Mutations in complement regulatory proteins predispose to preeclampsia: a genetic analysis of the PROMISSE cohort

Making sense of the spectrum of glomerular disease associated with complement dysregulation

Over recent years, complement has emerged as a major player in the development of a number of glomerular diseases, including atypical haemolytic uraemic syndrome, membranoproliferative glomerulonephritis and the recently described C3 glomerulonephritis. Some patients and pedigrees show overlapping features of these conditions. Intriguingly, a few complement gene mutations are common to different disease phenotypes. In this review, we explore the evidence for complement dysregulation in these diseases and the clinical interface between them, and present a hypothesis to explain the variable phenotype associated with dysregulation of the alternative complement pathway.

Spontaneous abortion is associated with elevated systemic C5a and reduced mRNA of complement inhibitory proteins in placenta

Spontaneous abortion in early pregnancy due to unknown reasons is a common problem. The excess complement activation and consequent placental inflammation and anti-angiogenic milieu is emerging as an important associated factor in many pregnancy-related complications. In the present study we sought to examine the expression of complement inhibitory proteins at the feto-maternal interface and levels of complement split products in the circulation to understand their role in spontaneous abortion. Consenting pregnant women who either underwent elective abortion due to non-clinical reasons (n = 13) or suffered miscarriage (n = 14) were recruited for the study. Systemic levels of complement factors C3a and C5a were measured by enzyme-linked immunosorbent assay (ELISA). Plasma C5 and C3 protein levels were examined by Western blot. Expressions of complement regulatory proteins such as CD46 and CD55 in the decidua were investigated by quantitative polymerase chain reaction (PCR) and Western blot. The median of plasma C3a level was 82·83 ng/ml and 66·17 ng/ml in elective and spontaneous abortion patients, respectively. Medians of plasma C5a levels in elective and spontaneous abortion patients were 0·96 ng/ml and 1·14 ng/ml, respectively. Only plasma C5a levels but not C3a levels showed significant elevation in spontaneous abortion patients compared to elective abortion patients. Further, there was a threefold decrease in the mRNA expressions of complement inhibitory proteins CD46 and CD55 in the decidua obtained from spontaneous abortion patients compared to that of elective abortion patients. These data suggested that dysregulated complement cascade may be associated with spontaneous abortion.

Pregnancy-associated systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that classically manifests itself with fever, arthralgia, and rash, predominantly in women of childbearing age. The autoimmunity is against nuclear and cytoplasmic components; therefore, any organ system can be affected, and the clinical presentation spectrum is wide. Although rare, de novo SLE can be diagnosed in pregnancy. Herein, a woman who had SLE diagnosed in early pregnancy is reported. This and a previous report imply that SLE has diverse clinical presentations in pregnancy.

Vitrification alters rabbit foetal placenta at transcriptomic and proteomic level

Although numerous studies have demonstrated that cryopreservation alters gene expression, less is known about those embryos that implanted successfully and continued in gestation. To raise the question of the neutrality of this technique, we examine the effects of vitrification through gestation in rabbit before and after the implantation. We monitored the distribution of losses of 569 vitrified morulae, observing that embryos which reach the last pre-implantatory stage are able to implant. However, we found that not all implanted embryos had the ability to continue with their gestation. The results reveal that vitrification decreased foetus and maternal placenta weights at mid-gestation, but led to a higher offspring birth weight. A novel finding is that while no differences in gene expression were detected in pre-implantatory embryos at day 6, vitrification affects a gene and protein expression in the placenta at day 14. Our results for first time reveal strong evidence of modifications in implanted embryos subjected to vitrification, suggesting that the crucial step that vitrified embryos must overcome is the placenta formation. On the basis of these findings, our work leaves the question open as to whether the effects we observed that cause vitrification during foetal development could give rise to some type of physiological or metabolic alteration in adulthood.

How I treat: the clinical differentiation and initial treatment of adult patients with atypical hemolytic uremic syndrome

Published data demonstrating the efficacy of complement inhibition therapy in patients with atypical hemolytic uremic syndrome (aHUS) are remarkable in contrast to the historically poor long-term prognosis for aHUS patients treated with plasma-based therapy. Although both aHUS and acquired thrombotic thrombocytopenic purpura (TTP) remain clinical diagnoses, an increased understanding of both conditions has improved our ability to differentiate aHUS from acquired TTP. These same data have also demonstrated the importance of a more rapid identification and diagnosis of aHUS as the recovery of end-organ injury present appears to be related to the time to initiate therapy with eculizumab. The diagnosis of acquired TTP can be confirmed by the finding of severely deficient ADAMTS13 activity (<10%) with evidence of an ADAMTS13 antibody inhibitor whereas merely deficient ADAMTS13 activity in the absence of an ADAMTS13 autoantibody is more consistent with congenital TTP. In the absence of an objective diagnostic test, clinicians must rely collectively on platelet count, serum creatinine, and ADAMTS13 activity in the context of the response to plasma exchange therapy to identify patients whose diagnosis is most consistent with aHUS, and thus be more likely to benefit from therapy with eculizumab.

Managing lupus patients during pregnancy

Systemic lupus erythematosus (SLE) is an auto-immune disease, primarily affecting young females. Pregnancy in a woman with SLE remains a high-risk situation with higher maternal and foetal mortality and morbidity. Although live births are achieved in majority of the pregnancies, active disease and major organ involvement can negatively affect the outcomes. A higher risk of foetal loss, pre-term birth, intra-uterine growth restriction (IUGR) and neonatal lupus syndromes (NLSs) are major foetal issues. Mothers are faced with disease flares, pre-eclampsia and other complications. Disease flares during SLE pregnancy pose the unique issue of recognition and differentiation between physiologic changes and disease state. Similarly, pre-eclampsia and lupus nephritis may lead to diagnostic confusion. Treatment choices during pregnancy are limited to a few safe drugs, further restricting the options. Refractory pregnancy loss associated with anti-phospholipid antibodies (aPLs) and complete heart block associated with anti-Ro antibodies remain unresolved issues. A multidisciplinary approach, with close monitoring, is essential for optimal outcomes.

Complement and its receptors: new insights into human disease

Although new activation and regulatory mechanisms are still being identified, the basic architecture of the complement system has been known for decades. Two major roles of complement are to control certain bacterial infections and to promote clearance of apoptotic cells. In addition, although inappropriate complement activation has long been proposed to cause tissue damage in human inflammatory and autoimmune diseases, whether this is indeed true has been uncertain. However, recent studies in humans, especially those using newly available biological therapeutics, have now clearly demonstrated the pathophysiologic importance of the complement system in several rare diseases. Beyond these conditions, recent genetic studies have strongly supported an injurious role for complement in a wide array of human inflammatory, degenerative, and autoimmune diseases. This review includes an overview of complement activation, regulatory, and effector mechanisms. It then focuses on new understandings gained from genetic studies, ex vivo analyses, therapeutic trials, and animal models as well as on new research opportunities.

14th International Congress on Antiphospholipid Antibodies: task force report on antiphospholipid syndrome treatment trends

Antiphospholipid Syndrome (APS) is characterized by vascular thrombosis and/or pregnancy morbidity occurring in patients with persistent antiphospholipid antibodies (aPL). The primary objective of the APS Treatment Trends Task Force, created as part of the 14th International Congress on aPL, was to systematically review the potential future treatment strategies for aPL-positive patients. The task force chose as future clinical research directions: a) determining the necessity for controlled clinical trials in venous thromboembolism with the new oral direct thrombin or anti-factor Xa inhibitors pending the results of the ongoing rivaroxaban in APS (RAPS) trial, and designing controlled clinical trials in other forms of thrombotic APS; b) systematically analyzing the literature as well as aPL/APS registries, and creating specific registries for non-warfarin/heparin anticoagulants; c) increasing recruitment for an ongoing primary thrombosis prevention trial, and designing secondary thrombosis and pregnancy morbidity prevention trials with hydroxychloroquine; d) determining surrogate markers to select patients for statin trials; e) designing controlled studies with rituximab and other anti-B-cell agents; f) designing mechanistic and clinical studies with eculizumab and other complement inhibitors; and g) chemically modifying peptide therapy to improve the half-life and minimize immunogenicity. The report also includes recommendations for clinicians who consider using these agents in difficult-to-manage aPL-positive patients.

Characterization of antibody specificities associated with preeclampsia

The presence of maternal autoantibodies has been previously associated with preeclampsia, although the composition of the antibody repertoire in preeclampsia has not been well characterized. Given this, we applied a bacterial display peptide library to identify peptides that preferentially react with plasma antibodies from patients with preeclampsia (n=15) versus healthy-outcome pregnancies (n=18). Screening using fluorescence-activated cell sorting identified 38 peptides that preferentially bind to antibodies from individuals with preeclampsia. These preeclampsia-specific peptides possessed similar motifs of R(G)/S(G)/-WW(G)/S, RWW(G)/S, or WGWGXX(R)/K distinct from the angiotensin II type 1 receptor epitope AFHYESQ. Seven library-isolated peptides and a cell surface-displayed angiotensin II type 1 receptor epitope were used to construct a diagnostic algorithm with a training set of 18 new preeclamptic and 22 healthy-outcome samples from geographically distinct cohorts. Cross-validation within the training group resulted in averaged areas underneath a receiver operating characteristic curve of 0.78 and 0.72 with and without the known receptor epitope, respectively. In a small validation set (12 preeclamptic; 8 healthy), the algorithm consisting only of library-isolated peptides correctly classified 10 preeclamptic and 6 healthy samples using a predefined cutoff that achieved 61% sensitivity (95% confidence interval, 36%-83%) at 95% specificity (95% confidence interval, 77%-100%) in training set (n=40) cross-validation. Our results indicate that antibodies with specificities other than anti-angiotensin II type 1 receptor are prevalent in preeclampsia patients and may be useful as diagnostic biomarkers.

Comparative incidence of pregnancy outcomes in treated obstetric antiphospholipid syndrome: the NOH-APS observational study

Among women with pure obstetric APS, late pregnancy complications are more frequent in cases of prior fetal loss. Late pregnancy complications are more frequent among women treated for pure obstetric APS than among nontreated controls.

Pregnancy outcomes following recovery from acquired thrombotic thrombocytopenic purpura

Pregnancy may precipitate acute episodes of thrombotic thrombocytopenic purpura (TTP), but pregnancy outcomes in women who have recovered from acquired TTP are not well documented. We analyzed pregnancy outcomes following recovery from TTP associated with acquired, severe ADAMTS13 deficiency (ADAMTS13 activity <10%) in women enrolled in the Oklahoma TTP-HUS Registry from 1995 to 2012. We also systematically searched for published reports on outcomes of pregnancies following recovery from TTP associated with acquired, severe ADAMTS13 deficiency. Ten women in the Oklahoma Registry had 16 subsequent pregnancies from 1999 to 2013. Two women had recurrent TTP, which occurred 9 and 29 days postpartum. Five of 16 pregnancies (31%, 95% confidence interval, 11%-59%) in 3 women were complicated by preeclampsia, a frequency greater than US population estimates (2.1%-3.2%). Thirteen (81%) pregnancies resulted in normal children. The literature search identified 382 articles. Only 6 articles reported pregnancies in women who had recovered from TTP associated with acquired, severe ADAMTS13 deficiency, describing 10 pregnancies in 8 women. TTP recurred in 6 pregnancies.

CONCLUSIONS

With prospective complete follow-up, recurrent TTP complicating subsequent pregnancies in Oklahoma patients is uncommon, but the occurrence of preeclampsia may be increased. Most pregnancies following recovery from TTP in Oklahoma patients result in normal children.

Thrombotic thrombocytopenic purpura and the atypical hemolytic uremic syndrome: an update

Since the last review in 2007 of thrombotic thrombocytopenic purpura (TTP) and microangiopathic hemolytic anemia in the Clinics, further understanding of the nature of TTP and atypical hemolytic uremic syndrome (aHUS) has led to increasing use of rituximab in the treatment of TTP and the approval in 2011 of eculizumab for the treatment of aHUS. With this new armamentarium, distinction of aHUS from TTP has become more critical than ever. This article updates the new knowledge, highlights the difference between aHUS and TTP, and presents a scheme for their diagnosis and management.

Urinary excretion of C5b-9 in severe preeclampsia: tipping the balance of complement activation in pregnancy

The complement cascade is activated in normal pregnancy, and excessive complement activation propagates the systemic inflammatory response in severe preeclampsia. Consequently, biomarkers of complement dysregulation may be useful for prediction or treatment of disease. Because renal damage with proteinuria is a characteristic pathological feature of preeclampsia, we hypothesized that complement markers in urine, rather than plasma, could better reflect complement dysregulation in disease. To investigate this, we performed a case-control study of pregnant women, enrolling 25 cases with severe preeclampsia, 25 controls with chronic hypertension, and 25 healthy controls without hypertension matched by gestational age and parity. Subjects were recruited from the Brigham and Women's Hospital from March 2012 to March 2013. Urine and blood samples were collected on the day of enrollment, with complement activation (C3a, C5a, and C5b-9) measured by ELISA. Severe preeclampsia was associated with marked elevations in urinary C5b-9 (median [interquartile range], 4.3 [1.2-15.1] ng/mL) relative to subjects with chronic hypertension (0 [0-0]) and healthy controls (0 [0-0]; P<0.0001). Urinary excretion of C5b-9 was detected in 96% of cases with severe preeclampsia, 12% of controls with chronic hypertension, and 8% of healthy controls. Cases were also notable for significantly greater urinary excretion of C3a and C5a. Plasma levels of C5a and C5b-9, but not C3a, were increased in the cases with severe preeclampsia compared with healthy controls; however, they did not distinguish preeclampsia from chronic hypertension, supporting our hypothesis that complement markers in urine, rather than plasma, better reflect complement dysregulation. Complement inhibition is an intriguing treatment option for patients with severe preeclampsia.

The complement cascade and renal disease

Serum complement cascade, a part of innate immunity required for host protection against invading pathogens, is also a mediator of various forms of disease and injury. It is activated by classical, lectin, and alternative pathways that lead to activation of C3 component by C3 convertases, release of C3b opsonin, C5 conversion and eventually membrane attack complex formation. The tightly regulated activation process yields also C3a and C5a anaphylatoxins, which target a broad spectrum of immune and non-immune cells. The review discusses the involvement of the complement cascade in kidney disease pathogenesis and injury. The role of the complement pathways in autoantibody-mediated forms of glomerulonephritis (lupus nephritis, anti-glomerular basement membrane disease, anti-neutrophil cytoplasmic autoantibody-induced or membranoproliferative glomerulonephritis, membranous nephropathy), C3 glomerulopathy, atypical forms of hemolytic uremic syndrome, ischemic-reperfusion injury of transplanted kidney, and antibody-mediated renal allograft rejection are discussed. The disturbances in complement activation and regulation with underlying genetics are presented and related to observed pathology. Also promising strategies targeting the complement system in complement-related disorders are mentioned.

A role for uric acid and the Nalp3 inflammasome in antiphospholipid antibody-induced IL-1β production by human first trimester trophoblast

Women with antiphospholipid syndrome (APS) are at risk of recurrent pregnancy loss and obstetrical disorders, such as preeclampsia and intrauterine growth restriction (IUGR). Antiphospholipid antibodies (aPL) directly target the placenta by binding beta₂-glycoprotein I (β₂GPI) expressed on the trophoblast. We recently demonstrated in human first trimester trophoblast cells that anti-β₂GPI antibodies (Abs) induce the secretion of IL-1β in a Toll-like receptor 4 (TLR4)-dependent manner. IL-1β secretion requires processing of pro-IL-1β and this is mediated by the inflammasome, a complex of Nalp3, apoptosis-associated speck-like protein containing a CARD (ASC) and caspase-1. The objective of this study was to determine if aPL induce IL-1β production in trophoblast via the inflammasome. Using a human first trimester trophoblast cell line, we demonstrated that a mouse anti-β₂GPI mAb and human polyclonal aPL-IgG induce IL-1β processing and secretion, which was partially blocked upon caspase-1 inhibition. Nalp3 and ASC knockdown also attenuated anti-β₂GPI Ab-induced IL-1β secretion. Furthermore, aPL stimulated the production of uric acid in a TLR4-dependent manner; and inhibition of uric acid prevented aPL-induced IL-1β production by the trophoblast. These findings demonstrate that aPL, via TLR4 activation, induce a uric acid response in human trophoblast, which in turn activates the Nalp3/ASC inflammasome leading to IL-1β processing and secretion. This novel mechanism may account for the inflammation at the maternal-fetal interface, which causes placental dysfunction and increases the risk of adverse pregnancy outcome in patients with APS.

Analysis of genes coding for CD46, CD55, and C4b-binding protein in patients with idiopathic, recurrent, spontaneous pregnancy loss

Since a tightly regulated complement system is needed for a successful pregnancy, we hypothesized that alterations in complement inhibitors may be associated with idiopathic, recurrent miscarriage. We sequenced all exons coding for three complement inhibitors: C4b-binding protein (C4BP), CD46, and CD55 in 384 childless women with at least two miscarriages that could not be explained by known risk factors. Several alterations were found in C4BPA, of which the R120H, I126T, and the G423T mutations affected the expression level and/or the ability of recombinant C4BP to serve as cofactor for factor I. The only variant in C4BPB was located in the C-terminal part, and did not impair the polymerization of the molecule. Our results identify for the first time alterations in C4BP in women experiencing recurrent miscarriages. We also found four CD46 alterations in individual patients that were not found in healthy controls. One of the rare variants, P324L, showed decreased expression, whereas N213I resulted in deficient protein processing as well as an impaired cofactor activity in the degradation of both C4b and C3b. The identified alterations may result in in vivo consequences and contribute to the disorder but the degree of association must be evaluated in larger cohorts.

New-onset systemic lupus erythematosus during pregnancy

Few studies have been published focusing on the clinical features of new-onset systemic lupus erythematosus (SLE) during pregnancy. This study examined the clinical characteristics of SLE during pregnancy or puerperium. The clinical characteristics and serological parameters of 48 patients with onset of SLE during pregnancy were retrospectively compared with those of age-matched new-onset SLE patients who were diagnosed in a period of more than 12 months without pregnancy (n = 65) and age-matched preeclampsia patients (n = 48). SLE tended to occur during the first and second trimesters (33 and 42 %, respectively). Lupus nephritis (LN) and severe thrombocytopenia were more commonly seen in new-onset SLE during pregnancy than in patients without pregnancy (68.8 vs 35.4 % and 25 vs 9.2 %, respectively, p < 0.05). However, pregnant patients had lower frequency of fever, arthritis, arthralgia, alopecia, oral ulcer, and hypocomplementemia than the nonpregnant controls (p < 0.05). Compared to LN patients without pregnancy (n = 23), LN patients with pregnancy (n = 33) had more prominent proteinuria and nephrotic syndrome (p < 0.05). On the other hand, when compared to patients with preeclampsia, patients with new-onset SLE during pregnancy had early onset of symptoms during gestation and were characterized by presence of fever, malar lesion, autoantibodies, hypocomplementemia, hyperuricemia, active urinary sediment, and multi-organ involvement. In conclusion, patients with their first onset of lupus during pregnancy generally have more severe disease with higher prevalence of renal and platelet involvement.

Defective complement inhibitory function predisposes to renal disease

The role of the complement system in mediating human renal disease has long been recognized in immune-complex excess syndromes such as systemic lupus erythematosus and in dense deposit disease in which no immunoglobulin (Ig) is present. Over the past 15 years, mutations in complement regulatory genes have been demonstrated to predispose to thrombotic microangiopathies including atypical hemolytic uremic syndrome, C3 and C1q glomerulopathies, and preeclampsia. Excessive complement activation on an endothelial cell, due to either an autoantibody or a regulatory protein deficiency, sets up a procoagulant state in these diseases as well as in the antiphospholipid syndrome. Knowledge of the genes involved and the functional consequences of alterations in their structure has led to therapy that blocks complement activation.

Use of eculizumab for atypical haemolytic uraemic syndrome and C3 glomerulopathies

In the past decade, a large body of evidence has accumulated in support of the critical role of dysregulation of the alternative complement pathway in atypical haemolytic uraemic syndrome (aHUS) and C3 glomerulopathies. These findings have paved the way for innovative therapeutic strategies based on complement blockade, and eculizumab, a monoclonal antibody targeting the human complement component 5, is now widely used to treat aHUS. In this article, we review 28 case reports and preliminary data from 37 patients enrolled in prospective trials of eculizumab treatment for episodes of aHUS involving either native or transplanted kidneys. Eculizumab may be considered as an optimal first-line therapy when the diagnosis of aHUS is unequivocal and this treatment has the potential to rescue renal function when administered early after onset of the disease. However, a number of important issues require further study, including the appropriate duration of treatment according to an individual's genetic background and medical history, the optimal strategy to prevent post-transplantation recurrence of aHUS and a cost-efficacy analysis. Data regarding the efficacy of eculizumab in the control of C3 glomerulopathies are more limited and less clear, but several observations suggest that eculizumab may act on the most inflammatory forms of this disorder.

Pathophysiology of thrombosis and pregnancy morbidity in the antiphospholipid syndrome

In patients with the antiphospholipid syndrome (APS), the presence of a group of pathogenic autoantibodies called antiphospholipid antibodies causes arteriovenous thrombosis and pregnancy complications. To date, the pathogenicity of the antiphospholipid antibodies has been the focus of analysis. Recently, the antibodies were reported to be capable of direct cell activation, and research on the underlying mechanism is ongoing. The antiphospholipid antibodies bind to the membranes of vascular endothelial cells, monocytes and platelets, provoking tissue factor expression and platelet aggregation. This activation functions as intracellular signalling, independent of the cell type, to activate p38MAPK and the transcription factor NFκB. Currently, there are multiple candidates for the membrane receptors of the antiphospholipid antibodies that are being tested for potential in specific therapy. Recently, APS was reported to have significant comorbidity with complement activation, and it was proposed that this results in placental damage and cell activation and, therefore, could be the primary factor for the onset of pregnancy complications and thrombosis. The detailed mechanism of complement activation remains unknown; however, an inflammation-inducing substance called anaphylatoxin, which appears during the activation process of the classical complement pathway, is thought to be a key molecule. Complement activation occurs in tandem, regardless of the pathology of APS or the type of antiphospholipid antibody, and it is thought that this completely new understanding of the mechanism will contribute greatly to comprehension of the pathology of APS.

Preeclampsia is characterized by placental complement dysregulation

Increasing evidence suggests that preeclampsia is associated with complement dysregulation. The origin of complement dysregulation in preeclampsia is unknown, and further unraveling this mechanism could provide both diagnostic tools and therapeutic targets. Because the placenta is believed to play a crucial role in the pathogenesis of preeclampsia, we investigated placentas from preeclamptic women (n=28) and controls (n=44) for the presence of complement activation products. Immunohistochemistry was performed for C1q, mannose-binding lectin, properdin, and C4d. Staining patterns were related to pregnancy outcome. Possible causes of complement activation were investigated, including the presence of immune deposits at the syncytiotrophoblast and changes in the placental mRNA expression of complement regulatory proteins. C4d was rarely present in placentas from healthy controls (3%), whereas it was observed in 50% of placentas obtained from preeclamptic women (P=0.001). In these placentas, C4d was observed in a focal (9/14) or diffuse (5/14) staining pattern at the syncytiotrophoblast. With respect to C1q, mannose-binding lectin, and properdin, no differences were observed between cases and controls. In preeclamptic women, diffuse placental C4d was associated with a significantly lower gestational age at delivery. Furthermore, the mRNA expression of the complement regulatory proteins CD55 and CD59 was significantly upregulated in preeclampsia. In conclusion, there is evidence for increased classical pathway activation and altered complement regulation in preeclampsia. The relation between C4d and lower gestational age at birth suggests that the extent of complement dysregulation is associated with the severity of preeclampsia. Inhibiting excessive complement activation may be a promising therapeutic approach in the management of preeclampsia.

STEC-HUS, atypical HUS and TTP are all diseases of complement activation

Haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopaenic purpura (TTP) are diseases characterized by microvascular thrombosis, with consequent thrombocytopaenia, haemolytic anaemia and dysfunction of affected organs. Advances in our understanding of the molecular pathology led to the recognition of three different diseases: typical HUS caused by Shiga toxin-producing Escherichia coli (STEC-HUS); atypical HUS (aHUS), associated with genetic or acquired disorders of regulatory components of the complement system; and TTP that results from a deficiency of ADAMTS13, a plasma metalloprotease that cleaves von Willebrand factor. In this Review, we discuss data indicating that complement hyperactivation is a common pathogenetic effector that leads to endothelial damage and microvascular thrombosis in all three diseases. In STEC-HUS, the toxin triggers endothelial complement deposition through the upregulation of P-selectin and possibly interferes with the activity of complement regulatory molecules. In aHUS, mutations in the genes coding for complement components predispose to hyperactivation of the alternative pathway of complement. In TTP, severe ADAMTS13 deficiency leads to generation of massive platelet thrombi, which might contribute to complement activation. More importantly, evidence is emerging that pharmacological targeting of complement with the anti-C5 monoclonal antibody eculizumab can effectively treat not only aHUS for which it is indicated, but also STEC-HUS and TTP in some circumstances.

Management of pregnancy in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoantibody-mediated systemic autoimmune disease, predominantly affecting young females. Pregnancy is increasingly common in the setting of SLE, as survival and quality of life of patients improve. Although live births can be achieved in the most cases, pregnancy in patients with SLE remains a high-risk condition. Maternal and fetal mortality and morbidity are considerably increased, compared with the general population. Aberrations in pregnancy-related maternal immune adaptations are likely contributors. Active maternal disease, renal involvement, specific autoantibody subsets and advanced organ damage are predictors of poor outcome. Therapeutic options are limited during pregnancy as maternal benefit has to be weighed against fetal risk. Prevention of preterm birth and refractory pregnancy loss, as well as management of established neonatal heart block remain unmet needs. Further research should address these important issues that affect young patients with SLE and their babies.

Obstetric nephrology: AKI and thrombotic microangiopathies in pregnancy

AKI in pregnancy remains a cause of significant fetomaternal mortality and morbidity, particularly in developing countries. Hypertensive complications of pregnancy (preeclampsia/eclampsia or hemolysis, elevated liver enzymes, and low platelets count syndrome) are the leading cause of AKI in pregnancy worldwide. Thrombotic microangiopathy is another peculiar and devastating cause of AKI in pregnancy. During the last decade, our understanding, and in some cases, our management, of these causes of AKI in pregnancy has dramatically improved. For instance, convincing data have linked pre-eclampsia/eclampsia to an increase in circulating antiangiogenic factors soluble Flt 1 and endoglin, which induce endothelial cell dysfunction, hypertension, and proteinuria. Several distinct pathogenic mechanisms underlying thrombotic microangiopathy, including thrombotic microangiopathy occurring during pregnancy, have been established. Thrombotic microangiopathy, which can present as hemolytic uremic syndrome or thrombotic thrombocytopenic purpura, can be reclassified in four potentially overlapping subtypes: disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 deficiency-related thrombotic microangiopathy, complement alternative pathway dysregulation-related thrombotic microangiopathy, secondary thrombotic microangiopathy (verotoxin and antiangiogenic drugs), and thrombotic microangiopathy of undetermined mechanism. In most cases, pregnancy is only a precipitating factor for thrombotic microangiopathy. Treatment of thrombotic microangiopathy occurring during pregnancy should be tailored to the underlying pathogenic mechanism: (1) restoration of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 serum activity in the setting of thrombotic thrombocytopenic purpura through plasma exchanges and in some cases, B cell-depleting therapy and (2) inhibition of complement alternative pathway activation in atypical hemolytic uremic syndrome using antiC5 blocking antibody (eculizumab).

Thrombotic microangiopathy and associated renal disorders

Thrombotic microangiopathy (TMA) is a pathological process involving thrombocytopenia, microangiopathic haemolytic anaemia and microvascular occlusion. TMA is common to haemolytic uraemic syndrome (HUS) associated with shiga toxin or invasive pneumococcal infection, atypical HUS (aHUS), thrombotic thrombocytopenic purpura (TTP) and other disorders including malignant hypertension. HUS complicating infection with shiga toxin-producing Escherichia coli (STEC) is a significant cause of acute renal failure in children worldwide, occurring sporadically or in epidemics. Studies in aHUS have revealed genetic and acquired factors leading to dysregulation of the alternative complement pathway. TTP has been linked to reduced activity of the ADAMTS13 cleaving protease (typically with an autoantibody to ADAMTS13) with consequent disruption of von Willebrand factor multimer processing. However, the convergence of pathogenic pathways and clinical overlap create diagnostic uncertainty, especially at initial presentation. Furthermore, recent developments are challenging established management protocols. This review addresses the current understanding of molecular mechanisms underlying TMA, relating these to clinical presentation with an emphasis on renal manifestations. A diagnostic and therapeutic approach is presented, based on international guidelines, disease registries and published trials. Early treatment remains largely empirical, consisting of plasma replacement/exchange with the exception of childhood STEC-HUS or pneumococcal sepsis. Emerging therapies such as the complement C5 inhibitor eculizumab for aHUS and rituximab for TTP are discussed, as is renal transplantation for those patients who become dialysis-dependent as a result of aHUS.

Genome-wide association study identifies a maternal copy-number deletion in PSG11 enriched among preeclampsia patients

Background

Specific genetic contributions for preeclampsia (PE) are currently unknown. This genome-wide association study (GWAS) aims to identify maternal single nucleotide polymorphisms (SNPs) and copy-number variants (CNVs) involved in the etiology of PE.

Methods

A genome-wide scan was performed on 177 PE cases (diagnosed according to National Heart, Lung and Blood Institute guidelines) and 116 normotensive controls. White female study subjects from Iowa were genotyped on Affymetrix SNP 6.0 microarrays. CNV calls made using a combination of four detection algorithms (Birdseye, Canary, PennCNV, and QuantiSNP) were merged using CNVision and screened with stringent prioritization criteria. Due to limited DNA quantities and the deleterious nature of copy-number deletions, it was decided a priori that only deletions would be selected for assay on the entire case-control dataset using quantitative real-time PCR.

Results

The top four SNP candidates had an allelic or genotypic p-value between 10^-5 and 10^-6, however, none surpassed the Bonferroni-corrected significance threshold. Three recurrent rare deletions meeting prioritization criteria detected in multiple cases were selected for targeted genotyping. A locus of particular interest was found showing an enrichment of case deletions in 19q13.31 (5/169 cases and 1/114 controls), which encompasses the PSG11 gene contiguous to a highly plastic genomic region. All algorithm calls for these regions were assay confirmed.

Conclusions

CNVs may confer risk for PE and represent interesting regions that warrant further investigation. Top SNP candidates identified from the GWAS, although not genome-wide significant, may be useful to inform future studies in PE genetics.

Epigenetics and microRNAs in preeclampsia

Strong evidence suggests a potential link among epigenetics, microRNAs (miRNAs), and pregnancy complications. Much research still needs to be carried out to determine whether epigenetic factors are predictive in the pathogenesis of preeclampsia (PE), a life-threatening disease during pregnancy. Recently, the importance of maternal epigenetic features, including DNA methylation, histone modifications, epigenetically regulated miRNA, and the effect of imprinted or non-imprinted genes on trophoblast growth, invasion, as well as fetal development and hypertension in pregnancy, has been demonstrated in a series of articles. This article discusses the current evidence of this complicated network of miRNA and epigenetic factors as potential mechanisms that may underlie the theories of disease for PE. Translating these basic epigenetic findings to clinical practice could potentially serve as prognostic biomarkers for diagnosis in its early stages and could help in the development of prophylactic strategies.

The complement system at the embryo implantation site: friend or foe?

An inflammatory-like process and vascular remodeling represent the main changes that occur in decidua in the early phase of pregnancy. These changes are partly induced by trophoblast cells that colonize the decidua and are also contributed by the complement system, which can easily be activated as a result of tissue remodeling. Local control by several complement regulators including surface-bound and soluble molecules is critical to prevent complement-mediated tissue damage in normal pregnancy. C7 expressed on the endothelial cells (ECs) surface has been recognized as a novel complement regulator involved in the control of the proinflammatory effect of the terminal complement complex. The protective role of placental complement regulators in pregnancy is underscored by the recent finding of an association of preeclampsia with mutations in the genes encoding for some of these proteins. Complement components produced at feto-maternal interface serve an important function in placental development. C1q synthesized by decidual ECs and expressed on the cell surface is particularly important in this regard because it acts as a molecular bridge between endovascular trophoblast and ECs. C1q is also produced by extravillous trophoblast and is used to favor trophoblast migration through the decidua. Defective expression of C1q by trophoblast is associated with impaired trophoblast invasion of decidua and may have important implications in pregnancy disorders such as preeclampsia characterized by reduced vascular remodeling.

The role of complement in the antiphospholipid syndrome: a novel mechanism for pregnancy morbidity

OBJECTIVES

Despite the experimental research data on antiphospholipid syndrome (APS), the pathogenesis of thrombosis and fetal loss remains unknown. The objective of this study was to analyze the major advances in the field of complement activation as a possible thrombosis mechanism in the APS.

METHODS

The authors conducted a systemic analysis of the English literature and summarized both animal and human data that indicate the inappropriate complement activation as a mechanism causing thrombosis in the APS.

RESULTS

The important role of complement activation in the pathogenesis of fetal loss was established using mice deficient in a complement regulatory protein. Further studies have shown that the infusion of human IgG antiphospholipid antibodies (aPL) induced fetal loss in pregnant mice, an effect that was abrogated by the concurrent administration of a C3 convertase inhibitor. Further studies suggested that C5a and neutrophils were the key components responsible for fetal injury. Moreover, use of F(ab)'2 fragments of aPL suggested the complement activation occurred mainly via the classical pathway. Other studies using models of induced thrombosis suggested that antibodies against β2GPI required the presence of terminal complement components to induce thrombus formation, and mice deficient in C3 or C5 were found to be resistant to aPL-induced thrombosis. Based on the aforementioned findings, it has been suggested that heparin prevents fetal loss in patients with APS by inhibiting complement activation rather than by its anticoagulant effect.

CONCLUSIONS

The studies on complement are significant because they shift the focus of research in APS from thrombosis to inflammation. However, as human data are limited, more clinical research is necessary before the above findings translate in changes in the management of APS.

Maternal deaths in women with lupus nephritis: a review of published evidence

BACKGROUND AND OBJECTIVES

Pregnancies in women with systemic lupus erythematosus (SLE) and lupus nephritis are considered high-risk due to high rates of maternal and fetal complications. However, there has not been a formal analysis addressing the issue of maternal deaths in these women. The aim of this study was to perform a literature review of the maternal deaths in women with SLE and lupus nephritis to: (1) identify the main causes of death and (2) discuss possible reasons for these causes, and strategies that may improve patient care and outcomes. DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENT: We performed an extensive electronic literature search from 1962 to 2009 using online databases (PubMed, Embase, Lilacs, Cochrane Controlled Trials Register, Medline, and Science Citation Index). Studies were included if they reported pregnancies in patients with SLE and lupus nephritis with at least one reported maternal death.

RESULTS

We identified 13 studies that reported a total of 17 deaths in the 6 week post-partum period that were attributable to SLE and lupus nephritis. In all cases, death occurred in the setting of active disease, and was attributed either to infection in 41.2% (n = 7), or disease activity in 29.4% (n = 5). The remaining deaths were due to pulmonary embolus in 11.8% (n = 2), pregnancy-associated cardiomyopathy in 5.9% (n = 1), adrenal failure due to abrupt steroid withdrawal in 5.9% (n = 1), and undefined in 5.9% (n = 1).

CONCLUSIONS

All maternal deaths in patients with SLE and lupus nephritis occurred in those with active disease, with disease activity/complications and infections (mainly opportunistic) being the two major causes. The presented evidence further supports timing of pregnancy relative to SLE activity, and the judicious use of immunosuppressive agents in pregnant patients.

Mechanisms and management of hypertension in pregnant women

Hypertension is the most common medical disorder encountered during pregnancy. A recent report highlighted hypertensive disorders as one of the major causes of pregnancy-related maternal deaths in the United States. Significant advances in our understanding of preeclampsia, a form of hypertension unique to pregnancy, have occurred in recent years. The optimal timing and choice of therapy for hypertensive pregnancy disorders involves carefully weighing the risk-versus-benefit ratio for each individual patient, with an overall goal of improving maternal and fetal outcomes. In this review, we summarize the mechanisms thought to be involved, review the current management guidelines for hypertensive pregnancy disorders as recommended by international guideline groups, and outline some newer perspectives on management.

Pros and cons for C4d as a biomarker

The introduction of C4d in daily clinical practice in the late nineties aroused an ever-increasing interest in the role of antibody-mediated mechanisms in allograft rejection. As a marker of classical complement activation, C4d made it possible to visualize the direct link between anti-donor antibodies and tissue injury at sites of antibody binding in a graft. With the expanding use of C4d worldwide several limitations of C4d were identified. For instance, in ABO-incompatible transplantations C4d is present in the majority of grafts but this seems to point at 'graft accommodation' rather than antibody-mediated rejection. C4d is now increasingly recognized as a potential biomarker in other fields where antibodies can cause tissue damage, such as systemic autoimmune diseases and pregnancy. In all these fields, C4d holds promise to detect patients at risk for the consequences of antibody-mediated disease. Moreover, the emergence of new therapeutics that block complement activation makes C4d a marker with potential to identify patients who may possibly benefit from these drugs. This review provides an overview of the past, present, and future perspectives of C4d as a biomarker, focusing on its use in solid organ transplantation and discussing its possible new roles in autoimmunity and pregnancy.

Complement-mediated injury and protection of endothelium: lessons from atypical haemolytic uraemic syndrome

The complement system provides a vital defence against invading pathogens. As an intrinsic system it is always 'on', in a state of constant, low level activation. This activation is principally mediated through the deposition of C3b on to pathogenic surfaces and host tissues. C3b is generated by spontaneous 'tick over' and formal activation of the alternative pathway, and by activation of the classical and lectin pathways. If the deposited C3b is not appropriately regulated, there is progression to terminal pathway complement activation via the C5 convertases, generating the potent anaphylotoxin C5a and the membrane attack complex C5b-9. Unsurprisingly, these highly active components have the potential to cause injury to bystander host tissue, including the vascular endothelium. As such, complement activation on endothelium is normally tightly controlled by a large number of fluid-phase and membrane bound inhibitors, in an attempt to ensure that propagation of complement activation is appropriately restricted to invading pathogens and altered 'self', e.g. apoptotic and necrotic cells. The kidney is increasingly recognised as a site at particular risk from complement-mediated endothelial injury. Both genetic and acquired defects which impact on complement regulation predispose to this susceptibility. The thrombotic microangiopathy, haemolytic uraemic syndrome (HUS), will be used to illustrate the mechanisms by which the endothelial cell injury occurs. Finally, the underlying rationale for current and future potential therapeutic interventions in HUS and also the opportunities for enhancing endothelial defence to prevent relapsing disease through increased complement cytoprotective strategies will be summarised.