Renal Compartments Research Articles

Spatial and single-cell transcriptome analysis reveals changes in gene expression in response to drug perturbation in rat kidney.

The kidney is a complex organ that consists of various types of cells. It is occasionally difficult to resolve molecular alterations and possible perturbations that the kidney experiences due to drug-induced damage. In this study, we performed spatial and single-cell transcriptome analysis of rat kidneys and constructed a precise rat renal cell atlas with spatial information. Using the constructed catalogue, we were able to characterize cells of several minor populations, such as macula densa or juxtaglomerular cells. Further inspection of the spatial gene expression data allowed us to identify the upregulation of genes involved in the renin regulating pathway in losartan-treated populations. Losartan is an angiotensin II receptor antagonist drug, and the observed upregulation of the renin pathway-related genes could be due to feedback from the hypotensive action of the drug. Furthermore, we found spatial heterogeneity in the response to losartan among the glomeruli. These results collectively indicate that integrated single-cell and spatial gene expression analysis is a powerful approach to reveal the detailed associations between the different cell types spanning the complicated renal compartments.

The Summarized Assessment of Endothelin A Receptor Expression in Renal Transplant Compartments Associated with Antibody-Mediated Rejection.

The occurrence of anti-endothelin A receptor antibodies may be useful in diagnosis of transplant damage. We noticed that the presence of the endothelin A receptor (ETA receptor) in biopsy compartments is yet to be defined. We decided therefore to analysed the presence and relevance of the ETA receptor in biopsy to define the cause. Our study aims to evaluate the expression of ETA receptors in renal recipients after a biopsy due to the worsening of transplant function. Methods: The expression of ETA receptors was analyzed in renal transplant biopsies using the immunohistochemical method. The evaluation of ETA receptors was performed on paraffin sections. ETA receptor expression was analyzed in four compartments of renal transplant biopsies: glomeruli; vessels; tubular epithelium; and interstitium. The assessment was presented using a three-step scale (0: lack of expression; 1: mild to moderate immunoreactivity; 2: high expression). The results of each compartment from a single biopsy were summarized and assessed in the context of antibody-mediated rejection (AMR). Results: We analyzed 156 patients who had a renal allograft biopsy after renal transplantation. For each patient, we created a summarized ETA receptor expression score. The summarized ETA receptor expression score analysis showed statistically significant differences in patients with and without AMR. In addition, we noticed that patients with AMR had a significantly higher mean summarized expression of ETA receptor score of 3.28 ± 1.56 compared to patients who had a biopsy for other reasons with a mean summarized ETA receptor expression score of 1.47 ± 1.35 (p < 0.000001). ROC analysis of the ETA receptor expression score for detecting AMR status showed that the most appropriate cut-off for the test of the chosen binary classifier is between 2 and 3 of the summarized ETA receptor expression score. Conclusions: The expression of endothelin A receptors in renal transplant compartments may be associated with antibody-mediated rejection. The positive ETA receptor staining might be a vital feature in the diagnosis of damage in AMR. The summarized ETA receptor expression score seems to be an exciting diagnostic tool in transplant injury assessment.

Healthy Kidney Segmentation in the Dce-Mr Images Using a Convolutional Neural Network and Temporal Signal Characteristics.

Quantification of renal perfusion based on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) requires determination of signal intensity time courses in the region of renal parenchyma. Thus, selection of voxels representing the kidney must be accomplished with special care and constitutes one of the major technical limitations which hampers wider usage of this technique as a standard clinical routine. Manual segmentation of renal compartments—even if performed by experts—is a common source of decreased repeatability and reproducibility. In this paper, we present a processing framework for the automatic kidney segmentation in DCE-MR images. The framework consists of two stages. Firstly, kidney masks are generated using a convolutional neural network. Then, mask voxels are classified to one of three regions—cortex, medulla, and pelvis–based on DCE-MRI signal intensity time courses. The proposed approach was evaluated on a cohort of 10 healthy volunteers who underwent the DCE-MRI examination. MRI scanning was repeated on two time events within a 10-day interval. For semantic segmentation task we employed a classic U-Net architecture, whereas experiments on voxel classification were performed using three alternative algorithms—support vector machines, logistic regression and extreme gradient boosting trees, among which SVM produced the most accurate results. Both segmentation and classification steps were accomplished by a series of models, each trained separately for a given subject using the data from other participants only. The mean achieved accuracy of the whole kidney segmentation was 94% in terms of IoU coefficient. Cortex, medulla and pelvis were segmented with IoU ranging from 90 to 93% depending on the tissue and body side. The results were also validated by comparing image-derived perfusion parameters with ground truth measurements of glomerular filtration rate (GFR). The repeatability of GFR calculation, as assessed by the coefficient of variation was determined at the level of 14.5 and 17.5% for the left and right kidney, respectively and it improved relative to manual segmentation. Reproduciblity, in turn, was evaluated by measuring agreement between image-derived and iohexol-based GFR values. The estimated absolute mean differences were equal to 9.4 and 12.9 mL/min/1.73 m2 for scanning sessions 1 and 2 and the proposed automated segmentation method. The result for session 2 was comparable with manual segmentation, whereas for session 1 reproducibility in the automatic pipeline was weaker.

Transcriptional Profiling of Renal Endothelial Compartments During Progression of Murine Diabetic Nephropathy

Transcriptional Profiling of Renal Endothelial Compartments During Progression of Murine Diabetic Nephropathy

Continuous diffusion spectrum computation for diffusion-weighted magnetic resonance imaging of the kidney tubule system

The use of rigid multi-exponential models (with a priori predefined numbers of components) is common practice for diffusion-weighted MRI (DWI) analysis of the kidney. This approach may not accurately reflect renal microstructure, as the data are forced to conform to the a priori assumptions of simplified models. This work examines the feasibility of less constrained, data-driven non-negative least squares (NNLS) continuum modelling for DWI of the kidney tubule system in simulations that include emulations of pathophysiological conditions. Non-linear least squares (LS) fitting was used as reference for the simulations. For performance assessment, a threshold of 5% or 10% for the mean absolute percentage error (MAPE) of NNLS and LS results was used. As ground truth, a tri-exponential model using defined volume fractions and diffusion coefficients for each renal compartment (tubule system: Dtubules , ftubules ; renal tissue: Dtissue , ftissue ; renal blood: Dblood , fblood ;) was applied. The impact of: (I) signal-to-noise ratio (SNR) =40-1,000, (II) number of b-values (n=10-50), (III) diffusion weighting (b-rangesmall =0-800 up to b-rangelarge =0-2,180 s/mm2), and (IV) fixation of the diffusion coefficients Dtissue and Dblood was examined. NNLS was evaluated for baseline and pathophysiological conditions, namely increased tubular volume fraction (ITV) and renal fibrosis (10%: grade I, mild) and 30% (grade II, moderate). NNLS showed the same high degree of reliability as the non-linear LS. MAPE of the tubular volume fraction (ftubules ) decreased with increasing SNR. Increasing the number of b-values was beneficial for ftubules precision. Using the b-rangelarge led to a decrease in MAPE ftubules compared to b-rangesmall. The use of a medium b-value range of b=0-1,380 s/mm2 improved ftubules precision, and further bmax increases beyond this range yielded diminishing improvements. Fixing Dblood and Dtissue significantly reduced MAPE ftubules and provided near perfect distinction between baseline and ITV conditions. Without constraining the number of renal compartments in advance, NNLS was able to detect the (fourth) fibrotic compartment, to differentiate it from the other three diffusion components, and to distinguish between 10% vs. 30% fibrosis. This work demonstrates the feasibility of NNLS modelling for DWI of the kidney tubule system and shows its potential for examining diffusion compartments associated with renal pathophysiology including ITV fraction and different degrees of fibrosis.

Systematic Scoring of Tubular Injury Patterns Reveals Interplay between Distinct Tubular and Glomerular Lesions in ANCA-Associated Glomerulonephritis.

Background: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a small vessel vasculitis, most frequently presenting as microscopic polyangiitis (MPA) or granulomatosis with polyangiitis (GPA). Acute tubular injury with the presence of tubulitis was previously reported to be of prognostic value in ANCA glomerulonephritis (GN). In particular, distinct tubular injury lesions were associated with the deterioration of kidney function at AAV disease onset, as well as renal resistance to treatment, and higher risk of progression to composite outcome in patients with AAV. To expand our knowledge regarding distinct tubular lesions in AAV, we aimed to describe acute tubular injury patterns in association with glomerular lesions in ANCA GN by systematic histological scoring. Methods: A total number of 48 renal biopsies with confirmed renal involvement of AAV admitted to the University Medical Center Göttingen from 2015 to 2020 were retrospectively examined. By systematic scoring of tubular injury lesions, the association between clinical parameters, laboratory markers, and histopathological findings was explored. Results: We have shown that cellular casts in renal biopsies were frequently observed in the majority of cases with ANCA GN. Furthermore, we showed that tubular epithelial simplification with dilatation correlated with MPA and MPO subtypes, C3c hypocomplementemia, severe renal involvement, and uACR. Red blood cell (RBC) casts were associated with increased levels of C-reactive protein (CRP), leukocyturia, and hematuria. Finally, we found that hyaline casts were associated with an increased fraction of glomeruli with global glomerular sclerosis. Conclusions: Acute tubular injury patterns were correlated with active ANCA GN, whereas tubular injury lesions reflecting the later stages of kidney disease correlated with chronic glomerular lesions. These results suggest an interplay between different renal compartments.

Enhanced Ultrasound Contrast of Renal‐Clearable Luminescent Gold Nanoparticles

AbstractRenal‐clearable nanoparticles are typically fast eliminated through the free glomerular filtration, which show weak interaction with the renal compartments and negligible ultrasound signals, raising challenges in direct imaging of kidney diseases. Here, we report the ultrasmall renal‐clearable luminescent gold nanoparticles (AuNPs) with both pH‐induced charge reversal and aggregation properties, and discover that enhanced ultrasound contrast could be facilely acquired through the increased tubular reabsorption and in situ aggregation of AuNPs in renal tubule cells in injured kidneys. The tuning elimination pathway of the renal‐clearable luminescent AuNPs is further demonstrated to provide a synergistical fluorescence and ultrasound imaging strategy for diagnosing early kidney injury with precise anatomical information.

Extracellular Vesicles and Renal Fibrosis: An Odyssey toward a New Therapeutic Approach.

Renal fibrosis is a complex disorder characterized by the destruction of kidney parenchyma. There is currently no cure for this devastating condition. Extracellular vesicles (EVs) are membranous vesicles released from cells in both physiological and diseased states. Given their fundamental role in transferring biomolecules to recipient cells and their ability to cross biological barriers, EVs have been widely investigated as potential cell-free therapeutic agents. In this review, we provide an overview of EVs, focusing on their functional role in renal fibrosis and signaling messengers responsible for EV-mediated crosstalk between various renal compartments. We explore recent findings regarding the renoprotective effect of EVs and their use as therapeutic agents in renal fibrosis. We also highlight advantages and future perspectives of the therapeutic applications of EVs in renal diseases.

COVID-19-induced endotheliitis: emerging evidence and possible therapeutic strategies.

The coronavirus disease 2019 (COVID‐19) pandemic, a viral illness caused by the severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2), 1 has produced at the time of this writing nearly 33 million cases of infection, with over a million deaths in 235 countries, 2 causing an unprecedented burden on healthcare systems and a severe global socioeconomic crisis. As the pandemic spreads, knowledge on the disease course, as well as potential risk factors and predictors of severity is increasing daily, and initial data from randomised controlled studies have allowed care providers to refine therapeutic strategies. Nonetheless, mortality is markedly elevated among those presenting with severe disease, long‐term sequelae among survivors are unknown, and vaccine‐based therapies currently remain at early stages of development. Most reported cases are asymptomatic or present with mild symptoms; however, 7–26% of hospitalised patients experience severe disease, often requiring admission to intensive care units (ICUs), with progressive multiple organ dysfunction and high mortality. 3 , 4 , 5 Such differences in clinical outcomes have led physicians to initiate diverse pharmacological therapies at various stages of the disease, generating challenges as to the most appropriate therapeutic choice for COVID‐19. In this context, the use of dexamethasone has significantly reduced mortality rates in critically ill patients requiring supplemental oxygen or mechanical ventilation, 6 and remdesivir has demonstrated clinical benefit in hospitalised patients, but with unknown survival benefit to date 7 ; additional effective treatment options are therefore urgently needed. In an initial attempt to provide a uniform and widely reproducible methodology to guide systematic treatment strategies, a three‐stage classification of COVID‐19 has been proposed. 8 The Stage I or ‘early infection’ occurs at the initial establishment of disease with high viral replication, and commonly presents with a range of complaints that can include mild and often non‐specific influenza‐like signs and symptoms. Stage II is the ‘pulmonary phase’, with preferential viral‐mediated injury of the lung parenchyma and this is characterised by shortness of breath, hypoxia and pulmonary infiltrates with some degree of lung inflammation. Stage III is characterised by an exaggerated host immune‐inflammatory response to the virus, leading to acute respiratory distress syndrome (ARDS) and multi‐organ failure (MOF).

Variable Expression of Programmed Cell Death Protein 1-Ligand 1 in Kidneys Independent of Immune Checkpoint Inhibition.

ContextDue to recent advantages in cancer therapy, immune checkpoint inhibitors (ICIs) are new classes of drugs targeting programmed cell death protein 1 (PD-1) or its ligand programmed cell death protein 1-ligand 1 (PD-L1) used in many cancer therapies. Acute interstitial nephritis (AIN) is a potential and deleterious immune-related adverse events (irAE) in the kidney observed in patients receiving ICIs and the most common biopsy-proven diagnosis in patients who develop acute kidney injury (AKI). Based on previous reports, AIN in patients receiving ICIs is associated with tubular positivity for PD-L1, implicating that PD-L1 positivity reflects susceptibility to develop renal complications with these agents. It remains unclear if PD-L1 positivity is acquired specifically during ICI therapy or expressed independently in the kidney.MethodsPD-L1 was analyzed in experimental mouse models of ischemia-reperfusion injury (IRI), folic acid-induced nephropathy (FAN), unilateral ureteral obstruction (UUO), and nephrotoxic serum nephritis (NTN) by immunostaining, SDS-PAGE, and subsequent immunoblotting. In addition, we included a total number of 87 human kidney samples (six renal biopsies with AIN related to ICI therapy, 13 nephrectomy control kidneys, and 68 ICI-naïve renal biopsies with various underlying kidney diseases to describe PD-L1 expression.ResultsWe here report distinct PD-L1 expression in renal compartments in multiple murine models of kidney injury and human cases with various underlying kidney diseases, including ICI-related AIN and renal pathologies independent of ICI therapy. PD-L1 is frequently expressed in various renal pathologies independent of ICI therapy and could potentially be a pre-requisit for susceptibility to develop AKI and deleterious immune-related AIN. In addition, we provide evidence that tubular PD-L1 positivity in the kidney is associated with detection of urinary PD-L1+ tubular epithelial cells.ConclusionOur study implicates that PD-L1 is frequently expressed in various renal pathologies independent of ICI therapy and could potentially be a pre-requisit for susceptibility to develop AKI and deleterious immune-related AIN. Because non-invasive detection of PD-L1+ cells in corresponding urine samples correlates with intrarenal PD-L1 positivity, it is attractive to speculate that further non-invasive detection of PD-L1+ cells may identify patients at risk for ICI-related AIN.

Connexin43 is differentially distributed within renal vasculature and mediates profibrotic differentiation in medullary fibroblasts.

Connexins (Cxs) form gap junctions for intercellular exchange of inorganic ions and messenger molecules. In the kidney, Cxs play essential roles within its compartments, but data on the precise cellular localization and cell type-related function of their isoforms are scarce. We tested whether Cx43 distribution is restricted to vascular and interstitial cells and whether medullary fibroblasts express Cx43 to coordinate profibrotic signaling. Confocal immunofluorescence techniques, ultrastructural labeling, and functional experiments in cell culture were performed. Cx43 was chiefly expressed in the vasculature but was absent from tubular epithelia. All arterial, arteriolar, and lymphatic endothelia showed continuous Cx43 signal along their borders. In the inner medulla, only the interstitium showed Cx43 signals, which were assigned to fibroblasts and their processes. Cultured Cx43-expressing medullary fibroblasts served to study the role of gap junctions in a profibrotic context. In a dye spreading assay, Cx43-sensitive diffusion of Lucifer yellow was dependent on gap junctional passage. The addition of transforming growth factor-β1 (5 ng/mL for 48 h) activated Cx43 biosynthesis and caused Cx43-sensitive transformation of the fibroblasts into a myofibroblast phenotype. This suggested that Cx43 gap junctional channels enable the coordination of profibrotic signaling between cells of the medullary interstitium. In summary, we demonstrate the presence of Cx43-expressing gap junctions within the two major renal compartments, the vasculature and interstitium. Endothelial Cx43 likely provides functions of an earlier-defined "electrical syncytium" within the vascular wall. Additionally, Cx43 facilitates profibrotic signaling between medullary interstitial fibroblasts.

P0423CLINICOPATHOLOGICAL STUDY OF RENAL AMYLOIDOSIS

Abstract Background and Aims Amyloidosis constitute a heterogenous group of disorders characterized by extracellular deposition of abnormally folded proteins in different tissues and organs leading to organ dysfunction. An emphasis has been made to classify, grade and score the amyloid deposits in different renal compartments and correlate them with the clinical features, type of amyloid and outcome. Method The study included all renal biopsies done in department of nephrology diagnosed as amyloidosis in association with Department of Pathology, SGPGIMS from January 2009 to December 2018 and retrospectively analysed. Besides biochemical parameters ,serum and urine electrophoresis ,immunofixation ,bone biopsy ,FNAC and kidney biopsy was done for the diagnosis. Results One hundred forty seven (147) renal biopsies diagnosed as Amyloidosis at the Department of Pathology, SGPGIMS, Lucknow from January 2009 and December 2018 .The mean age was 51.33 ± 14.50 years (Median: 52 year), most common age group affected with Renal Amyloidosis was 50-60 years(6 th decade) in males, while it was one decade younger in females (40-50years). Multiple myeloma as the primary disease was present in 18/147 (12.2%). History of chronic inflammatory disease was found in 65 patients (44%). Tuberculosis was the most common infection while rheumatoid arthritis (18.5%) was found to be the second most commonly associated chronic inflammatory condition. Mean serum creatinine was 2.04 ±1.72 mg/dl. Peripheral neuropathy and bleeding episodes were rarely seen (&amp;lt;5%). Nephrotic range proteinuria was found in 78% Only eight out of eighteen patients with Multiple myeloma showed reversal of A:G ratio. M-band was present in 34 patients . Lambda light chain was found more commonly associated with renal amyloidosis. Out of 71, 27 aspiration cytology smears revealed congophilic deposits which showed apple green birefringence on polarizing microscopy. Bone marrow biopsy was performed in 76, among them 17 patients showed &amp;gt; 10% plasma cells. Histology commonly seen was diffuse mesangio capillary in 77%, followed by advanced amyloidosis (20%). Most of the renal biopsies (84%) showed amyloid deposition in &amp;gt;50% area of glomeruli. Most of the renal biopsies (41.5%) showed mild tubular atrophy. Renal amyloid prognostic score (RAPS) was calculated combining all scores in different renal compartments revealed 74% patients belonged to Grade III. Immuno histochemistry for typing of renal amyloid revealed SAA in 61, two cases were placed in a different group, termed as dual AL+AA positive. one case with positive ALect2 deposits in renal biopsy. Survival analysis showed showed that AL had poor overall survival as compared to AA typePatients with high serum creatinine value (&amp;gt;2.0 mg/dl) had poor survival as compared to the patients with serum creatinine &amp;lt;2.0mg/dl. significant poor survival in patients withcardiomyopathy (p value=0.004) and hypotension (p value=0.026). High burden of plasma cells (&amp;gt; 10%) in bone marrow aspirate also showed significant poor survival. Conclusion Final typing of amyloid deposits in kidney biopsy with clinicopathological evaluation revealed AA was the predominant subtype comprising of 50% (n=73) of renal amyloidosis. AL was 33% (n=48) of all cases. The different class of pattern of amyloid deposition correlated well with the grade of amyloid deposition in renal biopsy. Poor survival outcomes are evident with patients with hypotension ,cardiomyopathy, higher grades of amyloid on histology, serum creatinine &amp;gt; 2 mg% and high burden of plasma cells (&amp;gt;10%) in bone marrow aspirate. Thus the number of patients with cardiomyopathy, hypotension and &amp;gt; 10% plasma cells in bone marrow aspirate performed poorly however the study is smalland needs to be validated on a larger cohort.

P0320KIDNEY DAMAGE IN THE NON-HODGKIN LYMPHOMA/LEUKEMIA AND HODGKIN'S LYMPHOMA - CLINICAL AND PATHOLOGY SPECTRUM IN THE REAL PRACTICE

Abstract Background and Aims Kidney damage in non-Hodgkin lymphoma/leukemia (NHL/CLL) and in Hodgkin’s lymphoma (HL) are caused by several mechanisms: tumor mass localization, clonal cell expansion, hormones, cytokines and growth factors secretion, metabolic, electrolyte and coagulation disturbances, infectious, drug-induced and radiation complications etc., which can affect urinary tract, renal arteries and veins and all renal parenchyma compartments. Clinical presentation of kidney involvement in the patients with NHL/CLL and HL include both acute kidney injury (AKI) and chronic kidney disease (CKD), the latter - with or without nephrotic syndrome (NS). Pre-renal AKI, tumor-lysis syndrome (TLS), or urinary tract compression by lymph nodes usually diagnosed on the clinical basis, but one cannot differentiate other conditions, particularly NS, in the clinical setting. Importantly, symptoms of kidney damage may dominate or even preclude overt NHL/CLL or HL, and only pathology data give the clue to the main diagnosis. Kidney biopsy or post-mortem pathology findings include various patterns of paraneoplastic glomerulonephritis (GN) as well as amyloidosis; as also as tubulointerstitial damages, mainly specific lymphoid interstitial infiltration and sometimes pyelonephritis Method In this retrospective study from a single nephrology centre, we retrieved charts of the patients with NHL/CLL and HL. Collected data were age, gender, main diagnosis, diagnosis of AKI or CKD, CKD stage, NS presence, the cause of AKI and CKD based on the clinical presentation, and pathology pattern, if available. Results Study group included 57 patients, 36 males and 21 females, median age 48 [18; 80] years. Kidney biopsy was performed in 22 (39%) of cases. Main clinical data and pathology shown in the Figure. Patients with B-cell NHL/HLL comprised almost ¾ of the study group, with AKI and CKD in a roughly equal proportion. Pathology showed specific infiltration in about ¼ of AKI and in a few CKD cases, and various paraneoplastic GN in every fifth case - minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), membranous nephropathy (MN), membranoproliferative GN (MPGN), and IgA-nephropathy (IgAN); two cases of AA amyloidosis, and one case of tubulointerstitial nephritis. There were only three patients with T-cell NCL/CLL, pathology findings were MCD in one case and lymphoid infiltration in another. Four out of 13 cases of HL demonstrated paraneoplastic GN – MCD, FSGS and IgAN, with just one case of AA amyloidosis. Totally 17 cases of AKI - pre-renal and caused by TLS or urinary tract compression by lymph nodes diagnosed on the clinical basis. Interestingly, in five cases we found a combination of various clinical settings and pathology patterns – compression with lymph nodes and TLS or acute pyelonephritis, AA amyloidosis and lymphoid infiltration or acute pyelonephritis, and finally IgAN and lymphoid infiltration. In 14 (24.5%) of the study group, the cause pf CKD remained unknown, as kidney biopsy was not performed due to severe anaemia and/or thrombocytopenia. Conclusion It is impossible to decipher many of AKI and most of CKD causes in the patients with NCL/CLL and HL without pathology evaluation. Nephrologist must perform kidney biopsy in all patients with NCL/CLL of HL CKD, and those with AKI of unknown origin, unless contraindicated, especially if the hematological diagnosis is uncertain.

The Renal Resistive Index: A New Biomarker for the Follow-up of Vascular Modifications in Systemic Sclerosis.

The aim of the present retrospective observational study was to evaluate the change of Renal Resistive Index (RRI) over time (ΔRRI) and under treatment in patients with systemic sclerosis (SSc) as well as to correlate these changes with disease complications. Two hundred thirty patients [29 male, median age 57 (IQR 48-67) yrs] were enrolled. At baseline and follow-up (3.43, IQR 2.81-4.45 yrs), we collected the following data: disease variables, nailfold videocapillaroscopy (NVC) pattern, forced vital capacity (FVC), diffusing lung capacity for carbon monoxide (DLCO), systolic pulmonary arterial pressure (sPAP), presence of interstitial lung disease, RRI, evaluation of glomerular filtration rate, and new onset of pulmonary arterial hypertension (PAH). RRI value is high in SSc patients with digital ulcers and anticentromere antibodies, active and late NVC patterns, and limited cutaneous SSc. A significant correlation was observed between ΔRRI and ΔsPAP (R = 0.17, P = 0.02), with statistically higher ΔRRI (0.08 ± 0.02 vs 0.03 ± 0.05, P = 0.04) in patients complicated by PAH onset. No other new-onset complication was associated with ΔRRI. The receiver-operating characteristic curve analysis confirmed the predictive role of ΔRRI in development of new PAH (area under the curve 0.84, 95% CI 0.75-0.93, P = 0.02). In patients with SSc never exposed to sildenafil, ΔRRI was higher (0.04 ± 0.05) compared to both patients exposed to sildenafil during the study period (0.01 ± 0.05, P = 0.03) or in those exposed at the time of baseline evaluation (0.00 ± 0.05, P = 0.01). RRI and its variation in time are a reliable marker of SSc-related vasculopathy, both in renal and extrarenal compartments.

Proximal Tubule Epithelial Cell Reabsorption of the Drug Delivery Protein Elastin‐like Polypeptide

Elastin like polypeptide (ELP) is a protein composed of a pentapeptide repeat domain found in human tropoelastin. ELP is used for drug delivery by altering the ELP coding sequence to attach drugs, therapeutic peptides, or therapeutic proteins. One of the focuses of our group has been development of ELP – delivered therapeutics for treatment of kidney disease. Thus, understanding how ELP is filtered, reabsorbed, and distributed within the kidney is of key importance. In vivo studies in our lab showed that ELPs accumulated preferentially in the kidney after systemic administration. Renal deposition and intra‐renal distribution was dependent on ELP size, with smaller ELPs accumulating exclusively in the renal cortex and larger ELPs having a more mixed cortical and medullary distribution. All ELPs were present at high levels in tubular epithelial cells. However, whether the tubular distribution is the result of ELP reabsorption after filtration and whether the amount or rate of reabsorption is dependent on ELP size is unknown.To address this issue, uptake and intracellular distribution of fluorescein‐5‐malemide labeled ELPs of varying sizes were determined in primary human proximal tubule epithelial cells (HRPteC). HRPteC were seeded in a 6 well plate (4x104/well) and incubated with fluorescein labeled ELP (10μM) for various times (24hr, 6hr, 4hr, 2hr and 1hr). HRPteC were collected, and mean cellular fluorescence intensity was measured using flow cytometry. Percentage of ELP internalization was determined by quenching the extracellular fluorescein label with trypan blue (0.13% v/v), then repeating the flow cytometric analysis to measure only intracellular fluorescence. To obtain a qualitative representation of ELP interaction with kidney cells, HRPteC were seeded in an 8‐chamber glass slide (2x103 cells/chamber) and incubated with fluorescein labeled ELP (10μM) for various times as above. Following fixation and staining with 4′,6‐diamidino‐2‐phenylindole (DAPI), cells were imaged by laser scanning confocal microscopy. Our data demonstrate that a longer incubation time led to a greater accumulation of ELP in the proximal tubule epithelial cells. Analysis of internalization rate revealed that all ELPs entered the cells slowly over the course of a 24‐hour time frame. This finding was supported by confocal microscopy. Between 1 and 12 hours, localization of ELP occurred at the cellular membrane of the proximal tubule cells, but at time points between 12 and 24 hours, ELP was visible in punctate cytoplasmic structures likely to be endocytic vesicles. A smaller ELP‐63 (~25 kDa) accumulated in cells at higher levels than did a larger ELP‐159 (~62 kDa) after 24 hours of incubation (390.7 ±5.0 versus 651.6 ±42.7 RFU; p&lt;0.05). These data suggest that there may be a common mechanism for tubular epithelial cell uptake of ELPs of various sizes, but that smaller ELPs may be internalized to a greater extent than larger ELPs. The results of these and future studies to determine the exact renal handling of ELPs of various sizes will be crucial to the design of ELPs for delivery of therapeutics to specific renal compartments or cell types.

An update to the pathogenesis for monoclonal gammopathy of renal significance.

Monoclonal gammopathy of renal significance (MGRS) is characterized by the nephrotoxic monoclonal immunoglobulin (MIg) secreted by an otherwise asymptomatic or indolent B-cell or plasma cell clone, without hematologic criteria for treatment. The spectrum of MGRS-associated disorders is wide, including non-organized deposits or inclusions such as C3 glomerulopathy with monoclonal glomerulopathy (MIg-C3G), monoclonal immunoglobulin deposition disease, proliferative glomerulonephritis with monoclonal immunoglobulin deposits and organized deposits like immunoglobulin related amyloidosis, type I and type II cryoglobulinaemic glomerulonephritis, light chain proximal tubulopathy, and so on. Kidney biopsy should be conducted to identify the exact disease associated with MGRS. These MGRS-associated diseases can involve one or more renal compartments, including glomeruli, tubules and vessels. Hydrophobic residues replacement, N-glycosylated, increase in isoelectric point in MIg causes it to transform from soluble form to tissue deposition, causing glomerular damage. Complement deposition is found in MIg-C3G, which is caused by an abnormality of the alternative pathway and may involve multiple factors including complement component 3 nephritic factor, anti-complement factor auto-antibodies or MIg which directly cleaves C3. The effect of transforming growth factor beta and platelet-derived growth factor-β on mesangial extracellular matrix is associated with glomerular and tubular basement membrane thickening, nodular glomerulosclerosis, and interstitial fibrosis. Furthermore, inflammatory factors, growth factors and virus infection may play an important role in the development of the diseases. In this review, for the first time, we discussed current highlights in the mechanism of MGRS-related lesions.

An update to the pathogenesis for monoclonal gammopathy of renal significance.

Monoclonal gammopathy of renal significance (MGRS) is characterized by the nephrotoxic monoclonal immunoglobulin secreted by an otherwise asymptomatic or indolent B cell or plasma cell clone, without hematologic criteria for treatment. These MGRS-associated diseases can involve one or more renal compartments, including glomeruli, tubules, and vessels. Hydrophobic residue replacement, N-glycosylated, increase in isoelectric point in monoclonal immunoglobulin (MIg) causes it to transform from soluble form to tissue deposition, and consequently resulting in glomerular damage. In addition to MIg deposition, complement deposition is also found in C3 glomerulopathy with monoclonal glomerulopathy, which is caused by an abnormality of the alternative pathway and may involve multiple factors including complement component 3 nephritic factor, anti-complement factor auto-antibodies, or MIg which directly cleaves C3. Furthermore, inflammatory factors, growth factors, and virus infection may also participate in the development of the diseases. In this review, for the first time, we discussed current highlights in the mechanism of MGRS-related lesions.

Ultrasound‐guided transmuscular quadratus lumborum block catheter technique: a reply

We would like to thank Andersen et al. 1 for their critical appraisal of our recent article 2. We agree that the ultrasound picture used as Fig. 2 may be misinterpreted and is difficult to align with the drawing beside it. Referring to an excellent anatomical depiction of the different modalities of quadratus lumborum (QL) block on the New York School of Regional Anaesthesia (NYSORA) website 3, we maintain that our target is similar to what they describe as transmuscular quadratus lumborum (TQL) block, although our approach is slightly posterolateral; with the aim to reach the fascia covering the anterior aspect of QL muscle next to the psoas muscle. This target area between the psoas muscle and QL block is comparable to the one Børglum et al. originally described 4. We have included a more detailed ultrasound image (Fig. 1) with an example of the needle trajectory we used in our series. The anatomical differences with regard to the QL block and psoas muscle depictions may also relate to the different lumbar levels and the quite pronounced individual anatomical variability we have observed. We appreciate the highly informative step-by-step description provided by Andersen et al., particularly in relation to the observation of respiratory movements in order to distinguish the renal fat compartments from the relevant muscles, which is very accurate. The comment that we did not find an overall significant difference between the two treatment modalities can be explained by the fact that we used a proven active control group (pre-peritoneal catheter technique) 5 in contrast to the saline control sham groups in the studies Andersen et al. refer to 6, 7. Our findings suggest that both techniques are equally effective in providing postoperative analgesia following abdominal surgery, with the pre-peritoneal catheter technique being a more cost effective and viable alternative. We believe that we have extended the application of TQL block by a continuous catheter technique and achieving sensory dermatomal coverage from T4 to L1. We argue that our technique is valid and once again admit that a better illustration in our published article would have resulted in less ambiguity in the interpretation of the needle trajectory. Therefore, we do not agree with the statement by Andersen et al. that our study should not be included in any possible future reviews regarding the TQL block.

Correlation between amyloid deposits affecting renal compartments and glomerular filtration rate during renal biopsy in a renal amyloidosis case series.

Amyloidosis comprises a group of disorders that accumulate modified autologous proteins in organs, mainly the kidneys. Few studies have addressed the amyloid compartmental distribution and associated clinical outcomes. The aim of this study was to present a case series of renal amyloidosis correlating histopathological data with glomerular filtration rate (GFR) during kidney biopsy. We studied 53 cases reviewed by nephropathologists from 2000 to 2018 in a single kidney biopsy center in Brazil. GFR was estimated using the CKD-EPI formula. Cases were divided into Group A ≥60 and Group B <60 mL·min−1·(1.73 m2)−1 using the estimated GFR during kidney biopsy. Semiquantitative histopathological study was performed, including extension and distribution of amyloid deposits by compartments (glomeruli, tubulointerstitial tissue, and vessels). Statistical analyses were made to understand associations with lower GFR. No difference was seen for age, gender, proteinuria, hematuria, subtype of amyloid protein, arteriosclerosis, interstitial fibrosis/infiltrate, or glomerular and interstitial amyloid deposits. After a previous P value <0.1 in the descriptive analysis, the following variables were selected: globally sclerotic glomeruli, high blood pressure, and the extension of vascular amyloid deposition. A binary logistic regression model with GFR as the dependent variable showed history of hypertension and vascular amyloid to be robust and independent predictors of Group B <60 mL·min−1·(1.73 m2)−1. Beyond the histopathologic diagnosis of amyloidosis, a semiquantitative approach on renal biopsy could provide new insights. Vascular amyloid is an independent predictor of renal dysfunction in cases of renal amyloidosis.

Macrophage polarization in chronic kidney disease: a balancing act between renal recovery and decline?

Macrophages are heterogenous cells of the innate immune system that can fluidly modulate their phenotype to respond to their local microenvironment. They are found throughout the renal compartments, where they contribute to homeostasis and function. However, renal injury activates molecular pathways that initially stimulate differentiation of macrophages into a proinflammatory M1 phenotype. Later in the course of healing, abundant apoptotic debris and anti-inflammatory cytokines induce the production of anti-inflammatory M2 macrophages, which contribute to tissue regeneration and repair. Thus, the dynamic balance of M1 and M2 populations may outline the burden of inflammation and process of tissue repair that define renal outcomes, which has been the impetus for therapeutic efforts targeting macrophages. This review will discuss the role of these phenotypes in the progression of chronic renal injury, potential pathogenic mechanisms, and the promise of macrophage-based therapeutic applications for chronic kidney disease.