 29 (8%) had no defect. Of the remaining 322 patients, 7 (2%) had a bleeding disorder: 3 with platelet dysfunction, 1 with Factor XIII deficiency, 3 with von Willebrand’s and 3 with Osler-Weber-Rendu. The remainder of the patients had a thrombophilia as follows: 195 (60%) had antiphospholipid syndrome, 64 (20%) had Sticky Platelet Syndrome, 38 (12%) had MTHFR mutation, 23 (7.1%) had PAI-1 polymorphism, 12 (3.7%) had Protein S deficiency, 12 (3.7%) had Factor V Leiden, 3 (1%), had AT deficiency, 3 (1%) had Heparin-Cofactor II deficiency, 3 (1%) had TPA deficiency, and 6 (2%) had Protein C deficiency. There were a total of 364 defects found in the 312 patients harboring thrombophilia; thus, several harbored two and a few harbored three separate defects. All patients with thrombophilia were treated with preconception ASA at 81 mg/day with the immediate post-conception addition of heparin or LMW heparin (Dalteparin). Both ASA and heparin/LMW heparin were used to term. The first 120 patients were treated with unfractionated heparin at 5,000 U every 24 hours, subcutaneously and the last 192 have been treated with Dalteparin at 5,000 U/day subcutaneously. The patients with MTHFR were also treated with folate at 5 mg/day + pyridoxine at 50 mg/day. All patients were carefully monitored with CBC and platelet counts, anti-Xa levels, frequent ultrasounds and physical exams. Only 2 of the thrombophilia patients suffered another miscarriage; all others had a normal term delivery. There were no pregnancy-related thromboses, no delivery complications and no episodes of post-partum thrombosis. The only bleeding consisted of 1-4 cm bruises at injection sites. No episodes of thrombocytopenia (HIT) were noted. In our experience, thrombophilia is a common cause of recurrent miscarriage and all patients with no anatomical, hormonal or chromosomal defect should be evaluated for thrombophilia or a bleeding disorder. The success rate of normal term delivery in these 312 patients was 94% using ASA + heparin or Dalteparin. In addition, side effects of therapy were minimal.

Recurrent pregnancy loss: evaluation and treatment

Recurrent pregnancy loss (RPL) is a multifactorial condition. Approximately half of patients with RPL will have no explanation for their miscarriages. De novo chromosome abnormalities are common in sporadic and recurrent pregnancy loss. Testing for embryonic abnormalities can provide an explanation for the miscarriage in many cases and prognostic information. Regardless of the cause of RPL, patients should be reassured that the prognosis for live birth with an evidence-based approach is excellent for most patients. The authors review current evidence for the evaluation and treatment of RPL and explore the proposed use of newer technology for patients with RPL.

Histopathology in the placentae of women with antiphospholipid antibodies: A systematic review of the literature

BACKGROUND

Antiphospholipid antibodies (aPLs) are a heterogenous group of autoantibodies associated with recurrent miscarriage, stillbirth, foetal growth restriction and premature birth. The cause of obstetric morbidity in women with aPLs is not completely understood. Workers have attempted to understand the role of aPLs in obstetric morbidity by investigating the histopathology of placentae from aPL-positive women. However, it is unclear from these diverse, and at times contradictory reports what histopathological lesions are common in the placentae of women with aPLs. This systematic review was undertaken to generate a complete picture of the placental features associated with aPLs in an attempt to understand the pathological processes that occur in pregnancies affected by aPLs.

METHODS

Pubmed, Scopus, Web of Science and Embase were searched on the 27th November 2014 using the keywords "placenta" OR "trophoblast" AND "antiphospholipid antibody" OR "antiphospholipid antibody syndrome". Records that were relevant and eligible were qualitatively assessed and given a score out of 24.

RESULTS

Of the 1112 records that were retrieved from the systematic search, 34 records were eligible for review, and were qualitatively scored. Of the 44 histopathological features that were reported in 580 placentae from aPL-positive women, six features appeared to be more common in the placentae of aPL-positive women compared to control women, including: placental infarction, impaired spiral artery remodelling, decidual inflammation, increased syncytial knots, decreased vasculosyncytial membranes and the deposition of complement split product C4d.

CONCLUSION

Based on the evidence in this systematic review, a human placental aPL fingerprint has been proposed. The diversity of the human placental aPL fingerprint suggests that multiple pathological processes may occur in pregnancies affected by aPL.

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.

Role of anti-annexin A5 in pathogenesis of hypercoagulable state in patients with antiphospholipid syndrome

AIM

Despite several attempts made during the last decade, the exact pathogenesis of exceedingly high thrombotic events and bad obstetric outcome in antiphospholipid syndrome (APS) remains elusive. Anti-annexin A5 (aANX IgG) is thought to have a role in pathophysiology of APS. We studied role of aANX IgG in the pathogenesis of hypercoagulable state in APS patients.

METHODS

We estimated levels of aANX IgG in 112 patients with APS (86 primary and 26 secondary). We also estimated aANX IgG levels in 40 age- and sex-matched healthy controls, 10 patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) each, without any history of thrombosis or pregnancy morbidity, 10 patients of non-APS thrombosis and 10 patients of pregnancy loss without APS.

RESULTS

Only three healthy controls, two SLE (P = 0.239), one RA patient (P = 0.794), three non-APS thrombosis patients (P = 0.086) and two patients with pregnancy loss without APS (P = 0.258) had marginally elevated values, whereas 53 primary APS (P < 0.001) and 16 secondary APS (P < 0.001) were positive. We also compared aANX IgG levels in different groups. Mean ± standard errors of the mean of healthy controls was 3.77 ± 0.49, in SLE patients it was 4.88 ± 1.17 (P = 1.000), in RA patients it was 4.67 ± 0.97 (P = 1.000), in non-APS thrombosis it was 7.93 ± 0.88 (P = 0.488) and in pregnancy loss without APS it was 6.80 ± 0.93 (P = 0.789). However, it was significantly elevated in primary APS (12.87 ± 1.07, P < 0.001), secondary APS (11.98 ± 1.41, P = 0.001) and total APS patients (12.68 ± 0.88, P < 0.001).

CONCLUSION

From the above observations it appears that aANX IgG plays a significant role in producing a hypercoagulable state in primary and secondary APS.

Evaluation and treatment of recurrent pregnancy loss: a committee opinion

The majority of miscarriages are sporadic and most result from genetic causes that are greatly influenced by maternal age. Recurrent pregnancy loss (RPL) is defined by two or more failed clinical pregnancies, and up to 50% of cases of RPL will not have a clearly defined etiology.

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.

Resistance to annexin A5 anticoagulant activity in women with histories for obstetric antiphospholipid syndrome

OBJECTIVE

The objective of the study was to investigate whether resistance to annexin A5 anticoagulant activity (AnxA5) occurs in women with histories for obstetric complications of antiphospholipid syndrome (Obs-APS) and whether this correlates with antibody recognition of domain 1 of β2-glycoprotein.

STUDY DESIGN

One hundred thirty-six women with antiphospholipid antibodies, including 70 with histories for Obs-APS and 30 controls, were investigated.

RESULTS

Women with Obs-APS showed resistance to AnxA5 activity (median, 216%; range, 130-282% vs controls; median, 247%; range, 217-283%; P < .0001) and elevated levels of anti-domain I immunoglobulin (Ig) G (optical density: median, 0.056; range, 0.021-0.489 vs median, 0.042; range, 0.020-0.323; P = .002). Those in the lowest tertile of AnxA5 anticoagulant ratios had an odds ratio for Obs-APS of 58.0 (95% confidence interval, 3.3-1021.5). There was an inverse correlation between levels of annexin A5 anticoagulant activity and anti-domain I IgG.

CONCLUSION

Resistance to AnxA5 anticoagulant activity is associated with antibody recognition of domain I of β2-glycoprotein I and identifies a subset of women with histories for Obs-APS.

Phosphatidylserine as an anchor for plasminogen and its plasminogen receptor, histone H2B, to the macrophage surface

BACKGROUND

Plasminogen (Plg) binding to cell surface Plg receptors (Plg-Rs) on the surface of macrophages facilitates Plg activation and migration of these cells. Histone H2B (H2B) acts as a Plg-R and its cell surface expression is up-regulated when monocytes are differentiated to macrophages via a pathway dependent on L-type Ca(2+) channels and intracellular Ca(2+).

OBJECTIVES

We sought to investigate the mechanism by which H2B, a protein without a transmembrane domain, is retained on the macrophage surface.

METHODS

THP-1 monocytoid cells were induced to differentiate with interferon gamma + Vitamin D3 or to undergo apoptosis by treatment with camptothecin. Flow cytometry and cell surface biotinylation followed by Western blotting were used to measure the interrelationship between Plg binding, cell surface expression of H2B and outer membrane exposure of phosphatidylserine (PS).

RESULTS

H2B interacted directly with PS via an electrostatic interaction. Anti-PS or PS binding proteins, annexin V and protein S, diminished H2B interaction with PS on the surface of differentiated or apoptotic cells and these same reagents inhibited Plg binding to these cells. L-type Ca(2+) channels played a significant role in PS exposure, H2B surface expression and Plg binding induced either by differentiation or apoptosis.

CONCLUSIONS

These data suggest that H2B tethers to the surface of cells by interacting with PS on differentiated or apoptotic monocytoid cells. L-type Ca(2+) channels regulate PS exposure on the surface of these cells. The exposed PS interacts directly with H2B and hence provides sites for Plg to bind to.

Hydroxychloroquine protects the annexin A5 anticoagulant shield from disruption by antiphospholipid antibodies: evidence for a novel effect for an old antimalarial drug. Blood. 2010;115:2292-2299. [PMID: 19965621 DOI: 10.1182/blood-2009-04-213520]

Annexin A5 (AnxA5) is a potent anticoagulant protein that crystallizes over phospholipid bilayers (PLBs), blocking their availability for coagulation reactions. Antiphospholipid antibodies disrupt AnxA5 binding, thereby accelerating coagulation reactions. This disruption may contribute to thrombosis and miscarriages in the antiphospholipid syndrome (APS). We investigated whether the antimalarial drug, hydroxychloroquine (HCQ), might affect this prothrombotic mechanism. Binding of AnxA5 to PLBs was measured with labeled AnxA5 and also imaged with atomic force microscopy. Immunoglobulin G levels, AnxA5, and plasma coagulation times were measured on cultured human umbilical vein endothelial cells and a syncytialized trophoblast cell line. AnxA5 anticoagulant activities of APS patient plasmas were also determined. HCQ reversed the effect of antiphospholipid antibodies on AnxA5 and restored AnxA5 binding to PLBs, an effect corroborated by atomic force microscopy. Similar reversals of antiphospholipid-induced abnormalities were measured on the surfaces of human umbilical vein endothelial cells and syncytialized trophoblast cell lines, wherein HCQ reduced the binding of antiphospholipid antibodies, increased cell-surface AnxA5 concentrations, and prolonged plasma coagulation to control levels. In addition, HCQ increased the AnxA5 anticoagulant activities of APS patient plasmas. In conclusion, HCQ reversed antiphospholipid-mediated disruptions of AnxA5 on PLBs and cultured cells, and in APS patient plasmas. These results support the concept of novel therapeutic approaches that address specific APS disease mechanisms.

Resistance to annexin A5 anticoagulant activity: a thrombogenic mechanism for the antiphospholipid syndrome

The phospholipid binding protein, annexin A5 (AnxA5), has potent anticoagulant properties that result from its forming 2-dimensional crystals over phospholipids, blocking the availability of the phospholipids for critical coagulation enzyme reactions. This article reviews the evidence that antiphospholipid antibodies can disrupt this anticoagulant shield and unmask thrombogenic anionic phospholipids, which may thereby contribute to thrombosis in patients with the antiphospholipid syndrome (APS). This mechanism for thrombosis in APS can be monitored with coagulation assays for resistance to anticoagulant activity of AnxA5.

A comprehensive screening analysis of antiphospholipid antibodies in Indian women with fetal loss

OBJECTIVE

The present study was aimed at a comprehensive analysis of acquired thrombophilia in a large series of Indian women with fetal loss.

STUDY DESIGN

Four hundred and thirty women (median age 26 years, range 18-39 years) with unexplained fetal loss (median number of abortions 3, range 1-13) were screened for the presence of antiphospholipid antibodies (APA), i.e. lupus anticoagulant (LA), IgG/M antibodies for cardiolipin (ACA), beta 2 glycoprotein 1 (beta2 GP1) and annexin V. We also studied 100 normal healthy women (median age 24 years, range 18-30 years) who had at least one healthy child and did not have any miscarriage or other obstetric complications.

RESULTS

The prevalence of persistently positive LA was 8.1% and 1% in the patients and controls, respectively (OR 8.7; 95% CI, 1.4-51; P<0.05). The overall prevalence of IgG and/or IgM antibodies for cardiolipin, beta 2 GP1 and annexin V were as follows-ACA 27.9% (OR 18.9; 95% CI, 5-70; P<0.05), beta 2 GP1 12.2% (OR 6.8; 95% CI, 1.8-25; P<0.05) and annexin V 14.6% (OR 17; 95% CI, 2.9-98; P<0.05). The conventional LA and ACA tests were positive 23.2% of the cases as against 1% in the controls (OR 14.8; 95% CI, 3.9-55; P<0.05). The prevalence of LA, ACA, beta 2 GP1 and annexin V antibodies as independent risk factors were observed in 0.5%, 16.5%, 5.4% and 7.8% in the patients as against 1% each in the controls. The overall positivity for any one of the APA studied was 42.6% (OR 10.2; 95% CI, 4.5-23; P<0.05).

CONCLUSION

The present study thus indicates the importance of APA in women experiencing fetal loss where all the conventional causes of miscarriages have been ruled out. It also suggests that conventional APA assays (LA and ACA) are effective in the detection of a majority of APA positive cases and by the addition of other cofactor-dependent (beta 2 GP1 and annexin V) APA assays, there is a considerable increase in the diagnostic efficiency in the detection of APA.

Antiphospholipid syndrome in pregnancy

During the past 5 years the author and his colleagues have assessed carefully 351 women referred for evaluation of thrombosis and hemostasis after they had suffered recurrent miscarriages. This article describes the flow protocol the author and associates follow to maximize success and keep the costs of evaluation of recurrent miscarriage syndrome/infertility at a minimum while providing the best chances for defining a cause and thus providing optimal therapy for successful term pregnancy outcome. It presents the outcomes of the author's protocol and those of others in treating women who have antiphospholipid syndrome and who have suffered recurrent miscarriages.

Gene expression profiling during Forskolin induced differentiation of BeWo cells by differential display RT-PCR

The differentiation of cytotrophoblasts into syncytiotrophoblasts in the placenta has been employed as a model to investigate stage specific expression as well as regulation of genes during this process. While the cytotrophoblasts are highly invasive and proliferative with relatively less capacity to synthesize pregnancy related proteins, the multinucleated syncytiotrophoblasts are non-proliferative and non-invasive. However, syncytiotrophoblasts are the site of synthesis of a variety of protein, peptide and steroid hormones as well as several growth factors. Both the freshly isolated cytotrophoblasts from human placenta as well as the BeWo cell, a choriocarcinoma cell line model which retain several characteristic of cytotrophoblasts has been employed by us to study regulation of differentiation. In the present study, we have employed the differential display RT-PCR analysis (DD-RT-PCR) to evaluate gene expression changes during Forskolin induced in vitro differentiation of BeWo cells. We have identified several genes which are differentially expressed during differentiation and the differential expression of 10 transcripts was confirmed by Northern blot analysis. Based on the identity of the transcripts an attempt has been made to relate the known function of the gene products, to changes observed during differentiation. Of the several transcripts, one of the transcripts, namely Secretory Leukocyte Protease Inhibitor (SLPI) which is known to have multiple functions was found to increase 15-fold in the syntiotrophoblast.

A role for tissue transglutaminase in stabilization of membrane-cytoskeletal particles shed from the human placenta

Tissue transglutaminase (TGM2; also known as TG2 or tTG) localizes to the syncytial microvillous membrane (MVM) of the human placenta, the primary interface between maternal and fetal tissue. To identify TGM2 substrates in the MVM, membrane vesicles were prepared and labeled with biotinylated acyl donor or acceptor probes. Biotinylated species were selected on an avidin affinity matrix and identified by mass spectrometry of tryptic peptides. The most abundant were cytoskeletal (actin, tubulin, and cytokeratin) and membrane-associated (annexins, integrins, and placental alkaline phosphatase) proteins. During pregnancy, apoptotic particulate material, the end product of the trophoblast life cycle, is shed from the MVM into maternal circulation. Shed material was isolated from primary trophoblast cultures in which syncytial-like masses develop by fusion. A substantial fraction of actin in the particles was in the form of covalent polymeric aggregates, in contrast to cellular actin, which dissociated completely into monomer in SDS-PAGE. When cells were cultured in the presence of transglutaminase inhibitors, actin in the shed particles remained exclusively in monomeric form, and a reduction in trophoblast intercellular fusion and differentiation was observed. These findings suggest that transglutaminase-mediated cross-linking stabilizes the particulate material shed from the placenta.

Correlation between antiphospholipid antibodies that recognize domain I of beta2-glycoprotein I and a reduction in the anticoagulant activity of annexin A5

The paradoxical correlation between thrombosis and the lupus anticoagulant (LAC) effect is an enigmatic feature of the antiphospholipid (aPL) syndrome. The Dutch authors previously reported that thrombosis-related anti-beta2-glycoprotein I (beta2GPI) antibodies recognize domain I and cause LAC. The American authors reported that aPLs disrupt an anticoagulant annexin A5 (AnxA5) crystal shield. We investigated whether antidomain I antibodies correlate with disruption of AnxA5-anticoagulant activity. We studied a well-characterized group of 33 patients including subgroups with beta2GPI-dependent LAC that recognize domain I (n=11), with beta2GPI-independent LAC (n=12), and lacking LAC (n=10). The effects on AnxA5-anticoagulant activity were determined with an AnxA5 resistance assay that measures coagulation times with and without AnxA5. Patients with beta2GPI-dependent LAC (group A, all with thrombosis) had significantly lower AnxA5-anticoagulant ratios than those with beta2GPI-independent LAC (group B, thrombosis n=4; 157.8% versus 235.6%, P<.001) and those without LAC (group C, thrombosis n=2; 157.8% versus 232.5%, P<.001). There was no difference in the ratios between groups B and C (P=.92). Plasmas with beta2GPI-dependent LAC that recognize domain I displayed significantly increased AnxA5 resistance, suggesting that specifically anti-beta2GPI antibodies compete with AnxA5 for anionic phospholipids. These results are consistent with a model in which aPL antibodies may promote thrombosis by interfering with the anticoagulant activity of AnxA5.

Analysis of circulating annexin A5 parameters during pregnancy: absence of differences between women with recurrent spontaneous pregnancy losses and controls

OBJECTIVE

We investigated whether levels of annexin A5 (AnxA5), AnxA5 anticoagulant activity and binding, and anti-AnxA5 antibodies might be altered in women with previous histories of recurrent spontaneous pregnancy losses (RSPL) when tested during pregnancy.

STUDY DESIGN

Ninety pregnant women with histories of 3 or more RSPL (cases) and 150 women without adverse pregnancy histories (controls) were assayed for these AnxA5 parameters.

RESULTS

There were no significant differences between cases and controls in AnxA5 levels (median, 23.1 ng/mL [range, 2.1-201.1 ng/mL] vs 19.7 ng/mL [2.1-151.5 ng/mL]; P = .20), AnxA5 anticoagulant activity (183% [101%-236%] vs 168% [128%-256%]; P = .39) and binding (6.0 ng/aliquot PL [2.1-19.5 ng/aliquot PL) vs 6.1 ng/aliquot PL [1.6-16.8 ng/aliquot PL]; P = .72), and anti-AnxA5 antibody levels.

CONCLUSIONS

AnxA5 parameters do not distinguish between cases and controls when tested during pregnancy. The pregnant state itself appears to be associated with altered levels of AnxA5 parameters.

The role of human endogenous retroviruses in trophoblast differentiation and placental development

A major portion of the human genome appears to be of retroviral origin. These endogenous retroviral elements are expressed in a variety of normal tissues and during disease states, such as autoimmune and malignant conditions. Recently, potential roles have been described for endogenous retroviral envelope proteins in normal differentiation of human villous cytotrophoblast into syncytiotrophoblast. This article provides a brief critical review of the current state of knowledge concerning the expression of the env regions of three endogenous retroviral elements: ERV-3, HERV-W, and HERV-FRD. A testable model of villous cytotrophoblast differentiation is constructed, in which a complementary expression of endogenous retroviral envelope proteins initiates hCG production, decreased cell proliferation, and intercellular fusion.

Pathogenic antiphospholipid antibody: an antigen-selected needle in a haystack

Antiphospholipid antibodies represent a heterogeneous group of autoantibodies directed against anionic phospholipids (PLs) usually linked to protein cofactors. Their presence during the antiphospholipid syndrome is associated with risks of thrombosis and fetal losses. Among 5 randomly selected monoclonal antiphospholipid antibodies, all originating from a single patient suffering from this autoimmune disease, only 1 induced fetal losses when passively injected into pregnant mice. Its antiphospholipid activity was dependent on annexin A5, and its variable regions contained mainly 3 replacement mutations. To clarify the role of these mutations in the pathogenicity of the antibody, they were in vitro reverted to the germ line configuration. The resulting “germ line” antibody reacted with multiple self-antigens and only partially lost its reactivity against PLs, but it was no more dependent on annexin A5 and, more importantly, was no more pathogenic. This study illustrates that the in vivo antigen-driven maturation process of natural autoreactive B cells can be responsible for pathogenicity. (Blood. 2004;104:1711-1715)

Syncytial fusion of human trophoblast depends on caspase 8

Differentiation of human placental villous trophoblast includes syncytial fusion of cytotrophoblast forming syncytiotrophoblast. Early stages of the apoptosis cascade were described to be involved in this differentiation process. We investigated the role of the initiator caspase 8 in syncytial fusion in vitro, cultivating placental villous explants with or without caspase 8 antisense oligonucleotides or peptide inhibitors for up to 120 h. Trophoblast fusion and differentiation were assessed by confocal microscopy, immunohistochemistry and Western blot analysis. Culture with caspase 8 antisense oligonucleotides or peptide inhibitors reduced the fusion of cytotrophoblast with the syncytiotrophoblast, and resulted in multilayered cytotrophoblast. Caspase 8 expression was suppressed by antisense oligonucleotides and caspase 8 activities were reduced by peptide inhibitors. The organic anion-transporter hOAT-4 normally expressed in the cytotrophoblast and transferred into the syncytiotrophoblast by syncytial fusion was retained in the cytotrophoblast due to lack of fusion. We conclude that expression and activity of caspase 8 is a prerequisite for differentiation and syncytial fusion of cytotrophoblast cells.

Antibody-mediated interference with annexins in the antiphospholipid syndrome

Targeting of the annexin A5 anticoagulant shield may be a significant mechanism for thrombosis and pregnancy losses in APS. This may occur via high affinity antibodies that recognize phospholipid-binding proteins that are capable of interfering with the assembly of the annexin A5 shield on phospholipid surfaces or via direct recognition of annexin A5 by autoantibodies. In addition, antibodies against other members of the annexin family of proteins may also have pathogenic roles in APS. It is anticipated that further research will elucidate the biologic functions of these proteins and their roles in the aPL disease processes.

Pregnancy outcome in women with antiphospholipid syndrome and alloimmunity: a case report

CONTEXT

Patients with antiphospholipid syndrome and alloimmunity have poor pregnancy outcomes. Several diagnostic and therapeutic options exist for these disorders, although there is no consensus as to the best treatment.

CASE REPORT

We present here the clinical course and treatment of a woman with a history of two miscarriages who joined our program 10 years ago and has been followed up ever since. After antiphospholipid syndrome and alloimmune failure were diagnosed, she was given preconceptional treatment using unfractionated heparin, aspirin, prednisone and lymphocyte immunizations. She delivered two premature babies in the following two pregnancies. At present both children are healthy and are attending school. The fifth pregnancy was unsuccessful, in spite of having undergone a similar but postconceptional therapeutic scheme. We discuss this case focusing on the pathogenic mechanisms and the therapeutic aspects of these disorders.

Anti-annexin A5 Antibodies in Reproductive Failures in Relation to Antiphospholipid Antibodies and Phosphatidylserine

PROBLEM

The presence of IgG anti-annexin A5 (IgGalphaA5) and/or antiphospholipid antibodies (aPL) are risk factors associated with recurrent spontaneous abortion. Problems are whether IgA antiannexin A5 (IgAalphaA5) is pathogenic, and how IgGalphaA5 works.

METHOD OF STUDY

Blood samples from 238 patients with early recurrent spontaneous abortion, 48 patients with recurrent in vitro fertilization-embryo transfer failure, 179 non-pregnant women and 120 pregnant controls were tested for IgAalphaA5 by enzyme-linked immunosorbent assay. We also determined if IgGalphaA5 appeared coincident with aPL. The antigenic epitope(s) recognized by IgGalphaA5 was investigated.

RESULTS

We observed no difference between patients and controls for IgAalphaA5. The prevalence of IgGalphaA5 was not different statistically between patient samples with or without aPL. Patient IgGalphaA5 bound annexin A5 when the latter was free/unbound but not when annexin A5 was associated with phospholipid.

CONCLUSIONS

The IgAalphaA5 does not appear to be pathogenic. IgGalphaA5 works to make a complex with annexin A5 without relation to aPLs, which may reduce annexin A5 available for binding to trophoblast.

The antiphospholipid syndrome

The antiphospholipid (aPL) antibody syndrome is an autoimmune condition in which vascular thrombosis and/or recurrent pregnancy losses occur in patients with laboratory evidence for antibodies that bind to phospholipids. There have been significant advances in the recognition of the role of phospholipid-binding cofactors, primarily beta2GPI, as the true immunologic targets of the antibodies. Recent evidence suggests that the antibodies disrupt phospholipid-dependent anticoagulant mechanisms and/or that aPL antibodies induce the expression of procoagulant and proadhesive molecules on endothelial cells. Current diagnosis is based on clinical findings and empirically derived tests, such as assays for antibodies that bind to phospholipids or putative cofactors and coagulation assays that detect inhibition of phospholipid-dependent coagulation reactions. Current treatment relies primarily on anticoagulant therapy. Research advances are expected to bring mechanistically based diagnostic tests and improved therapy that target the roots of the disease process.

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.

Maternal diabetes mellitus is associated with altered deposition of fibrin-type fibrinoid at the villous surface in term placentae

Placentae from control and diabetic patients were used to test three null hypothesis: (1) there are no significant group differences in the volumes of villous syncytiotrophoblast compartments or intervillous fibrin-type fibrinoid, (2) perivillous fibrin-type fibrinoid is deposited randomly at the surface of trophoblast, and (3) amounts and deposition patterns of perivillous fibrin-type fibrinoid do not vary between groups. Term placentae were collected from non-diabetic subjects and five groups of diabetic women classified according to duration, severity and insulin dependence. Tissue specimens and sections were obtained by uniform random sampling. Volumes and surface areas of fibrin-type fibrinoid and trophoblast compartments (thin, syncytial knot, syncytial bridge and denuded regions) were estimated stereologically and compared using variance, chi-squared and contingency table analyses. As to null hypothesis (1), no group differences in volumes of trophoblast compartments were found but volumes of intervillous fibrin-type fibrinoid were greater in the non-insulin-dependent diabetic group. As to null hypothesis (2), regardless of group, fibrin-type fibrinoid was deposited preferentially at sites of denudation in every placenta examined. As to null hypothesis (3), villous surface areas occupied by perivillous fibrin-type fibrinoid were greater in type 1 (insulin-dependent) diabetics with complications (diabetic nephropathy or retinopathy). The surfaces of trophoblast occupied by fibrin-type fibrinoid were also notably larger in non-insulin-dependent diabetics and type 1 diabetics with complications. Except for the surface of denudation sites (which also increased in diabetes), there were no differences in the surfaces of trophoblast regions. These results confirm that the haemostatic steady state is perturbed in the diabetic placenta, that perivillous fibrin-type fibrinoid is deposited preferentially at sites of epithelial loss/damage, and that some diabetic groups are affected differentially.

Antiphospholipid antibodies: discovery, definitions, detection and disease

Antiphospholipid antibodies (aPL) are immunoglobulins of IgG, IgM and IgA isotypes that target phospholipid (PL) and/or PL-binding plasma proteins. Detection of aPL in the laboratory is done currently by both immunoassays and functional coagulation tests. Convention defines aPL specificity in immunoassays according to the particular PL substrate present, for example aPS represents antiphosphatidylserine antibodies. This may be technically incorrect inasmuch as a particular PL may be responsible for binding and highly concentrating a specific plasma protein, the latter then becomes the target for the aPL. The binding of beta(2)GP-I (apolipoprotein H) to the negatively charged PL, cardiolipin (CL) provides a good example of this circumstance. In contrast, aPL which specifically prolong coagulation times in in vitro are called lupus anticoagulants (LA). The precise PL target(s) of the aPL responsible for LA activities are unknown and often debated. The persistent finding of aPL in patients in association with abnormal blood clotting and a myriad of neurological, obstetrical and rheumatic disorders often compounded by autoimmune diseases has led to an established clinical diagnosis termed antiphospholipid syndrome (APS). The common denominator for these APS patients is the presence of circulating aPL on two or more occasions and the observation of events attributable to abnormal or accelerated blood clotting somewhere in vivo. The purpose of this review is to collect, collate, and consolidate information concerning aPL.

The presence of antiphospholipid antibodies is not related to increased levels of annexin A5 in plasma

Annexin A5 has been proposed to be important for shielding of negatively charged phospholipids from blood, thereby preventing the binding of clotting factors. It has been suggested that antiphospholipid antibodies can disrupt the binding of annexin A5 from negatively phospholipid-containing surfaces, resulting in uncontrolled coagulation. If this hypothesis is correct, than the plasma levels of annexin A5 will be increased in patients with antiphospholipid antibodies. Therefore, we have measured plasma levels of annexin A5 of 175 patients with systemic lupus erythematosus (SLE), of which 104 had antiphospholipid antibodies and 23 patients had primary antiphospholipid syndrome. The annexin A5 levels were compared with the annexin A5 plasma levels measured in 23 patients with diabetes mellitus type 2 and 35 healthy volunteers. We found a significant increase of annexin A5 plasma levels in patients with SLE (median 6.7 ng mL(-1)) and primary antiphospholipid syndrome (median 7.1 ng mL(-1)) as compared to patients with diabetes mellitus type 2 (median 3.3 ng mL(-1)) and healthy volunteers (median 3.9 ng mL(-1)). However, no correlation was found with the presence of antiphospholipid antibodies or with a history of thromboembolic complications. Based on these observations, we conclude that displacement of annexin A5 from cellular surfaces by antiphospholipid antibodies is not a common mechanism in patients with antiphospholipid antibodies.

Antiphospholipid thrombosis syndromes

Antiphospholipid antibodies are associated strongly with thrombosis and are the most common of the acquired blood protein defects causing thrombosis. Although the precise mechanisms whereby antiphospholipid antibodies alter hemostasis to induce a hypercoagulable state remain unclear, numerous theories, as previously discussed, have been advanced. The most common thrombotic events associated with ACLAs are deep vein thrombosis and pulmonary embolus (type I syndrome), coronary or peripheral artery thrombosis (type II syndrome), or cerebrovascular/retinal vessel thrombosis (type III syndrome), and occasionally patients present with mixtures (type IV syndrome). Patients with type V disease are those with antiphospholipid antibodies and RMS. It is as yet unclear how many seemingly normal individuals who may never develop manifestations of antiphospholipid syndrome (type VI) harbor asymptomatic antiphospholipid antibodies. The relative frequency of ACLAs in association with arterial and venous thrombosis strongly suggests that they should be looked for in any individual with unexplained thrombosis; all three idiotypes (IgG, IgA, and IgM) should be assessed. Also, the type of syndrome (I-VI) should be defined, if possible, because this identification may dictate both the type and the duration of immediate and long-term anticoagulant therapy. Unlike those patients with ACLAs, patients with primary LA-thrombosis syndrome usually have venous thrombosis. Because the aPTT is unreliable in patients with LA (prolonged in only approximately 40%-50% of patients) and usually is not prolonged in patients with ACLAs, definitive tests, including ELISA for ACLA, the dilute Russell's viper venom time for LA, hexagonal phospholipid-neutralization procedure, and B-2-GP-I (IgG, IgA, and IgM) should be ordered immediately when suspecting antiphospholipid syndrome or in individuals with otherwise unexplained thrombotic or thromboembolic events. If these test results are negative, subgroups also should be assessedin the appropriate clinical setting. Most patients with antiphospholipid thrombosis syndrome will fail to respond to warfarin therapy, and except for retinal vascular thrombosis, may fail some types of antiplatelet therapy, so it is of major importance to make this diagnosis so patients can be treated with the most effective therapy for secondary prevention-LMWH or unfractionated heparin in most instances and clopidogrel in some instances.

True anti-anionic phospholipid immunoglobulin M antibodies can exert lupus anticoagulant activity

True (cofactor-independent) anticardiolipin antibodies (aCL) are thought to lack lupus anticoagulant (LA) activity and pathogenic potential. A serum monoclonal immunoglobulin Mlambda (mIgMlambda) with aCL and LA activities found in a man with a splenicIgMlambda+ B-cell lymphoplasmacytic lymphoma (LPL) without thrombotic events has been characterized. LPL-derived hybridoma clones (designated HY-FRO) producing the serum mIgMlambda were obtained. mIgMlambda secreted by HY-FRO grown in protein-free culture medium, like that purified from serum, (i) showed binding, in a cofactor-free system, to solid-phase CL and phosphatidylserine (PS) and to the membrane of PS-expressing cells (apoptotic cells and activated platelets); (ii) failed to bind neutral phospholipids (PL), beta2Glycoprotein, histone, ssDNA, dsDNA, human IgG and umbilical vein endothelial cells. Absorption with apoptotic cells abolished its binding to anionic plate-bound CL and PS. IgMlambda-FRO used poorly mutated VH and Vlambda region genes, with a pattern that was inconsistent with an antigen-driven selection. Basic amino acids were present in the IgH complementarity determining region 3 (CDR3), which can be important for binding to anionic PL. These findings demonstrate unequivocally that true anti-anionic PL IgM antibodies can exert LA and indicate this anti-PL type does not involve thrombophilia.

Preparation and functional characterization of villous cytotrophoblasts free of syncytial fragments

Recent studies suggest that purified villous cytotrophoblasts are largely contaminated by mononucleated syncytial fragments and therefore unsuitable for studies of trophoblast differentiation. We assessed highly purified (>99.99 per cent) populations of villous trophoblasts for fragment contamination using the syncytial markers placental alkaline phosphatase (PLAP, by immunohistochemistry) and exteriorized phosphatidyl serine (ePS, by flow cytometric analysis). The preparations contained from 4-46 per cent syncytial fragments. However, we find that PLAP negative cells preferentially adhere to tissue culture surfaces and that all preparations were <2 per cent PLAP positive after routine plating and washing procedures. A second purification procedure eliminated dead (propidium iodide permeable) cells and separated viable syncytial fragments (ePS-positive) from viable cytotrophoblasts (ePS-negative) by two colour fluorescence activated cell sorting (FACS). Viable ePS-positive cells were ultrastructurally apoptotic, adhered poorly in culture and those that adhered rapidly underwent apoptosis. Viable ePS-negative cells contained large heterochromic nuclei and cytoplasmic structures, adhered strongly in culture and remained viable. The latter population (putative true villous CT) differentiated into syncytialized cells when cultured with EGF. We conclude that villous CT can be routinely purified, are viable in culture and can undergo syncytial fusion without extensive preformed syncytium.

Hypobaric hypoxia and villous trophoblast: evidence that human pregnancy at high altitude (3600 m) perturbs epithelial turnover and coagulation-fibrinolysis in the intervillous space

Spatial relationships between fibrin-type fibrinoid and regions of villous trophoblast were examined in order to address two main questions: [1] is high-altitude pregnancy accompanied by changes in the sizes of trophoblast compartments (cytotrophoblast, syncytiotrophoblast, denudation sites)?, and [2] do highland placentae differ in the amounts and distribution patterns of perivillous fibrin-type fibrinoid? Placentae were collected from two ethnic groups completing term pregnancies at low (400 m above sea level; n=25) and high (3600 m; n=45) altitude in Bolivia. Masson trichrome-stained sections were sampled randomly and analysed stereologically to estimate compartment volumes and surfaces. Comparisons were drawn using variance, Chi-squared and contingency table analyses. At high altitude, birthweights were 265 g lower and placentas had a larger intervillous space (270 cf 181 cm(3)), less fibrin-type fibrinoid (4.1 cf 8.4 cm(3) by volume; 2570 cf 4430 cm(2) by surface area), less villous trophoblast (50 cf 73 cm(3)) and a smaller villous surface (5.6 cf 7.0 m(2)). Volumes were reduced in all syncytiotrophoblast compartments (with and without nuclear aggregations). Cytotrophoblast was maintained and its relative volume increased significantly (from 2.7 to 3.6 per cent of trophoblast volume). Decreases in villous surface area affected primarily thinner (nuclear aggregate-free) regions of syncytium. Regardless of altitude, fibrin-type fibrinoid was deposited non-randomly: it was preferentially located at sites of trophoblast denudation. Although no altitudinal differences in fibrin-type fibrinoid patterns were detected, absolute surfaces were diminished on denuded and thinner regions of trophoblast but not on syncytial knots or bridges. Ethnic differences at low altitude (relatively greater deposits on denudations in Amerindians) were minimized at high altitude. We conclude that pregnancy at high altitude alters the epithelial steady state (towards cytotrophoblast and away from syncytiotrophoblast) and the coagulation-fibrinolysis steady state in the intervillous space (to favour fibrinolysis over coagulation). Thinner regions of syncytiotrophoblast may be the main sites of greater fibrinolytic or anticoagulatory activity. The findings are partly consistent with results from in vitro studies which indicate that hypoxia stimulates proliferation of cytotrophoblast but impairs fusion into syncytium.

Molecular pathogenesis of the antiphospholipid syndrome

The antiphospholipid (aPL) syndrome is an acquired autoimmune disorder of unknown etiology in which patients present with thrombosis together with laboratory evidence for antibodies in blood that recognize anionic phospholipid-protein complexes. The main antigenic target for the aPL antibodies has been identified to be beta(2) glycoprotein I (beta(2)GPI), a phospholipid-binding protein. The high affinity of aPL antibody-beta(2)GPI complex for phospholipid membranes seems to be a critical step in the mechanism of this disease. This review focuses on some of the major mechanisms that have been proposed to explain this disorder.

Secretion of annexin V from cultured cells requires a signal peptide

Annexin V is an intracellular protein that lacks a hydrophobic signal peptide. However, there are several studies reporting the extracellular presence of annexin V. In this study, we designed transgenes of annexin V with or without an attached secretory signal peptide and investigated the secretion of the transgene products in COS-7 cells. The signal peptide, targeted annexin V to the endoplasmic reticulum (ER), the Golgi and culture media of transfected cells. In contrast, without the signal peptide, annexin V was present only in the cytoplasm and was not detected in the medium. To confirm our results we also evaluated the presence of extracellular annexin V in two cultured cell lines: BeWo, a choriocarcinoma cell model of placental trophoblasts, and human umbilical vein endothelial cells (HUVEC). Our results showed that annexin V was immunolocalized on the surfaces of both cells but could not be detected in the culture medium of either cell type. Our results suggest that the secretion of annexin V required the recombinant addition of a hydrophobic signal peptide and that the limited quantities of endogenous cell surface annexin V on BeWo and HUVEC cells is most likely derived from adjacent damaged cells.

Apoptosis and syncytial fusion in human placental trophoblast and skeletal muscle

Skeletal muscle fibers and placental villous trophoblast are the main representatives of syncytia in the human. Both syncytia are derived from fusion of mononucleated stem cells, show a high degree of differentiation, and have lost their generative potency. Consequently, for their growth both depend on fusion of additional stem cells. There is evidence that syncytial fusion is directly or indirectly related to apoptotic events: As early as in the differentiated stages of the mononucleated stem cells, initiation stages of the apoptosis cascade have been observed. After syncytial fusion progression of the cascade is retarded or blocked by a variety of mechanisms. In this review we emphasize the links between apoptosis cascade, differentiation pathways and syncytial fusion. It needs to be elucidated whether these processes simply take place in parallel, both temporally and spatially, or whether there are causal connections between apoptosis cascade and syncytial fusion. Based on recent data obtained for placental villous trophoblast, it is tempting to speculate that early molecular mechanisms of the apoptosis cascade are involved in differentiation and syncytial fusion. Data obtained in skeletal muscles support this assumption and reveal a considerable degree of homology in genesis, maintenance and turnover of both tissues.

Antiphospholipid thrombosis syndromes

Antiphospholipid antibodies are strongly associated with thrombosis and are the most common of the acquired blood protein defects causing thrombosis. Although the precise mechanism(s) whereby antiphospholipid antibodies alter hemostasis to induce a hypercoagutable state remain unclear, numerous theories, as previously discussed, have been advanced. The most common thrombotic events associated with anticardiolipin antibodies are deep vein thrombosis and pulmonary embolus (type I syndrome), coronary or peripheral artery thrombosis (type II syndrome), or cerebrovascular/retinal vessel thrombosis (type II syndrome); occasionally, patients present with mixtures of these types (type IV syndrome). Type V patients are those with antiphospholipid antibodies and RMS. It is as yet unclear how many seemingly normal individuals who may never develop manifestations of antiphospholipid syndrome (type VI) harbor asymptomatic antiphospholipid antibodies. The relative frequency of anticardiolipin antibodies in association with arterial and venous thrombosis strongly suggests that these should be looked for in any individual with unexplained thrombosis; all three idiotypes (IgG, IgA, and IgM) should be assessed. Also, the type of syndrome (I through VI) should be defined if possible, as this may dictate both type and duration of both immediate and long-term anticoagulant therapy. Unlike those with anticardiolipin antibodies, patients with primary lupus anticoagulant thrombosis syndrome usually experience venous thrombosis. Because the aPTT is unreliable inpatients with lupus anticoagulant (prolonged in only about 40 to 50% of patients) and is not usually prolonged in patients with anticardiolipin antibodies, definitive tests, including ELISA for anticardiolipin antibodies, the dRVVT for lupus anticoagulant, hexagonal phospholipid neutralization procedure, and beta-2-GP-I (IgG, IgA, and IgM) should be immediately ordered when suspecting antiphospholipid syndrome or in individuals with otherwise unexplained thrombotic or thromboembolic events. If results of these tests are negative, in the appropriate clinical setting, subgroups should also be assessed. Finally, most patients with antiphospholipid thrombosis syndrome will fail warfarin therapy and, except for retinal vascular thrombosis, may fail some types of antiplatelet therapy; thus it is of major importance to make this diagnosis so that patients can be treated with the most effective therapy for secondary prevention--LMWH or UH in most instances, and clopidogrel in some instances.

Anti-annexin V antibodies in patients with early pregnancy loss or implantation failures

OBJECTIVE

To describe the prevalence of annexin V antibodies (aANX) in women with early recurrent pregnancy losses (RPLs) or recurrent IVF-ET failure.

DESIGN

Retrospective data analysis.

SETTING

Tokai University Hospital, Kanagawa, Japan.

PATIENT(S)

Two hundred thirty-eight patients with RPLs, 48 patients with recurrent IVF-ET failure and 179 nonpregnant and 120 pregnant control group women.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

ELISA was used to measure autoantibodies to annexin V.

RESULT(S)

An ELISA system developed for aANX revealed a dose-dependent relationship between annexin V and aANX. The positive/negative cutoff was set at 7 multiples of the median based on the 99th percentile of normal nonpregnant control group patients. Patients with RPLs (5.5%) or recurrent IVF-ET failure (8.3%) had a significantly increased incidence of aANX (IgG) compared with normal nonpregnant (1.1%) or pregnant control group women (0), whereas the prevalence of aANX between both patient groups or between both control groups was not statistically different. Specificity was confirmed by absorption studies using annexin V and by immunoblots.

CONCLUSION(S)

Our data show that aANX are associated with both RPLs and IVF-ET failure. We propose that anti-annexin V antibodies should be considered a risk factor for these reproductive failures.

Villous trophoblast: morphometric perspectives on growth, differentiation, turnover and deposition of fibrin-type fibrinoid during gestation

Villous trophoblast growth and deposition of perivillous fibrin-type fibrinoid were examined in human placentas from 10-41 weeks of gestation. The main aims were: (1) to study growth of different trophoblast domains implicated in epithelial turnover (proliferation, differentiation, extrusion, denudation); (2) to test predictions about relationships between fibrinoid deposits and intervillous volume or villous surface area; and (3) to derive baseline data for future studies on complicated pregnancies. Microscopical fields on trichrome-stained paraffin sections were selected by systematic random sampling. Volumes were estimated stereologically by point counting and surface areas by intersection counting. Apparent differences were tested by analyses of variance and relationships by regression and contingency table analyses. All compartments increased in absolute volume and/or surface area although not at the same rates. Relative volumes of cytotrophoblast were greater at earlier stages (10-20 weeks) but, due to differential growth, syncytiotrophoblast nuclear aggregation sites (syncytial knots and 'bridges') occupied greater proportions of trophoblast volume and surface near term (37-41 weeks). Fibrinoid volume correlated positively with intervillous volume and villous surface area but, relative to intervillous volume, seemed to increase near term. Findings confirm that the incidence of syncytial knots increases during gestation and contributes to trophoblast thickness variability. Greater relative volumes and surfaces of syncytial 'bridges' are consistent with increased incidences of true intervillous bridges and/or villous branching points. These findings support the notion that fibrinoid deposition during normal gestation is influenced by the quality of vascular perfusion but also emphasize that the villous surface is another important factor. Haemostatic events operate at the maternal surface of trophoblastic epithelium and influence the steady state between coagulation and fibrinolysis. Fibrinoid is deposited at sites of trophoblast de-epithelialization and these arise following trauma (e.g. abruption of intervillous bridges) or during the extrusion phase of normal epithelial turnover. Like knots and bridges, sites of de-epithelialization also expand at a faster rate than overall villous surface area. These and other events in villous development can be interpreted in terms of a coherent concept of epithelial turnover in which proliferation early in gestation is mainly for growth whilst that at later stages is mainly for renewal and repair.