Glomerular Density Research Articles

Image analysis techniques to map pyramids, pyramid structure, glomerular distribution, and pathology in the intact human kidney from 3-D MRI.

Kidney pathologies are often highly heterogeneous. To comprehensively understand kidney structure and pathology, it is critical to develop tools to map tissue microstructure in the context of the whole, intact organ. Magnetic resonance imaging (MRI) can provide a unique, three-dimensional view of the kidney and allows for measurements of multiple pathological features. Here, we developed a platform to systematically render and map gross and microstructural features of the human kidney based on three-dimensional MRI. These features include pyramid number and morphology as well as the associated medulla and cortex. In a subset of these kidneys, we also mapped individual glomeruli and glomerular volumes using cationic ferritin-enhanced MRI to report intrarenal heterogeneity in glomerular density and size. Finally, we rendered and measured regions of nephron loss due to pathology and individual glomerular volumes in each pyramidal unit. This work provides new tools to comprehensively evaluate the kidney across scales, with potential applications in anatomic and physiological research, transplant allograft evaluation, biomarker development, biopsy guidance, and therapeutic monitoring. These image rendering and analysis tools could eventually impact the field of transplantation medicine to improve longevity matching of donor allografts and recipients and reduce discard rates through the direct assessment of donor kidneys.NEW & NOTEWORTHY We report the application of cutting-edge image analysis approaches to characterize the pyramidal geometry, glomerular microstructure, and heterogeneity of the whole human kidney imaged using MRI. This work establishes a framework to improve the detection of microstructural pathology to potentially facilitate disease monitoring or transplant evaluation in the individual kidney.

Proteinuria and Renal Dysfunction Due to Extremely Low Birth Weight in a Patient with Silver-Russell Syndrome.

A 36-year-old woman diagnosed with Silver-Russell syndrome during childhood presented to our department after a primary care physician suspected renal dysfunction. At birth, she had an extremely low weight (1210 g), and in childhood, she was diagnosed with Silver-Russell syndrome. At the age of 14 she was found to have proteinuria; however, the condition was never further examined. One month prior to her presentation to our department, the following were noted: 3+ urinary protein, 3.9 urinary protein/creatinine ratio, and 48 mL/min/1.73 m2 estimated glomerular filtration rate. Abdominal computed tomography revealed small kidneys difficult to visualize using ultrasound. Therefore, an open renal biopsy was performed. The renal biopsy revealed no significant findings in the glomerulus except glomerular hypertrophy, and the glomerular density in the cortical area was low (0.6/mm2). The patient was diagnosed with oligomeganephronia. Proteinuria and renal dysfunction were likely due to glomerular hyperfiltration resulting from a low nephron count caused by low birth weight. Silver-Russell syndrome is characterized by intrauterine growth retardation and additional developmental disorders after birth. Here, we detected oligomeganephronia following kidney biopsy in a patient with Silver-Russell syndrome. We suspect that a reduced number of nephrons due to low birth weight caused proteinuria and renal dysfunction.

MO089HISTOMORPHOMETRIC ANALYSIS OF GLOMERULI AND CAPILLARIES DENSITY IN THE INTERSTITIUM IN PREIMPLANTATION NEEDLE BIOPSIES OF PAIRED KIDNEYS HARVESTED FROM ADULT CADAVERIC DONORS

Abstract Background and Aims Preimplantation needle biopsy of kidney allows more precise interpretation of subsequent kidney biopsies performed after transplantation and potentially also may predict kidney graft survival. It is unknown, whether it is justified to perform the biopsy of one kidney only and then to transmit obtained results also to the second kidney or biopsies of both kidneys are mandatory. The aim of the study was to assess differences regarding glomerular volume, glomerular density and capillary density in the interstitium of both kidneys harvested from the same deceased donor. Method The study involved 40 pairs of kidneys (all together 80 kidneys) in which preimplantation kidney biopsies were performed. Kidneys were harvested from 40 deceased donors (17 females and 23 males; mean age 42.3 [37.6-47.0] years old) died because of intracranial haemorrhage (17 donors) or cerebral trauma due to accident (23 donors). Histomorphometric analysis was performed using “Olympus BX51” microscope (Olympus, Tokyo, Japan) coupled with “Olympus BX50” camera and the “cellSens Standard” software (Olympus, Tokyo, Japan). Weibel-Gomez formula was adapted to calculate glomerular volume. Results No significant differences were found between mean kidneys length [115.8 (112.4-119.1) vs.115.5 (112.5-118.5) mm], glomerular volume [2.59 (2.24-2.93) vs 2.49 (2.15-2.84) μm3 x106 ], glomerular density [3.43 (3.07-3.80) vs 3.24 (2.87-3.61) n/mm2] and interstitial capillaries density [233.58 (211.26) vs 217.80 (199.45-236.47) n/mm2] of both kidneys harvested from the same deceased donor. Conclusions 1. Both kidneys harvested from the same deceased donor did not differ significantly in kidney length, glomerular volume, glomerular density and capillary density. 2. Our results justify to preimplantation biopsy of only one kidney and the results from the histomorphometric analysis may be used in the future also for assessment of the second kidney.

MO467SINGLE NEPHRON GFR AND GLOMERULAR HYDROSTATIC PRESSURE IN JAPANESE HEALTHY SUBJECTS

Abstract Background and Aims Hemodynamic abnormalities such as intraglomerular hypertension and glomerular hyperfiltration associated with the nephron loss are deeply involved in renal damage progression. Recent studies in humans have described a new method to calculate single nephron GFR (SNGFR), which is defined as GFR divided by the estimated total number of non-sclerosed glomeruli. We have previously shown that a higher SNGFR, which indicates glomerular hyperfiltration, is associated with CKD risk factors. However, it is still unknown that the hemodynamic changes in humans within the glomerulus in response to SNGFR. In the present study, we analysed the renal microcirculatory dynamics with SNGFR in healthy individuals without CKD. Method We retrospectively identified 51 living kidney donors who underwent enhanced computed tomography and kidney biopsy at the time of donation from January 2007 till December 2020. Nglom was calculated as the cortical volume of both kidneys assessed on computed tomography times the 1-hour posttransplant renal biopsy-determined glomerular density. SNGFR was calculated by dividing GFR (calculated from the corrected creatinine clearance) by the non-sclerosed Nglom. Glomerular hydrostatic pressure (Pglom) and afferent / efferent arteriolar pressure were calculated from the Gomez / Ohm's formula. Results Age was 57.0 ± 10.4 years, mean blood pressure was 88.7 ± 13.2 mmHg, GFR was 73.3 ± 16.7 mL/min, and Nglom was 807,774 ± 401,0352 / kidney. SNGFR was significantly associated with renal blood flow and Pglom (p for trend = 0.02, and 0.02, respectively), but not with age, mean blood pressure, renal plasma flow, filtration fraction, afferent / efferent arteriolar pressure (Table1). Conclusion Our results showed that the increase in SNGFR is associated with elevated Pglom, indicating that glomerular hyperfiltration may lead to intraglomerular hypertension.

47149 Imaging Tools for Early Detection of Kidney Disease.

ABSTRACT IMPACT: Chronic kidney disease (CKD) affects ˜15% of the US population and the majority of patients are diagnosed too late to benefit from early intervention. We are developing a new diagnostic imaging tool (RadioCF-PET) for the kidney to enable early detection of diseases and to monitor overall kidney health. OBJECTIVES/GOALS: Nephron mass, or the number of functioning nephrons, is a measure of the functional capacity of the kidney. RadioCF-PET may enable early detection of nephron loss in patients with or at risk of CKD before changes are clinically detectable, facilitating early interventions to improve outcomes in these patients. METHODS/STUDY POPULATION: RadioCF-PET, labeled with Cu-64, has the advantage of using sub pharmacological doses for imaging, carrying low risk and can be used with the FDA’s exploratory IND (eIND) mechanism for early in human testing. We are developing the technology to be used in pre-eIND toxicology and pharmacology studies. We are also developing other aspects of translational science to propel this technology toward translation, including: market analysis, critical path to market, customer discovery, and commercialization strategy. RESULTS/ANTICIPATED RESULTS: Milestone 1: Apply technology in mouse model study and in human kidneys rejected for transplant. Anticipated Result 1: PET signal from RadioCF-PET correlates with glomerular density in healthy and diseased model male mice (R2 = 0.98). RadioCF-PET signal correlates with glomerular number in a donated human kidney (R2= 0.78). Milestone 2: Application to federal funding (STTR) and gap funding mechanisms to enable pre-eIND studies. Anticipated Result 1: Application for funding will aid to clarify and validate our market analysis and commercialization strategy. Milestone 3: Continued research and development with the technology in new studies. Other Anticipated Results: Future work with RadioCF-PET will enhance technology performance in preparation for pre-eIND studies. DISCUSSION/SIGNIFICANCE OF FINDINGS: We foresee a large clinical and commercial potential for RadioCF-PET to provide precise, early monitoring in patients at risk for or with CKD. The two biggest hurdles for clinical translation are validating safety and proving efficacy. This work targets both issues to facilitate RadioCF-PET toward clinical translation.

IL‐6/STAT3‐mediated autophagy participates in the development of age‐related glomerulosclerosis

The standard of age-related glomerulosclerosis is unclear. Both signal transducer and activator of transcription 3 (STAT3) and autophagy are involved in age-related kidney disease. Therefore, we aimed to explore the standard, as well as the potential mechanism(s). A total of 44 patients who underwent radical nephrectomy were enrolled. Pearson analysis was performed to investigate the parameters with ages. The patients were divided into the young-and aged-kidney groups. Kidney morphological changes were evaluated by histology staining, senescence was evaluated by senescence-associated-β-galactosidase (SA-β-gal) staining, and autophagosome was measured by transmission electron microscopy. Moreover, Western blot and/or immunohistochemistry were accomplished to assess the expression of p16, STAT3, and glycoprotein130 (GP130) and autophagy-related proteins. Furthermore, human glomerular mesangial cells were administrated with tocilizumab (TCZ) and/or IL-6, and then the above indexes were tested again. Sclerotic glomerular density and glomerular sclerosis rate were significantly higher in individuals more than 40 years old, and they were strongly correlated with ages. Moreover, the expression of p16, STAT3, GP130, and p62 was significantly increased, while LC3II and autophagosome were statistically decreased in the aged-kidney. Glomeruli were hardly to stain with SA-β-gal. For the in vitro experiments, we observed that IL-6 significantly increased p16, STAT3, GP130, and p62, induced higher SA-β-gal staining, while downregulated LC3II and autophagosome. Furthermore, TCZ statistically reversed the effects of IL-6 on the above expression of proteins. Glomerular sclerosis rate might be one standard for natural renal aging, and IL-6/STAT3-mediated autophagy may participate in the development of age-related glomerulosclerosis.

Morphometric analysis of glomeruli, clinical features and outcome in obese and non-obese focal segmental glomerulosclerosis patients

Background/Aim. In the past three decades focal segmental glomerulosclerosis (FSGS) was commonly regarded as a part of obesity related glomerulopathy (ORG) a distinct entity featuring proteinuria, glomerulomegalia, progressive glomerulosclerosis and renal functional decline. The aims of the present study were to evaluate the glomerular morphometry, clinical features and two years outcome in obese and non-obese FSGS patients. Methods. The study included 35 FSGS patients (23 males, age 46.5?15.2 years); divided in two groups: obese (BMI ?27 kg/m2- 18 patients, age 47.2?15.5 years) and non-obese (BMI <27 kg/m2- 17 patients, age 45.7?15.2 years). The serum concentrations of proteins, albumin, cholesterol, triglyceride and creatinine were determined at the time the biopsy, 6, 12, 24 months after the biopsy. Formulas Cockcroft- Gault (BMI <27 kg/m2) and Cockcroft-GaultLBW(BMI ?27 kg/m2) were calculated. Glomerular radius (GR), glomerular volume (GV) and glomerular density (GD) were compared morphometrically between two groups. Results. At the time of kidney biopsy and 6 months later the obese had significantly lower GFR compared to non-obese. After 24 months follow-up there wasn?t any difference between groups. Obese had significantly higher GR (109.44?6,03 ?m vs 98.53?14,38 ?m) and GV (3.13?0.49 x106 ?m3 vs 2.26?0.83 x106 ?m3),only midly lower GD (1.91?0.39/mm2 vs 1.95?0.61/mm2) compared to non-obese. Significant positive association between GV and BMI (r=0.439) was found. After 12 months follow-up significantly higher percentage of non-obese patients reached complete remission (71.4% vs 37.5%) compared to obese (?2=0.041), but after 24 months there were no significant difference. Conclusion. Obese patients at the time of kidney biopsy and 6 months later had already the significant lower kidney function compared to non-obese. However, after 12 and 24 months, this difference was still lower and without significance as well as after 24 months percentage of patients with complete remission between two groups.

Gender differences in ischemic heart disease among Middle-Eastern population

Background/Aim. In the past three decades, focal segmental glomerulosclerosis (FSGS) was commonly regarded as a part of obesity-related glomerulopathy (ORG), a distinct entity featuring proteinuria, glomerulomegaly, progressive glomerulosclerosis, and a decline of renal function. The present study aimed to evaluate the glomerular morphometry, clinical features, and a two-year outcome in the obese and non-obese FSGS patients. Methods. The study included 35 FSGS patients (23 males, aged 46.5 ? 15.2 years) divided into two groups: obese [body mass index (BMI) ? 27 kg/m2 (18 patients, aged 47.2 ? 15.5 years)] and non-obese [BMI < 27 kg/m2 (17 patients, aged 45.7 ? 15.2 years)]. The serum concentrations of proteins, albumin, cholesterol, tri-glyceride, and creatinine were determined at the time of the biopsy, and 6, 12, and 24 months after the biopsy. Cock-croft-Gault (BMI < 27 kg/m2) and Cockcroft-GaultLBW (BMI ? 27 kg/m2) formulas were calculated. Glomerular radius (GR), glomerular volume (GV), and glomerular density (GD) were compared morphometrically between the two groups. Results. At the time of the kidney biopsy and 6 months later, the obese had significantly lower glomerular filtration rate (GFR) compared to the non-obese. After 24 months of follow-up, there were not any differences between the groups. The obese had a significantly higher GR (109.44 ? 6.03 ?m vs. 98.53 ? 14.38 ?m) and GV (3.13 ? 0.49 ? 106 ?m3 vs. 2.26 ? 0.83 ? 106 ?m3), and only slightly lower GD (1.91 ? 0.39/mm2 vs. 1.95 ? 0.61/mm2) compared to the non-obese. A significant positive association between GV and BMI (r = 0.439) was found. After 12 months of follow-up, a significantly higher percentage of the non-obese patients reached complete remission compared to the obese (71.4% vs. 37.5%, respectively; p = 0.041), but after 24 months there were no significant differences. Conclusion. Obese patients, at the time of the kidney biopsy and 6 months later, had already a significantly lower kidney function compared to the non-obese ones. However, 12 and 24 months after, this difference was not statistically significant. Also, 24 months after, there was no significant difference between the two groups in the percentage of patients with complete remission of the nephrotic syndrome.

Mapping nephron mass in vivo using positron emission tomography.

Nephron number varies widely in humans. A low nephron endowment at birth or a loss of functioning nephrons is strongly linked to increased susceptibility to chronic kidney disease. In this work, we developed a contrast agent, radiolabeled cationic ferritin (RadioCF), to map functioning glomeruli in vivo in the kidney using positron emission tomography (PET). PET radiotracers can be detected in trace doses (<30 nmol), making them useful for rapid clinical translation. RadioCF is formed from cationic ferritin (CF) and with a radioisotope, Cu-64, incorporated into the ferritin core. We showed that RadioCF binds specifically to kidney glomeruli after intravenous injection in mice, whereas radiolabeled noncationic ferritin (RadioNF) and free Cu-64 do not. We then showed that RadioCF-PET can distinguish kidneys in healthy wild-type (WT) mice from kidneys in mice with oligosyndactylism (Os/+), a model of congenital hypoplasia and low nephron mass. The average standardized uptake value (SUV) measured by PET 90 min after injection was 21% higher in WT mice than in Os/+ mice, consistent with the higher glomerular density in WT mice. The difference in peak SUV from SUV at 90 min correlated with glomerular density in male mice from both WT and Os/+ cohorts (R2 = 0.98). Finally, we used RadioCF-PET to map functioning glomeruli in a donated human kidney. SUV within the kidney correlated with glomerular number (R2= 0.78) measured by CF-enhanced magnetic resonance imaging in the same locations. This work suggests that RadioCF-PET appears to accurately detect nephron mass and has the potential for clinical translation.

Magnetic resonance imaging accurately tracks kidney pathology and heterogeneity in the transition from acute kidney injury to chronic kidney disease

Acute kidney injury (AKI) increases the risk for chronic kidney disease (CKD). However, there are few tools to detect microstructural changes after AKI. Here, cationic ferritin-enhanced magnetic resonance imaging (CFE-MRI) was applied to examine the heterogeneity of kidney pathology in the transition from AKI to CKD. Adult male mice received folic acid followed by cationic ferritin and were euthanized at four days (AKI), four weeks (CKD-4) or 12 weeks (CKD-12). Kidneys were examined by histologic methods and CFE-MRI. In the CKD-4 and CKD-12 groups, glomerular number was reduced and atubular cortical lesions were observed. Apparent glomerular volume was larger in the AKI, CKD-4 and CKD-12 groups compared to controls. Glomerular hypertrophy occurred with ageing. Interglomerular distance and glomerular density were combined with other MRI metrics to distinguish the AKI and CKD groups from controls. Despite significant heterogeneity, the noninvasive (MRI-based) metrics were as accurate as invasive (histological) metrics at distinguishing AKI and CKD from controls. To assess the toxicity of cationic ferritin in a CKD model, CKD-4 mice received cationic ferritin and were examined one week later. The CKD-4 groups with and without cationic ferritin were similar, except the iron content of the kidney, liver, and spleen was greater in the CKD-4 plus cationic ferritin group. Thus, our study demonstrates the accuracy and safety of CFE-MRI to detect whole kidney pathology allowing for the development of novel biomarkers of kidney disease and providing a foundation for future invivo longitudinal studies in mouse models of AKI and CKD to track nephron fate.

Dietary Protein Intake and Single-Nephron Glomerular Filtration Rate.

High protein intake can increase glomerular filtration rate (GFR) in response to excretory overload, which may exacerbate the progression of kidney disease. However, the direct association between glomerular hemodynamic response at the single-nephron level and dietary protein intake has not been fully elucidated in humans. In the present study, we evaluated nutritional indices associated with single-nephron GFR (SNGFR) calculated based on corrected creatinine clearance (SNGFRCr). We retrospectively identified 43 living kidney donors who underwent enhanced computed tomography and kidney biopsy at the time of donation at Jikei University Hospital in Tokyo from 2007 to 2018. Total nephron number was estimated with imaging-derived cortical volume and morphometry-derived glomerular density. SNGFRCr was calculated by dividing the corrected creatinine clearance by the number of non-sclerosed glomeruli (NglomNSG). The mean (± standard deviation) NglomNSG/kidney and SNGFRCr were 685,000 ± 242,000 and 61.0 ± 23.9 nL/min, respectively. SNGFRCr was directly associated with estimated protein intake/ideal body weight (p = 0.005) but not with body mass index, mean arterial pressure, albumin, or sodium intake. These findings indicate that greater protein intake may increase SNGFR and lead to glomerular hyperfiltration.

Nephron Number and Time to Remission in Steroid-Sensitive Minimal Change Disease

Rationale & ObjectiveThe response to corticosteroid therapy may differ among patients with minimal change disease (MCD). Previous studies have suggested that glomerular hypertrophy or low areal glomerular density in biopsy specimens, which may be related to fewer nephrons, is associated with such a difference. We examined the associations between nephron number and the therapeutic response to corticosteroids in patients with MCD.Study DesignRetrospective cohort study.Setting & Participants75 adult patients with a histologic diagnosis of MCD.ExposureNephron number per kidney estimated based on the combination of unenhanced computed tomography and nonsclerotic volumetric glomerular density in kidney biopsy specimens.OutcomesComplete remission and relapse following corticosteroid therapy.Analytical ApproachMultivariable Cox proportional hazard analyses of associations between factors, including nephron number, and outcomes.ResultsMean age of patients was 45.9 years and 60.0% were men. Patients had an estimated glomerular filtration rate of 64.6 mL/min/1.73 m2 and proteinuria of 8.7 g/d. The estimated total number of nonsclerotic glomeruli ranged from 1.07 to 18.77 ×105 per kidney among all patients. There were no significant differences in total amounts or selectivity of urinary protein excretion at biopsy among the tertile groups categorized by nephron number. All patients responded to corticosteroid therapy, but those with fewer nephrons had a delayed achievement of complete remission. Multivariable Cox proportional hazard analyses identified nephron number as a significant independent explanatory variable for the achievement of complete remission, with a hazard ratio of 1.10 (95% CI, 1.02-1.19)/100,000 nephrons per kidney. Nephron number in these patients was not associated with achievement of partial remission or relapse following complete remission.LimitationRetrospective design and sampling bias of needle biopsy.ConclusionsA small nephron number in patients with MCD is associated with longer time to complete remission.

Ivabradine Ameliorates Kidney Fibrosis in L-NAME-Induced Hypertension.

Hypertension-induced renal injury is characterized by structural kidney alterations and function deterioration. Therapeutics for kidney protection are limited, thus novel renoprotectives in hypertension are being continuously sought out. Ivabradine, an inhibitor of the If current in the sinoatrial node reducing heart rate (HR), was shown to be of benefit in various cardiovascular pathologies. Yet, data regarding potential renoprotection by ivabradine in hypertension are sparse. Thirty-six adult male Wistar rats were divided into non-diseased controls and rats with NG-nitro-L-arginine methyl ester (L-NAME)-induced hypertension to assess ivabradine's site-specific effect on kidney fibrosis. After 4 weeks of treatment, L-NAME increased the average systolic blood pressure (SBP) (by 27%), decreased glomerular density (by 28%) and increased glomerular tuft area (by 44%). Moreover, L-NAME induced glomerular, tubulointerstitial, and vascular/perivascular fibrosis by enhancing type I collagen volume (16-, 19- and 25-fold, respectively). L-NAME also increased the glomerular type IV collagen volume and the tubular injury score (3- and 8-fold, respectively). Ivabradine decreased average SBP and HR (by 8 and 12%, respectively), increased glomerular density (by 57%) and reduced glomerular tuft area (by 30%). Importantly, ivabradine decreased type I collagen volume at all three of the investigated sites (by 33, 38, and 72%, respectively) and enhanced vascular/perivascular type III collagen volume (by 67%). Furthermore, ivabradine decreased the glomerular type IV collagen volume and the tubular injury score (by 63 and 34%, respectively). We conclude that ivabradine attenuated the alterations of glomerular density and tuft area and modified renal fibrosis in a site-specific manner in L-NAME-hypertension. It is suggested that ivabradine may be renoprotective in hypertensive kidney disease.

P0130THE MORPHOMETRIC ANALYSIS OF GLOMERULI IN OBESE AND NON-OBESE PATIENTS WITH GLOMERULAR DISEASES

Abstract Background and Aims The aim of the study was to evaluate glomerular morphometry in obese and non-obese patients with glomerular diseases: FSGS, IgA nephropathy, membranous glomerulonephritis (MGN) and membranoproliferative glomerulonephritis (MPGN). Method The study included 125 patients with glomerular diseases (77 males, mean age 46± 15.2 years): obese (BMI&amp;gt; 27kg/m2- 63 patients) and non-obese (BMI&amp;lt; 27kg/m2-62 patients). The serum concentration of creatinine, proteins, albumin, cholesterol, trygliceride, daily proteinuria were measured at the time of kidney biopsy. Formula Cockcroft-Gault#(Cockcroft-Gault: non-obese) and Cockcroft-GaultLBW: obese) was calculated. Glomerular radius (GR), glomerular volume (GV) and glomerular density (GD) were compared morphometrically between two groups. Results At the time of kidney biopsy the obese had significantly lower eGFR, significantly higher creatinine, trygliceride, daily proteinuria compared to non-obese. Obese FSGS patients had significantly higher GR (109.44±6.03 μm vs 98.53±14.38 μm) and GV (3.13±0.49 x106 μm?vs 2.26±0.83 x106 μm?, only midly lower GD (1.91±0.39/mm2 vs 1.95±0.61/mm2) compared to non-obese. Obese IgA nephropathy patients had higher GR (110.69± 15.24 μm vs 107.77±14.53 μm), significantly higher GV(3.34±1.78 x106 μm?vs 2.31± 1.51 x106 μm? and significantly lower GD (1.21±0.29/mm2 vs 2.14±0.54/mm2) in comparation with non-obese. Significant positive association between GV and BMI (r=0.439; p&amp;lt;0.01) in FSGS patients was found. Significant positive correlation between GV and BMI (r=0.683; p&amp;lt; 0.01), but significant negative correlation between GD and BMI (r=-0.710; p&amp;lt; 0.01) in IgA nephropathy patients were found. Obese MGN patients had lower GR (112.82± 13.65 μm vs 118.39± 14.52 μm), GV (3.57± 1.19 x106 μm?vs 4.07± 1.28 x106 μm? and GD (1.89± 0.17/ mm2 vs 1.91± 0.92/mm2) but without significance compared to non-obese. Obese MPGN patients had higher GR(105.89± 12.24 μm vs 92.73± 30.01 μm), GV (2.94± 0.91 x106 μm?vs 2.31± 1.27 x106 μm? and GD (2.32± 0.63/ mm2 vs 2.03± 0.73/ mm2) but without significance in comparation with non-obese. Significant negative association between GD and daily proteinuria (r=-0.417; p&amp;lt;0.01) in MGN patients was found. Conclusion Obese FSGS patients had significantly higher GV, lower GD compared to non-obese. Obese IgA nephropathy patients had significantly higher GV and significantly lower GD. Obese MGN patients had lower and obese MPGN patients had higher morphometric parameters of glomeruli compared to non-obese. Significant positive correlation between GV and BMI in FSGS and IgA nephropathy patients were found.

P0781ESTIMATION OF NEPHRON NUMBER IN CKD PATIENTS

Abstract Background and Aims The nephron number is thought to be associated with clinical outcomes of chronic kidney disease (CKD). If the nephron number can be estimated in a clinical setting, it could become a strong tool to predict the outcomes. This preliminary study estimated nephron number in CKD patients, and examined the relationship between the nephron number and patient characteristics. Method Data from a multicenter study of the National Hospital Organization of Japan were analyzed, including 565 CKD patients aged over 14 years who underwent a kidney biopsy. The nephron number was estimated by the glomerular density in biopsy specimens and the renal cortex volume. The renal cortex volume was calculated by the previously established equation using ultrasound measurement of the kidney. Linear regression models were used to investigate the associations of the nephron number separately with age, sex, and estimated glomerular filtration rate (eGFR). Results A total of 50% of the patients were women, and the mean (±SD) age of the patients was 51±19 years. The mean eGFR was 63±32 ml/min/1.73m2, and the mean estimated number of non-sclerotic nephrons was 660,000±320,000 per kidney. A larger number of estimated nephron number was associated with younger age, male sex, and higher eGFR. Conclusion To the best of our knowledge, this was the first study to estimate the renal cortex volume and nephron number of CKD patients in the general clinical setting. The results from this study should provide powerful tools for nephrologists in routine clinical practice. Further investigations will be needed to verify the associations between the nephron number and clinical outcomes of CKD patients.

P1620PROGNOSTIC VALUE OF RENAL BIOPSY QUANTITATIVE HISTOLOGY IN LIVING KIDNEY DONORS AND RECIPIENTS OF KIDNEYS FROM LIVING DONORS

Abstract Background and Aims Living kidney donors (LKD) have an increased risk of chronic kidney disease. Likewise, renal transplant recipients may experience early or unexplained loss of graft function. We examined the predictive value of stereology based on a CT-scan and a biopsy from the transplanted kidney in relation to renal function outcome in both LKD and recipients of kidneys from living donors. Method A pre-transplantation contrast-enhanced CT-scan was used to obtain cortical volume of both kidneys using the Cavalieri estimator. Glomerular number density in a baseline biopsy from the transplanted kidney (taken at the time of transplantation) was estimated by a model-based method and multiplied with cortex volume to estimate the total number of glomeruli in the donated kidney. Glomerular volume was estimated by the 2D nucleator (1). In addition, kidney fibrosis (point-counting), glomerular sclerosis, and arteriole dimensions (2D nucleator) were also calculated. Pre-donation single kidney glomerular filtration rate (GFR) was determined using 51chrome EDTA clearance together with a renography and the GFR measurement was repeated one year after transplantation in both donors and recipients. We examined the association between GFR at one-year follow-up and cortex volume and various histology parameters from the baseline biopsy after adjustment of age, sex, body mass index, smoking status, 24-hour mean blood pressure and single-kidney GFR before transplantation. Results CT-scans, GFR measurements and kidney histology from 49 LKD and 38 recipients of kidneys from living donors were available for analysis. Mean age of donors was 50±12 years (55% women) and of recipients 46±13 years (26% women). In donors, GFR decreased from 113±24 to 71±16 ml/min while in recipients GFR was 61±18 ml/min at one-year follow-up (all with a functioning graft). In donors, GFR at follow-up of the remaining kidney had increased by 28% as compared to baseline. Follow-up GFR correlated to cortex volume (P&amp;lt;0.001), but not to any of the histological parameters (total glomerular number, glomerular volume, % sclerosed glomeruli, % kidney fibrosis or arteriolar dimensions). In recipients, GFR at follow-up had increased by 8% as compared to single-kidney GFR before donation. Follow-up GFR correlated to % kidney fibrosis (P=0.02) and % sclerosed glomeruli (P=0.05), but not any of the other histological parameters or cortex volume. Conclusion When adjusted for relevant clinical confounders the estimation of cortex volume had predictive value for renal function outcome in LKD while % kidney fibrosis and % sclerosed glomeruli had predictive value in recipients of kidneys from living donors.

Kidney Structural Features from Living Donors Predict Graft Failure in the Recipient.

Nephrosclerosis, nephron size, and nephron number vary among kidneys transplanted from living donors. However, whether these structural features predict kidney transplant recipient outcomes is unclear. Our study used computed tomography (CT) and implantation biopsy to investigate donated kidney features as predictors of death-censored graft failure at three transplant centers participating in the Aging Kidney Anatomy study. We used global glomerulosclerosis, interstitial fibrosis/tubular atrophy, artery luminal stenosis, and arteriolar hyalinosis to measure nephrosclerosis; mean glomerular volume, cortex volume per glomerulus, and mean cross-sectional tubular area to measure nephron size; and calculations from CT cortical volume and glomerular density on biopsy to assess nephron number. We also determined the death-censored risk of graft failure with each structural feature after adjusting for the predictive clinical characteristics of donor and recipient. The analysis involved 2293 donor-recipient pairs. Mean recipient follow-up was 6.3 years, during which 287 death-censored graft failures and 424 deaths occurred. Factors that predicted death-censored graft failure independent of both donor and recipient clinical characteristics included interstitial fibrosis/tubular atrophy, larger cortical nephron size (but not nephron number), and smaller medullary volume. In a subset with 12 biopsy section slides, arteriolar hyalinosis also predicted death-censored graft failure. Subclinical nephrosclerosis, larger cortical nephron size, and smaller medullary volume in healthy donors modestly predict death-censored graft failure in the recipient, independent of donor or recipient clinical characteristics. These findings provide insights into a graft's "intrinsic quality" at the time of donation, and further support the use of intraoperative biopsies to identify kidney grafts that are at higher risk for failure.

In-vivo techniques for determining nephron number.

Many studies have suggested low nephron endowment at birth contributes to the risk of developing hypertension and chronic kidney disease (CKD) later in life. Loss of nephrons with age and disease is largely a subclinical process. New technologies are needed to count nephrons as glomerular filtration rate (GFR) is a poor surrogate for nephron number. Cortical volume, glomerular density, and percent globally sclerotic glomeruli are imperfect surrogates for nephron number. The disector-fractionator method is the most accurate method to count nephrons but is limited to autopsy settings. Glomerular density combined with kidney imaging and ultrafiltration coefficient-based methods require a kidney biopsy, and have been applied in living humans (kidney donors). Low nephron number predicts a higher postdonation urine albumin. Contrast-enhanced MRI has detected glomeruli without a biopsy, but so far, not in living humans. Currently, there is no accurate and well tolerated method for determining nephron number in living humans. A clinically useful method may allow GFR to be replaced by its more relevant determinants: nephron number and single nephron GFR. This could revolutionize nephrology by separating the measurement of chronic disease (nephron loss) from more reversible hemodynamic effects (nephron hyperfiltration/hypofiltration).

Estimation of nephron number in living humans by combining unenhanced computed tomography with biopsy-based stereology

Methods for estimating nephron number in a clinical setting may be useful for predicting renal outcomes. This study aimed to establish such a method using unenhanced computed tomography (CT) and biopsy-based stereology. Patients or living kidney donors simultaneously subjected to enhanced and unenhanced CT examinations were randomly assigned to development and validation groups. The enhanced CT-measured arterial phase and the venous phase images of kidneys were regarded as the true values for cortical volume and parenchymal volume, respectively. Linear multiple regression analysis was used to create models for estimating cortical volume using explanatory variables including unenhanced CT-measured parenchymal volume. Nephron number was determined as the product of cortical volume and the glomerular density in biopsies of donors. Five equations for estimating cortical volume were created and verified. In donors, estimated nephron number by unenhanced CT was consistent with that by enhanced CT, with minimal errors in all models (636–655 ± 210–219 vs. 648 ± 224 × 103/kidney). Clinical characteristics combined with parenchymal volume did not improve the equation over parenchymal volume alone. These results support the feasibility of estimating nephron number by a combination of unenhanced CT and biopsy-based stereology, with a possible application for renal disease patients who are often not suitable for contrast media.

The number of nephrons in different glomerular diseases.

BackgroundThe total number of nephrons has been measured mainly from post-mortem studies and only in selected populations. Data from living subjects are scanty, and direct comparisons among different glomerular diseases are lacking. The present work exploits modern methodology to estimate the total nephron number in glomerulopathies with prevalent proteinuria/nephrotic syndrome versus glomerulopathies with nephritic syndrome (IgA nephropathy (IgAN), lupus nephritis), thus extending previous observations about the number and function of glomeruli in different physiological and pathological states.MethodsThis is a retrospective study based on one hundred and seven patients who have undergone renal biopsy. The glomerular density has been estimated from the biopsy specimens and the total cortical volume has been obtained from ultrasound recordings. Stereological methods have been applied to calculate the total number of nephrons and their volume. The correlation between clinical parameters and quantitative morphological data have studied using the Pearson correlation coefficient (r).ResultsThe total number of nephrons inversely correlated with the systolic blood pressure (r = −0.4, p < 0.05). In proteinuric diseases, such as focal segmental glomerulo-sclerosis (FSGS), membranous nephropathy (MN) and diabetes, the change in estimated GFR (eGFR) directly correlated with the total number of non-sclerotic glomeruli (NSG) (r = 0.62, p < 0.01), whereas in nephritic syndrome no significant correlation was observed. The alterations in eGFR occurring in nephritic syndromes such as IgAN cannot be explained on the basis of the number of NSG.DiscussionThe fusion of the podocyte foot-processes that typically occurs in purely proteinuric diseases does not modify the glomerular filtration rate: therefore in these situations, the change in eGFR depends mainly on the number of available glomeruli. On the other side, the eGFR decrease occurring in nephritic syndromes, such as IgAN, cannot be explained simply on the basis of the number of NSG and likely depends on the substantial involvement of the mesangial axis. Future studies should verify whether these changes are reversible with appropriate therapy, thus reversing eGFR decrease.