Congophilic fibrils in the glomeruli with polyclonal immunoglobulin gamma staining - another cause for diagnostic overlap: A case report.

BACKGROUND: Glomerulopathy with fibrillary deposits is not uncommon in routine nephropathology practice, with amyloidosis and fibrillary glomerulonephritis being the two most frequently encountered entities. Renal amyloid heavy and light chain (AHL) is relatively uncommon and its biopsy diagnosis is usually limited to cases that show strong equivalent staining for a single immunoglobulin (Ig) heavy chain and a single light chain, further supported by mass spectrometry (MS) and serum studies for monoclonal protein. But polyclonal light chain staining can pose a challenge. CASE SUMMARY: Herein we present a challenging case of renal AHL with polyclonal and polytypic Ig gamma (IgG) staining pattern by immunofluorescence. The patient is a 62-year-old Caucasian male who presented to an outside institution with a serum creatinine of up to 8.1 mg/dL and nephrotic range proteinuria. Despite the finding of a polyclonal and polytypic staining pattern on immunofluorescence, ultrastructural study of the renal biopsy demonstrated the presence of fibrils with a mean diameter of 10 nm. Congo red was positive while DNAJB9 was negative. MS suggested a diagnosis of amyloid AHL type with IgG and lambda, but kappa light chains were also present supporting the immunofluorescence staining results. Serum immunofixation studies demonstrated IgG lambda monoclonal spike. The patient was started on chemotherapy. The chronic renal injury however was quite advanced and he ended up needing dialysis shortly after. CONCLUSION: Tissue diagnosis of AHL amyloid can be tricky. Thorough confirmation using other available diagnostic techniques is recommended in such cases.

CXCR5 + CD8 + T Cell-mediated Suppression of Humoral Alloimmunity and AMR in Mice Is Optimized With mTOR and Impaired With Calcineurin Inhibition.

BACKGROUND: Adoptive cellular therapy (ACT) with antibody-suppressor CXCR5 + CD8 + T cells (CD8 + T Ab-supp ) inhibits alloantibody production, antibody-mediated rejection (AMR), and prolongs graft survival in multiple transplant mouse models. However, it is not known how conventional immunosuppressive agents impact the efficacy of CD8 + T Ab-supp ACT. METHODS: We investigated the efficacy of CD8 + T Ab-supp cell ACT when combined with calcineurin inhibitor (CNi) or mammalian target of rapamycin inhibitor (mTORi) in a murine model of kidney transplant. RESULTS: ACT-mediated decrease in germinal center B cells, posttransplant alloantibody titer, and amelioration of AMR in high alloantibody-producing CCR5 knockout kidney transplant recipients were impaired when ACT was combined with CNi and enhanced when combined with mTORi. CNi (but not mTORi) reduced ACT-mediated in vivo cytotoxicity of IgG + B cells and was associated with increased quantity of germinal center B cells. Neither CNi nor mTORi treatment impacted the expression of cytotoxic effector molecules (FasL, Lamp1, perforin, granzyme B) by CD8 + T Ab-supp after ACT. Concurrent treatment with CNi (but not mTORi) reduced in vivo proliferation of CD8 + T Ab-supp after ACT. The increase in quantity of splenic CD44 + CXCR5 + CD8 + T cells that occurs after ACT was reduced by concurrent treatment with CNi but not by concurrent treatment with mTORi (dose-dependent). CONCLUSIONS: Impaired efficacy of ACT by CNi is attributed to reduced persistence and/or expansion of CD8 + T Ab-supp cells after ACT. In contrast, concurrent immunosuppression with mTORi preserves CD8 + T Ab-supp cells quantity, in vivo proliferation, and in vivo cytotoxic effector function after ACT and enhances suppression of humoral alloimmunity and AMR.

Kidney Biopsy Corner: Amyloidosis.

Amyloidosis is an infiltrative disease caused by misfolded proteins depositing in tissues. Amyloid infiltrates the kidney in several patterns. There are, as currently described by the International Society of Amyloidosis, 14 types of amyloid that can involve the kidney, and these types may have different locations or clinical settings. Herein we report a case of AA amyloidosis occurring in a 24-year-old male with a history of intravenous drug abuse and provide a comprehensive review of different types of amyloids involving the kidney.

Correlation of Red Blood Cell Casts With Renal Dysfunction in Patients With Infection-related Glomerulonephritis.

CONTEXT.­: Infection-related glomerulonephritis (IRGN) usually manifests as a proliferative immune-complex glomerulonephritis. The degree of renal dysfunction at presentation can vary. Association with histologic features on kidney biopsy remains unknown. OBJECTIVE.­: To study the correlation between renal function in IRGN at the time of biopsy and the severity of histologic features. DESIGN.­: Culture-proven IRGN cases at our facility were included and divided based on estimated glomerular filtration rate (eGFR) 15 ml/min/1.73 m2. Patients' demographic and pathologic findings were obtained from electronic medical records and kidney biopsy reports. RESULTS.­: In total, 104 cases were diagnosed with IRGN on biopsy (mean age, 55.6 ± 15.6 years; male, n = 79 [76%]; median eGFR, 14.5 mL/min/1.73 m2), and 51 of 104 showed eGFR <15 mL/min/1.73 m2. Among all the histologic features assessed, only percent tubules with red blood cell (RBC) casts showed statistical difference, being significantly higher in the lower eGFR group (P = .004). Multivariable logistic regression analysis also showed that %tubules with RBC casts were associated with lower eGFR (odds ratio, 1.12; 95% CI, 1.01-1.24; P = .01). Patients with 5% or more RBC casts (n = 31) showed a lower eGFR (P = .02) and a higher %cellular crescent (P < .001) compared with those with less than 5% RBC casts. Patients with concomitant anticoagulant therapy (n = 11) showed higher percentages of RBC casts than those without anticoagulants (P = .02). CONCLUSIONS.­: Particular attention to the extent of RBC casts on kidney biopsy is recommended in patients with IRGN because these portend worse renal dysfunction, more so in patients requiring anticoagulation (including for hemodialysis) because they are especially vulnerable to developing anticoagulant-related nephropathy.

N-acetylcysteine ameliorates hematuria-associated tubulointerstitial injury in 5/6 nephrectomy mice.

Chronic kidney disease (CKD) is characterized by increased interstitial fibrosis and tubular atrophy (IFTA) in the kidney. Chronic hematuria is a hallmark of several human kidney diseases and often is seen in patients on anticoagulation therapy. We had previously demonstrated that chronic hematuria associated with warfarin increases IFTA in 5/6 nephrectomy (5/6NE) rats, and such treatment increases reactive oxygen species (ROS) in the kidney. The goal of this study was to evaluate the effects of the antioxidant N-acetylcysteine (NAC) on the progression of IFTA in 5/6NE mice. 5/6NE C57BL/6 and 5/6NE 129S1/SvImJ mice were treated with warfarin alone or with warfarin and NAC for 23 weeks. Serum creatinine (SCr), hematuria, blood pressure (BP), and ROSs in the kidney were measured; kidney morphology was evaluated. Warfarin doses were titrated to achieve prothrombin time (PT) increase to the levels seen with therapeutic human doses. Warfarin treatment resulted in an increased SCr, systolic BP, hematuria, expression of TGF-ß and ROS in the kidney in both mouse strains. Tumor necrosis factor alpha (TNF-ɑ) levels in the serum were increased in 5/6NE mice treated with warfarin. IFTA was increased as compared with control 5/6NE mice, and this increase in IFTA was more prominent in 129S1/SvImJ than in C57BL/6 mice. NAC ameliorated the warfarin-associated increase in SCr and BP but not hematuria. IFTA, TGF-ß, and ROS in the kidney as well as TNF-ɑ levels in the serum were reduced in mice treated with NAC and warfarin as compared to mice treated with warfarin alone. NAC mitigates the increase in SCr and IFTA in mice with chronic hematuria by reducing oxidative stress in the kidney. This data open novel possibilities for treatments in CKD patients.

Isolated arterial mucoid intimal thickening lesion in early post-transplant kidney allograft biopsies.

INTRODUCTION: Thrombotic microangiopathy (TMA) on kidney biopsy shows a variable combination of features: arterial mucoid intimal thickening, acellular closure of glomerular capillary loops, fragmented red blood cells, fibrin thrombi, and arterial fibrinoid necrosis. However, some early post-transplant kidney biopsies show only arterial mucoid intimal thickening. We aimed to elucidate the importance of this finding. METHODS: We identified 19 biopsies showing isolated arterial mucoid intimal thickening and compared them with 22 bona fide TMA biopsies identified based on the pathological findings (excluding rejection) (2011-2020). Additionally, delayed graft function (DGF) (n = 237), and no DGF (control, n = 1314) groups were included for survival analysis. RESULTS: Seven of 19 cases with isolated arterial mucoid intimal thickening showed peripheral blood schistocytes but no other systemic features of TMA. Eight patients underwent adjustments in maintenance immunosuppression (mainly calcineurin inhibitors). None of the cases progressed to full-blown TMA on consecutive biopsies. The overall and death-censored graft survival rates in this group were comparable to the DGF group, but significantly better than the TMA group (P = .005 and .04, respectively). CONCLUSIONS: Isolated arterial mucoid intimal thickening in early post-transplant biopsies may be an early/mild form of TMA, probably requiring adjustment in immunosuppressive regimen. Careful exclusion of known causes of TMA, and donor-derived arterial injury are important.

The Diagnostic Conundrum of Glomerular Crescents With IgA Deposits.

Introduction: Glomerulonephritis (GN) with crescents and IgA deposits in kidney biopsy poses a frequent diagnostic and therapeutic dilemma because of multiple possibilities. Methods: Native kidney biopsies showing glomerular IgA deposition and crescents (excluding lupus nephritis) were identified from our biopsy archives between 2010 and 2021. Detailed clinicopathologic features were assessed. One-year clinical follow-up on a subset of cases was obtained. Results: A total of 285 cases were identified, and these clustered into IgA nephropathy (IgAN, n = 108), Staphylococcus or other infection-associated GN/infection-related GN (SAGN/IRGN, n = 43), and antineutrophil cytoplasmic antibody-associated GN (ANCA-GN, n = 26) based on a constellation of clinicopathologic features, but 101 cases (group X) could not be definitively differentiated. The reasons have been elucidated, most important being atypical combination of clinicopathologic features and lack of definitive evidence of active infection. Follow-up (on 72/101 cases) revealed that clinicians' working diagnosis was IgAN in 43%, SAGN/IRGN in 22%, ANCA-GN in 28%, and others in 7% of the cases, but treatment approach varied from supportive or antibiotics to immunosuppression in each subgroup. Comparing these cases as "received immunosuppression" versus "non-immunosuppression," only 2 features differed, namely C3-dominant staining, and possibility of recent infection (both higher in the no-immunosuppression group) (P < 0.05). Renal loss was higher in the non-immunosuppression subgroup, but not statistically significant (P = 0.11). Conclusion: Diagnostic overlap may remain unresolved in a substantial number of kidney biopsies with glomerular crescents and IgA deposits. A case-by-case approach, appropriate antibiotics if infection is ongoing, and consideration for cautious immunosuppressive treatment for progressive renal dysfunction may be needed for best chance of renal recovery.

Research Letter: Is the 129S1/SvImJ Mouse Strain More Suitable to Study Anticoagulant-Related Nephropathy Than the C57BL/6 Strain?

Background: We have previously demonstrated that excessive anticoagulation with warfarin or dabigatran may result in acute kidney injury with red blood cell (RBC) tubular casts in some patients with chronic kidney disease, and this condition was named anticoagulant-related nephropathy (ARN). 5/6 nephrectomy (5/6NE) rats treated with warfarin or dabigatran reproduce the main pathologic features of human ARN. We had reported that 5/6NE C57BL/6 mice only partially develop ARN with increased serum creatinine and hematuria but no RBC tubular casts in the kidney. Objectives: The aim of this study was to investigate whether ARN can develop in 5/6NE 129S1/SvImJ mice. Methods: 5/6NE was performed in 129S1/SvImJ mice. Three weeks after 5/6NE, mice were treated with warfarin (1.0 and 1.5 mg/kg/day) or vehicle for 7 days. Serum creatinine, hematuria, and prothrombin time (PT) were monitored daily. Renal morphology was evaluated at the end of the studies. Results: Treatment with warfarin resulted in PT elevation 2 to 3 folds from baseline (1.0 mg/kg/day warfarin) and 4 to 5 folds from baseline (1.5 mg/kg/day warfarin) by day 7. Serum creatinine and hematuria elevated by day 7 in a dose-dependent manner. Histologically, 2 of 8 (25%) 5/6NE mice had RBCs in the tubules, and there was acute tubular epithelial cell injury in all warfarin-treated 5/6NE 129S1/SvImJ mice. Conclusions: Our findings suggest that 129S1/SvImJ mouse strain is a more suitable murine model to study ARN than C57BL/6 mouse strain.

Contexte: Nous avons précédemment démontré qu'un traitement anticoagulant excessif par warfarine ou dabigatran pouvait entraîner une insuffisance rénale aiguë avec formation de cylindres urinaires avec globules rouges (GR) chez certains patients atteints d'insuffisance rénale chronique. Cette affection a été nommée « néphropathie liée à un anticoagulant ¼ (NLA). Les rats 5/6NE (néphrectomie 5/6) traités par warfarine ou dabigatran reproduisent les principales caractéristiques pathologiques d'une NLA chez l'humain. Nous avions rapporté que les souris 5/6NE C57BL/6 ne développaient qu'une NLA partielle, présentant une augmentation de la créatinine sérique et de l'hématurie, mais aucune formation de cylindres urinaires avec GR dans les reins. Objectif: Vérifier si une NLA peut se développer chez les souris 5/6 NE 129S1/SvImJ. Méthodologie: Une 5/6NE a été réalisée chez des souris 129S1/SvImJ. Trois semaines après l'intervention, les souris ont été traitées avec de la warfarine (1,0 mg/kg/jour et 1,5 mg/kg/jour) ou un placebo pendant 7 jours. La créatinine sérique, l'hématurie et le temps de prothrombine (TP) ont été surveillés quotidiennement. La morphologie rénale a été évaluée à la fin des études. Résultats: Au jour 7, le traitement par warfarine avait entraîné une augmentation du TP de 2 à 3 fois par rapport à la mesure initiale pour le groupe traité avec 1,0 mg/kg/jour, et de 4 à 5 fois pour le groupe traité avec 1,5 mg/kg/jour. Les taux de créatinine sérique et l'hématurie s'étaient élevés en fonction de la dose. Sur le plan histologique, 2 souris 5/6NE sur 8 (25 %) avaient des globules rouges dans les tubules, et toutes les souris 5/6NE 129S1/SvImJ traitées avec la warfarine présentaient une atteinte aiguë des cellules tubulaires épithéliales. Conclusion: Nos résultats suggèrent que la souche de souris 129S1/SvImJ serait un modèle murin plus approprié que la souche C57BL/6 pour étudier la néphropathie liée à un anticoagulant.

Zinc finger protein 24-dependent transcription factor SOX9 up-regulation protects tubular epithelial cells during acute kidney injury.

Transcriptional profiling studies have identified several protective genes upregulated in tubular epithelial cells during acute kidney injury (AKI). Identifying upstream transcriptional regulators could lead to the development of therapeutic strategies augmenting the repair processes. SOX9 is a transcription factor controlling cell-fate during embryonic development and adult tissue homeostasis in multiple organs including the kidneys. SOX9 expression is low in adult kidneys; however, stress conditions can trigger its transcriptional upregulation in tubular epithelial cells. SOX9 plays a protective role during the early phase of AKI and facilitates repair during the recovery phase. To identify the upstream transcriptional regulators that drive SOX9 upregulation in tubular epithelial cells, we used an unbiased transcription factor screening approach. Preliminary screening and validation studies show that zinc finger protein 24 (ZFP24) governs SOX9 upregulation in tubular epithelial cells. ZFP24, a Cys2-His2 (C2H2) zinc finger protein, is essential for oligodendrocyte maturation and myelination; however, its role in the kidneys or in SOX9 regulation remains unknown. Here, we found that tubular epithelial ZFP24 gene ablation exacerbated ischemia, rhabdomyolysis, and cisplatin-associated AKI. Importantly, ZFP24 gene deletion resulted in suppression of SOX9 upregulation in injured tubular epithelial cells. Chromatin immunoprecipitation and promoter luciferase assays confirmed that ZFP24 bound to a specific site in both murine and human SOX9 promoters. Importantly, CRISPR/Cas9-mediated mutation in the ZFP24 binding site in the SOX9 promoter in vivo led to suppression of SOX9 upregulation during AKI. Thus, our findings identify ZFP24 as a critical stress-responsive transcription factor protecting tubular epithelial cells through SOX9 upregulation.

Clinicopathological differences between Bartonella and other bacterial endocarditis-related glomerulonephritis - our experience and a pooled analysis.

Background: Although Staphylococcus aureus is the leading cause of acute infective endocarditis (IE) in adults, Bartonella spp. has concomitantly emerged as the leading cause of "blood culture-negative IE" (BCNE). Pre-disposing factors, clinical presentation and kidney biopsy findings in Bartonella IE-associated glomerulonephritis (GN) show subtle differences and some unique features relative to other bacterial infection-related GNs. We highlight these features along with key diagnostic clues and management approach in Bartonella IE-associated GN. Methods: We conducted a pooled analysis of 89 cases of Bartonella IE-associated GN (54 published case reports and case series; 18 published conference abstracts identified using an English literature search of several commonly used literature search modalities); and four unpublished cases from our institution. Results: Bartonella henselae and Bartonella quintana are the most commonly implicated species causing IE in humans. Subacute presentation, affecting damaged native and/or prosthetic heart valves, high titer anti-neutrophil cytoplasmic antibodies (ANCA), mainly proteinase-3 (PR-3) specificity, fastidious nature and lack of positive blood cultures of these Gram-negative bacilli, a higher frequency of focal glomerular crescents compared to other bacterial infection-related GNs are some of the salient features of Bartonella IE-associated GN. C3-dominant, but frequent C1q and IgM immunofluorescence staining is seen on biopsy. A "full-house" immunofluorescence staining pattern is also described but can be seen in IE -associated GN due to other bacteria as well. Non-specific generalized symptoms, cytopenia, heart failure and other organ damage due to embolic phenomena are the highlights on clinical presentation needing a multi-disciplinary approach for management. Awareness of the updated modified Duke criteria for IE, a high index of suspicion for underlying infection despite negative microbiologic cultures, history of exposure to animals, particularly infected cats, and use of send-out serologic tests for Bartonella spp. early in the course of management can help in early diagnosis and initiation of appropriate treatment. Conclusion: Diagnosis of IE-associated GN can be challenging particularly with BCNE. The number of Bartonella IE-associated GN cases in a single institution tends to be less than IE due to gram positive cocci, however Bartonella is currently the leading cause of BCNE. We provide a much-needed discussion on this topic.

Triple hit to the kidney-dual pathological crescentic glomerulonephritis and diffuse proliferative immune complex-mediated glomerulonephritis: A case report.

BACKGROUND: Anti-glomerular basement membrane (GBM) disease is a rare rapidly progressive glomerulonephritis, frequently associated with alveolar hemorrhage in the lungs and involving the kidney by crescentic glomerulonephritis. It has been described in association with other glomerulonephritides [such as anti-neutrophilic antibody (ANCA)-glomerulonephritis, membranous nephropathy, and immunoglobulin (Ig)A nephropathy]. CASE SUMMARY: Herein we present an unusual case of concurrent anti-GBM disease, ANCA-associated crescentic glomerulonephritis and diffuse proliferative immune complex mediated glomerulonephritis with predominant staining for IgA and C3 by immunofluorescence. The patient is a 46-year-old Caucasian male who presented to the emergency department with acute onset of flank pain and was found to have high serum creatinine levels of 15 mg/dL, proteinuria, and hematuria. He rapidly deteriorated and became anuric. He was found to have high anti-GBM antibodies titers (151 units) and high anti-neutrophil cytoplasmic-ANCA. Despite prompt and early treatment, the patient's condition worsened, and he succumbed to his illness. CONCLUSION: Our case emphasizes the importance of a renal biopsy in anti-GBM disease, even in the presence of positive serum anti-GBM antibodies, to identify other potential causes of rapidly progressive glomerulonephritis. The challenge in treating such cases lies in the different therapy modalities.

Genomic Study on Blood Culture Isolates From Patients With Staphylococcus Infection-associated Glomerulonephritis.

Introduction: Staphylococcus infection-associated glomerulonephritis (SAGN), is an autoimmune sequela of infection affecting a subset of infected patients without specific predictive factors, frequently presenting with acute nephritic syndrome and propensity for chronic kidney disease. We performed a comparative genotypic and phenotypic analysis of S. aureus isolates from patients that did and those that did not develop SAGN. Methods: We had 22 culture-proven cases of SAGN from Ohio State University Wexner Medical Center (OSUWMC) from 2004 to 2016, 9 of 22 being blood cultures, with archived isolates. These, along with blood culture isolates from 12 patients with no clinical evidence of SAGN (between ages 40 to 80 years) over the same period were used for genotyping. For host demographic comparison, we used all available SAGN cases (n = 85, including those with positive cultures other than blood; and patients with kidney biopsies received from referring hospitals) and all OSUWMC patients with positive Staphylococcus cultures without glomerulonephritis (GN) (n = 23,496). Results: Multiple sequence types (STs) suggesting strain diversity was seen in the GN isolates with mainly clonal complexes (CC) 5 and 59. Mutations in the agr operon were identified in significantly higher number of the GN isolates (83%) than non-GN isolates (16%). Significant differences in ß-hemolysis and biofilm formation was also observed between the groups. Conclusion: The functionality of these agr mutants remains to be seen, but the presently known effects of reduced agr function, namely increased surface adhesins, biofilm formation, and persistent bacteremia could be important microbial factors predisposing to SAGN and testing for them early during infection could help to predict its development.

Role of protease-activated receptor-1 (PAR-1) in the glomerular filtration barrier integrity.

Protease-activated receptors (PAR) play an important role in the regulation of cellular function by the coagulation system, and they are activated by thrombin. PAR-1 is expressed in both endothelial cells and podocytes in the kidney. The role of PAR1 in the maintenance of the glomerular filtration barrier is not clear. Anticoagulant-related nephropathy (ARN) is a kidney disease with glomerular hematuria and red blood cell tubular casts. We validated 5/6 nephrectomy (5/6NE) in rats as a model of ARN and had demonstrated that direct thrombin inhibitor (dabigatran) induces ARN. The aim of this study was to investigate the role of PAR-1 in the ARN pathogenesis. 5/6NE rats were treated with dabigatran (150 mg/kg/day), PAR-1 inhibitor SCH79797 (1 and 3 mg/kg/day) and PAR-1 agonist TFLLR-NH2 (0.25 and 0.50 µmol/kg/day) for 7 days. Serum creatinine and hematuria were assessed daily. Kidney morphology was evaluated at the end of the study. In 5/6NE rats treated with either dabigatran or combination with a PAR-1 modulator, there was an elevation in serum creatinine, glomerular hematuria, red blood casts in the tubules, and acute tubular epithelial cell injury. Interestingly, both PAR-1 modulators in a dose-depended manner had similar effects on the serum creatinine levels and hematuria as those of dabigatran. Dabigatran-induced increase in the systolic blood pressure was not affected by PAR-1 modulators. In conclusion, the normal function of PAR-1 is crucial to maintain the glomerular filtration barrier integrity. Either activation or blockage of PAR-1 leads to glomerular hematuria and subsequent acute tubular epithelial cell injury.