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.

Identifying individuals at risk of needing CKD associated medications in a European kidney disease cohort.

BACKGROUND: The consequences of chronic kidney disease (CKD) can be addressed with a range of pharmacotherapies primarily prescribed by nephrologists. More accurate information regarding future CKD-related pharmacotherapy requirements could guide clinical decisions including follow-up frequency. METHODS: Following assignment to derivation and validation groups (2,1), variables predicting individually future use of vitamin D receptor agonists (VDRA), phosphate binders, erythropoiesis stimulating agents (ESAs) and iron were identified using logistic regression in a prospective cohort study containing demography, comorbidity, hospitalization, laboratory, and mortality data in patients with CKD stage G4/G5 across six European countries. Discriminative ability was measured using C-statistics, and predicted probability of medication use used to inform follow-up frequency. RESULTS: A total of 2196 patients were included in the analysis. During a median follow-up of 735 days 648 initiated hemodialysis and 1548 did not. Combinations of age, diabetes status and iPTH, calcium, hemoglobin and serum albumin levels predicted the use of ESA, iron, phosphate binder or VDRA, with C-statistics of 0.70, 0.64, 0.73 and 0.63 in derivation cohorts respectively. Model performance in validation cohorts were similar. Sixteen percent of patients were predicted to have a likelihood of receiving any of these medications of less than 20%. CONCLUSIONS: In a multi-country CKD cohort, prediction of ESA and phosphate binder use over a two-year period can be made based on patient characteristics with the potential to reduce frequency of follow-up in individuals with low risk for requiring these medications.

The use of tissue clearing to study renal transport mechanisms and kidney remodelling.

PURPOSE OF REVIEW: Tissue clearing enables examination of biological structures at subcellular resolution in three dimensions. It uncovered the spatial and temporal plasticity of multicellular kidney structures that occur during homeostatic stress. This article will review the recent development in tissue clearing protocols and how it facilitated the study of renal transport mechanisms and remodelling of the kidney. RECENT FINDINGS: Tissue clearing methods have evolved from primarily labelling proteins in thin tissue or individual organs to visualizing both RNA and protein simultaneously in whole animals or human organs. The use of small antibody fragments and innovative imaging techniques improved immunolabelling and resolution. These advances opened up new avenues for studying organ crosstalk and diseases that affect multiple parts of the organism. Accumulating evidence suggests that tubule remodelling can occur rapidly in response to homeostatic stress or injury, allowing for adjustments in the quantitative expression of renal transporters. Tissue clearing helped to better understand the development of tubule cystogenesis, renal hypertension and salt wasting syndromes, and revealed potential progenitor cells in the kidney. SUMMARY: The continued evolution and improvement of tissue clearing methods can help to gain deep biological insights into the structure and function of the kidney, which will have clinical implications.

Acute effects of lithium augmentation on the kidney in geriatric compared with non-geriatric patients with treatment-resistant depression.

INTRODUCTION: Lithium augmentation (LA) of antidepressants is a first-line therapy option for treatment-resistant depression (TRD). Nevertheless, it is rarely used in geriatric patients mostly because of the fear of kidney toxicity. The purpose of this study is to investigate estimated glomerular filtration rate (eGFR) changes and number of acute kidney injuries (AKI) using LA in geriatric compared with non-geriatric patients. METHODS: In a prospective multicenter cohort study, eGFR changes were measured in 201 patients with unipolar depression (nage≥65years  = 29; nage<65years  = 172) at baseline and over 2-6 weeks of LA. We used linear mixed models to investigate changes in eGFR upon LA and assessed the number of AKIs, according to the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines. RESULTS: Both age groups showed a significant eGFR decline over the course of treatment with lower eGFR in geriatric patients. The lithium serum level (interpretable as "effect of LA") had a significant effect on eGFR decline. Both effects (age group and lithium serum level) on eGFR decline did not influence each other, meaning the effect of LA on eGFR decline did not differ between age groups. Two AKIs were observed in the geriatric age group when serum lithium levels exceeded the therapeutic range of >0.8 mmol/L. CONCLUSION: This is the first study investigating eGFR change and AKI upon LA for TRD in geriatric compared with non-geriatric patients. Our data suggest that LA, as an effective treatment option in geriatric patients, should be closely monitored to avoid AKIs.

[Cardiovascular treatment in chronic kidney disease]. / Kardiovaskuläre Therapie bei chronischer Nierenerkrankung.

Patients with combined cardiac and renal diseases are particularly challenging in the routine clinical practice due to the substantial risk profile for increased morbidity and mortality. As cardiorenal patients have often been underrepresented in randomized, controlled interventional trials, guideline recommendations regarding the choice of treatment are often weaker for these individuals than for cardiovascular patients without chronic kidney disease. Furthermore, there are limitations in the approval of certain medications depending on the kidney function. This review addresses some considerations in crucial treatment areas for patients with cardiovascular diseases, whose treatment is significantly influenced by concomitant chronic kidney disease.

Differential Prognostic Utility of Adiposity Measures in Chronic Kidney Disease.

OBJECTIVE: Adipose tissue contributes to adverse outcomes in chronic kidney disease (CKD), but there is uncertainty regarding the prognostic relevance of different adiposity measures. We analyzed the associations of neck circumference (NC), waist circumference (WC), and body mass index (BMI) with clinical outcomes in patients with mild to severe CKD. METHODS: The German Chronic Kidney Disease study is a prospective cohort study, which enrolled Caucasian adults with mild to severe CKD, defined as estimated glomerular filtration rate : 30-60 mL/min/1.73 m2, or >60 mL/min/1.73 m2 in the presence of overt proteinuria. Associations of NC, WC, and BMI with all-cause death, major adverse cardiovascular events (MACE: a composite of nonfatal stroke, nonfatal myocardial infarction, peripheral artery disease intervention, and cardiovascular death), and kidney failure (a composite of dialysis or transplantation) were analyzed using multivariable Cox proportional hazards regression models adjusted for confounders and the Akaike information criteria were calculated. Models included sex interactions with adiposity measures. RESULTS: A total of 4537 participants (59% male) were included in the analysis. During a 6.5-year follow-up, 339 participants died, 510 experienced MACE, and 341 developed kidney failure. In fully adjusted models, NC was associated with all-cause death in women (hazard ratio 1.080 per cm; 95% CI 1.009-1.155) but not in men. Irrespective of sex, WC was associated with all-cause death (hazard ratio 1.014 per cm; 95% CI 1.005-1.038). NC and WC showed no association with MACE or kidney failure. BMI was not associated with any of the analyzed outcomes. Models of all-cause death, including WC offered the best (lowest) Akaike information criteria. CONCLUSION: In Caucasian patients with mild to severe CKD, higher NC (in women) and WC were significantly associated with increased risk of death from any cause but BMI was not.

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.

Heart-Type Fatty Acid Binding Protein, Cardiovascular Outcomes, and Death: Findings From the German CKD Cohort Study.

RATIONALE & OBJECTIVE: Heart-type fatty acid binding protein (H-FABP) is a biomarker that has been shown to provide long-term prognostic information in patients with coronary artery disease independently of high-sensitivity troponin T (hs-TNT). We examined the independent associations of H-FABP with cardiovascular outcomes in patients with chronic kidney disease (CKD). STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: 4,951 patients enrolled in the German Chronic Kidney Disease (GCKD) study with an estimated glomerular filtration rate of 30-60 mL/min/1.73 m2 or overt proteinuria (urinary albumin-creatinine ratio > 300 mg/g or equivalent). EXPOSURE: Serum levels of H-FABP and hs-TNT were measured at study entry. OUTCOME: Noncardiovascular (non-CV) death, CV death, combined major adverse CV events (MACE), and hospitalization for congestive heart failure (CHF). ANALYTICAL APPROACH: Hazard ratios (HRs) for associations of H-FABP and hs-TNT with outcomes were estimated using Cox regression analyses adjusted for established risk factors. RESULTS: During a maximum follow-up of 6.5 years, 579 non-CV deaths, 190 CV deaths, 522 MACE, and 381 CHF hospitalizations were observed. In Cox regression analyses adjusted for established risk factors, H-FABP was associated with all 4 outcomes, albeit with lower HRs than those found for hs-TNT. After further adjustment for hs-TNT levels, H-FABP was found to be associated with non-CV death (HR, 1.57 [95% CI, 1.14-2.18]) and MACE (HR, 1.40 [95% CI, 1.02-1.92]) but with neither CV death (HR, 1.64 [95% CI, 0.90-2.99]) nor CHF hospitalizations (HR, 1.02 [95% CI, 0.70-1.49]). LIMITATIONS: Single-point measurements of H-FABP and hs-TNT. Uncertain generalizability to non-European populations. CONCLUSIONS: In this large cohort of patients with CKD, H-FABP was associated with non-CV death and MACE, even after adjustment for hs-TNT. Whether measurement of H-FABP improves cardiovascular disease risk prediction in these patients warrants further studies.

Cilastatin Ameliorates Rhabdomyolysis-induced AKI in Mice.

BACKGROUND: Rhabdomyolysis, the destruction of skeletal muscle, is a significant cause of AKI and death in the context of natural disaster and armed conflict. Rhabdomyolysis may also initiate CKD. Development of specific pharmacologic therapy is desirable because supportive care is nearly impossible in austere environments. Myoglobin, the principal cause of rhabdomyolysis-related AKI, undergoes megalin-mediated endocytosis in proximal tubule cells, a process that specifically injures these cells. METHODS: To investigate whether megalin is protective in a mouse model of rhabdomyolysis-induced AKI, we used male C57BL/6 mice and mice (14-32 weeks old) with proximal tubule-specific deletion of megalin. We used a well-characterized rhabdomyolysis model, injection of 50% glycerol in normal saline preceded by water deprivation. RESULTS: Inducible proximal tubule-specific deletion of megalin was highly protective in this mouse model of rhabdomyolysis-induced AKI. The megalin knockout mice demonstrated preserved GFR, reduced proximal tubule injury (as indicated by kidney injury molecule-1), and reduced renal apoptosis 24 hours after injury. These effects were accompanied by increased urinary myoglobin clearance. Unlike littermate controls, the megalin-deficient mice also did not develop progressive GFR decline and persistent new proteinuria. Administration of the pharmacologic megalin inhibitor cilastatin to wild-type mice recapitulated the renoprotective effects of megalin deletion. This cilastatin-mediated renoprotective effect was dependent on megalin. Cilastatin administration caused selective proteinuria and inhibition of tubular myoglobin uptake similar to that caused by megalin deletion. CONCLUSIONS: We conclude that megalin plays a critical role in rhabdomyolysis-induced AKI, and megalin interference and inhibition ameliorate rhabdomyolysis-induced AKI. Further investigation of megalin inhibition may inform translational investigation of a novel potential therapy.

Effects of Perfusion Pressures on Podocyte Loss in the Isolated Perfused Mouse Kidney.

BACKGROUND/AIMS: Podocytes are lost in most glomerular diseases, leading to glomerulosclerosis and progressive kidney disease. It is generally assumed, that podocytes are exposed to the filtration flow and thus to significant shear forces driving their detachment from the glomerular basement membrane (GBM). In this context, foot process effacement has been proposed as potential adaptive response to increase adhesion of podocytes to the GBM. METHODS: We have tested these hypotheses using optical clearing and high-resolution 3-dimensional morphometric analysis in the isolated perfused murine kidney. We investigated the dynamics of podocyte detachment at different perfusion pressures (50, 300 and more than 450 mmHg) in healthy young or old mice (20 vs. 71 weeks of age), or mice injected with anti-GBM serum to induce global foot process effacement. RESULTS: Results show that healthy podocytes in young mice are tightly attached onto the GBM and even supramaximal pressures did not cause significant detachment. Compared to young mice, in aged mice and mice with anti-GBM nephritis and foot process effacement, gradual progressive loss of podocytes had occurred already before perfusion. High perfusion pressures resulted in a relatively minor additional loss of podocytes in aged mice. In mice with anti-GBM nephritis significant additional podocyte loss occurred at this early time point when increasing perfusion pressures to 300 mmHg or higher. CONCLUSION: This work provides the first experimental evidence that podocytes are extraordinarily resistant to acutely increased perfusion pressures in an ex vivo isolated kidney perfusion model. Only in glomerular disease, significant numbers of injured podocytes detached following acute increases in perfusion pressure.

Distal convoluted tubule sexual dimorphism revealed by advanced 3D imaging.

The thiazide-sensitive Na+-Cl- cotransporter (NCC) is more abundant in kidneys of female subjects than of male subjects. Because morphological remodeling of the distal convoluted tubule (DCT) is dependent on NCC activity, it has been generally assumed that there is a corresponding sexual dimorphism in the structure of the DCT, leading to a larger female DCT. Until now, this has never been directly examined. Here, optical clearing techniques were combined with antibody labeling of DCT segment markers, state-of-the-art high-speed volumetric imaging, and analysis tools to visualize and quantify DCT morphology in male and female mice and study the DCT remodeling response to furosemide. We found an unexpected sex difference in the structure of the DCT. Compared with the male mice, female mice had a shorter DCT, a higher cellular density of NCC, and a greater capacity to elongate in response to loop diuretics. Our study revealed a sexual dimorphism of the DCT. Female mice expressed a greater density of NCC transporters in a shorter structure to protect Na+ balance in the face of greater basal distal Na+ delivery yet have a larger reserve and structural remodeling capacity to adapt to unique physiological stresses. These observations provide insight into mechanisms that may drive sex differences in the therapeutic responses to diuretics.

The acute kidney injury to chronic kidney disease transition in a mouse model of acute cardiorenal syndrome emphasizes the role of inflammation.

Acute cardiorenal syndrome is a common complication of acute cardiovascular disease. Studies of acute kidney injury (AKI) to chronic kidney disease (CKD) transition, including patients suffering acute cardiovascular disease, report high rates of CKD development. Therefore, acute cardiorenal syndrome associates with CKD, but no study has established causation. To define this we used a murine cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) model or sham procedure on male mice. CA was induced with potassium chloride while CPR consisted of chest compressions and epinephrine eight minutes later. Two weeks after AKI was induced by CA/CPR, the measured glomerular filtration rate (GFR) was not different from sham. However, after seven weeks the mice developed CKD, recapitulating clinical observations. One day, and one, two, and seven weeks after CA/CPR, the GFR was measured, and renal tissue sections were evaluated for various indices of injury and inflammation. One day after CA/CPR, acute cardiorenal syndrome was indicated by a significant reduction of the mean GFR (649 in sham, vs. 25 µL/min/100g in CA/CPR animals), KIM-1 positive tubules, and acute tubular necrosis. Renal inflammation developed, with F4/80 positive and CD3-positive cells infiltrating the kidney one day and one week after CA/CPR, respectively. Although there was functional recovery with normalization of GFR two weeks after CA/CPR, deposition of tubulointerstitial matrix proteins α-smooth muscle actin and fibrillin-1 progressed, along with a significantly reduced mean GFR (623 in sham vs. 409 µL/min/100g in CA/CPR animals), proteinuria, increased tissue transforming growth factor-ß, and fibrosis establishing the development of CKD seven weeks after CA/CPR. Thus, murine CA/CPR, a model of acute cardiorenal syndrome, causes an AKI-CKD transition likely due to prolonged renal inflammation.

Cardiovascular disease in patients with chronic kidney disease.

Patients with chronic kidney disease (CKD) are at increased risk for kidney failure, cardiovascular disease (CVD), and death. In fact, the likelihood of dying from CVD is markedly higher than that for reaching end-stage renal disease. Evidence-based management of comorbidities such as CVD remains challenging in patients with advanced CKD, as they were usually excluded from randomized controlled trials. This review focuses on the epidemiology, risk factors, and clinical manifestations of CVD in patients with advanced CKD. Specific topics of interest include diagnostic and therapeutic challenges of heart failure, coronary artery disease, and atrial fibrillation.

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.

Novel parietal epithelial cell subpopulations contribute to focal segmental glomerulosclerosis and glomerular tip lesions.

Beside the classical flat parietal epithelial cells (PECs), we investigated proximal tubular epithelial-like cells, a neglected subgroup of PECs. These cells, termed cuboidal PECs, make up the most proximal part of the proximal tubule and may also line parts of Bowman's capsule. Additionally, a third intermediate PEC subgroup was identified at the junction between the flat and cuboidal PEC subgroups at the tubular orifice. The transgenic mouse line PEC-rtTA labeled all three PEC subgroups. Here we show that the inducible Pax8-rtTA mouse line specifically labeled only cuboidal and intermediate PECs, but not flat PECs. In aging Pax8-rtTA mice, cell fate mapping showed no evidence for significant transdifferentiation from flat PECs to cuboidal or intermediate PECs or vice versa. In murine glomerular disease models of crescentic glomerulonephritis, and focal segmental glomerulosclerosis (FSGS), intermediate PECs became more numerous. These intermediate PECs preferentially expressed activation markers CD44 and Ki-67, suggesting that this subgroup of PECs was activated more easily than the classical flat PECs. In mice with FSGS, cuboidal and intermediate PECs formed sclerotic lesions. In patients with FSGS, cells forming the tip lesions expressed markers of intermediate PECs. These novel PEC subgroups form sclerotic lesions and were more prone to cellular activation compared to the classical flat PECs in disease. Thus, colonization of Bowman's capsule by cuboidal PECs may predispose to lesion formation and chronic kidney disease. We propose that tip lesions originate from this novel subgroup of PECs in patients with FSGS.

Novel 3D analysis using optical tissue clearing documents the evolution of murine rapidly progressive glomerulonephritis.

Recent developments in optical tissue clearing have been difficult to apply for the morphometric analysis of organs with high cellular content and small functional structures, such as the kidney. Here, we establish combinations of genetic and immuno-labelling for single cell identification, tissue clearing and subsequent de-clarification for histoimmunopathology and transmission electron microscopy. Using advanced light microscopy and computational analyses, we investigated a murine model of crescentic nephritis, an inflammatory kidney disease typified by immune-mediated damage to glomeruli leading to the formation of hypercellular lesions and the rapid loss of kidney function induced by nephrotoxic serum. Results show a graded susceptibility of the glomeruli, significant podocyte loss and capillary injury. These effects are associated with activation of parietal epithelial cells and formation of glomerular lesions that may evolve and obstruct the kidney tubule, thereby explaining the loss of kidney function. Thus, our work provides new high-throughput endpoints for the analysis of complex tissues with single-cell resolution.

Inverse correlation between vascular endothelial growth factor back-filtration and capillary filtration pressures.

Background: Vascular endothelial growth factor A (VEGF) is an essential growth factor during glomerular development and postnatal homeostasis. VEGF is secreted in high amounts by podocytes into the primary urine, back-filtered across the glomerular capillary wall to act on endothelial cells. So far it has been assumed that VEGF back-filtration is driven at a constant rate exclusively by diffusion. Methods: In the present work, glomerular VEGF back-filtration was investigated in vivo using a novel extended model based on endothelial fenestrations as surrogate marker for local VEGF concentrations. Single nephron glomerular filtration rate (SNGFR) and/or local filtration flux were manipulated by partial renal mass ablation, tubular ablation, and in transgenic mouse models of systemic or podocytic VEGF overexpression or reduction. Results: Our study shows positive correlations between VEGF back-filtration and SNGFR as well as effective filtration rate under physiological conditions along individual glomerular capillaries in rodents and humans. Conclusion: Our results suggest that an additional force drives VEGF back-filtration, potentially regulated by SNGFR.