Search

The syndromes of thrombotic microangiopathy (TMA) are diverse and represent severe endothelial damage caused by various mechanisms. The complement system plays a major role in a subset of patients with TMA, and its recognition is of clinical importance because it guides choice and duration of treatment. We studied a well-defined cohort of patients with TMA and hypothesized that assessment of serum-induced C5b9 formation on the endothelium and screening for rare variants in complement genes can better categorize TMA. Massive C5b9 formation was found in all patients with primary atypical hemolytic uremic syndrome (/ = 11/11) and in 59% of patients with TMA and coexisting conditions (/ = 30/51). Massive C5b9 formation was associated with rare genetic variants (45% [/ = 20/44] vs. 0% [/ = 0/21] patients with normal C5b9 formation; < 0.001). Massive C5b9 formation was associated with favorable renal response to therapeutic complement inhibition in patients with TMA and coexisting conditions (86% [/ = 12/14] vs. 31% [/ = 5/16] of untreated patients; < 0.001), indicating complement-mediated TMA rather than secondary disease. Among treated patients, the odds ratio for 1-year kidney survival was 12.0 (95% confidence interval 1.2-115.4). TMA recurrence was linked to rare genetic variants in all cases. Patients with normal C5b9 formation had an acute, nonrelapsing form of TMA. C5b9 formation and genetic testing appears to categorize TMAs into different groups because it identifies complement as a driving factor of disease, with potential therapeutic and prognostic implications.

BACKGROUND: Vascular calcification is an active process that increases cardiovascular disease (CVD) risk. There is still no consensus on an appropriate biomarker for vascular calcification. We reasoned that the biomarker for vascular calcification is the collection of all blood components that can be sensed and integrated into a calcification response by human vascular smooth muscle cells (hVSMCs). METHODS: We developed a new cell-based high-content assay, the BioHybrid assay, to measure in vitro calcification. The BioHybrid assay was compared with the o-Cresolphthalein assay and the T50 assay. Serum and plasma were derived from different cohort studies including chronic kidney disease (CKD) stages III, IV, V and VD (on dialysis), pseudoxanthoma elasticum (PXE) and other cardiovascular diseases including serum from participants with mild and extensive coronary artery calcification (CAC). hVSMCs were exposed to serum and plasma samples, and in vitro calcification was measured using AlexaFluor®-546 tagged fetuin-A as calcification sensor. RESULTS: The BioHybrid assay measured the kinetics of calcification in contrast to the endpoint o-Cresolphthalein assay. The BioHybrid assay was more sensitive to pick up differences in calcification propensity than the T50 assay as determined by measuring control as well as pre- and post-dialysis serum samples of CKD patients. The BioHybrid response increased with CKD severity. Further, the BioHybrid assay discriminated between calcification propensity of individuals with a high CAC index and individuals with a low CAC index. Patients with PXE had an increased calcification response in the BioHybrid assay as compared to both spouse and control plasma samples. Finally, vitamin K1 supplementation showed lower in vitro calcification, reflecting changes in delta Agatston scores. Lower progression within the BioHybrid and on Agatston scores was accompanied by lower dephosphorylated-uncarboxylated matrix Gla protein levels. CONCLUSION: Th

Introduction: Monitoring the microcirculation may be helpful in guiding resuscitation in patients with circulatory shock. Sublingual side-stream dark field imaging cameras allow for noninvasive, bedside evaluation of the microcirculation, although their use in clinical practice has not yet been validated. The GlycoCheck system automatically analyzes images to determine glycocalyx thickness, red blood cell filling percentage, and vessel density. Although GlycoCheck has been used to study microcirculation in critically ill patients, little is known about the reproducibility of measurements in this population. Materials and Methods: A total of 60 critically ill patients were studied. Three consecutive microcirculation measurements were performed with the GlycoCheck system in 40 of these patients by one of two experienced observers. Twenty patients were assessed by both observers. Intra- and interobserver variability were assessed using intraclass correlation coefficients (ICCs). Results: ICCs of single measurements were poor for glycocalyx thickness and good for filling percentage and vessel density. Reproducibility could be substantially increased for all parameters when three consecutive measurements were performed and averaged. Discussion: GlycoCheck can be used to study microcirculation. However, to obtain reliable results three consecutive measurements should be performed and averaged. The variation of the measurements currently hampers the clinical application in individual patients.

Heparins represent one of the most frequently used pharmacotherapeutics. Discovered around 1926, routine clinical anticoagulant use of heparin was initiated only after the publication of several seminal papers in the early 1970s by the group of Kakkar. It was shown that heparin prevents venous thromboembolism and mortality from pulmonary embolism in patients after surgery. With the subsequent development of low-molecular-weight heparins and synthetic heparin derivatives, a family of related drugs was created that continues to prove its clinical value in thromboprophylaxis and in prevention of clotting in extracorporeal devices. Fundamental and applied research has revealed a complex pharmacodynamic profile of heparins that goes beyond its anticoagulant use. Recognition of the complex multifaceted beneficial effects of heparin underscores its therapeutic potential in various clinical situations. In this review we focus on the anticoagulant and nonanticoagulant activities of heparin and, where possible, discuss the underlying molecular mechanisms that explain the diversity of heparin's biological actions.

Hypertensive emergency can cause thrombotic microangiopathy (TMA) in the kidneys with high rates of end-stage renal disease (ESRD) and vice versa. The conundrum of hypertension as the cause of TMA or consequence of TMA on the background of defects in complement regulation remains difficult. Patients with hypertensive emergency and TMA on kidney biopsy were tested for ex vivo C5b9 formation on the endothelium and rare variants in complement genes to identify complement-mediated TMA. We identified factors associated with defects in complement regulation and poor renal outcomes. Massive ex vivo C5b9 formation was found on resting endothelial cells in 18 (69%) out of 26 cases at the presentation, including the 9 patients who carried at least one rare genetic variant. Thirteen (72%, =18) and 3 (38%, =8) patients with massive and normal ex vivo complement activation, respectively, progressed to ESRD (=0.03). In contrast to BP control, inhibition of C5 activation prevented ESRD to occur in 5 (83%, =6) patients with massive ex vivo complement activation. TMA-related graft failure occurred in 7 (47%, =15) donor kidneys and was linked to genetic variants. The assessment of both ex vivo C5b9 formation and screening for rare variants in complement genes may categorize patients with hypertensive emergency and TMA into different groups with potential therapeutic and prognostic implications. We propose an algorithm to recognize patients at the highest risk for defects in complement regulation.

Pregnancy has been linked to various microangiopathies, including primary atypical haemolytic uraemic syndrome (aHUS). Complement dysregulation, often linked to rare variants in complement genes, is key for primary aHUS to manifest and may play a role in pregnancy complications of the mother and fetus. The burden of such complications is unknown, making counselling of women with primary aHUS and asymptomatic relatives difficult. We analyzed the maternal and fetal outcomes of 39 pregnancies from 17 women with primary aHUS and two asymptomatic relatives. Seven out of 39 pregnancies were complicated by pregnancy-associated aHUS. Five out of 32 pregnancies not linked to pregnancy-associated aHUS were complicated by pre-eclampsia or HELLP. Rare genetic variants were identified in 10 women (asymptomatic relatives, n = 2) who had a total of 14 pregnancies, including 10 uncomplicated pregnancies. Thirty-five out of 39 pregnancies resulted in live birth. Eight out of 19 women had progressed to end-stage kidney disease, with an incidence of 2·95 (95% confidence interval, 1·37-5·61) per 100 person-years after the first pregnancy. Thus, we emphasized the frequency of successful pregnancies in women with primary aHUS and asymptomatic relatives. Pregnancies should be monitored closely. Rare genetic variants cannot predict the risk of a given pregnancy.

Background Severe hypertension can induce thrombotic microangiopathy (TMA) in the renal vasculature, the occurrence of which has been linked to mechanical stress to the endothelium. Complement defects may be the culprit of disease in patients who present with severe renal disease and often progress to ESRD, despite BP control.Methods We studied a well defined cohort of 17 patients with hypertension-associated TMA to define the prevalence of complement defects by a specific ex vivo serum-based microvascular endothelial cell assay.Results Compared with normal human serum and samples from patients with hypertensive arterionephrosclerosis, 14 of 16 (87.5%) serum samples collected at presentation from 16 patients with hypertension-associated TMA induced abnormal C5b9 formation on microvascular endothelial cells. We detected rare variants in complement genes in eight of 17 (47%) patients. ESRD occurred in 14 of 17 (82%) patients, and recurrent TMA after transplant occurred in seven of 11 (64%) donor kidneys. Eculizumab improved the renal function in three patients and prevented TMA recurrence in an allograft recipient.Conclusions These observations point to complement defects as the key causative factor of ESRD and recurrent TMA after transplant in patients presenting with severe hypertension. Complement defects can be identified by measurements of complement activation on microvascular endothelial cells, which should substantially influence treatment and prognosis.

ADAMTS13 (a disintegrin and metalloprotease with a thrombospondin type-1 motif, member 13) and von Willebrand factor (VWF) can be considered as scale weights which control platelet adhesion during primary haemostasis. In a very uncommon condition designated thrombotic thrombocytopenic purpura (TTP), functional absence of ADAMTS13 tips the balance toward VWF-mediated platelet adhesion in the microcirculation. TTP is associated with a high mortality and arises from either a congenital or acquired autoimmune deficiency of the plasma enzyme ADAMTS13. In case of acquired ADAMTS13 deficiency, autoantibodies bind to and inhibit the function of ADAMTS13. Currently available treatments of TTP aim to supply ADAMTS13 through plasma exchange or are aimed at B-cell depletion with rituximab. None of the available therapeutics, however, aims at protection of ADAMTS13 from circulating autoantibodies. In this review, our aim is to describe the structure-function relationship of ADAMTS13 employing homology models and previously published crystal structures. Structural bioinformatics investigation of ADAMTS13 reveals many insights and explains how mutations and autoantibodies may lead to the pathophysiology of TTP. The results of these studies provide a roadmap for the further development of rationally designed therapeutics for the treatment of patients with acquired TTP. In addition, we share our opinion on the state of the art of the open-closed conformations of ADAMTS13 which regulate the activity of this highly specific VWF cleaving protease.

Thrombotic microangiopathy (TMA) is a pattern of endothelial damage that can be found in association with diverse clinical conditions such as malignant hypertension. Although the pathophysiological mechanisms differ, accumulating evidence links complement dysregulation to various TMA syndromes and in particular the atypical hemolytic uremic syndrome. Here, we evaluated the role of complement in nine consecutive patients with biopsy-proven renal TMA attributed to severe hypertension. Profound hematologic symptoms of TMA were uncommon. In six Out of nine patients, we found mutations C3 in three, CFI in one, CD46 in one, and/or CFH in two patients either with or without the risk CFH-H3 haplotype in four patients. Elevated levels of the soluble C5b-9 and renal deposits of C3c and C5b-9 along the vasculature and/or glomerular capillary wall, confirmed complement activation in vivo. In contrast to patients without genetic defects, patients with complement defects invariably progressed to end-stage renal disease, and disease recurrence after kidney transplantation seems common. Thus, a subset of patients with hypertension-associated TMA falls within the spectrum of complement-mediated TMA, the prognosis of which is poor. Hence, testing for genetic complement abnormalities is warranted in patients with severe hypertension and TMA on renal biopsy to adopt suitable treatment options and prophylactic measures.

BACKGROUND: Extracellular histones are cytotoxic molecules that are related to cell stress and death. They have been shown to play a crucial role in multiple pathophysiologic processes like sepsis, inflammation, vascular dysfunction, and thrombosis. Their role in organ donation and graft function and survival is still unknown. The aim of this study was to assess whether an association exists between the presence of extracellular histones in machine perfusates and deceased donor kidney viability.METHODS: Machine perfusates of 390 donations after circulatory death kidneys were analyzed for histone concentration, and corresponding graft function and survival were assessed.RESULTS: Extracellular histone concentrations were significantly higher in perfusates of kidneys with posttransplant graft dysfunction (primary nonfunction and delayed graft function) and were an independent risk factor for delayed graft function (odds ratio, 2.152; 95% confidence interval [95% CI], 1.199-3.863) and 1 year graft failure (hazard ratio, 1.386; 95% CI, 1.037-1.853), but not for primary nonfunction (odds ratio, 1.342; 95% CI, 0.900-2.002). One year graft survival was 12% higher in the group with low histone concentrations (P = 0.008) as compared with the group that contained higher histone concentrations.CONCLUSIONS: This study warrants future studies to probe for a possible role of cytotoxic extracellular histones in organ viability and suggests that quantitation of extracellular histones might contribute to assessment of posttransplant graft function and survival.