Mapping cardiac remodeling in chronic kidney disease.

Patients with advanced chronic kidney disease (CKD) mostly die from sudden cardiac death and recurrent heart failure. The mechanisms of cardiac remodeling are largely unclear. To dissect molecular and cellular mechanisms of cardiac remodeling in CKD in an unbiased fashion, we performed left ventricular single-nuclear RNA sequencing in two mouse models of CKD. Our data showed a hypertrophic response trajectory of cardiomyocytes with stress signaling and metabolic changes driven by soluble uremia-related factors. We mapped fibroblast to myofibroblast differentiation in this process and identified notable changes in the cardiac vasculature, suggesting inflammation and dysfunction. An integrated analysis of cardiac cellular responses to uremic toxins pointed toward endothelin-1 and methylglyoxal being involved in capillary dysfunction and TNFα driving cardiomyocyte hypertrophy in CKD, which was validated in vitro and in vivo. TNFα inhibition in vivo ameliorated the cardiac phenotype in CKD. Thus, interventional approaches directed against uremic toxins, such as TNFα, hold promise to ameliorate cardiac remodeling in CKD.

Magnesium Improves Cardiac Function in Experimental Uremia by Altering Cardiac Elastin Protein Content.

Cardiovascular complications are accompanied by life-threatening complications and represent the major cause of death in patients with chronic kidney disease (CKD). Magnesium is important for the physiology of cardiac function, and its deficiency is common in CKD. In the present study, we investigated the impact of oral magnesium carbonate supplementation on cardiac function in an experimental model of CKD induced in Wistar rats by an adenine diet. Echocardiographic analyses revealed restoration of impaired left ventricular cardiac function in animals with CKD. Cardiac histology and real-time PCR confirmed a high amount of elastin protein and increased collagen III expression in CKD rats supplemented with dietary magnesium as compared with CKD controls. Both structural proteins are crucial in maintaining cardiac health and physiology. Aortic calcium content increased in CKD as compared with tissue from control animals. Magnesium supplementation numerically lowered the increases in aortic calcium content as it remained statistically unchanged, compared with controls. In summary, the present study provides evidence for an improvement in cardiovascular function and aortic wall integrity in a rat model of CKD by magnesium, as evidenced by echocardiography and histology.

Spatial multi-omic map of human myocardial infarction.

Myocardial infarction is a leading cause of death worldwide1. Although advances have been made in acute treatment, an incomplete understanding of remodelling processes has limited the effectiveness of therapies to reduce late-stage mortality2. Here we generate an integrative high-resolution map of human cardiac remodelling after myocardial infarction using single-cell gene expression, chromatin accessibility and spatial transcriptomic profiling of multiple physiological zones at distinct time points in myocardium from patients with myocardial infarction and controls. Multi-modal data integration enabled us to evaluate cardiac cell-type compositions at increased resolution, yielding insights into changes of the cardiac transcriptome and epigenome through the identification of distinct tissue structures of injury, repair and remodelling. We identified and validated disease-specific cardiac cell states of major cell types and analysed them in their spatial context, evaluating their dependency on other cell types. Our data elucidate the molecular principles of human myocardial tissue organization, recapitulating a gradual cardiomyocyte and myeloid continuum following ischaemic injury. In sum, our study provides an integrative molecular map of human myocardial infarction, represents an essential reference for the field and paves the way for advanced mechanistic and therapeutic studies of cardiac disease.

Mapping the cardiac vascular niche in heart failure.

The cardiac vascular and perivascular niche are of major importance in homeostasis and during disease, but we lack a complete understanding of its cellular heterogeneity and alteration in response to injury as a major driver of heart failure. Using combined genetic fate tracing with confocal imaging and single-cell RNA sequencing of this niche in homeostasis and during heart failure, we unravel cell type specific transcriptomic changes in fibroblast, endothelial, pericyte and vascular smooth muscle cell subtypes. We characterize a specific fibroblast subpopulation that exists during homeostasis, acquires Thbs4 expression and expands after injury driving cardiac fibrosis, and identify the transcription factor TEAD1 as a regulator of fibroblast activation. Endothelial cells display a proliferative response after injury, which is not sustained in later remodeling, together with transcriptional changes related to hypoxia, angiogenesis, and migration. Collectively, our data provides an extensive resource of transcriptomic changes in the vascular niche in hypertrophic cardiac remodeling.

Carboxylative efficacy of trans and cis MK7 and comparison with other vitamin K isomers.

Carboxylative enzymes are involved in many pathways and their regulation plays a crucial role in many of these pathways. In particular, γ-glutamylcarboxylase (GGCX) converts glutamate residues (Glu) into γ-carboxyglutamate (Gla) of the vitamin K-dependent proteins (VKDPs) activating them. VKDPs include at least 17 proteins involved in processes such as blood coagulation, blood vessels calcification, and bone mineralization. VKDPs are activated by the reduced form of vitamin K, naturally occurring as vitamin K1 (phylloquinone) and K2 (menaquinones, MKs). Among these, MK7 is the most efficient in terms of bioavailability and biological effect. Similarly to other trans isomers, it is produced by natural fermentation or chemically in both trans and cis. However, the efficacy of the biological effect of the different isomers and the impact on humans are unknown. Our study assessed carboxylative efficacy of trans and cis MK7 and compared it with other vitamin K isomers, evaluating both the expression of residues of carboxylated Gla-protein by western blot analysis and using a cell-free system to determine the GGCX activity by HPLC. Trans MK7H2 showed a higher ability to carboxylate the 70 KDa GLA-protein, previously inhibited in vitro by warfarin treatment. However, cis MK7 also induced a carboxylation activity albeit of a small extent. The data were confirmed chromatographically, in which a slight carboxylative activity of cis MK7H2 was demonstrated, comparable with both K1H2 and oxidized trans MK7 but less than trans MK7H2 . For the first time, a difference of biological activity between cis and trans configuration of menaquinone-7 has been reported.

Carbamylated sortilin associates with cardiovascular calcification in patients with chronic kidney disease.

Sortilin, an intracellular sorting receptor, has been identified as a cardiovascular risk factor in the general population. Patients with chronic kidney disease (CKD) are highly susceptible to develop cardiovascular complications such as calcification. However, specific CKD-induced posttranslational protein modifications of sortilin and their link to cardiovascular calcification remain unknown. To investigate this, we examined two independent CKD cohorts for carbamylation of circulating sortilin and detected increased carbamylated sortilin lysine residues in the extracellular domain of sortilin with kidney function decline using targeted mass spectrometry. Structure analysis predicted altered ligand binding by carbamylated sortilin, which was verified by binding studies using surface plasmon resonance measurement, showing an increased affinity of interleukin 6 to in vitro carbamylated sortilin. Further, carbamylated sortilin increased vascular calcification in vitro and ex vivo that was accelerated by interleukin 6. Imaging by mass spectrometry of human calcified arteries revealed in situ carbamylated sortilin. In patients with CKD, sortilin carbamylation was associated with coronary artery calcification, independent of age and kidney function. Moreover, patients with carbamylated sortilin displayed significantly faster progression of coronary artery calcification than patients without sortilin carbamylation. Thus, carbamylated sortilin may be a risk factor for cardiovascular calcification and may contribute to elevated cardiovascular complications in patients with CKD.

Altered vitamin K biodistribution and metabolism in experimental and human chronic kidney disease.

Chronic kidney disease (CKD) is accompanied with extensive cardiovascular calcification, in part correlating with functional vitamin K deficiency. Here, we sought to determine causes for vitamin K deficiency beyond reduced dietary intake. Initially, vitamin K uptake and distribution into circulating lipoproteins after a single administration of vitamin K1 plus K2 (menaquinone 4 and menaquinone 7, respectively) was determined in patients on dialysis therapy and healthy individuals. The patients incorporated very little menaquinone 7 but more menaquinone 4 into high density lipoprotein (HDL) and low-density lipoprotein particles than did healthy individuals. In contrast to healthy persons, HDL particles from the patients could not be spiked with menaquinone 7 in vitro and HDL uptake was diminished in osteoblasts. A reduced carboxylation activity (low vitamin K activity) of uremic HDL particles spiked with menaquinone 7 vs. that of controls was confirmed in a bioassay using human primary vascular smooth muscle cells. Kidney menaquinone 4 tissue levels were reduced in 5/6-nephrectomized versus sham-operated C57BL/6 mice after four weeks of a vitamin K rich diet. From the analyzed enzymes involved in vitamin K metabolism, kidney HMG-CoA reductase protein was reduced in both rats and patients with CKD. In a trial on the efficacy and safety of atorvastatin in 1051 patients with type 2 diabetes receiving dialysis therapy, no pronounced vitamin K deficiency was noted. However, the highest levels of PIVKA-II (biomarker of subclinical vitamin K deficiency) were noted when a statin was combined with a proton pump inhibitor. Thus, profound disturbances in lipoprotein mediated vitamin K transport and metabolism in uremia suggest that menaquinone 7 supplementation to patients on dialysis therapy has reduced efficacy.

Hepatic and Vascular Vitamin K Status in Patients with High Cardiovascular Risk.

Vitamin K dependent proteins (VKDP), such as hepatic coagulation factors and vascular matrix Gla protein (MGP), play key roles in maintaining physiological functions. Vitamin K deficiency results in inactive VKDP and is strongly linked to vascular calcification (VC), one of the major risk factors for cardiovascular morbidity and mortality. In this study we investigated how two vitamin K surrogate markers, dephosphorylated-undercarboxylated MGP (dp-ucMGP) and protein induced by vitamin K absence II (PIVKA-II), reflect vitamin K status in patients on hemodialysis or with calcific uremic arteriolopathy (CUA) and patients with atrial fibrillation or aortic valve stenosis. Through inter- and intra-cohort comparisons, we assessed the influence of vitamin K antagonist (VKA) use, vitamin K supplementation and disease etiology on vitamin K status, as well as the correlation between both markers. Overall, VKA therapy was associated with 8.5-fold higher PIVKA-II (0.25 to 2.03 AU/mL) and 3-fold higher dp-ucMGP (843 to 2642 pM) levels. In the absence of VKA use, non-renal patients with established VC have dp-ucMGP levels similar to controls (460 vs. 380 pM), while in HD and CUA patients, levels were strongly elevated (977 pM). Vitamin K supplementation significantly reduced dp-ucMGP levels within 12 months (440 to 221 pM). Overall, PIVKA-II and dp-ucMGP showed only weak correlation (r2 ≤ 0.26) and distinct distribution pattern in renal and non-renal patients. In conclusion, VKA use exacerbated vitamin K deficiency across all etiologies, while vitamin K supplementation resulted in a vascular VKDP status better than that of the general population. Weak correlation of vitamin K biomarkers calls for thoughtful selection lead by the research question. Vitamin K status in non-renal deficient patients was not anomalous and may question the role of vitamin K deficiency in the pathogenesis of VC in these patients.

Vitamin K and cardiovascular complications in chronic kidney disease patients.

Vitamin K, well known for its role in coagulation, encompasses 2 major subgroups: vitamin K1 is exclusively synthesized by plants, whereas vitamin K2 mostly originates from bacterial synthesis. Vitamin K serves as a cofactor for the enzyme γ-glutamyl carboxylase, which carboxylates and thereby activates various vitamin K-dependent proteins. Several vitamin K-dependent proteins are synthesized in bone, but the role of vitamin K for bone health in chronic kidney disease patients, in particular the prevention of osteoporosis, is still not firmly established. Herein, we focus on another prominent action of vitamin K, in particular vitamin K2 (namely, the activation of matrix γ-carboxyglutamic acid protein, the most potent inhibitor of cardiovascular calcifications). Multiple observational studies link relative vitamin K deficiency or low intake to cardiovascular calcification progress, morbidity, and mortality. Patients with advanced chronic kidney disease are particularly vitamin K deficient, in part because of dietary restrictions but possibly also due to impaired endogenous recycling of vitamin K. At the same time, this population is characterized by markedly accelerated cardiovascular calcifications and mortality. High-dose dietary supplementation with vitamin K2, in particular the most potent form, menaquinone 7, can potently reduce circulating levels of dephosphorylated uncarboxylated (i.e., inactive matrix γ-carboxyglutamic acid protein) in patients with end-stage kidney disease. However, despite this compelling data basis, several randomized controlled trials with high-dose menaquinone 7 supplements in patients with advanced chronic kidney disease have failed to confirm cardiovascular benefits. Herein, we discuss potential reasons and solutions for this.

Low adherence to CKD-specific dietary recommendations associates with impaired kidney function, dyslipidemia, and inflammation.

BACKGROUND/OBJECTIVES: A diet following chronic kidney disease (CKD)-specific recommendations is considered essential for optimal management of patients with CKD. However, data on the adherence to these recommendations and its implications for health-relevant biomarkers are lacking. The objectives were to estimate adherence to CKD-specific dietary recommendations, to identify characteristics and lifestyle variables associated with poor adherence, and to investigate the relationship of adherence with biomarkers. METHODS: In this cross-sectional analysis, average dietary intake was estimated in 3193 participants with moderately severe CKD enrolled into the observational multicenter German CKD study using a food frequency questionnaire. A CKD diet score was developed to assess adherence to CKD-specific dietary recommendations based on intake of sodium, potassium, fiber, protein, sugar, and cholesterol. The associations of dietary adherence with characteristics, lifestyle variables, and biomarker levels were determined. RESULTS: Logistic regression analysis revealed younger age, higher body mass index, male gender, lower educational attainment, various lifestyle variables (cigarette smoking, infrequent alcohol consumption, low physical activity), and lower estimated glomerular filtrate rate associated with lower adherence to dietary recommendations. Low adherence to dietary recommendations was further associated with dyslipidemia, higher uric acid, and C-reactive protein levels. Associations between low dietary adherence and biomarkers were mostly driven by low intake of fiber and potassium, and high intake of sugar and cholesterol. CONCLUSIONS: This study revealed differential characteristics and biomarkers associated with lower adherence to CKD-specific dietary recommendations. Promotion of CKD-specific dietary recommendations may help to mitigate the adverse prognosis in CKD patients.

Decoding myofibroblast origins in human kidney fibrosis.

Kidney fibrosis is the hallmark of chronic kidney disease progression; however, at present no antifibrotic therapies exist1-3. The origin, functional heterogeneity and regulation of scar-forming cells that occur during human kidney fibrosis remain poorly understood1,2,4. Here, using single-cell RNA sequencing, we profiled the transcriptomes of cells from the proximal and non-proximal tubules of healthy and fibrotic human kidneys to map the entire human kidney. This analysis enabled us to map all matrix-producing cells at high resolution, and to identify distinct subpopulations of pericytes and fibroblasts as the main cellular sources of scar-forming myofibroblasts during human kidney fibrosis. We used genetic fate-tracing, time-course single-cell RNA sequencing and ATAC-seq (assay for transposase-accessible chromatin using sequencing) experiments in mice, and spatial transcriptomics in human kidney fibrosis, to shed light on the cellular origins and differentiation of human kidney myofibroblasts and their precursors at high resolution. Finally, we used this strategy to detect potential therapeutic targets, and identified NKD2 as a myofibroblast-specific target in human kidney fibrosis.

Mechanism of action of SNF472, a novel calcification inhibitor to treat vascular calcification and calciphylaxis.

BACKGROUND AND PURPOSE: No therapy is approved for vascular calcification or calcific uraemic arteriolopathy (calciphylaxis), which increases mortality and morbidity in patients undergoing dialysis. Deposition of hydroxyapatite (HAP) crystals in arterial walls is the common pathophysiologic mechanism. The mechanism of action of SNF472 to reduce HAP deposition in arterial walls was investigated. EXPERIMENTAL APPROACH: We examined SNF472 binding features (affinity, release kinetics and antagonism type) for HAP crystals in vitro, inhibition of calcification in excised vascular smooth muscle cells from rats and bone parameters in osteoblasts from dogs and rats. KEY RESULTS: SNF472 bound to HAP with affinity (KD ) of 1-10 µM and saturated HAP at 7.6 µM. SNF472 binding was fast (80% within 5 min) and insurmountable. SNF472 inhibited HAP crystal formation from 3.8 µM, with complete inhibition at 30.4 µM. SNF472 chelated free calcium with an EC50 of 539 µM. Chelation of free calcium was imperceptible for SNF472 1-10 µM in physiological calcium concentrations. The lowest concentration tested in vascular smooth muscle cells, 1 µM inhibited calcification by 67%. SNF472 showed no deleterious effects on bone mineralization in dogs or in rat osteoblasts. CONCLUSION AND IMPLICATIONS: These experiments show that SNF472 binds to HAP and inhibits further HAP crystallization. The EC50 for chelation of free calcium is 50-fold greater than a maximally effective SNF472 dose, supporting the selectivity of SNF472 for HAP. These findings indicate that SNF472 may have a future role in the treatment of vascular calcification and calcific uraemic arteriolopathy in patients undergoing dialysis.

Cardiac Remodeling in Chronic Kidney Disease.

Cardiac remodeling occurs frequently in chronic kidney disease patients and affects quality of life and survival. Current treatment options are highly inadequate. As kidney function declines, numerous metabolic pathways are disturbed. Kidney and heart functions are highly connected by organ crosstalk. Among others, altered volume and pressure status, ischemia, accelerated atherosclerosis and arteriosclerosis, disturbed mineral metabolism, renal anemia, activation of the renin-angiotensin system, uremic toxins, oxidative stress and upregulation of cytokines stress the sensitive interplay between different cardiac cell types. The fatal consequences are left-ventricular hypertrophy, fibrosis and capillary rarefaction, which lead to systolic and/or diastolic left-ventricular failure. Furthermore, fibrosis triggers electric instability and sudden cardiac death. This review focuses on established and potential pathophysiological cardiorenal crosstalk mechanisms that drive uremia-induced senescence and disease progression, including potential known targets and animal models that might help us to better understand the disease and to identify novel therapeutics.

Magnesium but not nicotinamide prevents vascular calcification in experimental uraemia.

BACKGROUND: Optimal phosphate control is an unmet need in chronic kidney disease (CKD). High serum phosphate increases calcification burden and is associated with mortality and cardiovascular disease in CKD. Nicotinamide (NA) alone or in combination with calcium-free phosphate binders might be a strategy to reduce phosphate levels and calcification and thus impact cardiovascular disease in CKD. METHODS: We studied the effect of NA alone and in combination with magnesium carbonate (MgCO3) as a potential novel treatment strategy. CKD was induced in dilute brown non-agouti/2 mice by subtotal nephrectomy followed by a high-phosphate diet (HP) and 7 weeks of treatment with NA, MgCO3 or their combination. Control mice underwent subtotal nephrectomy and received an HP or underwent sham surgery and received standard chow plus NA. RESULTS: CKD mice showed increased serum fibroblast growth factor 23 and calcium-phosphate product that was normalized by all treatment regimes. NA alone increased soft tissue and vascular calcification, whereas any treatment with MgCO3 significantly reduced calcification severity in CKD. While MgCO3 supplementation alone resulted in decreased calcification severity, it resulted in increased intestinal expression of the phosphate transporters type II sodium-dependent phosphate transporter 1 (Pit-1). Combined therapy of MgCO3 and NA reduced tissue calcification and normalized expression levels of intestinal phosphate transporter proteins. CONCLUSIONS: In conclusion, the data indicate that NA increases while MgCO3 reduces ectopic calcification severity. Augmented expression of intestinal phosphate transporters by MgCO3 treatment was abolished by the addition of NA. However, the clinical relevance of the latter remains to be explored. Importantly, the data suggest no benefit of NA regarding treatment of calcification in addition to MgCO3.

Association Between Dietary Patterns and Kidney Function in Patients With Chronic Kidney Disease: A Cross-Sectional Analysis of the German Chronic Kidney Disease Study.

OBJECTIVE: In the general population, "healthy" dietary patterns are associated with improved health outcomes, but data on associations between observance of specific dietary patterns and kidney function in patients with chronic kidney disease (CKD) are sparse. METHODS: Dietary intake was evaluated using food frequency questionnaires in patients with moderately severe CKD under nephrology care enrolled into the observational multicenter German CKD study. The Dietary Approaches to Stop Hypertension (DASH) diet score, Mediterranean diet score, and German Food Pyramid Index (GFPI) were calculated and their association with estimated glomerular filtration rate (eGFR) and albuminuria was assessed by multivariable linear regression analysis, adjusted for gender, age, body mass index, energy intake, smoking status, alcohol intake, education, high-density lipoprotein-cholesterol (HDL- cholesterol), low-density lipoprotein-cholesterol (LDL-cholesterol), hypertension, and diabetes mellitus. RESULTS: A total of 2,813 patients (41% women; age 60.1 ± 11.6 years) were included in the analysis. High DASH diet score and GFPI were associated with lower systolic blood pressure and lower intake of antihypertensive medication, higher HDL, and lower uric acid levels. Mediterranean-style diet was associated with lower prevalence of diabetes mellitus. Higher DASH and Mediterranean diet scores were associated with higher eGFR (ß-coefficient = 1.226, P < .001; ß-coefficient = 0.932, P = .007, respectively). In contrast, GFPI was not associated with eGFR. For the individual components of the dietary patterns, higher intake of nuts and legumes, cereals, fish, and polyunsaturated fats was associated with higher eGFR and higher intake of dairy, composed of low- and whole-fat dairy, was associated with lower eGFR. No association was found between dietary patterns and albuminuria. CONCLUSION: Higher observance of the DASH or Mediterranean diet, but not German food pyramid recommendations, was associated with higher eGFR among patients with CKD. Improving dietary habits may offer an opportunity to better control comorbidities and kidney function decline in patients with CKD.

Sclerostin in chronic kidney disease-mineral bone disorder think first before you block it!

Canonical Wnt signalling activity is a major player in physiological and adaptive bone metabolism. Wnt signalling is regulated by soluble inhibitors, with sclerostin being the most widely studied. Sclerostin's main origin is the osteocyte and its major function is blockade of osteoblast differentiation and function. Therefore, sclerostin is a potent inhibitor of bone formation and mineralization. Consequently, blocking sclerostin via human monoclonal antibodies (such as romosozumab) represents a promising perspective for the treatment of (postmenopausal) osteoporosis. However, sclerostin's physiology and the effects of sclerostin monoclonal antibody treatment are not limited to the skeleton. Specifically, the potential roles of sclerostin in chronic kidney disease (CKD) and associated pathologies covered by the term chronic kidney disease and mineral bone disorder (CKD-MBD), which also includes accelerated cardiovascular calcification, warrant specific attention. CKD-MBD is a complex disease condition in which sclerostin antibodies may interfere at different levels and influence the multiform interplay of hyperparathyroidism, renal osteodystrophy and vascular calcification, but the clinical sequelae remain obscure. The present review summarizes the potential effects of sclerostin blockade in CKD-MBD. We will address and summarize the urgent research targets that are being identified and that need to be addressed before a valid risk-benefit ratio can be established in the clinical setting of CKD.

Sclerostin deficiency modifies the development of CKD-MBD in mice.

Sclerostin is a soluble antagonist of canonical Wnt signaling and a strong inhibitor of bone formation. We present experimental data on the role of sclerostin in chronic kidney disease - bone mineral disorder (CKD-MBD). METHODS: We performed 5/6 nephrectomies in 36-week-old sclerostin-deficient (SOST-/-) B6-mice and in C57BL/6J wildtype (WT) mice. Animals received a high phosphate diet for 11weeks. The bones were analyzed by high-resolution micro-computed tomography (µCT) and quantitative bone histomorphometry. Aortic tissue was analyzed regarding the extent of vascular calcification. RESULTS: All nephrectomized mice had severe renal failure, and parathyroid hormone was highly increased compared to corresponding sham animals. All SOST-/- animals revealed the expected high bone mass phenotype. Overall, the bone compartment in WT and SOST-/- mice responded similarly to nephrectomy. In uremic WT animals, µCT data at both the distal femur and lumbar spine revealed significantly increased trabecular volume compared to non-uremic WTs. In SOST-/- mice, the differences between trabecular bone volume were less pronounced when comparing uremic with sham animals. Cortical thickness and cortical bone density at the distal femur decreased significantly and comparably in both genotypes after 5/6 nephrectomy compared to sham animals (cortical bone density -18% and cortical thickness -32%). Overall, 5/6 nephrectomy and concomitant hyperparathyroidism led to a genotype-independent loss of cortical bone volume and density. Overt vascular calcification was not detectable in either of the genotypes. CONCLUSION: Renal osteodystrophy changes were more pronounced in WT mice than in SOST-/- mice. The high bone mass phenotype of sclerostin deficiency was detectable also in the setting of chronic renal failure with severe secondary hyperparathyroidism.

Clot Structure: A Potent Mortality Risk Factor in Patients on Hemodialysis.

Patients with CKD on hemodialysis exhibit increased cardiovascular risk. Fibrin clot structure and clot lysis are crucially involved in development of cardiovascular events, but little is known about the influence of clot density on outcome in patients on hemodialysis. We determined fibrin clot structure parameters and effect on mortality in a prospective cohort of 171 patients on chronic hemodialysis (mean±SD age =59±11 years old; 54% men) using a validated turbidimetric assay. Kaplan-Meier analysis revealed that patients on hemodialysis with a denser clot structure had increased all-cause and cardiovascular mortality risks (log rank P=0.004 and P=0.003, respectively). Multivariate Cox regression models (adjusted for age, diabetes, sex, and duration of dialysis or fibrinogen, C-reactive protein, and complement C3) confirmed that denser clots are independently related to mortality risk. We also purified fibrinogen from healthy controls and patients on hemodialysis using the calcium-dependent IF-1 mAb against fibrinogen for additional investigation using mass spectrometric analysis and electron microscopy. Whereas purified fibrinogen from healthy controls displayed no post-translational modifications, fibrinogen from patients on hemodialysis was glycosylated and guanidinylated. Clots made of purified fibrinogen from patients on hemodialysis exhibited significantly thinner fibers compared with clots from fibrinogen of control individuals (mean±SD =63±2 and 77±2 nm, respectively; P<0.001). In vitro guanidinylation of fibrinogen from healthy subjects increased the formation of thinner fibers, suggesting that difference in fiber thickness might be at least partially due to post-translational modifications. Thus, in patients on hemodialysis, a denser clot structure may be a potent independent risk factor for mortality.

Calcific uraemic arteriolopathy (calciphylaxis): data from a large nationwide registry.

Background: Calcific uraemic arteriolopathy (CUA, calciphylaxis) is a rare disease predominantly in dialysis patients and associated with high mortality. Painful skin ulcerations and calcification of cutaneous arterioles characterize calciphylaxis. Methods: We established an observational, Internet-based registry allowing online notification for all German CUA cases. The registry recorded data about patient characteristics, biochemistry and therapies. Blood samples were stored in a central biobank. Results: Between 2006 and 2015, 253 CUA patients were recorded: median age 70 [interquartile range (IQR) 61-76] years, 60% females and 86% ( n = 207) dialysis patients, translating into an estimated annual incidence rate of 0.04% in German dialysis patients. Fifty-two per cent received vitamin K antagonists (VKAs) prior to CUA. Skin lesions were localized in 71% on the legs or gluteal region. In dialysis CUA patients median total serum calcium was 2.20 (IQR 2.06-2.37) mmol/L, phosphorus 1.67 (IQR 1.35-2.03) mmol/L, intact parathyroid hormone 147 (IQR 72-276) pg/mL and fetuin-A 0.21 (IQR 0.16-0.26) g/L (normal range 0.35-0.95). Median sclerostin, osteoprotegerin, TRAP5b, bone-specific alkaline phosphatase and c-terminal FGF23 levels were all elevated. The most frequently recorded therapeutic procedures in dialysis CUA patients were as follows: wound debridement (29% of cases), stopping VKA (25%), lowering calcium supply (24%), sodium thiosulphate (22%), application of vitamin K (18%), increase of dialysis duration/frequency (17%) and stoping active vitamin D (16%). Conclusions: Approximately 50% of CUA patients used VKA. Our data suggest that uncontrolled hyperparathyroidism is not the key determinant of calciphylaxis. Therapeutic strategies were heterogeneous. The experience of the German registry will help substantially to initiate a large-scale multinational CUA registry.