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 in vivo longitudinal studies in mouse models of AKI and CKD to track nephron fate.

An Integrated Transcriptomic Approach to Identify Molecular Markers of Calcineurin Inhibitor Nephrotoxicity in Pediatric Kidney Transplant Recipients.

Calcineurin inhibitors are highly efficacious immunosuppressive agents used in pediatric kidney transplantation. However, calcineurin inhibitor nephrotoxicity (CNIT) has been associated with the development of chronic renal allograft dysfunction and decreased graft survival. This study evaluated 37 formalin-fixed paraffin-embedded biopsies from pediatric kidney transplant recipients using gene expression profiling. Normal allograft samples (n = 12) served as negative controls and were compared to biopsies exhibiting CNIT (n = 11). The remaining samples served as positive controls to validate CNIT marker specificity and were characterized by other common causes of graft failure such as acute rejection (n = 7) and interstitial fibrosis/tubular atrophy (n = 7). MiRNA profiles served as the platform for data integration. Oxidative phosphorylation and mitochondrial dysfunction were the top molecular pathways associated with overexpressed genes in CNIT samples. Decreased ATP synthesis was identified as a significant biological function in CNIT, while key toxicology pathways included NRF2-mediated oxidative stress response and increased permeability transition of mitochondria. An integrative analysis demonstrated a panel of 13 significant miRNAs and their 33 CNIT-specific gene targets involved with mitochondrial activity and function. We also identified a candidate panel of miRNAs/genes, which may serve as future molecular markers for CNIT diagnosis as well as potential therapeutic targets.

Nephron loss detected by MRI following neonatal acute kidney injury in rabbits.

BACKGROUND: Acute kidney injury affects nearly 30% of preterm neonates in the intensive care unit. We aimed to determine whether nephrotoxin-induced AKI disrupted renal development assessed by imaging (CFE-MRI). METHODS: Neonatal New Zealand rabbits received indomethacin and gentamicin (AKI) or saline (control) for four days followed by cationic ferritin (CF) at six weeks. Ex vivo images were acquired using a gradient echo pulse sequence on 7 T MRI. Glomerular number (Nglom) and apparent glomerular volume (aVglom) were determined. CF toxicity was assessed at two and 28 days in healthy rabbits. RESULTS: Nglom was lower in the AKI group as compared to controls (74,034 vs 198,722, p < 0.01). aVglom was not different (AKI: 7.3 × 10-4 vs control: 6.2 × 10-4 mm3, p = 0.69). AKI kidneys had a band of glomeruli distributed radially in the cortex that were undetectable by MRI. Following CF injection, there was no difference in body or organ weights except for the liver, and transient changes in serum iron, platelets and white blood cell count. CONCLUSIONS: Brief nephrotoxin exposure during nephrogenesis results in fewer glomeruli and glomerular maldevelopment in a unique pattern detectable by MRI. Whole kidney evaluation by CFE-MRI may provide an important tool to understand the development of CKD following AKI.

Iatrogenic Disease of the Genitourinary Tract.

Iatrogenic disease is defined as illness caused by diagnostic procedures or treatment given by health care professionals. More recently described treatment complications involving the genitourinary tract include newly recognized variants of renal carcinoma in the setting of dialysis/end-stage renal disease, treatment effect in genitourinary carcinomas, and medical renal disease caused by drug therapies, including immunotherapy. The objective of this review is to cover iatrogenic inflammatory diseases, pseudotumors and tumors of the kidney, bladder, prostate, testis and paratestis of most interest to surgical pathologists. For this reason, disease caused by the following will not be covered: iatrogenic glomerulonephritis, self-inflicted injury including the introduction of foreign bodies, surgical error, drugs of abuse and herbal medications, and iatrogenic disease in the transplant setting including ischemia/reperfusion injury. Emphasis is placed upon commonly encountered diseases in order to ensure that the review is of utility to practicing pathologists. The clinical context, pathophysiology and histopathology of each disease entity are covered.

Diagnostic histochemistry in medical diseases of the kidney.

The value of histochemical analysis in the diagnosis of medical renal diseases has long been known, and its use continues currently. Depending on the particular disorder in question, a variety of "special" stains may be applied to renal biopsies. These include the periodic acid-Schiff, Masson trichrome, Jones, von Kossa, Verhoeff-van Gieson, Congo Red, and toluidine blue methods, among others. This review considers the application of such techniques in the assessment of vascular, glomerular, and tubulointerstitial lesions of the kidney.

Immunolocalization of TAR DNA-binding protein of 43 kDa (TDP-43) in mouse seminiferous epithelium.

TAR DNA-binding protein of 43 kDa (TDP-43) is an evolutionarily conserved, ubiquitously expressed, multi-functional DNA/RNA-binding protein with roles in gene transcription, mRNA splicing, stability, transport, micro RNA biogenesis, and suppression of transposons. Aberrant expression of TDP-43 in testis and sperm was recently shown to be associated with male infertility, which highlights the need to understand better the expression of TDP-43 in the testis. We previously cloned TDP-43 from a mouse testis cDNA library, and showed that it functions as a transcriptional repressor and regulates the precise spatiotemporal expression of the Acrv1 gene, which encodes the acrosomal protein SP-10, during spermatogenesis. Here, we performed immunoblotting and immunohistochemistry of the mouse testis using four separate antibodies recognizing the amino and carboxyl termini of TDP-43. TDP-43 is present in the nuclei of germ cells as well as Sertoli cells. TDP-43 expression begins in type B/intermediate spermatogonia, peaks in preleptotene spermatocytes, and becomes undetectable in leptotene and zygotene spermatocytes. Pachytene spermatocytes and early round spermatids again express TDP-43, but its abundance diminishes later in spermatids (at steps 5-8). Interestingly, two of the four antibodies showed TDP-43 expression in spermatids at steps 9-10, which coincides with the initial phase of the histone-to-protamine transition. Immunoreactivity patterns observed in the study suggest that TDP-43 assumes different conformational states at different stages of spermatogenesis. TDP-43 pathology has been extensively studied in the context of neurodegenerative diseases; its role in spermatogenesis warrants further detailed investigation of the involvement of TDP-43 in male infertility.

The urine microRNA profile may help monitor post-transplant renal graft function.

Noninvasive, cost-effective biomarkers that allow accurate monitoring of graft function are needed in kidney transplantation. Since microRNAs (miRNAs) have emerged as promising disease biomarkers, we sought to establish an miRNA signature in urinary cell pellets comparing kidney transplant patients diagnosed with chronic allograft dysfunction (CAD) with interstitial fibrosis and tubular atrophy and those recipients with normal graft function. Overall, we evaluated 191 samples from 125 deceased donor primary kidney transplant recipients in the discovery, initial validation, and the longitudinal validation studies for noninvasive monitoring of graft function. Of 1733 mature miRNAs studied using microarrays, 22 were found to be differentially expressed between groups. Ontology and pathway analyses showed inflammation as the principal biological function associated with these miRNAs. Twelve selected miRNAs were longitudinally evaluated in urine samples of an independent set of 66 patients, at two time points after kidney transplant. A subset of these miRNAs was found to be differentially expressed between groups early after kidney transplant before histological allograft injury was evident. Thus, a panel of urine miRNAs was identified as potential biomarkers for monitoring graft function and anticipating progression to CAD in kidney transplant patients.

DICER1 mutations in childhood cystic nephroma and its relationship to DICER1-renal sarcoma.

The pathogenesis of cystic nephroma of the kidney has interested pathologists for over 50 years. Emerging from its initial designation as a type of unilateral multilocular cyst, cystic nephroma has been considered as either a developmental abnormality or a neoplasm or both. Many have viewed cystic nephroma as the benign end of the pathologic spectrum with cystic partially differentiated nephroblastoma and Wilms tumor, whereas others have considered it a mixed epithelial and stromal tumor. We hypothesize that cystic nephroma, like the pleuropulmonary blastoma in the lung, represents a spectrum of abnormal renal organogenesis with risk for malignant transformation. Here we studied DICER1 mutations in a cohort of 20 cystic nephromas and 6 cystic partially differentiated nephroblastomas, selected independently of a familial association with pleuropulmonary blastoma and describe four cases of sarcoma arising in cystic nephroma, which have a similarity to the solid areas of type II or III pleuropulmonary blastoma. The genetic analyses presented here confirm that DICER1 mutations are the major genetic event in the development of cystic nephroma. Further, cystic nephroma and pleuropulmonary blastoma have similar DICER1 loss of function and 'hotspot' missense mutation rates, which involve specific amino acids in the RNase IIIb domain. We propose an alternative pathway with the genetic pathogenesis of cystic nephroma and DICER1-renal sarcoma paralleling that of type I to type II/III malignant progression of pleuropulmonary blastoma.

Weber-Christian disease associated with the tip variant of focal segmental glomerulosclerosis: a case report.

Weber-Christian disease (W-CD) is associated with relapsing nodular panniculitis and a variety of systemic findings. Renal parenchymal involvement has been rarely reported. The authors describe a case of nephrotic syndrome in an African-American man with a W-CD flare. The patient had chills and low-grade fever with painful lower extremity skin lesions. A renal biopsy demonstrated the tip variant of focal segmental glomerulosclerosis (FSGS). The kidney biopsy also suggested parenchymal involvement by W-CD disease, with supportive ultrastructural findings. The synchronous W-CD flare and biopsy-proven FSGS and the rapid and sustained response of both to limited treatment suggest a causative association.

Adenovirus Infection and Transplantation.

Adenoviruses result in a wide array of clinical presentations, including primarily respiratory, gastrointestinal, genitourinary, or systemic infections. Although adenovirus causes mild disease limited to a single organ system in immunocompetent individuals, severe and life-threatening infections do rarely occur. Disseminated disease and severe localized disease resulting in significant morbidity and mortality have been well described in the immunocompromised populations. Although asymptomatic viremia, respiratory tract, and gastrointestinal infections are the most common disease in most transplant patients, renal transplant patients more commonly experience urinary tract infections, including hemorrhagic cystitis or nephritis. Diagnosis requires astute clinical awareness of the patient's clinical presentation that would be compatible with adenovirus combined with cultures, molecular testing, polymerase chain reaction, and tissue sampling. There is no Food and Drug Administration-approved treatment for adenovirus; however, several studies have evaluated therapeutic options including cidofovir, brincidofovir, and immunotherapy. This article will summarize our current understanding of adenovirus in the transplant population.

Unexpected Fabry disease in a renal allograft kidney: an underrecognized cause of poor allograft function.

Fabry disease is an X-linked recessive lysosomal storage disease caused by a deficiency of α-galactosidase A, with characteristic ultrastructural cytoplasmic myelin-like inclusions. Renal lesions are seen in male and variably in heterozygous female patients. One previous report has described Fabry disease involving a renal allograft from a deceased female donor with no history of Fabry disease. The authors describe another case, in which suspicion for Fabry disease was raised ultrastructurally. This serves as a reminder that proteinuria after renal transplantation may be due to donor-derived disease. Fabry disease is probably an underrecognized cause of graft dysfunction. This case provides further justification for ultrastructural examination of renal allograft biopsies.

IgA Nephropathy Secondary to Ipilimumab Use.

Ipilimumab is a human monoclonal antibody targeting cytotoxic T-lymphocyte-associated protein 4 approved for the treatment of non-small-cell lung cancer (NSCLC) and other malignancies. Despite a high prevalence of other immune-related adverse events (irAEs), checkpoint inhibitor (CPI)-related nephrotoxicity has been reported less frequently. In this clinical case report, we describe the evaluation of a 70-year-old female with stage IV NSCLC who presented with nephrotic range proteinuria 4 weeks after receiving her first cycle of ipilimumab. She underwent a renal biopsy and was found to have IgA nephropathy that was presumed to be secondary to ipilimumab use, given recent initiation of therapy and clinical history. Unfortunately, despite prompt initiation of corticosteroids, her acute kidney injury progressed and she required hemodialysis, later transitioning to hospice. To our knowledge, this is one of few reported cases of IgA nephropathy secondary to CPI use. With increasing use of CPIs, this case further emphasizes the need for continued surveillance for irAEs, which can occur at any point in a patient's treatment course.

Knockout of Nephron ATP6AP2 Impairs Proximal Tubule Function and Prevents High-Fat Diet-Induced Obesity in Male Mice.

ATP6AP2 expression is increased in the nephron during high-fat diet (HFD) and its knockout (ATP6AP2 KO) reduces body weight (WT) in mice. We evaluated the contribution of ATP6AP2 to urinary glucose (UG) and albumin (Ualb) handling during HFD. We hypothesized that nephron ATP6AP2 KO increases UG and Ualb and minimizes HFD-induced obesity. Eight-week-old male C57BL/6J mice with inducible nephron-specific ATP6AP2 KO and noninduced controls were fed either normal diet (ND, 12% kcal fat) or HFD (45% kcal fat) for 6 months. ATP6AP2 KO mice on ND had 20% (P < 0.01) lower WT compared with controls. HFD-fed mice had 41% (P < 0.05) greater WT than ND-fed control mice. In contrast, ATP6AP2 KO abrogated the increase in WT induced by HFD by 40% (P < 0.05). Mice on HFD had less caloric intake compared with ND controls (P < 0.01). There were no significant differences in metabolic rate between all groups. UG and Ualb was significantly increased in ATP6AP2 KO mice on both ND and HFD. ATP6AP2 KO showed greater levels of proximal tubule apoptosis and histologic evidence of proximal tubule injury. In conclusion, our results demonstrate that nephron-specific ATP6AP2 KO is associated with glucosuria and albuminuria, most likely secondary to renal proximal tubule injury and/or dysfunction. Urinary loss of nutrients may have contributed to the reduced WT of knockout mice on ND and lack of WT gain in response to HFD. Future investigation should elucidate the mechanisms by which loss of renal ATP6AP2 causes proximal tubule injury and dysfunction.

Relationship between HLA class I antigen processing machinery component expression and the clinicopathologic characteristics of bladder carcinomas.

PURPOSE: The goal of this study was to analyze protein expression of antigen processing machinery (APM) components in bladder carcinoma (BC), and to assess the clinical significance of defects in their expression. EXPERIMENTAL DESIGN: Tissue from 167 cystectomies for primary BC was used to create a tissue microarray. 128 tumors were urothelial carcinoma (UC). Immunohistochemistry was performed using 14 monoclonal antibodies to APM components (beta2-microglobulin, calnexin, calreticulin, delta, Z, MB1, LMP2, LMP7, LMP10, HLA class I heavy chain, tapasin, TAP1, TAP2 and ERp57) and MHC class I-related antigen (MICA). Sections of normal urothelium from six subjects were used as controls. RESULTS: All APM components except MB1, LMP2 and TAP2 had significantly lower staining in UC than in normal urothelium. No significant differences were found in APM component scores between different grades of UC. Squamous cell carcinoma had the highest scores, with UC intermediate and other types of BC lowest. High-stage UC demonstrated significantly lower staining for calnexin, LMP2, LMP7 and LMP10 than low-stage UC. With mean 3.6 years follow up, significantly worse survival was associated with a higher delta score in UC (P = 0.038) and a lower calreticulin score in all tumor types (P = 0.028). CONCLUSIONS: Most APM components were downregulated in UC. High-stage UC had lower scores for immunoproteasome components compared to low-stage UC. Delta and calreticulin protein expression was associated with survival in UC and in all types of BC, respectively. These findings suggest that APM defects play a role in the clinical course of BC and should be considered in developing immunotherapeutic approaches for its control.

Anti-Neurofascin-Associated Nephrotic-Range Proteinuria in Chronic Inflammatory Demyelinating Polyneuropathy.

There are few case reports of concomitant chronic inflammatory demyelinating polyneuropathy (CIDP) and focal segmental glomerulosclerosis. A rare autoantibody to a neuronal and podocyte structural component, neurofascin, may be contributory. A Black man in his 40s presented with worsening polyneuropathy requiring mechanical ventilation and initially acute inflammatory demyelinating polyneuropathy was diagnosed. After a poor response to intravenous immunoglobulin, plasmapheresis was initiated. The patient also had concomitant new-onset nephrotic-range proteinuria. A limited kidney biopsy was interpreted as minimal change disease and was treated with prednisone. After some improvement, the patient was extubated; however, he later re-presented with worsening symptoms requiring mechanical ventilation and was re-treated with plasmapheresis. Due to the protracted course and poor response to intravenous immunoglobulin, acute-onset CIDP was diagnosed and a neuromuscular antibody workup returned positive for neurofascin, supporting the diagnosis of seropositive acute-onset CIDP. A repeat kidney biopsy demonstrated focal segmental glomerulosclerosis and acute tubular damage. The patient was treated with steroids and tacrolimus and later transitioned to rituximab. Neurofascin enzyme-linked immunosorbent assay then tested negative with concomitant resolution of both neuropathy and proteinuria. Further studies will help validate these findings and the treatment strategy.

Does renal mass biopsy influence multidisciplinary treatment recommendations?

Purpose: To examine how a multidisciplinary team approach incorporating renal mass biopsy (RMB) into decision making changes the management strategy.Methods: A multidisciplinary team comprised of a radiology proceduralist, a pathologist and urologists convened monthly for renal mass conference with a structured presentation of patient demographics, co-mborbidities, tumor pathology, laboratory and radiographic features. Biopsy protocol was standardized to an 18-gauge core needle biopsy using a sheathed apparatus under renal ultrasound guidance. Biopsy diagnostic rate, and concordance with nephrectomy specimens were summarized. Descriptive statistics were used to evaluate influence of RMB on management decisions.Results: A total of 83 patients with a ≤4 cm mass were discussed, and 66% of patients underwent RMB. Of those, 87% were diagnostic with 9% of core biopsies showing benign pathology. Active surveillance (AS) was recommended for 34% of patients with biopsy data as compared to 64% of those without biopsy. Ablation was recommended for 38% of the biopsy cohort compared to 7% without biopsy. Partial nephrectomy rates were similar for both cohorts, approximately 17% and 22%, respectively. Our complication rate was 1.5%, with only 1 Clavien-Dindo Grade 2 complication. Histology was concordant in 93% of patients that ultimately underwent partial nephrectomy after biopsy.Conclusions: Over half of our SRM patients underwent a RMB that provided a diagnosis in 85% of cases. RMB aided in shared decision making by providing insight into the biology of renal masses, which helps to guide multidisciplinary management and consideration of nephron sparing options.

Compartmentalization of neutrophils in the kidney and lung following acute ischemic kidney injury.

During renal ischemia-reperfusion, local and distant tissue injury is caused by an influx of neutrophils into the affected tissues. Here we measured the kinetics of margination and transmigration of neutrophils in vivo in the kidney and lungs following renal ischemia-reperfusion. After bilateral renal injury, kidney neutrophil content increased threefold at 24 h. The neutrophils were found primarily in the interstitium and to a lesser degree marginated to the vascular endothelium. These interstitial neutrophils had significantly lower levels of intracellular IFN-gamma, IL-4, IL-6, and IL-10 a tendency for decreased amounts of IL-4 and TNF-alpha compared to the marginated neutrophils. Localization of the neutrophils to the kidney interstitium was confirmed by high resolution microscopy and these sites of transmigration were directly associated with areas of increased vascular permeability. Activation of the adenosine 2A receptor significantly decreased both kidney neutrophil transmigration by about half and vascular permeability by about a third. After unilateral renal ischemia-reperfusion, the unclipped kidney and lungs did not accumulate interstitial neutrophils or have increased vascular permeability despite a marked increase of neutrophil margination in the lungs. Our findings suggest there is a sequential recruitment and transmigration of neutrophils from the vasculature into the kidney interstitium at the site of tissue injury following renal ischemia-reperfusion.

Podoplanin is a better immunohistochemical marker for sarcomatoid mesothelioma than calretinin.

Immunohistochemistry using a broad panel of markers is an invaluable tool for diagnosing sarcomatoid mesothelioma. Membranous podoplanin staining has been proposed as a specific and sensitive marker to distinguish epithelioid mesothelioma from adenocarcinoma. We found that cytoplasmic podoplanin staining was present in sarcomatoid mesotheliomas, and wanted to explore the reproducibility and specificity of this staining pattern. Immunohistochemistry for podoplanin, using 2 podoplanin antibodies (antipodoplanin and D2-40), was performed in 55 mesotheliomas (24 epithelioid, 18 sarcomatoid, and 13 biphasic), 80 pulmonary adenocarcinomas, 8 synovial sarcomas, and 16 sarcomatoid carcinomas. Expression of calretinin, vimentin, MOC31, and TTF-1 was also examined in all adenocarcinomas, sarcomatoid carcinomas, 7 synovial sarcomas, and 21 of the mesotheliomas. Calretinin staining performed previously on an additional 31 mesotheliomas was reviewed. Using membranous or cytoplasmic staining as indicative of positivity, we found that antipodoplanin and D2-40 each stained 84% of mesotheliomas (antipodoplanin: 46/55; D2-40: 38/44), including 72% of sarcomatoid mesotheliomas (antipodoplanin: 13/18; D2-40: 11/14). With antipodoplanin antibody, no staining was seen in the pulmonary adenocarcinomas (0/80, 0%) or the synovial sarcomas (0/8, 0%), and weak cytoplasmic staining was seen in only 1 sarcomatoid carcinoma (1/15, 7%). D2-40 showed similar results, staining 3% (2/80) of pulmonary adenocarcinomas, 13% (1/8) of synovial sarcomas, and 8% (1/13) of sarcomatoid carcinomas. Overall sensitivities and specificities were 84% and 99% for antipodoplanin, and 86% and 96% for D2-40. These findings suggest that cytoplasmic podoplanin expression may be useful in the diagnosis of sarcomatoid mesothelioma, although it should be used with caution on biopsy material.

Cutaneous pseudosarcomatous polyp: a recently described lesion.

Three cases of cutaneous pseudosarcomatous polyp, a lesion recently described in the dermatopathology literature, are reported here. These benign proliferations display dramatic cytologic pleomorphism, but despite their disquieting morphological features, they have behaved in a benign fashion to date. All 3 lesions in this study were clinically innocuous, with 1 having been present for 1 year and another for 2 years. The first lesion arose on the back of a 30-year-old man, the second on the nasal columella of a 65-year-old woman, and the third on the back of a 91-year-old woman. All 3 had the typical architecture of a fibroepithelial polyp (acrochordon) with widely separated stellate cells occupying a myxoid to collagenous stroma. Markedly pleomorphic stellate cells were widely dispersed, with an increased density of atypical cells beneath the epidermis and in small foci of adipose tissue in 1 case. Multinucleated cells, some with a floret-type configuration, were also observed. One of the polyps demonstrated focal mild hyalinization of vessel walls. Only rare mitotic figures were identified in 2 cases, but 1 showed atypical forms. Immunohistochemically, the atypical cells reacted diffusely for vimentin and variably for CD34 and factor XIIIa, but they lacked smooth muscle actin and desmin. Cutaneous pseudosarcomatous polyps can be added to the list of pathologic entities with symplastic or pseudomalignant features.