Zuo, Yu

Objective Antiphospholipid syndrome (APS) is a thromboinflammatory disorder characterized by clinical and mechanistic heterogeneity that complicates early diagnosis and hinders targeted treatment. We aimed to identify distinct molecular endotypes among antiphospholipid antibody (aPL)–positive patients using whole‐blood transcriptomics. Methods Whole‐blood RNA sequencing was performed on 174 aPL‐positive patients, including those with primary APS (n = 102), secondary APS (n = 29), and aPL positivity without classifiable APS (n = 43). Unsupervised machine learning and immune cell deconvolution defined transcriptomic clusters and immune landscapes. Results Four transcriptionally distinct clusters were identified. At one end of the spectrum, cluster 1 showed up‐regulation of ribosomal and metabolic pathways and down‐regulation of mechanistic target of rapamycin (mTOR), NETosis, and Hippo/interleukin‐6 (IL‐6) signaling. In contrast, cluster 4 exhibited the opposite pattern, with strong up‐regulation of mTOR, NETosis, and Hippo/IL‐6 signaling. Cluster 2 demonstrated modest enrichment in messenger RNA processing and amino acid metabolism, and cluster 3 showed biosynthetic suppression with mild Hippo/IL‐6 activation. Clinically, cluster 4 stood out with higher IgG anticardiolipin and anti–β 2 ‐glycoprotein I positivity, elevated neutrophil counts, and increased urine protein‐to‐creatinine ratios. Immune deconvolution revealed distinct cell type profiles: cluster 1 was lymphoid predominant; cluster 2 had a balanced composition; cluster 3 was enriched in Treg cells, natural killer cells, macrophages, mast cells, and memory B cells; and cluster 4 was dominated by myeloid cells, including neutrophils, eosinophils, and dendritic cells. Distinct immune pathway activations were linked to clinical features, including white matter lesions, seizures, and cardiac valve disease. Conclusion This study reveals four endotypes of aPL‐positive patients, a step toward personalized medicine for APS through pathway‐informed stratification and therapy.

BACKGROUND: Whereas antiphospholipid syndrome (APS) is best known for increasing the risk of macrovascular thrombosis, APS vasculopathy is characterized by the abnormal proliferation of endothelial and smooth muscle cells, leading to occlusion of small blood vessels in the skin, kidneys, and heart, among other organs. The underlying mechanisms remain unclear, and targeted treatment options for patients with APS are lacking. METHODS: To identify and analyze APS microvascular endothelial cells (MVECs), skin biopsies of patients with APS complicated by livedo racemosa were characterized using single-cell RNA sequencing. CCN1 (cellular communication network factor 1) and CCN2 were identified in skin and kidney biopsies by immunofluorescence microscopy and in plasma by ELISA. Healthy dermal MVECs were cultured with APS patient–derived serum or immunoglobulin G (IgG), and relevant signaling pathways were characterized using quantitative PCR, immunoblotting, and immunofluorescence microscopy. The proliferation and migration of vascular smooth muscle cells were determined after exposure to conditioned medium from APS IgG–stimulated MVECs. A mouse model of APS IgG–accelerated neointima formation was developed. Anti-CCN2 monoclonal antibodies were tested in vascular smooth muscle cell functional assays and the mouse model. RESULTS: Increased endothelial cell expression of CCN1 and CCN2 was identified by single-cell RNA sequencing and further confirmed in APS skin by microscopy as well as in APS plasma by ELISA. Exposure of healthy MVECs to patient IgG triggered the upregulation of CCN1 and CCN2 via Toll-like receptor 4– and YAP1 (yes-associated protein 1)–mediated signaling. CCN2, originating from APS IgG–stimulated MVECs led to the proliferation and migration of vascular smooth muscle cells, phenotypes that were inhibited by an anti-CCN2 antibody or depletion of EGFR (epidermal growth factor receptor). We further observed increased expression of CCN2, along with evidence of YAP1 nuclear translocation, in kidney vessels of APS nephropathy biopsies. Finally, CCN2 inhibition with an anti-CCN2 monoclonal antibody significantly reduced neointima thickening and cell proliferation in a mouse model of APS IgG–accelerated neointima formation. CONCLUSIONS: This study revealed activation of YAP1-mediated signaling in APS dermal microvessels and demonstrated that the YAP1 target CCN2 plays a role in facilitating pro-proliferative communication between MVECs and vascular smooth muscle cells. These findings offer insights into the cellular and molecular mechanisms underlying APS vasculopathy, providing potential therapeutic targets for patients.

Background/Purpose APS ACTION Registry was created to study the natural course of antiphospholipid syndrome (APS) over 10 years in persistently antiphospholipid antibody (aPL) positive patients with or without systemic autoimmune rheumatic diseases (SARDs). Our primary objective was to compare the characteristics of aPL-positive patients with or without thrombocytopenia (TP) and/or autoimmune hemolytic anemia (AIHA). Methods The registry inclusion criteria are positive aPL based on the Revised Sapporo APS Classification Criteria, tested at least twice within 1 year prior to enrollment. For the primary comparison of demographic, clinical, and serologic characteristics in this retrospective study, we divided patients into two groups: TP/AIHA ever and never. Thrombocytopenia was defined as a platelet count of <100,000 x 10 9 /L tested twice at least 12 weeks apart, and AIHA was defined as anemia with hemolysis and a positive direct antiglobulin test (DAT). For the secondary analysis, we compared patients with TP versus AIHA, and the immunosuppressive use stratified by systemic lupus erythematosus (SLE) classification. Results As of April 2022, of 1,039 patients (primary aPL/APS: 618 [59%]; SLE classification: 334 [31%]) included in the registry, 228 (22%) had baseline (historical or current) TP and/or AIHA (TP only: 176 [17%]; AIHA only: 35 [3%], and both: 17 [2%]). Thrombocytopenia and/or AIHA was significantly associated with Asian race, SLE classification, cardiac valve disease, catastrophic/microvascular APS, triple aPL (lupus anticoagulant, anticardiolipin antibody, and anti-β 2 -glycoprotein-I antibody) positivity, and SLE-related serologic and inflammatory markers. When 101/618 (16%) primary aPL/APS patients and 101/334 (34%) SLE patients with TP and/or AIHA were compared, azathioprine and mycophenolate mofetil were more commonly reported in lupus patients, however corticosteroid, intravenous immunoglobulin, and rituximab use were similar between groups. Conclusion In our large multi-center international cohort of persistently aPL-positive patients, approximately one-fifth had active or historical TP and/or AIHA at registry entry; half of these patients had additional SLE. Cardiac valve disease, catastrophic/microvascular APS, and triple aPL-positivity were aPL-related clinical and laboratory manifestations associated with TP and/or AIHA, suggesting a more severe APS clinical phenotype in aPL-patients with TP and/or AIHA.

ObjectiveWhile thrombosis and pregnancy loss are the best‐known clinical features of antiphospholipid syndrome (APS), many patients also exhibit “extra‐criteria” manifestations, such as thrombocytopenia. The mechanisms that drive APS thrombocytopenia are not completely understood, and no clinical biomarkers are available for predicting antiphospholipid antibody (aPL)–mediated thrombocytopenia. Calprotectin is a heterodimer of S100A8 and S100A9 that is abundant in the neutrophil cytoplasm and released upon proinflammatory neutrophil activation. Here, we sought to evaluate the presence, clinical associations, and potential mechanistic roles of circulating calprotectin in a cohort of primary APS and aPL‐positive patients.MethodsLevels of circulating calprotectin were determined in plasma by the QUANTA Flash chemiluminescent assay. A viability dye‐based platelet assay was used to assess the potential impact of calprotectin on aPL‐mediated thrombocytopenia.ResultsCirculating calprotectin was measured in 112 patients with primary APS and 30 aPL‐positive (without APS criteria manifestations or lupus) patients as compared to patients with lupus (without APS), patients with unprovoked venous thrombosis (without aPL), and healthy controls. Levels of calprotectin were higher in patients with primary APS and aPL‐positive patients compared to healthy controls. After adjustment for age and sex, calprotectin level correlated positively with absolute neutrophil count (r = 0.41, P < 0.001), positively with C‐reactive protein level (r = 0.34, P = 0.002), and negatively with platelet count (r = −0.24, P = 0.004). Mechanistically, we found that calprotectin provoked aPL‐mediated thrombocytopenia by engaging platelet surface toll‐like receptor 4 and activating the NLRP3‐inflammasome, thereby reducing platelet viability in a caspase‐1‐dependent manner.ConclusionThese data suggest that calprotectin has the potential to be a functional biomarker and a new therapeutic target for APS thrombocytopenia.image

ObjectiveThis study assessed patient‐reported outcomes (PROs) in individuals with persistently positive antiphospholipid antibodies (aPL) to better understand how living with aPL may affect their quality of life.MethodsPatients completed Patient‐Reported Outcomes Measurement Information System Physical Function (PF) and Cognitive Function (CF) Short Forms as well as the pain intensity (PI) rating (scale of 1‐10). Patients were characterized for demographics, clinical manifestations of antiphospholipid syndrome (APS), cardiovascular risk factors, laboratory test results, and medication usage. Multivariate modeling was done via linear regression.ResultsOf 139 patients, 89 had primary APS, 21 had secondary APS, and 29 had persistent aPL without meeting clinical criteria for APS. The average T scores (±SD) for PF and CF were 45.4 ± 9.2 and 48.6 ± 11.6, respectively; the average for PI was 3.0 ± 2.6. Approximately half of the patients (47%) endorsed at least mild impairment in PF (T score < 45). Mean PF, CF, and PI did not differ between diagnostic groups. Individuals who endorsed more impairment on one measure also tended to endorse more impairment on another (Pearson r = 0.43‐0.59). In the multivariate models, age, smoking, pain medications, and serotonergic medications were associated with impairment in at least one PRO domain. The Damage Index for APS was significantly correlated with both PF and CF.ConclusionIndividuals living with APS endorsed more impairment in PF (and potentially CF) than expected for the general population. The relationship between certain medications and PROs warrants further study, as does the longitudinal trajectory of these and other PROs.

Abstract Objective Leucocyte immunoglobulin-like receptor A3 (LILRA3) belongs to a family of leucocyte receptors. Our previous study reported LILRA3 transcripts were markedly upregulated in neutrophils from patients with APS. We undertook this study to investigate clinical implications of LILRA3 in APS and its potential role in APS-associated thrombosis. Methods Two independent cohorts were studied. The first consisted of 294 APS patients, 48 asymptomatic aPL carriers and 150 healthy controls (HCs) from Peking University People’s Hospital. The second included 99 APS patients, 25 aPL carriers and 40 HCs from United States APS centres. Serum or plasma concentrations of LILRA3 and MPO-DNA complexes were measured. Additionally, 35 patients with thrombotic APS (tAPS) were evaluated to determine potential effects of immunosuppressive therapy on serum concentrations of LILRA3 and MPO-DNA complexes. Results Both positivity and serum concentration of LILRA3 were significantly increased in APS patients, especially in those with tAPS. LILRA3-positive tAPS patients displayed more severe thrombotic manifestations. Serum LILRA3 was positively correlated with MPO-DNA complexes in LILRA3-positive tAPS. After immunosuppressive treatment, LILRA3 and MPO-DNA complexes were consistently decreased in tAPS patients. Key findings from the Peking cohort were confirmed in the United States cohort. Conclusion Our study provides first evidence that LILRA3 is aberrantly expressed in APS, especially in patients with tAPS. Serum LILRA3 correlated with MPO-DNA complexes, and the two indices were consistently decreased in tAPS patients after treatment. LILRA3 may play a role in thrombosis of APS and may serve as a biomarker and/or therapeutic target in tAPS.

Purpose of review Antiphospholipid syndrome (APS), more common than once believed, is an autoimmune disease best known for its high risk of incident and recurrent thrombotic events. The approach to treatment potentially differs from treatment of thrombosis in the general population, and this article endeavors to review the latest updates on this topic. Recent findings The epidemiology of APS is being increasingly elucidated by large population-based studies, with APS perhaps affecting as many as 1 in 2000 individuals. Vitamin K antagonists, aspirin, and heparinoids continue to have obvious roles in the management of patients with APS. There has recently been intensive study of direct oral anticoagulants in APS, with the most recent randomized studies raising concerns about their inferiority to vitamin K antagonists, at least in some subgroups. Other approaches to treating APS beyond anticoagulants and antiaggregants are also receiving increased attention in mechanistic and preclinical studies with an eye toward future roles in patients with refractory and/or microvascular disease. Pediatric APS is identified as an area in desperate need of additional prospective research. Summary Progress continues to be made in pursuit of improving the lives of individuals afflicted with APS. The most important future directions would seem to involve leveraging modern molecular technologies in order to improve subphenotyping of antiphospholipid antibody-positive individuals. This will help personalize risk profiles and ideally define the optimal approach to therapy based on future risk, rather than past morbid events.