Process Effacement Research Articles

The sodium-glucose cotransporter 2 inhibitor tofogliflozin prevents diabetic kidney disease progression in type 2 diabetic mice.

Trials on cardiovascular and renal outcomes in patients with type 2 diabetes have consistently demonstrated that sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce the risk of diabetic kidney disease (DKD) progression. However, their renal protective mechanisms have yet to be completely understood and the effect on albuminuria reduction in animal models is controversial. We investigated these issues using KK and KK-Ay mice as a control (CTRL) and as a model for type 2 diabetes (DKD), respectively. KK-Ay mice were treated with 0.015% tofogliflozin, which is an SGLT2 inhibitor, starting at seven weeks of age for eight weeks. Compared with the CTRL mice, the DKD mice had higher HbA1c levels and albuminuria. Although tofogliflozin treatment significantly lowered HbA1c levels, it did not reverse albuminuria. Tofogliflozin treatment enhanced damage in both the glomerular (i.e., enlarged mesangial area, increased foot process effacement rate, and decreased number of WT-1-positive cells) and tubulointerstitial (increased protein levels of KIM-1 and MCP-1, increased number of macrophages, and abnormal mitochondrial morphology) areas. Our results suggest that tofogliflozin may prevent glomerular and tubulointerstitial damage, partly by ameliorating hyperglycemia, renal inflammation, and abnormalmitochondrial morphology.

Glomerular filtration barrier dysfunction in a self-limiting, RNA virus-induced glomerulopathy resembles findings in idiopathic nephrotic syndromes

Podocyte injury has recently been described as unifying feature in idiopathic nephrotic syndromes (INS). Puumala hantavirus (PUUV) infection represents a unique RNA virus-induced renal disease with significant proteinuria. The underlying pathomechanism is unclear. We hypothesized that PUUV infection results in podocyte injury, similar to findings in INS. We therefore analyzed standard markers of glomerular proteinuria (e.g. immunoglobulin G [IgG]), urinary nephrin excretion (podocyte injury) and serum levels of the soluble urokinase plasminogen activator receptor (suPAR), a proposed pathomechanically involved molecule in INS, in PUUV-infected patients. Hantavirus patients showed significantly increased urinary nephrin, IgG and serum suPAR concentrations compared to healthy controls. Nephrin and IgG levels were significantly higher in patients with severe proteinuria than with mild proteinuria, and nephrin correlated strongly with biomarkers of glomerular proteinuria over time. Congruently, electron microcopy analyses showed a focal podocyte foot process effacement. suPAR correlated significantly with urinary nephrin, IgG and albumin levels, suggesting suPAR as a pathophysiological mediator in podocyte dysfunction. In contrast to INS, proteinuria recovered autonomously in hantavirus patients. This study reveals podocyte injury as main cause of proteinuria in hantavirus patients. A better understanding of the regenerative nature of hantavirus-induced glomerulopathy may generate new therapeutic approaches for INS.

In situ evaluation of podocytes in patients with focal segmental glomerulosclerosis and minimal change disease.

Podocyte injury in focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) results from the imbalance between adaptive responses that maintain homeostasis and cellular dysfunction that can culminate in cell death. Therefore, an in situ analysis was performed to detect morphological changes related to cell death and autophagy in renal biopsies from adult patients with podocytopathies. Forty-nine renal biopsies from patients with FSGS (n = 22) and MCD (n = 27) were selected. In situ expression of Wilms Tumor 1 protein (WT1), light chain microtubule 1-associated protein (LC3) and caspase-3 protein were evaluated by immunohistochemistry. The foot process effacement and morphological alterations related to podocyte cell death and autophagy were analyzed with transmission electronic microscopy. Reduction in the density of WT1-labeled podocytes was observed for FSGS and MCD cases as compared to controls. Foot process width (FPW) in control group was lower than in cases of podocytopathies. In FSGS group, FPW was significantly higher than in MCD group and correlated with proteinuria. A density of LC3-labeled podocytes and the number of autophagosomes in podocytes/ pedicels were higher in the MCD group than in the FSGS group. The number of autophagosomes correlated positively with the estimated glomerular filtration rate in cases of MCD. The density of caspase-3-labeled podocytes in FSGS and MCD was higher than control group, and a higher number of podocytes with an evidence of necrosis was detected in FSGS cases than in MCD and control cases. Podocytes from patients diagnosed with FSGS showed more morphological and functional alterations resulting from a larger number of lesions and reduced cell adaptation.

Novel Evidence of Acute Kidney Injury in COVID-19.

The coronavirus 2019 (COVID-19) pandemic has caused a huge impact on health and economic issues. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes cellular damage by entry mediated by the angiotensin-converting enzyme 2 of the host cells and its conjugation with spike proteins of SARS-CoV-2. Beyond airway infection and acute respiratory distress syndrome, acute kidney injury is common in SARS-CoV-2-associated infection, and acute kidney injury (AKI) is predictive to multiorgan dysfunction in SARS-CoV-2 infection. Beyond the cytokine storm and hemodynamic instability, SARS-CoV-2 might directly induce kidney injury and cause histopathologic characteristics, including acute tubular necrosis, podocytopathy and microangiopathy. The expression of apparatus mediating SARS-CoV-2 entry, including angiotensin-converting enzyme 2, transmembrane protease serine 2 (TMPRSS2) and a disintegrin and metalloprotease 17 (ADAM17), within the renal tubular cells is highly associated with acute kidney injury mediated by SARS-CoV-2. Both entry from the luminal and basolateral sides of the renal tubular cells are the possible routes for COVID-19, and the microthrombi associated with severe sepsis and the dysregulated renin–angiotensin–aldosterone system worsen further renal injury in SARS-CoV-2-associated AKI. In the podocytes of the glomerulus, injured podocyte expressed CD147, which mediated the entry of SARS-CoV-2 and worsen further foot process effacement, which would worsen proteinuria, and the chronic hazard induced by SARS-CoV-2-mediated kidney injury is still unknown. Therefore, the aim of the review is to summarize current evidence on SARS-CoV-2-associated AKI and the possible pathogenesis directly by SARS-CoV-2.

Mechanisms of vascular dysfunction in the interleukin-10–deficient murine model of preeclampsia indicate nitric oxide dysregulation

Preeclampsia is a pregnancy-specific hypertensive disorder characterized by proteinuria, and vascular injury in the second half of pregnancy. We hypothesized that endothelium-dependent vascular dysfunction is present in a murine model of preeclampsia based on administration of human preeclamptic sera to interleukin-10-/- mice and studied mechanisms that underlie vascular injury. Pregnant wild type and IL-10-/- mice were injected with either normotensive or severe preeclamptic patient sera (sPE) during gestation. A preeclampsia-like phenotype was confirmed by blood pressure measurements; assessment of albuminuria; measurement of angiogenic factors; demonstration of foot process effacement and endotheliosis in kidney sections; and by accumulation of glycogen in placentas from IL-10-/- mice injected with sPE sera (IL-10-/-sPE). Vasomotor function of isolated aortas was assessed. The IL-10-/-sPE murine model demonstrated significantly augmented aortic contractions to phenylephrine and both impaired endothelium-dependent and, to a lesser extent, endothelium-independent relaxation compared to wild type normotensive mice. Treatment of isolated aortas with indomethacin, a cyclooxygenase inhibitor, improved, but failed to normalize contraction to phenylephrine to that of wild type normotensive mice, suggesting the additional contribution from nitric oxide downregulation and effects of indomethacin-resistant vasoconstricting factors. In contrast, indomethacin normalized relaxation of aortas derived from IL-10-/-sPE mice. Thus, our results identify the role of IL-10 deficiency in dysregulation of the cyclooxygenase pathway and vascular dysfunction in the IL-10-/-sPE murine model of preeclampsia and point towards a possible contribution of nitric oxide dysregulation. These compounds and related mechanisms may serve both as diagnostic markers and therapeutic targets for preventive and treatment strategies in preeclampsia.

Identification of Lupus Podocytopathy with Coexistent Glomerular Diseases – A Case Report

Abstract Introduction/Objective Lupus podocytopathy (LP), featured by nephrotic syndrome, is a unique subtype of lupus nephritis that mimics minimal change disease or primary focal segmental glomerulosclerosis (FSGS) on renal biopsy with diffuse podocyte foot process effacement and no capillary-loop immune deposits. LP usually presents on a background of ISN/RPS class I or class II lupus nephritis, and very rarely may present without immune deposits. Diagnosis of LP, when confounded by other glomerular diseases associated with nephrotic syndrome, can be very challenging and requires thorough clinical and pathology correlations. Methods Here we report a case of LP in a patient with nephrotic syndrome and multiple comorbidities affecting kidneys. A 24-year-old female with type-I diabetes, psoriasis, and intermittent arthritis/rash of unknown etiology, presented with abrupt onset of nephrotic proteinuria attributed to recent low dose prednisone therapy, and renal insufficiency. A renal biopsy showed nodular glomerulosclerosis and FSGS. No immune deposits were identified by immunofluorescence or electron microscopy. Ultrastructurally there was also diffuse glomerular basement membrane thickening and over 90% podocyte foot process effacement. With no established systemic lupus erythematosus (SLE), the case was initially diagnosed as diabetic nephropathy with coexistent FSGS as the etiologies for nephrotic proteinuria, and the patient was put on ACEI and diuretics. However, massive proteinuria persisted, and the patient also developed pancytopenia. Serology concurrent with the biopsy came out later showing positive autoantibodies against dsDNA, Smith, and Histone. With continued worsening of creatinine, a renal biopsy was repeated revealing essentially similar findings to the first biopsy. Results Integrating the serology results and clinical presentation, SLE was favored. The pathology findings were re- evaluated and considered to be most consistent with LP and coexistent diabetic nephropathy, with FSGS either a component of LP or an independent lesion secondary to diabetes or hypertension. The patient was started with high dose prednisone at 60 mg/day. One month later, her proteinuria, serum creatinine, pancytopenia, skin rash, and arthritis were all significantly improved. Conclusion LP can be easily masked by coexistent glomerular diseases. Sufficient awareness of the entity is necessary for the appropriate diagnosis and treatment.

The Rare First Manifestation Of Mantle Cell Lymphoma As Immune Complex Glomerulonephritis With Crescents And Membranoproliferative Features

Abstract Introduction/Objective Initial presentation of Non-Hodgkin Lymphoma (NHL) with immune complex glomerulonephritis (ICGN) is rare. Mantle cell lymphoma (MCL) is a rare aggressive lymphoma comprising 3–7 % of all NHL and ICGN as the first manifestation of MCL is very unusual. Methods We report a 73 year-old-man with increased serum creatinine (2.1 mg/dl) from normal baseline 3 months ago. Urinalysis showed the presence of dysmorphic RBCs, RBC casts and 300 mg/dl of protein. Physical examination revealed diffuse lymphadenopathy. Hepatitis C and B Ab, HIV screen, ANA, ANCA, Anti dsDNA Ab, Anti GBM Ab, and Serum protein electrophoresis were normal or negative. Results The renal biopsy showed Immune complex glomerulonephritis with (25%) fibrocellular/cellular crescents and focal membranoproliferative (MPGN) features. There were foci of dense monomorphic lymphoid aggregates of small lymphocytes and 30% interstitial fibrosis with corresponding tubular atrophy. No tubulitis was present. Direct Immunofluorescence showed 2+ to 4+ granular mesangial and capillary loop staining for Total Ig, IgG, IgA, IgM, C1q, C3 and C4. The lymphoid aggregate was monoclonal Kappa. Electron microscopy showed widespread podocyte foot process effacement, subendothelial and rare mesangial dense deposits. Excisional lymph node biopsy flow cytometry showed a monoclonal population of CD19+, CD20+, CD22+, CD5+, skappa-restricted, CD10-, CD11c-, CD23-, CD25- CD38-, CD103-, CD200- B- cells. Cyclin D1 was positive on immunostain, consistent with stage IV (renal) MCL. He received chemotherapy with steroids, bendamustine, and rituximab leading to resolution of lymphadenopathy and proteinuria and improvement in serum creatinine. Conclusion It is important to recognize that the first manifestation of MCL may present as renal involvement in the form of ICGN and, as in this case, with fibrocellular/cellular crescents and a focal MPGN pattern. This is an extremely rare, but important, cause of renal insufficiency that can be successfully treated with lymphoma chemotherapy.

A Murine Model Of Kidney Injury: The role of SMPDL3b In Radiation And Cisplatin-Induced Nephrotoxicity

Cisplatin is widely used as a chemotherapeutic agent and a known radiosensitizer. The current study aimed to investigate the role of lipid-modulating enzyme sphingomyelin phosphodiesterase acid-like 3B (SMPDL3b) in cisplatin toxicity. Nephrotoxicity is dose-limiting toxicity. Cultured oocytes were treated with rituximab mAb (100 μg/ml) or IgG (100 μg/ml) 30 minutes before irradiation with 0-8 Gy, with or without Cisplatin (2μM). In other experiments, 10–14-week old C57BL/6 male and female mice were given bilateral kidney X-irradiation (4Gyx1, 6 Gyx5, and 2Gyx24) with or without Cisplatin (6mg/kg, IP). Animals received rituximab mAb (RTX) or IgG (50mg/kg; IV) 30 minutes before radiation treatment. Functional kidney parameters (serum BUN, hematocrit, and creatinine), histopathological assessments (oil red staining, H&E, Periodic Acid-Schiff, and TEM) and biochemical changes were studied at baseline, 10- and 20-weeks post-chemo-radiotherapy. Glomerular filtration rate (GFR) was estimated at 10- and 20-weeks post-radiation using FITC-sinistrin based transdermal monitor and iSMAART dynamic contrast-enhanced (DCE) imaging. RT and concurrent Cisplatin (2 μM) produced time-dependent apoptosis in wild-type human podocytes, causing an 85% increase in caspase 3 activity 2h post-RT (8Gy). Different doses of RT, 1x4Gy, 1x10Gy, and 1x14Gy increased glomerular base membrane (GBM) thickness in irradiated mice significantly (100%, 150%, and 200% respectively). Cisplatin and RT (1x4Gy) increased GBM thickness from 225nm to 425nm, respectively (p = 0.01). The eGFR values changed significantly from 1010±214 to 718±205, 687±175, 508±56, 596±180, and 639±221 mL/min after x4Gy, 1x10Gy, 1x14Gy, 5x6Gy, and 24x2Gy, respectively. RTX pretreatment improved eGFR and other functional parameters (serum BUN, hematocrit, serum creatinine, and urine albumin/creatinine ratio (ACR) significantly post chemoradiotherapy. RTX pretreatment protected podocytes cytoskeletal remodeling in vitro and foot process effacement in vivo. SMPDL3b expression and podocytes count significantly decreased post chemoradiotherapy. RTX ameliorated SMPDL3b down-regulation, and improved podocytes count significantly. This study shows that RTX pretreatment protects podocytopathy in vitro and chemoradiation induced kidney injury in vivo. SMPDL3b may be an important therapeutic target for radiation-induced kidney injuries in cancer patients.

Aging and chronic high-fat feeding negatively affect kidney size, function, and gene expression in CTRP1-deficient mice.

C1q/TNF-related protein 1 (CTRP1) is an endocrine factor with metabolic, cardiovascular, and renal functions. We previously showed that aged Ctrp1-knockout (KO) mice fed a control low-fat diet develop renal hypertrophy and dysfunction. Since aging and obesity adversely affect various organ systems, we hypothesized that aging, in combination with obesity induced by chronic high-fat feeding, would further exacerbate renal dysfunction in CTRP1-deficient animals. To test this, we fed wild-type and Ctrp1-KO mice a high-fat diet for 8 mo or longer. Contrary to our expectation, no differences were observed in blood pressure, heart function, or vascular stiffness between genotypes. Loss of CTRP1, however, resulted in an approximately twofold renal enlargement (relative to body weight), ∼60% increase in urinary total protein content, and elevated pH, and changes in renal gene expression affecting metabolism, signaling, transcription, cell adhesion, solute and metabolite transport, and inflammation. Assessment of glomerular integrity, the extent of podocyte foot process effacement, as well as renal response to water restriction and salt loading did not reveal significant differences between genotypes. Interestingly, blood platelet, white blood cell, neutrophil, lymphocyte, and eosinophil counts were significantly elevated, whereas mean corpuscular volume and hemoglobin were reduced in Ctrp1-KO mice. Cytokine profiling revealed increased circulating levels of CCL17 and TIMP-1 in KO mice. Compared with our previous study, current data suggest that chronic high-fat feeding affects renal phenotypes differently than similarly aged mice fed a control low-fat diet, highlighting a diet-dependent contribution of CTRP1 deficiency to age-related changes in renal structure and function.

Prolonged podocyte depletion in larval zebrafish resembles mammalian focal and segmental glomerulosclerosis.

Focal and segmental glomerulosclerosis (FSGS) is a histological pattern frequently found in patients with nephrotic syndrome that often progress to end-stage kidney disease. The initial step in development of this histologically defined entity is injury and ultimately depletion of podocytes, highly arborized interdigitating cells on the glomerular capillaries with important function for the glomerular filtration barrier. Since there are still no causal therapeutic options, animal models are needed to develop new treatment strategies. Here, we present an FSGS-like model in zebrafish larvae, an eligible vertebrate model for kidney research. In a transgenic zebrafish strain, podocytes were depleted, and the glomerular response was investigated by histological and morphometrical analysis combined with immunofluorescence staining and ultrastructural analysis by transmission electron microscopy. By intravenous injection of fluorescent high-molecular weight dextran, we confirmed leakage of the size selective filtration barrier. Additionally, we observed severe podocyte foot process effacement of remaining podocytes, activation of proximal tubule-like parietal epithelial cells identified by ultrastructural cytomorphology, and expression of proximal tubule markers. These activated cells deposited extracellular matrix on the glomerular tuft which are all hallmarks of FSGS. Our findings indicate that glomerular response to podocyte depletion in larval zebrafish resembles human FSGS in several important characteristics. Therefore, this model will help to investigate the disease development and the effects of potential drugs in a living organism.

Murine Epsins Play an Integral Role in Podocyte Function.

Epsins, a family of evolutionarily conserved membrane proteins, play an essential role in endocytosis and signaling in podocytes. Podocyte-specific Epn1, Epn2, Epn3 triple-knockout mice were generated to examine downstream regulation of serum response factor (SRF) by cell division control protein 42 homolog (Cdc42). Podocyte-specific loss of epsins resulted in increased albuminuria and foot process effacement. Primary podocytes isolated from these knockout mice exhibited abnormalities in cell adhesion and spreading, which may be attributed to reduced activation of cell division control protein Cdc42 and SRF, resulting in diminished β1 integrin expression. In addition, podocyte-specific loss of Srf resulted in severe albuminuria and foot process effacement, and defects in cell adhesion and spreading, along with decreased β1 integrin expression. Epsins play an indispensable role in maintaining properly functioning podocytes through the regulation of Cdc42 and SRF-dependent β1 integrin expression.

S2401 Hidden Immune Complexes: A Rare Case of Renal Failure Secondary to Hepatitis C Following Sustained Virologic Response

INTRODUCTION: Patients with cleared Hep C may still experience extrahepatic immunologic phenomena. CASE DESCRIPTION/METHODS: A 63 year-old woman with hepatitis C cirrhosis presented with a 20-pound weight gain and edema refractory to diuretics. She had been treated with sofosbuvir and ribavirin in 2013 with sustained virologic response (SVR) and was listed for liver transplant. She was hemodynamically stable and had 4+ pitting lower extremity edema. There was no jugular venous distention, crackles, or ascites. Labs showed sodium of 122 and creatinine of 1.43 compared to 137 and 0.61 three months prior, respectively, low complement levels and antinuclear antibody titer 1:320. Urine studies noted 6 gm of protein with protein/creatinine ratio of 6.3, 11–25 RBC, sodium 11, and osmolality 188. She was treated aggressively with diuretics with improvement of hyponatremia, but renal function worsened. She subsequently underwent a renal biopsy which revealed mesangial proliferation, foot process effacement, endocapillary proliferation, and immunofluorescence positive for C3, IgG, IgA, C1q, kappa, and lambda, all consistent with membranoproliferative glomerulonephritis (MPGN). Autoimmune causes including lupus, occult infections, dysproteinemias, and lymphoma were ruled out which raised the question of HCV as the etiology despite curative therapy. She underwent liver transplantation a week later and received mycophenolate and tacrolimus with marked improvement in renal function. DISCUSSION: MPGN is an uncommon cause of renal failure that can be complement- or mmune complex-mediated. The latter is most commonly associated with hepatitis C virus (HCV), although it can also be seen with hepatitis B. Our patient did not have any etiologies of secondary MPGN other than chronic HCV treated remotely. Given SVR, HCV was not initially thought to be a contributing factor. However, one previous study confirmed the presence of HCV-antigen-specific immune complexes without virions in 56.6% of patients involved who had spontaneous or treatment-induced clearance of HCV. Furthermore, another study demonstrated persistent HCV-associated cryoglobulinemic glomerulonephritis in those who achieved SVR with direct-acting antiviral therapy and postulated this may be due to residual rheumatoid factor-producing B-cell clones. This suggests that despite resolution of HCV and absence of ongoing viral replication, the accompanying immunologic phenomena may persist. Therefore, treated HCV should not be dismissed as potential cause of MPGN.

Severity of foot process effacement is associated with proteinuria in patients with IgA nephropathy.

BackgroundProteinuria is a significant risk factor for progression of IgA nephropathy (IgAN) and has a positive correlation with severity of foot process effacement (FPE). We evaluated the relationship of FPE with proteinuria and histologic characteristics, including the Oxford classification.MethodsPatients who underwent renal biopsy and were diagnosed with IgAN at a single center were retrospectively reviewed. Patients aged less than 18 years and those with the possibility of secondary causes were excluded from the study. Subsequently, we evaluated the association between degree of proteinuria, severity of FPE, and histologic characteristics, including the Oxford classification and other immunofluorescence stains.ResultsA total of 805 cases of renal biopsy was performed at our institution, and 327 patients were diagnosed with IgAN. Among them, 82 patients were excluded. Severity of FPE had an impact on the degree of proteinuria. Notably, the group with diffuse FPE had more than about 1.3 g/day of urine protein compared to those with rare FPE. Among the histologic characteristics, M1 score and immune deposition of IgG affected severity of FPE (hazard ratios [95% confidence interval], 1.90 [1.10 to 3.26], and 3.77 [1.66 to 8.54], respectively).ConclusionSeverity of FPE had an impact on the degree of proteinuria and may be associated with the pathogenesis of IgAN.

A case of minimal change disease after the administration of anti receptor activator of nuclear factor kappa B ligand (RANKL) monoclonal antibody: a case report

BackgroundMinimal change disease (MCD) is one of the causes of idiopathic nephrotic syndrome in adults. The pathogenesis of proteinuria in MCD has not been fully understood. Recently, it has been reported that the receptor activator of nuclear factor-kappa B (RANK)/RANK ligand (RANKL) may contribute to the podocyte biology in kidney diseases. Denosumab is a human anti-RANKL monoclonal antibody used to treat osteoporosis. Here we report a case of MCD after denosumab administration.Case presentationA 59-year-old male without any episodes of proteinuria was given denosumab to treat osteoporosis. Two weeks after its administration, he noticed a foamy urine and bilateral pretibial edema. Laboratory tests revealed that he had severe proteinuria (15g/g Cr), hypoproteinemia (4.0g/dL), and hypoalbuminemia (1.5g/dL). Based on the results, he was diagnosed with nephrotic syndrome. The proteinuria selectivity index was 0.05, indicating selective proteinuria. Renal biopsy showed minor glomerular abnormality with less tubulointerstitial damage, and electron microscopy showed extensive foot process effacement, indicating MCD. With all these results, glucocorticoid therapy of 50mg/day prednisolone was started. After 4weeks of treatment, the urinary protein level remains high (3.1g/g Cr). Prednisolone therapy was continued, and the levels of proteinuria decreased gradually to the range of partial remission (1.2g/g Cr) with another 7weeks of prednisolone treatment, but complete remission was not achieved.ConclusionsThis might be a case wherein RANKL inhibition is associated with the pathogenesis of MCD. Further studies will be needed to elucidate the causal relationship of RANK-RANKL signaling to the pathogenesis of MCD.

Unveiling the Features of Mercury-Associated Minimal Change Disease: Comparison with Primary Minimal Change Disease

Introduction: Long-term exposure to mercury can cause minimal change disease. However, the current understanding of mercury-associated minimal change disease (M-MCD) is inadequate. To improve the understanding of M-MCD, this study retrospectively analyzed the clinicopathological, ultrastructural, and prognostic features of M-MCD, in comparison with primary minimal change disease (P-MCD). Methods: We retrospectively analyzed the clinicopathological data of 21 M-MCD patients and 21 P-MCD patients. Electron micrographs of glomerular capillaries were taken, and the foot process width (FPW) was measured. A receiver operating characteristics (ROC) curve analysis was performed to determine the optimum cutoff value of FPW that can differentiate the M-MCD from P-MCD. Results: M-MCD patients presented similar clinical and routine pathological characteristics with P-MCD patients but had lower levels of FPW (935.0 [interquartile range (IQR) 853.7–1,176.7] nm vs. 1,403.2 [IQR 1,089.2–1,841.8] nm, p = 0.002). ROC curve analysis showed that FPW value below 1,385 nm might help to differentiate M-MCD from P-MCD (area under the curve of 0.787, sensitivity of 94.7%, and specificity of 52.4%). For patients with M-MCD, 77.8% achieved complete remission after mercury detoxification monotherapy. Patients with M-MCD had a lower relapse rate than patients with P-MCD (0 vs. 47.1%, p = 0.003). In addition, there was no significant difference in remission time between M-MCD patients treated with mercury detoxification monotherapy and those initially treated with immunosuppressive therapy (2.0 [IQR 1.0–6.0] months vs. 2.0 [IQR 1.5–2.5] months, p = 0.606). Conclusions: M-MCD patients showed similar clinicopathological features with P-MCD patients, but with less severe foot process effacement, suggesting different pathogenesis of these 2 disease entities. The treatment of mercury detoxification was highly effective for patients with M-MCD and can be considered as a primary choice in clinical practice.

Protective Role of Tangshen Formula on the Progression of Renal Damage in db/db Mice by TRPC6/Talin1 Pathway in Podocytes.

Tangshen Formula (TSF) is a Chinese Medicine formula that has been reported to alleviate proteinuria and protect renal function in humans and animals with diabetic kidney disease (DKD). However, little is known about its mechanism in improving proteinuria. The dysregulation of podocyte cell-matrix adhesion has been demonstrated to play an important role in the pathogenesis and progression of proteinuric kidney diseases including DKD. In the present study, the underlying protective mechanism of TSF on podocytes was investigated using the murine model of type 2 DKD db/db mice in vivo and advanced glycation end products (AGEs)-stimulated primary mice podocytes in vitro. Results revealed that TSF treatment could significantly mitigate reduction of podocyte numbers and foot process effacement, reduce proteinuria, and protect renal function in db/db mice. There was a significant increase in expression of transient receptor potential canonical channel 6 (TRPC6) and a decrease in expression of talin1 in podocytes of db/db mice. The results of AGEs-stimulated primary mice podocytes showed increased cell migration and actin-cytoskeleton rearrangement. Moreover, primary mice podocytes stimulated by AGEs displayed an increase in TRPC6-dependent Ca2+ influx, a loss of talin1, and translocation of nuclear factor of activated T cell (NFATC) 2. These dysregulations in mice primary podocytes stimulated by AGEs could be significantly attenuated after TSF treatment. 1-Oleoyl-2-acetyl-sn-glycerol (OAG), a TRPC6 agonist, blocked the protective role of TSF on podocyte cell-matrix adherence. In conclusion, TSF could protect podocytes from injury and reduce proteinuria in DKD, which may be mediated by the regulation of the TRPC6/Talin1 pathway in podocytes.

Podocyte Involvement in Renal Thrombotic Microangiopathy: A Clinicopathological Study

Background: The current study aimed to evaluate the associations between podocyte injury and clinicopathological features in renal thrombotic microangiopathy (TMA) based on a Chinese cohort, which might be underscored in this disease. Methods: The clinical, laboratory, and renal histopathological data of patients with renal biopsy-proven TMA from 2000 to 2015 in our institute were collected. Foot process effacement (FPE) was quantified by foot process width (FPW) by electron microscopy. Podocytes in the renal specimens were also detected by stainings for podocyte-specific markers, including Wilms tumor 1 (WT-1), synaptopodin, and podocalyxin. The associations between FPW and clinico-histopathological data were further analyzed. A composite end-point was defined by all-cause death or end-stage renal disease to address the predictive value of FPW. Results: Sixty-three patients with renal biopsy-proven TMA were enrolled. The FPW of renal TMA patients was 1,090 ± 637 nm (range, 572–4,748 nm), which was significantly higher than the normal range in our center (p = 0.005). By immunohistochemistry and immunofluorescence assays, we found decreased expressions of synaptopodin, podocalyxin, and WT-1 and continued stainings of WT-1 in some podocytes without detectable synaptopodin stainings in the areas of sclerotic tufts and cellular crescents. The FPW value was correlated with the serum albumin concentration (r_s = −0.281, p = 0.026), proteinuria amount (r_s = 0.255, p = 0.047), serum creatinine levels (r_s = 0.339, p = 0.007), and eGFR (r_s = −0.335, p = 0.007). According to ROC curve analysis, the optimal cutoff level of FPW for predicting the composite end-point was 869 nm. In patients with FPW ≥ 869 nm, FPW levels were further correlated with the severity of mesangiolysis (r_s = 0.351, p = 0.033) and glomerulosclerosis (r_s = 0.369, p = 0.025) in pathological evaluations. Patients without clinical remission also had higher FPW than those with remission (1,240 ± 793 vs. 925 ± 344 nm, p = 0.013). The multivariate Cox hazard model showed that FPW ≥ 869 nm was an independent risk factor for the composite end-point (hazard ratio: 3.64, 95% CI: 1.37–9.66, p = 0.009). Conclusion: The podocyte injury was prevalent and the FPW levels were closely associated with clinicopathological features, especially prognosis, in renal TMA patients.

Minimal Change Disease With Nephrotic Syndrome Associated With Coronavirus Disease 2019 After Apolipoprotein L1 Risk Variant Kidney Transplant: A Case Report

Kidney injury is a well-known complication in people with coronavirus disease 2019 (COVID-19). In kidney transplant recipients with COVID-19, presentation with nephrotic syndrome has not been well described. We report on a 49-year-old black female kidney transplant recipient who presented 25 years after transplant with clinical features of nephrotic syndrome following a diagnosis of COVID-19. Histologic examination showed acute tubular injury with unremarkable glomeruli on light microscopy and diffuse foot process effacement of podocytes on electron microscopy, consistent with minimal change–like podocyte injury. Apolipoprotein L1 (APOL1) genetic testing confirmed 2 high-risk APOL1 alleles in the kidney donor. We speculate that COVID-19–induced systemic or local cytokine release could serve as a second hit in the presence of APOL1 risk alleles and mediate a podocytopathy manifesting as nephrotic syndrome. The presented case with minimal change–like disease, occurring in the context of the donor high-risk APOL1 genotype, extends the spectrum of clinical manifestations in COVID-19–associated nephropathy.

Genetic or pharmacologic Nrf2 activation increases proteinuria in chronic kidney disease in mice

The nuclear factor erythroid 2-related factor 2 (Nrf2) pathway upregulates key cellular defenses. Clinical trials are utilizing pharmacologic Nrf2 inducers such as bardoxolone methyl to treat chronic kidney disease, but Nrf2 activation has been linked to a paradoxical increase in proteinuria. To understand this effect, we examined genetically engineered mice with elevated Nrf2 signaling due to reduced expression of the Nrf2 inhibitor, Kelch-like ECH-associated protein 1 (Keap1). These Keap1FA/FA mice lacked baseline proteinuria but exhibited increased proteinuria in experimental models evoked by adriamycin, angiotensin II, or protein overload. After injury, Keap1FA/FA mice had increased glomerulosclerosis, nephrin disruption and shedding, podocyte injury, foot process effacement, and interstitial fibrosis. Keap1FA/FA mice also had higher daytime blood pressures and lower heart rates measured by radiotelemetry. Conversely, Nrf2 knockout mice were protected from proteinuria. We also examined the pharmacologic Nrf2 inducer CDDO-Im. Compared to angiotensin II alone, the combination of angiotensin II and CDDO-Im significantly increased proteinuria, a phenomenon not observed in Nrf2 knockout mice. This effect was not accompanied by additional increases in blood pressure. Finally, Nrf2 was found to be upregulated in the glomeruli of patients with focal segmental glomerulosclerosis, diabetic nephropathy, fibrillary glomerulonephritis, and membranous nephropathy. Thus, our studies demonstrate that Nrf2 induction in mice may exacerbate proteinuria in chronic kidney disease.

Characterization of IgA Deposition in the Kidney of Patients with IgA Nephropathy and Minimal Change.

Approximately 5% of patients with IgA nephropathy (IgAN) exhibit mild mesangial lesions with acute onset nephrotic syndrome and diffuse foot process effacement representative of minimal change disease (MCD). It is not clear whether these unusual cases of IgAN with MCD (IgAN-MCD) are variant types of IgAN or coincidental deposition of IgA in patients with MCD. In a retrospective multicenter cohort study of 18 hospitals in Korea, we analyzed 46 patients with IgAN-MCD. Patients with endocapillary proliferation, segmental sclerosis, and crescent were excluded, and the clinical features and prognosis of IgAN-MCD were compared with those of pure MCD. In addition, we performed galactose-deficient IgA1 (KM55) staining to characterize IgAN-MCD. Among the 21,697 patients with glomerulonephritis enrolled in the database, 46 patients (0.21%) were diagnosed with IgAN-MCD, and 1610 patients (7.4%) with pure MCD. The 46 patients with IgAN-MCD accounted for 0.6% of primary IgAN patients (n = 7584). There was no difference in prognosis between patients with IgAN-MCD and those with only MCD. IgA and KM55 showed double positivity in all patients with IgAN-MCD (n = 4) or primary IgAN (n = 5) under double immunofluorescent staining. However, in four patients with lupus nephritis, mesangial IgA was deposited, but galactose-deficient-IgA1 (Gd-IgA1) was not. These findings suggest that IgAN-MCD is a dual glomerulopathy in which MCD was superimposed on possibly indolent IgAN. We confirmed by KM55 staining that IgAN-MCD is true IgAN, enabling better characterizations of the disease. Furthermore, IgAN-MCD shows a good prognosis when treated according to the usual MCD treatment modality.