Collagenofibrotic glomerulopathy in a kidney transplant recipient: A first report.

Collagenofibrotic glomerulopathy (CG) is a rare disease characterized by the deposition of collagen type 3 fibrils in the glomeruli. Patients may have proteinuria, hematuria, and/or renal dysfunction. CG is considered a progressive disease with variable rates of progression. The definitive diagnosis is made by electron microscopy with the presence of characteristic subendothelial and mesangial curved, comma-like, banded collagen type 3 fibers of 40-65 nm periodicity. We are reporting the first case of CG in a kidney transplant recipient with kidney disease of unknown cause.

Urine interleukin-9 and tumor necrosis factor-α for prognosis of human acute interstitial nephritis.

BACKGROUND: We previously demonstrated that urine interleukin (IL)-9 and tumor necrosis factor (TNF)-α can distinguish acute interstitial nephritis (AIN) from other causes of acute kidney injury. Here we evaluated the role of these biomarkers to prognosticate kidney function in patients with AIN. METHODS: In a cohort of participants with biopsy-proven, adjudicated AIN, we tested the association of histological features and urine biomarkers (IL-9 and TNF-α) with estimated glomerular filtration rate measured 6 months after diagnosis (6 m-eGFR) controlling for eGFR before AIN and albuminuria. We also evaluated subgroups in whom corticosteroid use was associated with 6 m-eGFR. RESULTS: In the 51 (93%) of the 55 participants with complete data, median (interquartile range) eGFR before and 6 m after AIN were 41 (27-69) and 28 (13-47) mL/min/1.73 m2, respectively. Patients with higher severity of interstitial fibrosis had lower 6 m-eGFR, whereas those with higher tubulointerstitial infiltrate had higher 6 m-eGFR. IL-9 levels were associated with lower 6 m-eGFR only in the subset of patients who did not receive corticosteroids [6m-eGFR per doubling of IL-9, -6.0 (-9.4 to -2.6) mL/min/1.73 m2]. Corticosteroid use was associated with higher 6 m-eGFR [20.9 (0.2, 41.6) mL/min/1.73 m2] only in those with urine IL-9 above the median (>0.66 ng/g) but not in others. CONCLUSIONS: Urine IL-9 was associated with lower 6 m-eGFR only in participants not treated with corticosteroids. Corticosteroid use was associated with higher 6 m-eGFR in those with high urine IL-9. These findings provide a framework for IL-9-guided clinical trials to test efficacy of immunosuppressive therapy in patients with AIN.

Regulated necrosis and failed repair in cisplatin-induced chronic kidney disease.

Cisplatin is an effective chemotherapeutic agent, but significant nephrotoxicity limits its clinical use. Despite extensive investigation of the acute cellular and molecular responses to cisplatin, the mechanisms of progression from acute to chronic kidney injury have not been explored. We used functional and morphological metrics to establish a time-point when the transition from acute and reversible kidney injury to chronic and irreparable kidney disease is clearly established. In mice administered 1 or 2 doses of intraperitoneal cisplatin separated by 2 weeks, kidney function returned toward baseline two weeks after the first dose, but failed to return to normal two weeks following a second dose. Multiphoton microscopy revealed increased glomerular epithelial and proximal tubular damage in kidneys exposed to two doses of cisplatin compared with those exposed to a single dose. In contrast, there was no evidence of fibrosis, macrophage invasion, or decrease in endothelial cell mass in chronically diseased kidneys. Pathway analysis of microarray data revealed regulated necrosis as a key determinant in the development of chronic kidney disease after cisplatin administration. Western blot analysis demonstrated activation of proteins involved in necroptosis and increased expression of kidney injury markers, cellular stress response regulators, and upstream activators of regulated necrosis, including Toll-like receptors 2 and 4. These data suggest that unresolved injury and sustained activation of regulated necrosis pathways, rather than fibrosis, promote the progression of cisplatin-induced acute kidney injury to chronic kidney disease.

Update on the Native Kidney Biopsy: Core Curriculum 2019.

The kidney biopsy is an invaluable tool that has become the gold standard for the diagnosis of pathologic kidney diseases since the early 1950s. Throughout the years, immunohistologic and ultrastructural microscopy techniques have improved and provide more information on the cause and classification of kidney diseases than that available from simple light microscopy alone. Kidney biopsy has become a preferred method to obtain critical information that can be used in conjunction with serologic, urinary, and genetic testing to diagnose a variety of kidney diseases, both acute and chronic. The kidney biopsy procedure carries relatively low risk and yields substantial information. Potential complications include bleeding requiring transfusion, gross hematuria, arteriovenous fistula formation, and perinephric hematoma, among others. Percutaneous kidney biopsies are typically performed using real-time ultrasound or computed tomographic imaging. This Core Curriculum briefly outlines the history of the kidney biopsy, then discusses indications, complications, and specific procedural aspects.

Hypergranulotic dyscornification: 30 cases of a striking epithelial reaction pattern.

BACKGROUND: Hypergranulotic dyscornification (HD) is a rarely reported histological reaction pattern that may be observed in solitary benign keratoses. OBJECTIVE AND METHODS: We retrospectively reviewed all cases described as displaying "hypergranulotic dyscornification" at our institution between January 1st 1990 to September 1st 2018. We excluded cases that on retrospective review displayed changes of epidermolytic hyperkeratosis. We conducted electron microscopy (EM) of two lesions. RESULTS: Thirty cases were identified in our search. Eleven patients were men and 19 were women. Their mean age was 56.9 ± 21.2 years. In contrast to previous reports, we found that HD does not spare the head and neck area. Frequent clinical impressions were inflamed seborrheic keratosis, Bowen disease or inflamed verruca. The most distinctive histopathologic finding was the presence of a prominent granular layer with clumped perinuclear keratohyaline granules. Some cases had mounds of rounded, anucleate glassy eosinophilic corneocytes in the stratum corneum. We observed one case of incidental HD occurring in an epidermoid cyst. EM of HD showed dense perinuclear bands which appeared to match areas of positive staining by keratin immunohistochemistry, without evidence of pale cytoplasmic areas devoid of keratin filaments, characteristic of epidermolytic hyperkeratosis. CONCLUSION: HD is a reproducible finding in some benign keratoses, probably because of abnormal keratinization. Awareness of this unique reaction pattern will help prevent misdiagnosis.

Telavancin-associated acute kidney injury
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Telavancin is a lipoglycopeptide semi-synthetic derivative of vancomycin used for select infections caused by Gram-positive bacteria including Staphylococcus aureus. Human clinical trials suggest that telavancin is potentially nephrotoxic, however there is no histopathologic description of acute kidney injury (AKI) in humans. An animal model has recently characterized the histologic changes associated with telavancin-induced AKI as proximal tubular injury with numerous phagolysosomes. We present a case of a 47-year-old man with methicillin-resistant Staphylococcus aureus bacteremia treated with telavancin, who developed AKI after 5 weeks of intravenous therapy. Acute tubular injury with lysosomal proliferation and acute interstitial nephritis were observed on kidney biopsy. To our knowledge, this is the first reported case of AKI due to telavancin that has documented kidney histopathology.
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TREX1 Mutation Causing Autosomal Dominant Thrombotic Microangiopathy and CKD-A Novel Presentation.

Renal thrombotic microangiopathy (TMA) involves diverse causes and clinical presentations. Genetic determinants causing alternate pathway complement dysregulation underlie a substantial proportion of cases. In a significant proportion of TMAs, no defect in complement regulation is identified. Mutations in the major mammalian 3' DNA repair exonuclease 1 (TREX1) have been associated with autoimmune and cerebroretinal vasculopathy syndromes. Carboxy-terminal TREX1 mutations that result in only altered localization of the exonuclease protein with preserved catalytic function cause microangiopathy of the brain and retina, termed retinal vasculopathy and cerebral leukodystrophy (RVCL). Kidney involvement reported with RVCL usually accompanies significant brain and retinal microangiopathy. We present a pedigree with autosomal dominant renal TMA and chronic kidney disease found to have a carboxy-terminal frameshift TREX1 variant. Although symptomatic brain and retinal microangiopathy is known to associate with carboxy-terminal TREX1 mutations, this report describes a carboxy-terminal TREX1 frameshift variant causing predominant renal TMA. These findings underscore the clinical importance of recognizing TREX1 mutations as a cause of renal TMA. This case demonstrates the value of whole-exome sequencing in unsolved TMA.

Histones and Neutrophil Extracellular Traps Enhance Tubular Necrosis and Remote Organ Injury in Ischemic AKI.

Severe AKI is often associated with multiorgan dysfunction, but the mechanisms of this remote tissue injury are unknown. We hypothesized that renal necroinflammation releases cytotoxic molecules that may cause remote organ damage. In hypoxia-induced tubular epithelial cell necrosis in vitro, histone secretion from ischemic tubular cells primed neutrophils to form neutrophil extracellular traps. These traps induced tubular epithelial cell death and stimulated neutrophil extracellular trap formation in fresh neutrophils. In vivo, ischemia-reperfusion injury in the mouse kidney induced tubular necrosis, which preceded the expansion of localized and circulating neutrophil extracellular traps and the increased expression of inflammatory and injury-related genes. Pretreatment with inhibitors of neutrophil extracellular trap formation reduced kidney injury. Dual inhibition of neutrophil trap formation and tubular cell necrosis had an additive protective effect. Moreover, pretreatment with antihistone IgG suppressed ischemia-induced neutrophil extracellular trap formation and renal injury. Renal ischemic injury also increased the levels of circulating histones, and we detected neutrophil infiltration and TUNEL-positive cells in the lungs, liver, brain, and heart along with neutrophil extracellular trap accumulation in the lungs. Inhibition of neutrophil extracellular trap formation or of circulating histones reduced these effects as well. These data suggest that tubular necrosis and neutrophil extracellular trap formation accelerate kidney damage and remote organ dysfunction through cytokine and histone release and identify novel molecular targets to limit renal necroinflammation and multiorgan failure.

A case of severe nephrotoxicity associated with long-term dietary supplement use.

Dietary supplements are widely used for their perceived health benefits without side effects and hence have minimal regulation. However, they have been associated with various toxicities including kidney disease. We report a 65-year-old male who had very heavy daily intake of dietary supplements for 3 years. He presented with acute kidney injury and nephrotic-range proteinuria. The renal biopsy showed acute tubular necrosis with vacuolization, acute interstitial nephritis, and secondary membranous nephropathy, consistent with an non-steroidal anti-inflammatory drug (NSAID)-like nephropathy. This was postulated to be related to the cyclooxygenase (COX) inhibitors (anthocyanins) in cherry extract that was a significant part of the patient's dietary supplement use. His proteinuria completely resolved and serum creatinine stabilized after discontinuation of all dietary supplements and a prolonged (5 months) course of prednisone. Clinicians are advised to specifically inquire about dietary supplements, especially cherry extract, as a potential cause of new-onset renal failure and proteinuria.
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GM-CSF Promotes Macrophage Alternative Activation after Renal Ischemia/Reperfusion Injury.

After kidney ischemia/reperfusion (I/R) injury, monocytes home to the kidney and differentiate into activated macrophages. Whereas proinflammatory macrophages contribute to the initial kidney damage, an alternatively activated phenotype can promote normal renal repair. The microenvironment of the kidney during the repair phase mediates the transition of macrophage activation from a proinflammatory to a reparative phenotype. In this study, we show that macrophages isolated from murine kidneys during the tubular repair phase after I/R exhibit an alternative activation gene profile that differs from the canonical alternative activation induced by IL-4-stimulated STAT6 signaling. This unique activation profile can be reproduced in vitro by stimulation of bone marrow-derived macrophages with conditioned media from serum-starved mouse proximal tubule cells. Secreted tubular factors were found to activate macrophage STAT3 and STAT5 but not STAT6, leading to induction of the unique alternative activation pattern. Using STAT3-deficient bone marrow-derived macrophages and pharmacologic inhibition of STAT5, we found that tubular cell-mediated macrophage alternative activation is regulated by STAT5 activation. Both in vitro and after renal I/R, tubular cells expressed GM-CSF, a known STAT5 activator, and this pathway was required for in vitro alternative activation of macrophages by tubular cells. Furthermore, administration of a neutralizing antibody against GM-CSF after renal I/R attenuated kidney macrophage alternative activation and suppressed tubular proliferation. Taken together, these data show that tubular cells can instruct macrophage activation by secreting GM-CSF, leading to a unique macrophage reparative phenotype that supports tubular proliferation after sterile ischemic injury.

Antiphospholipid Antibody Syndrome: Raised Intracranial Pressure Without Cerebral Venous Sinus Thrombosis.

Antiphospholipid antibody syndrome (APS) has been reported to cause elevated intracranial pressure, but usually this is due to cerebral venous sinus thrombosis (CVST). We present a 36-year old man with APS with elevated intracranial pressure with neuro-ophthalmic, renal and hematological involvement without identifiable CVST.

Role of medullary progenitor cells in epithelial cell migration and proliferation.

This study is aimed at characterizing medullary interstitial progenitor cells and to examine their capacity to induce tubular epithelial cell migration and proliferation. We have isolated a progenitor cell side population from a primary medullary interstitial cell line. We show that the medullary progenitor cells (MPCs) express CD24, CD44, CXCR7, CXCR4, nestin, and PAX7. MPCs are CD34 negative, which indicates that they are not bone marrow-derived stem cells. MPCs survive >50 passages, and when grown in epithelial differentiation medium develop phenotypic characteristics of epithelial cells. Inner medulla collecting duct (IMCD3) cells treated with conditioned medium from MPCs show significantly accelerated cell proliferation and migration. Conditioned medium from PGE2-treated MPCs induce tubule formation in IMCD3 cells grown in 3D Matrigel. Moreover, most of the MPCs express the pericyte marker PDGFR-b. Our study shows that the medullary interstitium harbors a side population of progenitor cells that can differentiate to epithelial cells and can stimulate tubular epithelial cell migration and proliferation. The findings of this study suggest that medullary pericyte/progenitor cells may play a critical role in collecting duct cell injury repair.

Early B-cell factor 1 is an essential transcription factor for postnatal glomerular maturation.

The coordination of multiple cytokines and transcription factors with their downstream signaling pathways has been shown to be integral to nephron maturation. Here we present a completely novel role for the helix-loop-helix transcription factor Early B-cell factor 1 (Ebf1), originally identified for B-cell maturation, for the proper maturation of glomerular cells from mesenchymal progenitors. The expression of Ebf1 was both spatially and temporally regulated within the developing cortex and glomeruli. Using Ebf1-null mice, we then identified biochemical, metabolic, and histological abnormalities in renal development that arose in the absence of this transcription factor. In the Ebf1 knockout mice, the developed kidneys show thinned cortices and reduced glomerular maturation. The glomeruli showed abnormal vascularization and severely effaced podocytes. The mice exhibited early albuminuria and elevated blood urea nitrogen levels. Moreover, the glomerular filtration rate was reduced >66% and the expression of podocyte-derived vascular endothelial growth factor A was decreased compared with wild-type control mice. Thus, Ebf1 has a significant and novel role in glomerular development, podocyte maturation, and the maintenance of kidney integrity and function.

Cytomegalovirus glomerulopathy and cytomegalovirus interstitial nephritis on sequential transplant kidney biopsies.

Cytomegalovirus (CMV) nephropathy may be seen in kidney transplant biopsy specimens. We report a CMV-negative patient who received a kidney transplant from a CMV-positive donor and subsequently developed CMV glomerulopathy and CMV-associated interstitial nephritis, as observed in 2 sequential kidney biopsies. The first biopsy specimen showed CMV-positive endothelial cells in glomerular capillaries and CMV-infected monocytes in glomerular capillary lumens. The second biopsy specimen showed CMV-positive cells in the interstitium with associated lymphoplasmacytic infiltrate and tubular injury, but no evidence of direct CMV infection in tubular epithelial cells. Moreover, the second biopsy specimen showed persistent monocytes with cytoplasmic viral particles within glomerular capillary loops by electron microscopy. Our case shows that CMV glomerulopathy can be caused by direct CMV infection of glomerular capillary endothelial cells. CMV-positive circulating monocytes may play an important role in the different histopathologic manifestations of CMV nephropathy in kidney transplant grafts.

Chitinase-like protein Brp-39/YKL-40 modulates the renal response to ischemic injury and predicts delayed allograft function.

Kidney hypoperfusion during episodes of systemic hypotension or after surgical procurement for transplantation can lead to tubular cell death via necrosis and apoptosis, which trigger a series of responses that promote repair. The factors that contribute to the repair phase after kidney injury are not well understood. Using a urine proteomic screen in mice, we identified the macrophage-secreted chitinase-like protein Brp-39, the murine protein product of the chitinase 3-like 1 gene, as a critical component of this reparative response that serves to limit tubular cell apoptotic death via activation of Akt, improving animal survival after kidney ischemia/reperfusion. Examination of graded times of renal ischemia revealed a direct correlation between the degree of kidney injury and both Chi3l1/Brp-39 expression in the kidney and its levels in the urine. In samples collected from patients undergoing deceased-donor kidney transplantation, we found higher levels of the orthologous human protein, YKL-40, in urine and blood from allografts subjected to sufficient peri-transplant ischemia to cause delayed graft function than from allografts with slow or immediate graft function. Urinary levels of YKL-40 obtained within hours of transplant predicted the need for subsequent dialysis in these patients. In summary, these data suggest that Brp-39/YKL-40 is a sensor of the degree of injury, a critical mediator of the reparative response, and a possible biomarker to identify patients at greatest risk of sustained renal failure after transplantation.

Macrophage-specific deletion of transforming growth factor-ß1 does not prevent renal fibrosis after severe ischemia-reperfusion or obstructive injury.

Macrophage infiltration is a prominent feature of the innate immune response to kidney injury. The persistence of macrophages is associated with tubulointerstitial fibrosis and progression of chronic kidney disease. Macrophages are known to be major producers of transforming growth factor-ß1 (TGF-ß1), especially in the setting of phagocytosis of apoptotic cells. TGF-ß1 has long been implicated as a central mediator of tissue scarring and fibrosis in many organ disease models, including kidney disease. In this study, we show that homozygous deletion of Tgfb1 in myeloid lineage cells in mice heterozygous for Tgfb1 significantly reduces kidney Tgfb1 mRNA expression and Smad activation at late time points after renal ischemia-reperfusion injury. However, this reduction in kidney Tgfb1 expression and signaling results in only a modest reduction of isolated fibrosis markers and does not lead to decreased interstitial fibrosis in either ischemic or obstructive injury models. Thus, targeting macrophage-derived TGF-ß1 does not appear to be an effective therapy for attenuating progressive renal fibrosis after kidney injury.

NALP3-mediated inflammation is a principal cause of progressive renal failure in oxalate nephropathy.

Oxalate nephropathy with renal failure is caused by multiple disorders leading to hyperoxaluria due to either overproduction of oxalate (primary hyperoxaluria) or excessive absorption of dietary oxalate (enteric hyperoxaluria). To study the etiology of renal failure in crystal-induced kidney disease, we created a model of progressive oxalate nephropathy by feeding mice a diet high in soluble oxalate (high oxalate in the absence of dietary calcium). Renal histology was characterized by intratubular calcium-oxalate crystal deposition with an inflammatory response in the surrounding interstitium. Oxalate nephropathy was not found in mice fed a high oxalate diet that also contained calcium. NALP3, also known as cryopyrin, has been implicated in crystal-associated diseases such as gout and silicosis. Mice fed the diet high in soluble oxalate demonstrated increased NALP3 expression in the kidney. Nalp3-null mice were completely protected from the progressive renal failure and death that occurred in wild-type mice fed the diet high in soluble oxalate. NALP3 deficiency did not affect oxalate homeostasis, thereby excluding differences in intestinal oxalate handling to explain the observed phenotype. Thus, progressive renal failure in oxalate nephropathy results primarily from NALP3-mediated inflammation.

APOBEC-1 deletion enhances cisplatin-induced acute kidney injury.

Cisplatin (CP) induces acute kidney injury (AKI) whereby proximal tubules undergo regulated necrosis. Repair is almost complete after a single dose. We now demonstrate a role for Apolipoprotein B mRNA editing enzyme, catalytic polypeptide 1 (Apobec-1) that is prominently expressed at the interface between acute and chronic kidney injury (CKD), in the recovery from AKI. Apobec-1 knockout (KO) mice exhibited greater mortality than in wild type (WT) and more severe AKI in both CP- and unilateral ischemia reperfusion (IR) with nephrectomy. Specifically, plasma creatinine (pCr) 2.6 ± 0.70 mg/dL for KO, n = 10 and 0.16 ± 0.02 for WT, n = 6, p < 0.0001 in CP model and 1.34 ± 0.22 mg/dL vs 0.75 ± 0.06, n = 5, p < 0.05 in IR model. The kidneys of Apobec-1 KO mice showed increased necrosis, increased expression of KIM-1, NGAL, RIPK1, ASCL4 and increased lipid accumulation compared to WT kidneys (p < 0.01). Neutrophils and activated T cells were both increased, while macrophages were reduced in kidneys of Apobec-1 KO animals. Overexpression of Apobec-1 in mouse proximal tubule cells protected against CP-induced cytotoxicity. These findings suggest that Apobec-1 mediates critical pro-survival responses to renal injury and increasing Apobec-1 expression could be an effective strategy to mitigate AKI.

Defining the molecular correlate of arteriolar hyalinosis in kidney disease progression by integration of single cell transcriptomic analysis and pathology scoring.

Arteriolar hyalinosis in kidneys is an independent predictor of cardiovascular disease, the main cause of mortality in chronic kidney disease (CKD). The underlying molecular mechanisms of protein accumulation in the subendothelial space are not well understood. Using single cell transcriptomic data and whole slide images from kidney biopsies of patients with CKD and acute kidney injury in the Kidney Precision Medicine Project, the molecular signals associated with arteriolar hyalinosis were evaluated. Co-expression network analysis of the endothelial genes yielded three gene set modules as significantly associated with arteriolar hyalinosis. Pathway analysis of these modules showed enrichment of transforming growth factor beta / bone morphogenetic protein (TGFß / BMP) and vascular endothelial growth factor (VEGF) signaling pathways in the endothelial cell signatures. Ligand-receptor analysis identified multiple integrins and cell adhesion receptors as over-expressed in arteriolar hyalinosis, suggesting a potential role of integrin-mediated TGFß signaling. Further analysis of arteriolar hyalinosis associated endothelial module genes identified focal segmental glomerular sclerosis as an enriched term. On validation in gene expression profiles from the Nephrotic Syndrome Study Network cohort, one of the three modules was significantly associated with the composite endpoint (> 40% reduction in estimated glomerular filtration rate (eGFR) or kidney failure) independent of age, sex, race, and baseline eGFR, suggesting poor prognosis with elevated expression of genes in this module. Thus, integration of structural and single cell molecular features yielded biologically relevant gene sets, signaling pathways and ligand-receptor interactions, underlying arteriolar hyalinosis and putative targets for therapeutic intervention.

Inorganic phosphate stimulates fibronectin expression in renal fibroblasts.

Elevated plasma phosphate levels are signifcantly associated with progression of chronic kidney disease (CKD). Interstitial fibrosis is an important factor in the progression of CKD. In this study we investigate the role of inorganic phosphate in stimulating fibronectin (FN) synthesis in a kidney fibroblast cell line (NRK-49F). We find that phosphate increases FN abundance and message in a dose-dependent fashion and that both ERK1/2 and AKT are important signaling pathways that mediate phosphate-dependent FN expression in NRK-49F cells. Moreover phosphate srimulates the expression of the transcription factors osterix and NFATc1, which form complexes and mediate FN synthesis. Another transcription factor involved in phosphate-dependent FN synthesis is the AP1 family member c-Fos. In summary we show that even mildly elevated serum phosphate levels can induce synthesis of the interstitial matrix protein fibronectin through activation of ERK1/2 and AKT signaling pathways in kidney fibroblasts and that the synthesis of fibronectin is mediated by a transcriptional complex consisting of NFATc1, osterix and c-Fos.