Differences in Endothelial Activation and Dysfunction Induced by Antiphospholipid Antibodies Among Groups of Patients With Thrombotic, Refractory, and Non-refractory Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by pregnancy morbidity or thrombosis and persistent antiphospholipid antibodies (aPL) that bind to the endothelium and induce endothelial activation, which is evidenced by the expression of adhesion molecules and the production of reactive oxygen species (ROS) and subsequent endothelial dysfunction marked by a decrease in the synthesis and release of nitric oxide (NO). These endothelial alterations are the key components for the development of severe pathological processes in APS. Patients with APS can be grouped according to the presence of other autoimmune diseases (secondary APS), thrombosis alone (thrombotic APS), pregnancy morbidity (obstetric APS), and refractoriness to conventional treatment regimens (refractory APS). Typically, patients with severe and refractory obstetric APS exhibit thrombosis and are classified as those having primary or secondary APS. The elucidation of the mechanisms underlying these alterations according to the different groups of patients with APS could help establish new therapies, particularly necessary for severe and refractory cases. Therefore, this study aimed to evaluate the differences in endothelial activation and dysfunction induced by aPL between patients with refractory obstetric APS and other APS clinical manifestations. Human umbilical vein endothelial cells (HUVECs) were stimulated with polyclonal immunoglobulin-G (IgG) from different groups of patients n = 21), including those with primary (VTI) and secondary thrombotic APS (VTII) and refractory primary (RI+), refractory secondary (RII+), and non-refractory primary (NR+) obstetric APS. All of them with thrombosis. The expression of adhesion molecules; the production of ROS, NO, vascular endothelial growth factor (VEGF), and endothelin-1; and the generation of microparticles were used to evaluate endothelial activation and dysfunction. VTI IgG induced the expression of adhesion molecules and the generation of microparticles and VEGF. RI+ IgG induced the expression of adhesion molecules and decreased NO production. RII+ IgG increased the production of microparticles, ROS, and endothelin-1 and reduced NO release. NR+ IgG increased the production of microparticles and endothelin-1 and decreased the production of VEGF and NO. These findings reveal differences in endothelial activation and dysfunction among groups of patients with APS, which should be considered in future studies to evaluate new therapies, especially in refractory cases.

Antiphospholipid Antibodies From Women With Pregnancy Morbidity and Vascular Thrombosis Induce Endothelial Mitochondrial Dysfunction, mTOR Activation, and Autophagy

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by thrombosis and pregnancy morbidity (PM) obstetric events together with persistent high titers of circulating antiphospholipid antibodies (aPL). Several mechanisms that explain the development of thrombosis and PM in APS include the association of aPL with alterations in the coagulation cascade and inflammatory events. Other mechanisms disturbing cellular homeostases, such as mitochondrial dysfunction, autophagy, and cell proliferation, have been described in other autoimmune diseases. Therefore, the objective of this study was to investigate the impact of aPL from different patient populations on endothelial cell mitochondrial function, activation of the mammalian target of rapamycin (mTOR) and autophagy pathways, and cellular growth. Using an in vitro model, human umbilical vein endothelial cells (HUVECs) were treated with polyclonal immunoglobulin G (IgG) purified from the serum of women with both PM and vascular thrombosis (PM/VT), with VT only (VT), or with PM and non-criteria aPL (seronegative-obstetric APS, SN-OAPS). We included IgG from women with PM without aPL (PM/aPL-) and healthy women with previous uncomplicated pregnancies (normal human serum, NHS) as control groups. Mitochondrial function, mTOR activation, autophagy, and cell proliferation were evaluated by Western blotting, flow cytometry, and functional assays. IgG from women with PM/VT increased HUVEC mitochondrial hyperpolarization and activation of the mTOR and autophagic pathways, while IgG from patients with VT induced endothelial autophagy and cell proliferation in the absence of elevated mTOR activity or mitochondrial dysfunction. IgG from the SN-OAPS patient group had no effect on any of these HUVEC responses. In conclusion, aPL from women with PM and vascular events induce cellular stress evidenced by mitochondrial hyperpolarization and increased activation of the mTOR and autophagic pathways which may play a role in the pathogenesis of obstetric APS.

Coexistent antiphospholipid syndrome and myeloproliferative neoplasm

Antiphospholipid syndrome (APS) and myeloproliferative neoplasms (MPN) are associated with an increased risk of thrombosis. The optimal management of patients with coexistent APS and MPN has not been defined. A single centre and systematic literature review of patients with coexistent APS and MPN was performed. Cases were divided into two groups based on whether they met international consensus criteria for APS. Of the 12 studies identified, eight were excluded (leaving five of a total 54 patients), as although antiphospholipid antibodies (aPL) were documented, the diagnosis of APS was not conclusively demonstrated. Another ten patients with definite APS were identified at our centre. Fifteen patients (ten females, five males) were therefore included in this analysis (eleven definite APS and four highly likely), median age 44 (range: 13–71) years. Nine had polycythaemia vera and six, essential thrombocythaemia. Thirteen of the 15 patients (86.7%) had thrombotic APS (seven with initial venous events and six arterial) and two (13.3%) had obstetric APS. Nine patients were single-positive, and six double-positive for aPL. None were triple aPL-positive. Four patients at our centre had recurrent thrombotic/obstetric events, including while on anticoagulation/antiplatelet treatment.

Clinical characteristics and prognosis of patients with isolated thrombotic vs. obstetric antiphospholipid syndrome: a prospective cohort study

Background Several studies suggested that thrombotic and obstetric antiphospholipid syndromes could be independent identities, but few have systematically compared their clinical characteristics and prognosis. Objective The objective of this study is to identify key differences between thrombotic APS (tAPS) and obstetric APS (oAPS). Methods This single-center, prospective study included consecutive patients with primary antiphospholipid syndrome (APS) receiving treatment at the Peking Union Medical College Hospital during a period from 2013 to 2020. Results Screening of the database yielded a total of 244 women with positive antiphospholipid antibody (aPL). Among the 105 women with primary APS, 39 (37.14%) had isolated tAPS (ItAPS), 44 (41.90%) had isolated oAPS (IoAPS), and 9 (8.57%) had both tAPS and tAPS+oAPS. In comparison to those with IoAPS, patients with ItAPS had older age (41.92 ± 11.97 vs. 33.16 ± 4.22 years, P < 0.01), higher rate of cardiovascular risk (at least one positive of coronary heart disease, hypertension, obesity, diabetes, and hyperlipidemia) (41.03% vs. 6.82%, P < 0.01), and higher frequency of thrombocytopenia (43.59% vs. 20.45%, P < 0.05). Antibody profiles were generally similar among the groups, but isolated anti-β2GPI positivity was more common in patients with IoAPS (52.27% vs. 17.94% for ItAPS, P = 0.01). Triple aPL positivity was more common in patients with both tAPS and oAPS (66.67% vs. 46.15% for ItAPS vs. 25% for IoAPS, P = 0.022). Blood homocysteine was higher in patients with ItAPS (11.20 vs. 9.90 μmol/L for IoAPS, P < 0.05), but there were no differences in inflammatory markers or complements. Recurrence rate of thrombosis was higher in patients with ItAPS (33.33% vs. 2.27% for IoAPS, P ≤ 0.001) with a mean follow-up of 61 months. Conclusion Despite generally similar antibody and biochemical profiles, patients with ItAPS had much higher risk of recurrent thrombosis than IoAPS, supporting distinct mechanisms of pathogenesis.

Extracellular Vesicles and Antiphospholipid Syndrome: State-of-the-Art and Future Challenges

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterized by thromboembolism, obstetric complications, and the presence of antiphospholipid antibodies (aPL). Extracellular vesicles (EVs) play a key role in intercellular communication and connectivity and are known to be involved in endothelial and vascular pathologies. Despite well-characterized in vitro and in vivo models of APS pathology, the field of EVs remains largely unexplored. This review recapitulates recent findings on the role of EVs in APS, focusing on their contribution to endothelial dysfunction. Several studies have found that APS patients with a history of thrombotic events have increased levels of EVs, particularly of endothelial origin. In obstetric APS, research on plasma levels of EVs is limited, but it appears that levels of EVs are increased. In general, there is evidence that EVs activate endothelial cells, exhibit proinflammatory and procoagulant effects, interact directly with cell receptors, and transfer biological material. Future studies on EVs in APS may provide new insights into APS pathology and reveal their potential as biomarkers to identify patients at increased risk.

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

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

16th International Congress on Antiphospholipid Antibodies Task Force Report on Obstetric Antiphospholipid Syndrome

Obstetric antiphospholipid syndrome (APS) remains a clinical challenge for practitioners, with several controversial points that have not been answered so far. This Obstetric APS Task Force met on the 16th International Congress on Antiphospholipid Antibodies in Manchester, England, to discuss about treatment, diagnostic and clinical aspects of the disease. This report will address evidence-based medicine related to obstetric APS, including limitations on our current management, the relationship between antibodies against domain 1 of β2GPI and obstetric morbidity, hydroxychloroquine use in patients with obstetric APS and factors associated with thrombosis after obstetric APS. Finally, future directions for better understanding this complex condition are also reported by the Task Force coordinators.

Is There an Additional Value in Detecting Anticardiolipin and Anti-β2 glycoprotein I IgA Antibodies in the Antiphospholipid Syndrome?

Background Anticardiolipin (aCL) and anti-β2 glycoprotein I (aβ2GPI) immunoglobulin A (IgA) antiphospholipid antibodies (aPL) have shown to associate with thrombosis and pregnancy morbidity. However, inclusion of IgA aPL in the classification criteria of the antiphospholipid syndrome (APS) has been debated. We investigated the value of aCL and aβ2GPI IgA aPL in the detection of thrombosis and pregnancy morbidity in addition to the current aPL panel for APS. Methods We included 1,068 patients from eight European medical centers: 259 thrombotic APS patients, 122 obstetric APS patients, 204 non-APS thrombosis patients, 33 non-APS obstetric patients, 60 APS patients with unspecified clinical manifestations, 196 patients with autoimmune diseases, and 194 controls. aCL and aβ2GPI IgG/M/A were detected with four commercial assays and lupus anticoagulant was determined by the local center. Results Positivity for IgA aPL was found in 17 to 26% of the patients with clinical manifestations of APS and in 6 to 13% of the control population. Both aCL and aβ2GPI IgA were significantly associated with thrombosis and pregnancy morbidity. Isolated IgA positivity was rare in patients with clinical manifestations of APS (0.3–5%) and not associated with thrombosis and/or pregnancy morbidity. Addition of IgA to the current criterion panel did not increase odds ratios for thrombosis nor pregnancy morbidity. Conclusion aCL and aβ2GPI IgA are associated with clinical manifestations of APS. However, isolated IgA positivity was rare and not associated with thrombosis or pregnancy morbidity. These data do not support testing for aCL and aβ2GPI IgA subsequent to conventional aPL assays in identifying patients with thrombosis or pregnancy morbidity.

Obstetric antiphospholipid syndrome is not associated with an increased risk of subclinical atherosclerosis

Objectives The persistent positivity of aPLs, either isolated or associated with thrombotic and/or obstetric events (APS), has been associated with the increase of intima-media thickness (IMT) and carotid plaques. Despite the fact that aPLs can promote both thrombotic and obstetric complications, some pathogenic differences have been documented between the two entities. This study aimed to evaluate whether the atherosclerotic risk differs between subjects with obstetric and thrombotic APS. Methods A total of 167 APS women (36 obstetric and 131 thrombotic) were compared with 250 aPLs negative controls. IMT of the common carotid artery (CCA) and of the bulb and the prevalence of carotid plaques were assessed. Results CCA- and bulb-IMT were significantly higher in women with thrombotic APS, while being similar between the obstetric APS and the controls [CCA-IMT: mean (s.d.) 0.97 (0.49), 0.78 (0.22) and 0.81 (0.12) mm for the thrombotic, obstetric and control groups, respectively, P &lt; 0.001 between thrombotic and controls, P = 0.002 between thrombotic and obstetric; bulb-IMT: mean (s.d.) 1.38 (0.79), 0.96 (0.27) and 0.96 (0.51) mm for the thrombotic, obstetric and control groups, P &lt; 0.001]. Women with thrombotic APS had significantly increased risk of presenting carotid plaques. This risk was significantly lower in obstetric APS. Conclusion Unlike thrombotic APS, obstetric APS is not associated with an increase of markers of subclinical atherosclerosis. If confirmed on wider populations, these results could suggest different pathogenetic role of aPLs in promoting atherosclerosis in vascular and obstetric APS, and raise questions on the risk–benefit profile of thromboprophylaxis in obstetric APS outside pregnancy periods.