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.

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.

Immunostaining for galactose-deficient immunoglobulin A is not specific for primary immunoglobulin A nephropathy.

BACKGROUND: Primary immunoglobulin A nephropathy (IgAN) is characterized by IgA1-dominant or codominant glomerular deposits, postulated to be galactose deficient (Gd). However, glomerular IgA deposition can also occur in nonrenal diseases such as liver cirrhosis, psoriasis and inflammatory bowel disease ('secondary IgAN') or be an incidental finding in biopsies with other pathologies. A glomerulonephritis resembling IgAN can develop in patients with bacterial, mainly staphylococcal infections [staphylococcal infection-associated glomerulonephritis (SAGN)]. There are no specific histological features to distinguish between these, but differentiation is critical for appropriate management. The aim of this study was to investigate whether a recently described antibody to Gd-IgA1 (KM-55) could aid in differentiating primary IgAN from other conditions with glomerular IgA deposition, especially SAGN. METHODS: We performed a retrospective cohort study of patients who underwent kidney biopsy for clinical indications and were found to have glomerular IgA deposits. RESULTS: We evaluated 100 biopsies, including primary IgAN (n = 44), secondary IgAN (n = 27), SAGN (n = 13), incidental IgA deposition (n = 8) and lupus nephritis (n = 8). There was no difference in Gd-IgA staining intensity or the proportion of positive cases between primary and secondary IgAN. SAGN and cases with incidental IgA deposits had significantly lower Gd-IgA staining intensity than primary IgAN, but up to 69% of SAGN cases were positive (albeit weaker). CONCLUSIONS: Gd-IgA staining is present not only in primary IgAN, but also in biopsies with secondary IgAN, SAGN and incidental IgA. Weak or negative staining may favor SAGN, especially in the setting of infection, or incidental IgA in the absence of nephritic symptoms or in the presence of other unrelated glomerular pathologies. However, positive staining for Gd-IgA alone is not specific enough for a diagnosis of primary IgAN.

Diffuse "background" monoclonal light chain staining on kidney biopsies in the absence of electron-dense deposits - putting it into perspective: A retrospective cohort study.

BACKGROUND: Pathologic diagnosis of monoclonal gammopathy (MIg)-associated kidney disease requires specific morphologic and immunofluorescence (IF) findings with deposits on electron microscopy. We have encountered kidney biopsies showing only diffuse "background" monoclonal light chain staining, without characteristic morphologic or ultrastructural findings. Such staining is often overlooked if weak, or over-diagnosed as MIg-associated kidney disease if strong, causing dilemma over the need for immediate clone-directed therapy. We performed a clinicopathologic study to better understand its significance. MATERIALS AND METHODS: Database search revealed 32 such cases over 12 years. Demographic, laboratory, and pathology data were retrieved along with a mean follow-up of 13 months. RESULTS: 15/32 (47%) patients did have active myeloma on hematologic testing (without myeloma casts) warranting immediate clone-directed therapy; but 11/32 (34%) did not develop active myeloma; 3/32 (9%) did not even have detectable paraprotein; 3/32 (9%) were lost to follow-up. Importantly, strong background light chain staining was seen even in some non-myeloma biopsies and conversely, weak staining was seen in some myeloma biopsies, complicating diagnosis. CONCLUSION: It is important to recognize and document this finding in the biopsy report, but by itself, it should not be classified as MIg-associated kidney disease even in the face of strong staining intensity. A thorough hematologic work-up is critically important to unmask underlying active myeloma, which many patients may have. But equally important is to avoid inadvertent clone-directed therapy in patients who do not have active myeloma despite the background monoclonal staining. A protocol for periodic monitoring with hematologic and renal parameters to watch for possible malignant transformation is recommend for timely implementation of therapy to minimize renal damage.

Eculizumab deposits in vessel walls in thrombotic microangiopathy.

Terminal complement inhibition therapy with eculizumab (a humanized monoclonal antibody to C5) has revolutionized the treatment of patients with thrombotic microangiopathy (TMA). Successful responders are often placed on long-standing therapy to prevent disease recurrence in the native kidney or allograft. The tissue deposition of eculizumab in patients with C3 glomerulopathy has been described but no studies have yet investigated tissue deposition of eculizumab in cases where it was indicated for thrombotic microangiopathy which, unlike C3 glomerulopathy, does not usually show immune-type electron dense deposits. To evaluate this, we reviewed biopsies from 13 patients who received eculizumab for TMA treatment or prevention of recurrence. We found IgG2, IgG4, and kappa positivity within arterioles corresponding to eculizumab deposits, with similar distribution to C5b-9, in all but one patient. In that patient eculizumab therapy had been discontinued 24 months prior to biopsy. Deposits in arterioles could be seen as early as one day after infusion and after a single dose of eculizumab, and were detected up to 162 days after therapy discontinuation. This may play a role in controlling local complement activation-associated vascular changes in these patients. Thus, IgG subclass staining by immunofluorescence is important to avoid misdiagnoses of immune-complex or monoclonal immunoglobulin deposition disease in patients with TMA who received eculizumab.

Complete biopsy-proven resolution of deposits in recurrent proliferative glomerulonephritis with monoclonal IgG deposits (PGNMIGD) following rituximab treatment in renal allograft.

BACKGROUND: Proliferative glomerulonephritis with monoclonal IgG deposits (PGNMIGD) is a disease entity classified under the group of "Monoclonal gammopathy-related kidney diseases", and can recur after transplant. Clinical remission of proteinuria in patients with PGNMIGD has been previously shown following anti-B cell and/or anti-plasma cell therapies. Our case is the first to show complete histologic resolution of the glomerular monoclonal IgG kappa deposits in a case of recurrent PGNMIGD in renal allograft after rituximab and steroid treatment. This is a novel finding and it shows that the deposits are amenable to therapy. This case also highlights the importance of IgG subclass staining in the recognition of the monoclonal nature of the deposits. It is particularly important in PGNMIGD because only 20 to 30% of patients with this disease are reported to have detectable monoclonal gammopathy, and the deposits do not have any organized substructure on electron microscopic examination. Morphologically, they resemble polyclonal immune-type deposits seen in other immune complex glomerulonephritides such as lupus nephritis, infection-associated glomerulonephritis, and membranoproliferative glomerulonephritis (MPGN type I). CASE PRESENTATION: The patient is a 44 year old Caucasian male who received a living unrelated donor kidney transplant for end-stage renal disease diagnosed 7 years before transplant. The reported native kidney biopsy diagnosis was membranoproliferative glomerulonephritis (MPGN) with IgG, C3 and kappa restricted deposits. Fourteen months post-transplant, he presented with abrupt worsening of graft function, proteinuria and serum IgG kappa monoclonal spike. Allograft biopsy was consistent with recurrent PGNMIGD, considering the native kidney diagnosis and interval post-transplant. He underwent plasmapheresis, IV pooled immune globulin, steroid pulse and taper, and anti-CD-20 Rituximab therapy. Patient had gradual decline in proteinuria and complete resolution of the immune deposits on repeat biopsy 3 months later. Unfortunately he subsequently developed chronic antibody-mediated rejection and transplant glomerulopathy and graft failure 34 months post-transplant. CONCLUSIONS: In a transplant setting, repeat allograft biopsies are frequently performed for graft dysfunction. This provides a good opportunity to study the evolution of the immune deposits following treatment. Our case shows complete histologic resolution of the deposits in allograft PGNMIGD.

Differential gene expression pattern in biopsies with renal allograft pyelonephritis and allograft rejection.

Differentiating acute pyelonephritis (APN) from acute rejection (AR) in renal allograft biopsies can sometimes be difficult because of overlapping clinical and histologic features, lack of positive urine cultures,and variable response to antibiotics. We wanted to study differential gene expression between AR and APN using biopsy tissue. Thirty-three biopsies were analyzed using NanoString multiplex platform and PCR (6 transplant baseline biopsies, 8 AR, 15 APN [8 culture positive, 7 culture negative], and 4 native pyelonephritis [NP]). Additional 22 biopsies were tested by PCR to validate the results. CXCL9, CXCL10, CXCL11, and IDO1 were the top differentially expressed genes, upregulated in AR. Lactoferrin (LTF) and CXCL1 were higher in APN and NP. No statistically significant difference in transcript levels was seen between culture-positive and culture-negative APN biopsies. Comparing the overall mRNA signature using Ingenuity pathway analysis, interferon-gamma emerged as the dominant upstream regulator in AR and allograft APN, but not in NP (which clustered separately). Our study suggests that chemokine pathways in graft APN may differ from NP and in fact resemble AR, due to a component of alloreactivity, resulting in variable response to antibiotic treatment. Therefore, cautious addition of steroids might help in resistant cases of graft APN.

An unexpected cause of acute kidney injury in a patient with ANCA associated vasculitis.

Diagnostic kidney biopsies sometimes yield clinically unsuspected diagnoses. We present a case of a 69-year-old woman with established ANCA-associated vasculitis (AAV) of 4 years duration who was in clinical remission following cytotoxic therapy and was on maintenance immunosuppression. She presented to the hospital with acute kidney injury (AKI), symptoms suggestive of a systemic vasculitis, and in addition had hypercalcemia, metabolic alkalosis. A relapse in the AAV was suspected but a diagnostic kidney biopsy showed acute tubular necrosis, patchy interstitial inflammation, and calcium phosphate deposits. It was found that the patient recently started consuming large doses of over-the-counter calcium-containing antacids and vitamin Dcontaining multivitamin supplements. Cessation of these drugs led to improvement of renal function to baseline. This case highlights several teaching points: (1) the kidney biopsy can prove to be critically important even in cases where there appears to be a more obvious clinical diagnosis, (2) AK due to calcium-alkali syndrome has characteristic histopathological changes, and (3) that the triad of hypercalcemia, metabolic alkalosis, and AKI is exclusively associated with the ingestion of excessive quantities of calcium-containing antacids. The physician should keep this in mind, and pro-actively seek pertinent medication history from the patient. A brief review of calcium-alkali syndrome is given.

Brodifacoum induces early hemoglobinuria and late hematuria in rats: novel rapid biomarkers of poisoning.

INTRODUCTION: Brodifacoum (BDF) is a superwarfarin that is used primarily as a rodenticide. There have been increasing numbers of reports of human cases of accidental or intentional BDF ingestion with high mortality rate. Its broad availability and high lethality suggest that BDF should be considered a potential chemical threat. Currently, there is no biomarker for early detection of BDF ingestion in humans; patients typically present with severe coagulopathy. Since we demonstrated earlier that warfarin can induce acute kidney injury with hematuria, we tested whether BDF would also lead to change in urinary biomarkers. MATERIAL AND METHODS: BDF was administered to Sprague Dawley rats via oral gavage. N-acetylcysteine (NAC) was given per os in drinking water 24 h prior to BDF. Urinalysis was performed at different times after BDF administration. Anticoagulation and serum creatinine levels were analyzed in the blood. RESULTS: We observed that within a few hours the animals developed BDF-dose-dependent transient hemoglobinuria, which ceased within 24 h. This was accompanied by a transient decrease in hematocrit, gross hemolysis and an increase in free hemoglobin in the serum. At later times, animals developed true hematuria with red blood cells in the urine, which was associated with BDF anticoagulation. NAC prevented early hemoglobinuria, but not late hematuria associated with BDF. CONCLUSIONS: We propose that transient early hemoglobinuria (associated with oxidative stress) with consecutive late hematuria (associated with anticoagulation) are novel biomarkers of BDF poisoning, and they can be used in clinical setting or in mass casualty with BDF to identify poisoned patients.

Acute kidney injury and hyperbilirubinemia in a young male after ingestion of Tribulus terrestris.

Acute tubular necrosis (ATN), especially from toxic injury is frequently accompanied by tubular casts and crystals. Myeloma casts, myoglobin, red blood cell and granular casts are well described. However, bile casts in tubules are rarely seen. We describe a case of Tribulus terrestris toxicity in a young healthy male, presenting with severe hyperbilirubinemia followed by acute renal failure and bile containing casts in the tubules. Tribulus terrestris is an herb often used by athletes as a nutritional supplement for performance enhancement. Although it is thought to be relatively safe, serious side effects have been reported before. Our aim is to increase awareness of the potential toxicities of performance enhancing herbal medications. These are often sold over-the-counter and therefore casually used, especially by young healthy individuals. Beneficial effects are controversial. Under-reporting by patients and infrequent documentation by health-care providers can delay diagnosis. We elaborately describe the kidney biopsy findings in Tribulus terrestris toxicity, and also provide a concise overview of the spectrum of tubular casts and their staining patterns, found in various kidney diseases.

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.

N-acetylcysteine ameliorates acute kidney injury but not glomerular hemorrhage in an animal model of warfarin-related nephropathy.

Warfarin-related nephropathy (WRN) occurs under conditions of overanticoagulation with warfarin. WRN is characterized by glomerular hemorrhage with occlusive tubular red blood cell (RBC) casts and acute kidney injury (AKI). Herein we test the hypothesis that oxidative stress plays a role in the AKI of WRN. 5/6 Nephrectomy rats were treated with either warfarin (0.04 mg·kg⁻¹·day⁻¹) alone or with four different doses of the antioxidant N-acetylcysteine (NAC). Also tested was the ability of our NAC regimen to mitigate AKI in a standard ischemia-reperfusion model in the rat. Warfarin resulted in a threefold or greater increase in prothrombin time in each experimental group. Serum creatinine (Scr) increased progressively in animals receiving only warfarin + vehicle. However, in animals receiving warfarin + NAC, the increase in Scr was lessened, starting at 40 mg·kg⁻¹·day⁻¹ NAC, and completely prevented at 80 mg·kg⁻¹·day⁻¹ NAC. NAC did not decrease hematuria or obstructive RBC casts, but mitigated acute tubular injury. Oxidative stress in the kidney was increased in animals with WRN and it was decreased by NAC. The NAC regimen used in the WRN model preserved kidney function in the ischemia-reperfusion model. Treatment with deferoxamine (iron chelator) did not affect WRN. No iron was detected in tubular epithelial cells. In conclusion, this work taken together with our previous works in WRN shows that glomerular hematuria is a necessary but not sufficient explanation for the AKI in WRN. The dominant mechanism of the AKI of WRN is tubular obstruction by RBC casts with increased oxidative stress in the kidney.

Henoch-Schönlein purpura-like presentation in IgA-dominant Staphylococcus infection - associated glomerulonephritis - a diagnostic pitfall.

BACKGROUND: In children and adults, Henoch-Schönlein purpura (HSP) has a characteristic clinical presentation that includes a purpuric lower extremity skin rash, IgA-dominant glomerulonephritis, and abdominal and joint pain. A similar clinical presentation can be seen in adults who have a systemic infection with methicillin-resistant Staphylococcus aureus. It is critically important to distinguish the IgAdominant glomerulonephritis of HSP from the IgA-dominant glomerulonephritis of staphylococcal infection, because HSP may need to be treated with corticosteroids and immunosuppressives, while Staphylococcus infection-associated glomerulonephritis requires antibiotics. DESIGN: We searched our renal biopsy database for cases of Staphylococcus infection-associated IgA-dominant glomerulonephritis, to identify those with an HSP-like presentation. Their clinical, laboratory, and biopsy findings are reviewed. RESULTS: Between 2004 and 2011, we identified 37 patients with culture-proven Staphylococcus infection-associated glomerulonephritis. Of these, 8 (22%) had an HSP-like presentation manifested by lower extremity purpuric skin rash. Mesangial IgA and C3 deposits were consistent findings on kidney biopsy. Crescents were uncommon. Four of the 8 patients received glucocorticoid (steroid) therapy for a presumed diagnosis of HSP. Renal function worsened in 3 patients, and 1 patient ultimately improved but developed sepsis during the course. Overall, renal outcome was poor in 71% of the cases despite mild chronic renal injury in the biopsy. CONCLUSION: In adult patients with an HSPlike presentation, a high index of suspicion for underlying Staphylococcal infection is warranted. Blood cultures are frequently negative. Cultures from the site of infection should be performed. Steroid treatment did not improve outcomes. Renal outcomes were frequently poor.

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.

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.

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.

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.

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.