Renal Senescence, Telomere Shortening and Nitrosative Stress in Feline Chronic Kidney Disease

Kidney tissues from cats with naturally occurring chronic kidney disease (CKD) and adult and senior cats without CKD were assessed to determine whether telomere shortening and nitrosative stress are associated with senescence in feline CKD. The histopathologic assessment of percent global glomerulosclerosis, inflammatory infiltrate, and fibrosis was performed. Senescence and nitrosative stress were evaluated utilizing p16 and iNOS immunohistochemistry, respectively. Renal telomere length was evaluated using telomere fluorescent in situ hybridization combined with immunohistochemistry. CKD cats were found to have significantly increased p16 staining in both the renal cortex and corticomedullary junction compared to adult and senior cats. Senior cats had significantly increased p16 staining in the corticomedullary junction compared to adult cats. p16 staining in both the renal cortex and corticomedullary junction were found to be significantly correlated with percent global glomerulosclerosis, cortical inflammatory infiltrate, and fibrosis scores. p16 staining also correlated with age in non-CKD cats. Average telomere length was significantly decreased in CKD cats compared to adult and senior cats. CKD cats had significantly increased iNOS staining compared to adult cats. Our results demonstrate increased renal senescence, telomere shortening, and nitrosative stress in feline CKD, identifying these patients as potential candidates for senolytic therapy with translational potential.

A Higher Foci Density of Interstitial Fibrosis and Tubular Atrophy Predicts Progressive Chronic Kidney Disease after a Radical Nephrectomy for Tumor

Background Chronic tubulointerstitial injury on kidney biopsy is usually quantified by the percentage of cortex with interstitial fibrosis/tubular atrophy (IF/TA). Whether other patterns of IF/TA or inflammation in the tubulointerstitium have prognostic importance beyond percentage IF/TA is unclear. Methods We obtained, stained, and digitally scanned full cortical thickness wedge sections of renal parenchyma from patients who underwent a radical nephrectomy for tumor in 2000 to 2015 and morphometrically analyzed the tubulointerstitium of the cortex for percentage IF/TA, IF/TA density (foci per mm2 cortex), percentage subcapsular IF/TA, striped IF/TA, percentage inflammation (both within and outside IF/TA regions), and percentage subcapsular inflammation. Patients were followed with visits every 6-12 months. Progressive chronic kidney disease (CKD) was defined as dialysis, kidney transplantation, or 40% decline from the postnephrectomy estimated glomerular filtration rate (eGFR). Cox models assessed risk of CKD or noncancer mortality with morphometric measures of tubulointerstitial injury after adjustment for percentage IF/TA and clinical characteristics. Results Among 936 patients (mean age, 64 years; postnephrectomy baseline eGFR, 48 ml/min per 1.73m2), 117 progressive CKD events and 183 noncancer deaths occurred over a median 6.4 years. Higher IF/TA density predicted both progressive CKD and noncancer mortality after adjustment for percentage IF/TA and predicted progressive CKD after further adjustment for clinical characteristics. Independent of percentage IF/TA, age, and sex, higher IF/TA density correlated with lower eGFR, smaller nonsclerosed glomeruli, more global glomerulosclerosis, and smaller total cortical volume. Conclusions Higher density of IF/TA foci (a more scattered pattern with more and smaller foci) predicts higher risk of progressive CKD after radical nephrectomy compared with the same percentage of IF/TA but with fewer and larger foci.

Indirect podocyte injury manifested in a partial podocytectomy mouse model

In progressive glomerular diseases, segmental podocyte injury often expands, leading to global glomerulosclerosis by unclear mechanisms. To study the expansion of podocyte injury, we established a new mosaic mouse model in which a fraction of podocytes express hCD25 and can be injured by the immunotoxin LMB2. hCD25-positive (+) and negative (-) podocytes were designed to express tdTomato and EGFP, respectively, which enabled cell sorting analysis of podocytes. After the injection of LMB2, mosaic mice developed proteinuria and glomerulosclerosis. Not only tdTomato(+) podocytes but also EGFP(+) podocytes were decreased in number and showed damage, as evidenced by a decrease in nephrin and an increase in desmin at both the protein and RNA levels. Transcriptomics analysis found a decrease in Glcci1 and an increase in Thbs4, Hbegf, and Tgfb2 in EGFP(+) podocytes; these genes may be candidate mediators of secondary podocyte damage. Pathway analysis suggested that focal adhesion, integrin-mediated cell adhesion, and focal adhesion-PI3K-Akt-mTOR signaling are involved in the secondary podocyte injury. Finally, treatment of mosaic mice with angiotensin II receptor blocker markedly ameliorated secondary podocyte injury. This mosaic podocyte injury model has distinctly demonstrated that damaged podocytes cause secondary podocyte damage, which may be a promising therapeutic target in progressive kidney diseases.

Podometrics in Japanese Living Donor Kidneys: Associations with Nephron Number, Age, and Hypertension

BackgroundPodocyte depletion, low nephron number, aging, and hypertension are associated with glomerulosclerosis and CKD. However, the relationship between podometrics and nephron number has not previously been examined.MethodsTo investigate podometrics and nephron number in healthy Japanese individuals, a population characterized by a relatively low nephron number, we immunostained single paraffin sections from 30 Japanese living-kidney donors (median age, 57 years) with podocyte-specific markers and analyzed images obtained with confocal microscopy. We used model-based stereology to estimate podometrics, and a combined enhanced–computed tomography/biopsy-specimen stereology method to estimate nephron number.ResultsThe median number of nonsclerotic nephrons per kidney was 659,000 (interquartile range [IQR], 564,000–825,000). The median podocyte number and podocyte density were 518 (IQR, 428–601) per tuft and 219 (IQR, 180–253) per 106μm3, respectively; these values are similar to those previously reported for other races. Total podocyte number per kidney (obtained by multiplying the individual number of nonsclerotic glomeruli by podocyte number per glomerulus) was 376 million (IQR, 259–449 million) and ranged 7.4-fold between donors. On average, these healthy kidneys lost 5.63 million podocytes per kidney per year, with most of this loss associated with glomerular loss resulting from global glomerulosclerosis, rather than podocyte loss from healthy glomeruli. Hypertension was associated with lower podocyte density and larger podocyte volume, independent of age.ConclusionsEstimation of the number of nephrons, podocytes, and other podometric parameters in individual kidneys provides new insights into the relationships between these parameters, age, and hypertension in the kidney. This approach might be of considerable value in evaluating the kidney in health and disease.

A Deep Learning Instance Segmentation Approach for Global Glomerulosclerosis Assessment in Donor Kidney Biopsies

The histological assessment of glomeruli is fundamental for determining if a kidney is suitable for transplantation. The Karpinski score is essential to evaluate the need for a single or dual kidney transplant and includes the ratio between the number of sclerotic glomeruli and the overall number of glomeruli in a kidney section. The manual evaluation of kidney biopsies performed by pathologists is time-consuming and error-prone, so an automatic framework to delineate all the glomeruli present in a kidney section can be very useful. Our experiments have been conducted on a dataset provided by the Department of Emergency and Organ Transplantations (DETO) of Bari University Hospital. This dataset is composed of 26 kidney biopsies coming from 19 donors. The rise of Convolutional Neural Networks (CNNs) has led to a realm of methods which are widely applied in Medical Imaging. Deep learning techniques are also very promising for the segmentation of glomeruli, with a variety of existing approaches. Many methods only focus on semantic segmentation—which consists in segmentation of individual pixels—or ignore the problem of discriminating between non-sclerotic and sclerotic glomeruli, so these approaches are not optimal or inadequate for transplantation assessment. In this work, we employed an end-to-end fully automatic approach based on Mask R-CNN for instance segmentation and classification of glomeruli. We also compared the results obtained with a baseline based on Faster R-CNN, which only allows detection at bounding boxes level. With respect to the existing literature, we improved the Mask R-CNN approach in sliding window contexts, by employing a variant of the Non-Maximum Suppression (NMS) algorithm, which we called Non-Maximum-Area Suppression (NMAS). The obtained results are very promising, leading to improvements over existing literature. The baseline Faster R-CNN-based approach obtained an F-Measure of 0.904 and 0.667 for non-sclerotic and sclerotic glomeruli, respectively. The Mask R-CNN approach has a significant improvement over the baseline, obtaining an F-Measure of 0.925 and 0.777 for non-sclerotic and sclerotic glomeruli, respectively. The proposed method is very promising for the instance segmentation and classification of glomeruli, and allows to make a robust evaluation of global glomerulosclerosis. We also compared Karpinski score obtained with our algorithm to that obtained with pathologists’ annotations to show the soundness of the proposed workflow from a clinical point of view.

P0661DIAGNOSTIC VALUE OF FULL AGE SPECTRUM EQUATION AS A PREDICTOR OF MORPHOLOGICAL LESIONS IN PATIENTS WITH GLOMERULONEPHRITIS

Background and Aims Glomerular filtration rate (GFR) is generally accepted as a best overall index of kidney function. However, it remains controversial to choose the optimal equation to estimate GFR in patients with glomerulonephritis (GN). Recent studies have reported that newly developed full age spectrum equation based on normalized serum creatinine (FASsCr) showed improved validity and was less biased, more accurate than currently recommended sCr-based eGFR equations. Our aim was to assess FASsCr equation as a predictor of various morphological lesions in patients with GN. Method 100 patients [48 female, age Me 39 (27; 54) years] with biopsy proven primary GN and without acute kidney injury, infectious diseases, severe heart failure, respiratory insufficiency, cancer were included in the study. Minimal change disease was diagnosed in 9% of cases based on the results of kidney biopsy, in 28% – focal segmental glomerulosclerosis, in 26% – membranous nephropathy and in 37% – IgA-nephropathy. Serum creatinine (sCr) level was measured by enzymatic method (Uni Cel DxC 800 PRO, «Beckman Coulter»,USA). eGFR was calculated using FASsCr equation. The extent of global glomerulosclerosis (GS) was assessed quantitatively as a sum of full and focal sclerotic glomeruli. Tubulo-interstitial fibrosis (TIF) and tubular atrophy (TA) were assessed semi-quantitatively (0-lesions absent; 1-mild focal tubular and interstitial lesions; 2-moderate tubular and interstitial lesions; 3 - diffuse tubular and interstitial lesions). All patients consistently were separated into 2 groups according to the degree of each morphological lesion (GS, TIF or TA): “mild” (GS<25% or TIF/TA grade 0 or 1) and “severe” (GS ≥ than 25% or TIF/TA grade 2-3). Results eGFR using FASsCr equation positively correlated (p<0,001 in all cases) with GS (r=0,44), TIF (r=0,64) and TA (r=0,61) and was significantly higher in patients with “mild” GS, TIF and TA (p<0,001) in comparison with “severe” group. Using ROC-analysis all patients were separated (p<0.001) in 2 groups using FASsCr equation according to the degree of morphological lesions (“mild” or “severe”): GS (Sn – 48.8%, Sp – 88.1%, ACC – 72.0%, AUC – 0.696, cut-off value – 47 ml/min/1.73m2), TIF (Sn - 75.4%, Sp – 76.9%, ACC – 76.0%, AUC – 0.815, cut-off value – 72 ml/min/1.73m2), TA (Sn – 65.9%, Sp – 88.8%, ACC – 70.0%, AUC – 0.798, cut-off value – 74 ml/min/1.73m2), (Figure). Conclusion Our results show that FASsCr equation is a significant marker of various morphological lesions in patients with GN. FASsCr equation predominantly can be used as a predictor of mild degree of interstitial sclerosis and tubular atrophy with high diagnostic value. Figure: ROC curves with 95% CI of BM panel for A – GS; B – TIF; C – TA

High Blood Pressure Is Associated with Tubulointerstitial Damage along with Glomerular Damage in Glomerulonephritis. A large Cohort Study

The key role of arterial hypertension in chonic kidney disease (CKD) progression is widely recognized, but its contribution to tubulointerstitial damage (TID) in glomerulonephritis (GN) remains uncertain. Hence, the objective of this study is to clarify whether TID is associated with glomerular damage, and whether the damage at the tubulointerstitial compartment is more severe in hypertensive patients. The study included retrospectively consecutive patients referred to the Nephrology Unit with diagnoses of primary glomerulonephritis, lupus nephritis (LN), and nephroangiosclerosis (NAS) at biopsy. At least six glomeruli per biopsy were analysed through light and immunofluorescence microscopy. Global glomerulosclerosis (GGS%), TID, and arteriolar hyalinosis (AH) were used as markers of CKD severity. Of the 448 patients of the cohort, 403 received a diagnosis of GN, with the remaining being diagnosed with NAS. Hypertension was found in 52% of the overall patients, with no significant differences among those with GN, and reaching 88.9% prevalence rate in NAS. The hypertensive patients with GN had more marked damage in glomerular and tubular compartments than normotensives independently of the amount of proteinuria. Moreover, hypertension and GGS% were found to be strongly associated with TID in GN. In GN patients, not only the severity of glomerular damage but also the extent of TID was associated with high blood pressure.