A web-based tool for real-time adequacy assessment of kidney biopsies.

The escalating incidence of kidney biopsies providing insufficient tissue for diagnosis poses a dual challenge, straining the healthcare system and jeopardizing patients who may require rebiopsy or face the prospect of an inaccurate diagnosis due to an unsampled disease. Here, we introduce a web-based tool that can provide real-time, quantitative assessment of kidney biopsy adequacy directly from photographs taken with a smartphone camera. The software tool was developed using a deep learning-driven automated segmentation technique, trained on a dataset comprising nephropathologist-confirmed annotations of the kidney cortex on digital biopsy images. Our framework demonstrated favorable performance in segmenting the cortex via 5-fold cross-validation (Dice coefficient: 0.788±0.130) (n=100). Offering a bedside tool for kidney biopsy adequacy assessment has the potential to provide real-time guidance to the physicians performing medical kidney biopsies, reducing the necessity for re-biopsies. Our tool can be accessed through our web-based platform: http://www.biopsyadequacy.org.

Metaproteomics-An Advantageous Option in Studies of Host-Microbiota Interaction.

Gut microbiome contributes to host health by maintaining homeostasis, increasing digestive efficiency, and facilitating the development of the immune system. Manipulating gut microbiota is being recognized as a therapeutic target to manage various chronic diseases. The therapeutic manipulation of the intestinal microbiome is achieved through diet modification, the administration of prebiotics, probiotics, or antibiotics, and more recently, fecal microbiome transplantation (FMT). In this opinion paper, we give a perspective on the current status of application of multi-omics technologies in the analysis of host-microbiota interactions. The aim of this paper was to highlight the strengths of metaproteomics, which integrates with and often relies on other approaches.

NELL1 is a target antigen in malignancy-associated membranous nephropathy.

Patients with membranous nephropathy have an increased risk of malignancy compared to the general population, but the target antigen for malignancy-associated membranous nephropathy is unknown. To explore this, we utilized mass spectrometry for antigen discovery in malignancy-associated membranous nephropathy examining immune complexes eluted from frozen kidney biopsy tissue using protein G bead immunoglobulin capture. Antigen discovery was performed comparing cases of membranous nephropathy of unknown and known type. Mass spectrophotometric analysis revealed that nerve epidermal growth factor-like 1 (NELL1) immune complexes were uniquely present within the biopsy tissue in membranous nephropathy. Additional NELL1-positive cases were subsequently identified by immunofluorescence. In a consecutive series, 3.8% of PLA2R- and THSD7A-negative cases were NELL1-positive. These NELL1-positive cases had segmental to incomplete IgG capillary loop staining (93.4%) and dominant or co-dominant IgG1-subclass staining (95.5%). The mean age of patients with NELL1-positive membranous nephropathy was 66.8 years, with a slight male predominance (58.2%) and 33% had concurrent malignancy. Compared with PLA2R- and THSD7A-positive cases of membranous nephropathy, there was a greater proportion of cases with malignancies in the NELL1-associated group. Thus, NELL1-associated membranous nephropathy has a unique histopathology characterized by incomplete capillary loop staining, IgG1-predominance, and is more often associated with malignancy than other known types of membranous nephropathy.

Neural cell adhesion molecule 1 is a novel autoantigen in membranous lupus nephritis.

Membranous lupus nephritis is a frequent cause of nephrotic syndrome in patients with systemic lupus erythematosus. It has been shown in phospholipase A2 receptor positive membranous nephropathy that known antibodies can be detected within sera, determination of the target autoantigen can have diagnostic significance, inform prognosis, and enable non-invasive monitoring of disease activity. Here we utilized mass spectrometry for antigen discovery in laser captured microdissected glomeruli from formalin-fixed paraffin embedded tissue and tissue protein G immunoprecipitation studies to interrogate immune complexes from frozen kidney biopsy tissue. We identified neural cell adhesion molecule 1 (NCAM1) to be a target antigen in some cases of membranous lupus nephritis and within rare cases of primary membranous nephropathy. The prevalence of NCAM1 association was 6.6% of cases of membranous lupus nephritis and in 2.0% of primary membranous nephropathy cases. NCAM1 was found to colocalize with IgG within glomerular immune deposits by confocal microscopy. Additionally, serum from patients with NCAM1-associated membranous nephropathy showed reactivity to NCAM1 recombinant protein on Western blotting and by indirect immunofluorescence assay, demonstrating the presence of circulating antibodies. Thus, we propose that NCAM1 is a target autoantigen in a subset of patients with membranous lupus nephritis. Future studies are needed to determine whether anti-NCAM1 antibody levels correlate with disease activity or response to therapy.

Resistant starch slows the progression of CKD in the 5/6 nephrectomy mouse model.

BACKGROUND: Resistant Starch (RS) improves CKD outcomes. In this report, we study how RS modulates host-microbiome interactions in CKD by measuring changes in the abundance of proteins and bacteria in the gut. In addition, we demonstrate RS-mediated reduction in CKD-induced kidney damage. METHODS: Eight mice underwent 5/6 nephrectomy to induce CKD and eight served as healthy controls. CKD and Healthy (H) groups were further split into those receiving RS (CKDRS, n = 4; HRS, n = 4) and those on normal diet (CKD, n = 4, H, n = 4). Kidney injury was evaluated by measuring BUN/creatinine and by histopathological evaluation. Cecal contents were analyzed using mass spectrometry-based metaproteomics and de novo sequencing using PEAKS. All the data were analyzed using R/Bioconductor packages. RESULTS: The 5/6 nephrectomy compromised kidney function as seen by an increase in BUN/creatinine compared to healthy groups. Histopathology of kidney sections showed reduced tubulointerstitial injury in the CKDRS versus CKD group; while no significant difference in BUN/creatinine was observed between the two CKD groups. Identified proteins point toward a higher population of butyrate-producing bacteria, reduced abundance of mucin-degrading bacteria in the RS fed groups, and to the downregulation of indole metabolism in CKD groups. CONCLUSION: RS slows the progression of chronic kidney disease. Resistant starch supplementation leads to active bacterial proliferation and the reduction of harmful bacterial metabolites.

A diagnostician's field guide to crystalline nephropathies.

The kidney's role in filtration of blood and production of urine occurs via a combination of size and charge filtration at the glomerular basement membrane and resorption and excretion of molecules through a complex tubular system embedded within an ion gradient. This delicate system provides the kidney with a unique propensity for substrate saturation and crystal nucleation within the nephron. While crystalline nephropathies may seem exotic to the uninitiated, they are comprised of easily recognizable morphologies and generally lack complicated classification schemas. Additionally, unlike many intrinsic kidney diseases, crystalline nephropathies are often associated with systemic conditions that, upon further investigation, may elucidate critically important information. This review focuses on practical, diagnostically relevant and high yield information that can be utilized by diagnosticians. Our hope is to equip the reader who reviews renal tissue with a practical toolkit that they feel empowered to use when faced with crystal formation in a kidney biopsy, pre-implantation biopsy, or nephrectomy specimen. Short Abstract The kidney's role in filtration of blood and production of urine provides a unique propensity for substrate saturation and crystal nucleation within the nephron. While crystalline nephropathies may seem exotic to the uninitiated, they are comprised of easily recognizable morphologies and generally lack complicated classification. Additionally, crystalline nephropathies are often associated with systemic conditions that, upon further investigation, may elucidate critically important information.

A practical approach to the pathology of renal intratubular casts.

The identification and proper characterization of pathologic renal intratubular casts can be an arduous task, especially since they often admixed with non-pathologic casts, obfuscating debris and inflammation. The list of pathologic intratubular casts is long, and they can be easily missed or misdiagnosed without a thorough understanding of their pathophysiology and morphologic variety. Correct characterization of tubular casts is important since each cast type has a unique pathogenic mechanism, with specific treatment and prognostic implications. This review discusses the clinicopathologic characteristics of the six most common pathologic casts: light chain, hemoglobin, myoglobin, red cell, neutrophilic and bile casts. We also discuss hyaline and uromodulin casts, the commonly encountered "benign" cast types that share certain histologic features with pathologic casts. We limit the discussion to proteinaceous and cellular intratubular casts, with crystalline casts discussed in a separate review within the same journal issue. While not exhaustive, this review covers pathogenesis, clinical and prognostic significance, and a practical discussion of the histomorphologic spectrum of each cast type, along with commonly encountered pitfalls.

Hemolysis-associated hemoglobin cast nephropathy results from a range of clinicopathologic disorders.

Intravascular hemolysis is relatively rare but can lead to acute kidney injury (AKI), from increased destruction of erythrocytes and release of free hemoglobin. Since hemolysis and hemoglobinuria are known causes of acute kidney injury we sought to define clinicopathologic findings and outcomes of patients with hemolysis-associated hemoglobin cast nephropathy through a retrospective analysis of 27 cases. The mean patient age was 47 years (range 19-79) and the female-to-male ratio was 1.3:1. All patients presented with AKI with a mean serum creatinine of 8.0 (range 2.9-17.0) mg/dL. Etiologies included autoimmune hemolytic anemia (30%), medication (26%), paroxysmal nocturnal hemoglobinuria (7%), procedural/mechanical causes (7%), transfusion of incompatible blood (4%), toxin ingestion (4%), disseminated intravascular coagulation (4%), and hemoglobinopathy (4%). All biopsies showed acute tubular injury and pigmented, proteinaceous casts characterized by positive hemoglobin immunohistochemistry. After a mean follow-up of nine months (range 0.5-26), the mean serum creatinine was 1.3 (range 0.6-3.3) mg/dL, with 78% of patients returning to normal kidney function. Thus, based on our clinicopathologic case series, hemolysis-associated hemoglobin cast nephropathy is an important entity for clinicians and pathologists to recognize as treatment hinges upon elimination of the pathogenic driver of intravascular hemolysis.

Localization of arm representation in the cerebral peduncle of the non-human primate.

Motor deficit severity and the potential for recovery in patients with brain injury depend on the integrity of descending corticofugal projections. Clinical assessment of these conditions following subtotal brain trauma requires a comprehensive understanding of the anatomical structures involved in the lesion as well as those structures that are spared. To assist in this endeavor, we investigated motor fiber organization in the crus cerebri of the cerebral peduncle (ccCP) in the rhesus monkey. Fibers originating from the arm representations of the primary (M1), supplementary (M2), rostral cingulate (M3), caudal cingulate (M4), dorsolateral pre- (LPMCd) and ventrolateral pre- (LPMCv) motor cortices were studied. The projections from the frontal and cingulate motor cortices formed descending longitudinal bundles that occupied the medial three-fifths of the ccCP at superior and middle levels. Although considerable overlap characterized these corticofugal projections, a general topography was discernable. Fibers from M1 and M4 occupied the central subsector of the ccCP, and fibers from M3 resided medially. The main distribution of LPMCd, LPMCv, and M2 fibers occupied the centromedial region and overlapped extensively. Progressing inferiorly, all fiber bundles in the central and centromedial sectors gradually extended medially, and overlap increased. A common location of fiber passage occurred at the midbrain-pontine isthmus where all of the fiber bundles overlapped. Our findings indicate that the widespread distribution of corticofugal motor projections may account for the favorable levels of motor recovery that accompany subtotal midbrain injury. At superior and mid-levels of the ccCP anteromedial lesions may disrupt projections from M3, whereas anterolateral lesions may disrupt projections from M1 and M4. Fibers from M2, LPMCv, and LPMCd may be compromised to some degree in both situations. The compact and commixed nature of motor fiber organization at inferior levels and the midbrain-pontine isthmus suggests a vulnerable region of passage for comprehensive disruption of frontal and cingulate corticofugal projection fibers.