A new, deep learning-based method for the analysis of autopsy kidney samples used to study sex differences in glomerular density and size in a forensic population.

Artificial intelligence (AI) is increasingly used in forensic anthropology and genetics to identify the victim and the cause of death. The large autopsy samples from persons with traumatic causes of death but without comorbidities also offer possibilities to analyze normal histology with AI. We propose a new deep learning-based method to rapidly count glomerular number and measure glomerular density (GD) and volume in post-mortem kidney samples obtained in a forensic population. We assessed whether this new method detects glomerular differences between men and women without known kidney disease. Autopsies performed between 2009 and 2015 were analyzed if subjects were aged ≥ 18 years and had no known kidney disease, diabetes mellitus, or hypertension. A large biopsy was taken from each kidney, stained with hematoxylin and eosin, and scanned. An in-house developed deep learning-based algorithm counted the glomerular density (GD), number, and size. Out of 1165 forensic autopsies, 86 met all inclusion criteria (54 men). Mean (± SD) age was 43.5 ± 14.6; 786 ± 277 glomeruli were analyzed per individual. There was no significant difference in GD between men and women (2.18 ± 0.49 vs. 2.30 ± 0.57 glomeruli/mm2, p = 0.71); glomerular diameter, area, and volume also did not differ. GD correlated inversely with age, kidney weight, and glomerular area. Glomerular area and volume increased significantly with age. In this study, there were no sex differences in glomerular density or size. Considering the size of the kidney samples, the use of the presented deep learning method can help to analyze large renal autopsy biopsies and opens perspectives for the histological study of other organs.

Estimating Nephron Number from Biopsies: Impact on Clinical Studies.

BACKGROUND: Accumulating evidence supports an association between nephron number and susceptibility to kidney disease. However, it is not yet possible to directly measure nephron number in a clinical setting. Recent clinical studies have used glomerular density from a single biopsy and whole kidney cortical volume from imaging to estimate nephron number and single nephron glomerular filtration rate. However, the accuracy of these estimates from individual subjects is unknown. Furthermore, it is not clear how sample size or biopsy location may influence these estimates. These questions are critical to study design, and to the potential translation of these tools to estimate nephron number in individual subjects. METHODS: We measured the variability in estimated nephron number derived from needle or virtual biopsies and cortical volume in human kidneys declined for transplantation. We performed multiple needle biopsies in the same kidney, and examined the three-dimensional spatial distribution of nephron density by magnetic resonance imaging. We determined the accuracy of a single-kidney biopsy to predict the mean nephron number estimated from multiple biopsies from the same kidney. RESULTS: A single needle biopsy had a 15% chance and virtual biopsy had a 60% chance of being within 20% of the whole-kidney nephron number. Single needle biopsies could be used to detect differences in nephron number between large cohorts of several hundred subjects. CONCLUSIONS: The number of subjects required to accurately detect differences in nephron number between populations can be predicted on the basis of natural intrakidney variability in glomerular density. A single biopsy is insufficient to accurately predict nephron number in individual subjects.

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.

Change in glomerular volume and its clinicopathological impact after kidney transplantation.

BACKGROUND: Both immunological and non-immunological etiologies affect graft function after kidney transplantation, including acute rejection, calcineurin inhibitor toxicity, and a recurrence of glomerulonephritis. Glomerular enlargement or glomerular sclerosis due to glomerular hyperfiltration related to increased renal blood flow is another cause. Although the glomerular volume in baseline biopsies predicts late allograft function, the relationship between allograft function and the annual changes in glomerular volume after kidney transplantation are unclear. AIM: We investigated changes in glomerular volume after kidney transplantation and their clinicopathological relationship. METHODS: We enrolled 23 patients with stable kidney function without an episode of rejection or any complication resulting in a functional decrease in the graft. We measured glomerular volume (GV) using the Weibel-Gomez method and glomerular density (GD) using 0,1 h biopsy samples as baseline controls and 1 yr biopsy samples and investigated the association between the changes in them and clinical parameters, including graft function, proteinuria, and renal hemodynamic markers, including effective renal plasma flow (ERPF) and filtration fraction (FF). The ERPF was calculated from a 99mTc-mercaptoacetyltriglycine (MAG3) renogram. RESULTS: The GV and ERPF increased significantly 1 yr after kidney transplantation. In contrast, proteinuria decreased significantly and Δproteinuria (1 yr - 1 month after transplantation) was correlated with ΔGV (P < 0.05, rs = -0.467). CONCLUSION: Glomerular enlargement 1 yr after transplantation may be related to improved proteinuria. It is possible that glomerular enlargement serves as a renal adaptation after kidney transplantation.

Obesity-related glomerulopathy and the nephron complement.

Obesity-related glomerulopathy (ORG) is a secondary form of glomerular disease that can occur in individuals with obesity. However, the absolute risk for an obese individual to develop progressive renal deterioration is low. Therefore, obesity alone appears to be insufficient to develop such severe renal injury, and there are likely other factors that contribute to the development of this entity. The glomerular hyperfiltration found in patients with ORG has been postulated to lead to structural abnormalities in glomeruli, such as glomerulomegaly and focal segmental glomerular sclerosis, in a manner analogous to that described in patients with reduced renal mass. In fact, recent studies suggest that a reduction in nephron mass is implicated in patients with ORG and synergistically contributes to the development of this renal complication together with obesity-induced changes in renal hemodynamics.

Practical application of stereological methods in experimental kidney animal models. / Aplicación práctica de métodos estereológicos renales en modelos animales experimentales.

The kidneys are vital organs responsible for excretion, fluid and electrolyte balance and hormone production. The nephrons are the kidney's functional and structural units. The number, size and distribution of the nephron components contain relevant information on renal function. Stereology is a branch of morphometry that applies mathematical principles to obtain three-dimensional information from serial, parallel and equidistant two-dimensional microscopic sections. Because of the complexity of stereological studies and the lack of scientific literature on the subject, the aim of this paper is to clearly explain, through animal models, the basic concepts of stereology and how to calculate the main kidney stereological parameters that can be applied in future experimental studies.

Glomerulopathy Associated With Moderate Obesity.

INTRODUCTION: Obesity-related glomerulopathy is an established secondary glomerular disease that may occur in obese individuals with a body mass index (BMI) of ≥30 kg/m2. However, patients with moderate obesity (BMI ≤ 30 kg/m2) may also develop this disease. METHODS: A total of 20 patients with grade 1 obesity (25 ≤ BMI < 30 kg/m2) with persistent proteinuria, without evidence of other renal diseases, were analyzed retrospectively. These patients were compared with 20 patients with grade 2 or higher obesity (BMI ≥ 30 kg/m2) with persistent proteinuria. Biopsies of 31 kidney transplant donors as healthy controls were used to compare histologic parameters. RESULTS: Similar to the grade 2 or higher obesity group, the grade 1 obesity group had a male predominance (85%) and showed a high incidence of hypertension (80%). Urinary protein excretion and renal outcome parameters were comparable between the groups. Patients with grade 1 obesity showed typical histologic features of obesity-related glomerulopathy: low glomerular density with glomerulomegaly. The glomerular density and mean glomerular volume in the grade 1 group, the grade 2 or higher group, and the kidney transplant donors with grade 1 obesity were 1.6 ± 0.8 versus 1.4 ± 0.6 versus 3.0 ± 1.1 (per mm2) and 6.1 ± 2.1 versus 6.4 ± 1.6 versus 2.9 ± 0.8 (×106 µm3), respectively. DISCUSSION: A glomerulopathy similar to obesity-related glomerulopathy can occur in moderately obese individuals. Renal factor(s), such as low glomerular density, may thus underlie susceptibility to this disease entity as well as BMI.

Glomerular Density in Biopsy-Proven Hypertensive Nephrosclerosis.

BACKGROUND: Previous autopsy studies suggested that a reduced nephron number is associated with increased risk of hypertension and chronic kidney disease. However, the significance of the nephron number estimated from a renal biopsy in patients with hypertensive nephrosclerosis (HNS) has not yet been elucidated. METHODS: In this cross-sectional study, we examined the clinicopathological findings of biopsy-proven HNS patients with preserved renal function (estimated glomerular filtration rate ≥ 60 ml/min/1.73 m(2)). The glomerular density (GD; the number of glomeruli per total renal cortical area) in biopsy specimens was evaluated as a surrogate of the nephron number. Renal biopsies from kidney transplant donors were used as healthy controls. RESULTS: A total of 58 HNS patients were enrolled. The GD value in the HNS patients was low compared with those in the kidney transplant donors (2.0 vs. 3.2 /mm(2)). These differences remained significant when globally sclerotic glomeruli were included in the calculation of the GD. Of note, the GD in HNS patients with overt proteinuria (≥1 g/day) was significantly lower than that of HNS patients with mild proteinuria (<1g/day; 1.8 vs. 2.2/mm(2), P = 0.014). In contrast, other histopathological parameters, including the severity of global glomerulosclerosis, interstitial fibrosis/tubular atrophy and arterial and arteriole lesions were comparable between the 2 HNS subgroups. In addition, the GD was identified as a factor that was associated with the amount of urinary protein excretion at biopsy, independent of other clinicopathological factors. CONCLUSIONS: These results suggest that a low GD is a renal histological characteristic of HNS patients, especially those with overt proteinuria.