Collapsing glomerulopathy superimposed on diabetic nephropathy: insights into etiology of an under-recognized, severe pattern of glomerular injury

Evidence from the large VALIGA cohort validates the subclassification of focal segmental glomerulosclerosis in IgA nephropathy

Evidence from the Oxford IgA nephropathy (IgAN) cohort supports the clinical value of subclassifying focal segmental glomerulosclerosis lesions (S1). Using the larger Validation in IgA (VALIGA) study cohort, we investigated the association between podocytopathic changes and higher proteinuria, kidney outcome and response to immunosuppressive therapy. All biopsies were evaluated for glomeruli with segmental capillary occlusion by matrix ("not otherwise specified", NOS lesion), simple capsular adhesion without capillary occlusion (Adh), tip lesions, and podocyte hypertrophy (PH). S1 required a NOS lesion and/or Adh. A Chi-Squared Automatic Interaction Detection method was used to identify subgroups of FSGS lesions associated with distinctive proteinuria at biopsy. We assessed survival from a combined event (kidney failure or 50% decline in estimated glomerular filtration rate). Finally, we evaluated within each subgroup if immunosuppression was associated with a favorable outcome using propensity analysis. In 1147 patients, S1 was found in 70% of biopsies. Subclassification found NOS lesions in 44%, Adh in 59%, PH in 13%, and tip lesions in 3%, with much overlap. Four subgroups were identified with progressively higher proteinuria: from lowest, S1 without NOS, S1 with NOS but without Adh/PH, to highest, S1 with NOS and Adh but without PH, and S1 with NOS and PH. These four subgroups showed progressively worse kidney survival. Immunosuppression was associated with a better outcome only in the two highest proteinuria subgroups. Propensity analysis in these two groups, adjusted for clinical and pathological findings, found a significantly reduced time-dependent hazard of combined outcome with corticosteroids. Podocyte hypertrophy and glomeruli with simple adhesions appeared to reflect active lesions associated with a response to corticosteroids, while other S1 lesions defined chronicity. Thus, our findings support subclassifying S1 lesions in IgAN.

The presence of exudative thickening of Bowman's capsule predict poor prognosis in diabetic kidney disease

BACKGROUND

The relationship between Bowman's capsule thickening and progression of diabetic kidney disease (DKD) remains uncertain.

METHODS

Renal biopsy specimens from 145 DKD patients and 20 control subjects were evaluated for Bowman's capsule thickness. Immunohistochemical staining assessed col4α2, laminin β1, and albumin expression. In a discovery cohort of 111 DKD patients with eGFR ≥ 30 ml/min/1.73 m2, thickening was classified as fibrotic or exudative. The composite endpoint included CKD stage 5, dialysis initiation, and renal disease-related death. Prognosis was analyzed using Kaplan-Meier and Cox regression analyses. Two validation cohorts were included.

RESULTS

Three types of thickening were observed: fibrotic, exudative, and periglomerular fibrosis. Parietal epithelial cell matrix protein accumulation contributed to fibrotic thickening, while albumin was present in exudative thickening. Bowman's capsule was significantly thicker in DKD patients (5.74 ± 2.09 μm) compared to controls (3.38 ± 0.43 μm, P < 0.01). In discovery cohort, the group of exudative thickning had a poorer prognosis(median time 20 months vs 57 months, P = 0.000). Cox multivariate analysis revealed that exudative thickening of Bowman's capsule were associated with a poor prognosis. The validation cohorts confirmed the result.

CONCLUSIONS

Various mechanisms contribute to Bowman's capsule thickening in DKD. The proportion of exudative thickening may serve as a valuable prognostic indicator for DKD patients.

Idiopathic collapsing glomerulopathy is associated with APOL1 high-risk genotypes or Mendelian variants in most affected individuals in a highly admixed population

Collapsing glomerulopathy (CG) is most often associated with fast progression to kidney failure with an incidence apparently higher in Brazil than in other countries. However, the reason for this occurrence is unknown. To better understand this, we performed an integrated analysis of clinical, histological, therapeutic, causative genetic and genetic ancestry data in a highly genetically admixed cohort of 70 children and adult patients with idiopathic CG (ICG). The disease onset occurred at 23 (interquartile range: 17-31) years and approximately half of patients progressed to chronic kidney disease requiring kidney replacement therapy (CKD-KRT) 36 months after diagnosis. Causative genetic bases, assessed by targeted-gene panel or whole-exome sequencing, were identified in 58.6% of patients. Among these cases, 80.5% harbored APOL1 high-risk genotypes (HRG) and 19.5% causative Mendelian variants (MV). Self-reported non-White patients more frequently had HRG. MV was an independent risk factor for progression to CKD-KRT by 36 months and the end of follow-up, while remission was an independent protective factor. All patients with HRG manifested CG at 9-44 years of age, whereas in those with APOL1 low-risk genotype, the disease arose throughout life. HRGs were associated with higher proportion of African genetic ancestry. Novel causative MVs were identified in COL4A5, COQ2 and PLCE1 and previously described causative MVs were identified in MYH9, TRPC6, COQ2, COL4A3 and TTC21B. Three patients displayed HRG combined with a variant of uncertain significance (ITGB4, LAMA5 or PTPRO). MVs were associated with worse kidney prognosis. Thus, our data reveal that the genetic status plays a major role in ICG pathogenesis, accounting for more than half of cases in a highly admixed Brazilian population.

Impact of Diabetic Lesions on Pathology, Treatment, and Outcomes of Glomerular Diseases

Key Points

People with glomerular disease (GD) and comorbid diabetes have similar baseline characteristics irrespective of superimposed diabetic lesions. Immunosuppression for GD with comorbid diabetes is the same regardless of superimposed diabetic glomerular lesions. ESKD or death is more rapid in GD and comorbid diabetes only in the presence of moderate-severe diabetic glomerular lesions.

Background

We aimed to evaluate whether concomitant diabetic glomerulosclerosis (DGS) and its severity affect the treatment and outcomes of primary glomerular diseases (GDs) with comorbid diabetes.

Methods

We conducted a retrospective review of people with diabetes and GD. We searched the GD Collaborative Network for biopsies from 2008 to 2015 among persons with diabetes and any of the following diagnoses: FSGS, IgA nephropathy, minimal change disease, membranous nephropathy, or antineutrophil cytoplasmic autoantibody GN. Data were abstracted from health records and histologic diabetic glomerular class scored. The primary composite end point was ESKD or death. Multivariable Cox regression models tested whether any or the severity of diabetes histopathology affected the primary end point.

Results

Data from 134 cases were available for analysis (78 DGS+GD and 56 GD alone). Diabetes duration and glycemic control were similar between the two groups (P = 0.2; P = 0.09, respectively). Use of immunosuppression did not differ between the two groups (P = 0.3). The composite end point was significantly higher in DGS+GD (22.5 cases per 100 person-years [95% confidence interval (CI), 16.6 to 30.5]) versus GD alone (10.2 cases per 100 person-years [95% CI, 6.4 to 16.2]). Regression analyses demonstrated that compared with the GD-alone group, the risk for the composite end point was similar in the group with mild DGS+GD (DGS class 1, 2a) (hazard ratio, 1.15 [95% CI, 0.54 to 2.43]) while the group with severe DGS+GD (DGS class 2b, 3, 4) had a greater risk (hazard ratio, 3.60 [1.79 to 7.22]).

Conclusions

Among people with diabetes and GD, mild diabetic glomerular lesions on biopsy do not affect outcomes, but moderate-severe lesions increase the risk for ESKD and death. Whether use of immunosuppression, particularly glucocorticoids, is less successful in inducing GD remission in people with moderate-severe diabetic lesions will be a focus of future study in a larger population.

The metabolic effects of APOL1 in humans

Harboring apolipoprotein L1 (APOL1) variants coded by the G1 or G2 alleles of the APOL1 gene increases the risk for collapsing glomerulopathy, focal segmental glomerulosclerosis, albuminuria, chronic kidney disease, and accelerated kidney function decline towards end-stage kidney disease. However, most subjects carrying APOL1 variants do not develop the kidney phenotype unless a second clinical condition adds to the genotype, indicating that modifying factors modulate the genotype-phenotype correlation. Subjects with an APOL1 high-risk genotype are more likely to develop essential hypertension or obesity, suggesting that carriers of APOL1 risk variants experience more pronounced insulin resistance compared to noncarriers. Likewise, arterionephrosclerosis (the pathological correlate of hypertension-associated nephropathy) and glomerulomegaly take place among carriers of APOL1 risk variants, and these pathological changes are also present in conditions associated with insulin resistance, such as essential hypertension, aging, and diabetes. Insulin resistance may contribute to the clinical features associated with the APOL1 high-risk genotype. Unlike carriers of wild-type APOL1, bearers of APOL1 variants show impaired formation of lipid droplets, which may contribute to inducing insulin resistance. Nascent lipid droplets normally detach from the endoplasmic reticulum into the cytoplasm, although the proteins that enable this process remain to be fully defined. Wild-type APOL1 is located in the lipid droplet, whereas mutated APOL1 remains sited at the endoplasmic reticulum, suggesting that normal APOL1 may participate in lipid droplet biogenesis. The defective formation of lipid droplets is associated with insulin resistance, which in turn may modulate the clinical phenotype present in carriers of APOL1 risk variants.

Diabetic nephropathy with marked extra-capillary cell proliferation: a case report

BACKGROUND

Extra-capillary hypercellularity is a common finding in crescentic glomerulonephritis (GN) and focal segmental glomerulosclerosis (FSGS). In diabetic nephropathy (DN), extra-capillary hypercellularity is often observed as a finding of complications such as IgA nephropathy or microscopic polyangiitis superimposed on DN. However, in rare cases, epithelial cell proliferation may accompany DN. We experienced a case of nodular diabetic glomerulosclerosis with marked extra-capillary hypercellularity and revealed the origin of this atypical lesion using immunostainings.

CASE PRESENTATION

A man in his 50 s was admitted to the hospital with nephrotic syndrome, and a renal biopsy was performed. Diffuse nodular lesions and extra-capillary hypercellularity were observed, but the results of serological examination or immunofluorescent assays did not implicate any other crescentic GN. Immunostaining for claudin-1 and nephrin was performed to identify the origin of the extra-capillary lesions. Given the clinical course and pathological findings, a diagnosis of DN-associated extra-capillary cell proliferation was made.

CONCLUSIONS

Extra-capillary hypercellularity, which resembles FSGS or crescentic GN, is a rare finding in DN and should therefore be treated with caution. In such cases, co-staining for claudin-1 and nephrin may facilitate the diagnosis of DN.

Histological Manifestations of Diabetic Kidney Disease and its Relationship with Insulin Resistance

Histological manifestations of diabetic kidney disease (DKD) include mesangiolysis, mesangial matrix expansion, mesangial cell proliferation, thickening of the glomerular basement membrane, podocyte loss, foot process effacement, and hyalinosis of the glomerular arterioles, interstitial fibrosis, and tubular atrophy. Glomerulomegaly is a typical finding. Histological features of DKD may occur in the absence of clinical manifestations, having been documented in patients with normal urinary albumin excretion and normal glomerular filtration rate. Furthermore, the histological picture progresses over time, while clinical data may remain normal. Conversely, histological lesions of DKD improve with metabolic normalization following effective pancreas transplantation. Insulin resistance has been associated with the clinical manifestations of DKD (nephromegaly, glomerular hyperfiltration, albuminuria, and kidney failure). Likewise, insulin resistance may underlie the histological manifestations of DKD. Morphological changes of DKD are absent in newly diagnosed type 1 diabetes patients (with no insulin resistance) but appear afterward when insulin resistance develops. In contrast, structural lesions of DKD are typically present before the clinical diagnosis of type 2 diabetes. Several heterogeneous conditions that share the occurrence of insulin resistance, such as aging, obesity, acromegaly, lipodystrophy, cystic fibrosis, insulin receptor dysfunction, and Alström syndrome, also share both clinical and structural manifestations of kidney disease, including glomerulomegaly and other features of DKD, focal segmental glomerulosclerosis, and C3 glomerulopathy, which might be ascribed to the reduction in the synthesis of factor H binding sites (such as heparan sulfate) that leads to uncontrolled complement activation. Alström syndrome patients show systemic interstitial fibrosis markedly similar to that present in diabetes.

Collapsing Glomerulopathy Superimposed on Diabetic Nephropathy

Diabetic nephropathy (DN) is characterized by progressive increase in proteinuria and decline in renal functions. Various forms of nondiabetic kidney disease may be superimposed on DN, which can alter the progression of DN. Collapsing glomerulopathy (CG) may superimpose on DN, and is characterized by rapid worsening of renal failure and has poor prognosis. In our institute, renal biopsies were performed in diabetic patients for increasing proteinuria or worsening renal functions. There were seven cases of CG superimposed on DN. All patients except one had a history of long standing diabetes mellitus. All patients had nephrotic range proteinuria. Four patients had severe renal failure at presentation. Renal biopsy showed CG superimposed on DN. Six patients progressed to end-stage renal disease during follow-up; one patient is in chronic kidney disease-stage 3b. The development of CG contributes to an increased level or new onset proteinuria in DN, and can lead to rapid worsening of renal failure. The diagnosis of CG superimposed on DN is of prognostic significance.

Case Report: Collapsing Focal Segmental Glomerulosclerosis After Initiation of Ado-Trastuzumab Emtansine Therapy

Ado-trastuzumab emtansine (T-DM1) is an antibody-drug conjugate consisting of the monoclonal antibody trastuzumab linked to the maytansinoid DM1 with potential antineoplastic activity and is approved for human epidermal growth factor receptor 2 (HER2)-positive breast cancer. An analysis of the US Food and Drug Administration (FDA) Adverse Event Reporting System identified 124/1,243 (10%) renal adverse events for trastuzumab. However, there are no published case reports describing kidney biopsy findings related to nephrotoxicity of either trastuzumab or T-DM1. We report kidney biopsy findings in a case of nephrotic range proteinuria due to collapsing focal segmental glomerulosclerosis (FSGS) and tubular injury after initiation of T-DM1 therapy. After systematic exclusion of other causes, it is likely that the observed collapsing FSGS was associated with the prior initiation of T-DM1 therapy. This is further supported by the clinical course with improvement of proteinuria and kidney function 3 weeks after discontinuation of T-DM1 therapy without further specific treatment. In summary, we provide the first report of kidney biopsy findings in a case of nephrotic range proteinuria after initiation of T-DM1 therapy due to collapsing FSGS. This issue is especially relevant since T-DM1 is widely used, and nephrologists have to be aware of this potentially rare but severe complication.

Modified arteriosclerosis score predicts the outcomes of diabetic kidney disease

BACKGROUND

The significance of renal arteriosclerosis in the prediction of the renal outcomes of diabetic kidney disease (DKD) remains undetermined.

METHODS

We enrolled 174 patients with DKD from three centres from January 2010 to July 2017. The severity and extent of arteriosclerosis were analysed on sections based on dual immunohistochemical staining of CD31 and α-smooth muscle actin. An X-tile plot was used to determine the optimal cut-off value. The primary endpoint was renal survival (RS), defined as the duration from renal biopsy to end-stage renal disease or death.

RESULTS

The baseline estimated glomerular filtration rate (eGFR) of 135 qualified patients was 45 (29 ~ 70) ml/min per 1.73 m², and the average 24-h urine protein was 4.52 (2.45 ~ 7.66) g/24 h. The number of glomeruli in the biopsy specimens was 21.07 ± 9.7. The proportion of severe arteriosclerosis in the kidney positively correlated with the Renal Pathology Society glomerular classification (r = 0.28, P < 0.012), interstitial fibrosis and tubular atrophy (IFTA) (r = 0.39, P < 0.001), urine protein (r = 0.213, P = 0.013), systolic BP (r = 0.305, P = 0.000), and age (r = 0.220, P = 0.010) and significantly negatively correlated with baseline eGFR (r = - 0.285, P = 0.001). In the multivariable model, the primary outcomes were significantly correlated with glomerular class (HR: 1.72, CI: 1.15 ~ 2.57), IFTA (HR: 1.96, CI: 1.26 ~ 3.06) and the modified arteriosclerosis score (HR: 2.21, CI: 1.18 ~ 4.13). After risk adjustment, RS was independently associated with the baseline eGFR (HR: 0.97, CI: 0.96 ~ 0.98), urine proteinuria (HR: 1.10, CI: 1.04 ~ 1.17) and the modified arteriosclerosis score (HR: 2.01, CI: 1.10 ~ 3.67), and the nomogram exhibited good calibration and acceptable discrimination (C-index = 0.82, CI: 0.75 ~ 0.87).

CONCLUSIONS

The severity and proportion of arteriosclerosis may be helpful prognostic indicators for DKD.

Endothelial Endothelin Receptor A Expression Is Associated With Podocyte Injury and Oxidative Stress in Patients With Focal Segmental Glomerulosclerosis

Introduction

The podocyte is thought to be the mainly affected cell type in focal segmental glomerulosclerosis (FSGS). However, recent studies have also indicated a role for glomerular endothelial cells and podocyte−endothelial crosstalk in FSGS development. An experimental model for podocyte injury showed that increased endothelin-1 (ET-1) signaling between podocytes and endothelial cells induces endothelial oxidative stress and subsequent podocyte loss. In the current study, we investigated endothelial endothelin receptor A (ET_AR) expression in patients with FSGS and its association with podocyte injury and glomerular oxidative stress.

Methods

We selected 39 biopsy samples of patients with FSGS and 8 healthy control subjects, and stained them for ET_AR, nephrin and 8-oxo-guanine, a DNA lesion caused by oxidative damage. Glomeruli with ET_AR-positive endothelium and with nephrin loss were scored, and the 8-oxo-guanine−positive glomerular area was measured.

Results

The mean percentage of glomeruli with ET_AR-positive endothelial cells in patients with FSGS was higher compared to that in healthy control subjects (52% vs. 7%; P < 0.001). The presence of glomerular ET_AR-positive endothelium was strongly associated with nephrin loss both on the biopsy level (rho = 0.47; P < 0.01), as on the level of individual glomeruli (odds ratio = 2.0; P < 0.001). Moreover, glomeruli with ET_AR-positive endothelium showed more 8-oxo-guanine−positive staining (1.9% vs. 2.4%; P = 0.037). Finally, 8-oxo-guanine positivity in glomeruli was associated with increased levels of proteinuria.

Conclusion

Taking together our findings, we show that ET_AR is increased in glomerular endothelial cells of patients with FSGS and associated with podocyte damage and glomerular oxidative stress. These findings support the hypothesis that ET-1 signaling in glomerular endothelial cells contributes to disease development in patients with FSGS.

Arteriolar hyalinosis is related to rapid GFR decline and long-standing GFR changes observed on renal biopsies in normo-microalbuminuric type 2 diabetic patients

AIMS

Whether or not renal structural changes, especially arteriolar hyalinosis, are related to the rate of renal functional decline and increase in urinary albumin excretion (UAE) at the early stage of diabetic nephropathy in patients with type 2 diabetes is still unknown. Our previous study determined that arteriolar hyalinosis is an independent risk factor for low GFR. We sought to determine whether arteriolar hyalinosis is also a risk factor for rapidly progressive decline in GFR.

METHODS

We evaluated 22 type 2 diabetic patients with normo- or microalbuminuria who took part in the previous study, to clarify which renal histological factors were associated with changes in UAE and the glomerular filtration rate (GFR) during 11.0 ± 3.0 years of follow-up. Light and electron microscopy-based morphometric analyses were performed to quantitatively evaluate the glomerular and interstitial structural changes.

RESULTS

In all 22 patients, the GFR was significantly decreased from baseline to follow-up, while the UAE did not change markedly between the 2 periods. After 11 ± 3 years of follow-up, the GFR was significantly lower in the rapid decliner group (annual rate of GFR decline ≥3.0%) than in the non-rapid decliner group (p = 0.017). The index of arteriolar hyalinosis (IAH) at baseline in the rapid decliners was significantly larger than in the non-rapid decliners (p = 0.015). The IAH showed a significant negative correlation with the GFR at follow-up (r = 0.50, p = 0.018) and the annual rate in the GFR decline (r = 0.47, p = 0.027) and significant positive correlations with UAE at follow-up (r = 0.46, p = 0.034) and the annual rate in the UAE increase (r = 0.57, p = 0.005). The GFR at follow-up in patients with IAH ≥2.0 was significantly decreased from baseline (p = 0.042) and significantly lower than that of the patients with IAH <2.0 (p = 0.026), which did not decrease significantly from baseline. The frequency of rapid decliners was larger in the IAH ≥2.0 than in the IAH <2.0 patients (p = 0.037).

CONCLUSIONS

Aggravated arteriolar hyalinosis was a risk factor for a rapid GFR decline. This finding might reflect initial changes in early diabetic nephropathy.

Renal comorbidities in collapsing variant focal segmental glomerulosclerosis: more than a coincidence?

BACKGROUND

Collapsing focal segmental glomerulosclerosis (FSGS) has various underlying etiologies and often leads to renal failure. The impact of biopsy-proven renal comorbidities in promoting collapsing glomerulopathy (CG) has not been systematically evaluated in large comparative studies. Those data are reported here.

METHODS

Biopsies with the initial diagnosis of CG in native (n = 321) or transplant kidneys (n = 30) were identified in the University of North Carolina nephropathology database (1 January 2011 to 1 January 2016). Two cohorts were defined: 'sole' CG without and 'accompanied' CG with significant morphologic renal comorbidities. Tip-variant FSGS (T-FSGS) and time-matched biopsies served as control cohorts for comparative analyses.

RESULTS

CG was significantly more common in native (4.4%) and transplant biopsies (4.1%) compared with T-FSGS (0.7 and <0.1%, respectively, difference versus CG P < 0.01). 'Associated' disease was significantly more common in CG (native: 151/321; 47.0%, transplant: 21/30; 70%, P < 0.05) versus T-FSGS (native: 14/51; 27.5%, transplant: exceptional; all differences versus CG P < 0.05). In native biopsies with 'accompanied' CG but not in control groups, stenosing vasculopathies including thrombotic microangiopathies were significantly more prevalent (P < 0.01). In transplants, the high incidence of 'accompanied' CG was linked to de novo diseases, mainly rejection and vascular injury. In native kidneys, membranous glomerulopathies were prevalent in 'accompanied' T-FSGS (36%) and CG (14%) (difference versus time-matched controls P < 0.01 and P < 0.05, respectively); they were uncommon in transplants.

CONCLUSIONS

CG but not T-FSGS shows a high rate of comorbidities, with prominent vasculopathies presumably driving 'ischemic' CG-specific glomerular injury and also the disease course. These findings facilitate future studies into therapy, prognosis and reversibility of 'accompanied' CG.

APOL1 risk variants and the development of HIV-associated nephropathy

HIV-associated nephropathy (HIVAN) remains a concern among untreated HIV patients, notably of African descent, as patients can reach end-stage renal disease within 3 years. Two variants (G1 and G2) of the APOL1 gene, common in African populations to protect against African sleeping sickness, have been associated with an increased risk of several glomerular disorders including HIVAN, hypertension-attributed chronic kidney disease, and idiopathic focal segmental glomerulosclerosis and are accordingly named renal risk variants (RRVs). This review examines the mechanisms by which APOL1 RRVs drive glomerular injury in the setting of HIV infection and their potential application to patient management. Innate antiviral mechanisms activated by chronic HIV infection, especially those involving type 1 interferons, are of particular interest as they have been shown to upregulate APOL1 expression. Additionally, the downregulation of miRNA 193a (a repressor of APOL1) is also associated with the upregulation of APOL1. Interestingly, glomerular damage affected by APOL1 RRVs is caused by both loss- and gain-of-function changes in the protein, explicitly characterizing these effects. Their intracellular localization offers a further understanding of the nuances of APOL1 variant effects in promoting renal disease. Finally, although APOL1 variants have been recognized as a critical genetic player in mediating kidney disease, there are significant gaps in their application to patient management for screening, diagnosis, and treatment.

Diabetic Kidney Disease: Past and Present

Diabetes mellitus (DM) afflicting humans has been recognized as a disease for >3000 years. However, very little was known about its etiology and pathogenesis until about a century ago when increasing knowledge about anatomy and physiology of the human body gradually led to our understanding that the hormone insulin produced by the Islets of Langerhans in the pancreas plays a crucial role in the metabolism of glucose and maintaining the blood sugar level within a normal range. DM is caused by inadequate insulin production (type 1) or insulin resistance (type 2). For thousands of years, DM has been considered as a disease of the kidney; however, with the understanding of the pathogenesis of DM, it became clear that diabetic kidney disease (DKD) is a complication and not a cause of DM. DKD is associated with increased matrix expansion that manifests morphologically as a diffuse or nodular expansion of the mesangium and diffuse thickening of the glomerular and tubular basement membranes. Hyperglycemia plays a crucial role in the development of pathologic changes within the kidney. Once established, DKD usually undergoes a slow but relentless progression to end-stage renal disease. However, recent studies have shown that its progression can be slowed or even reversed by strict control of hyperglycemia. Morphologically, DKD may resemble several other glomerular diseases that must be ruled out before a definitive diagnosis. Patients with DM may also develop nondiabetic glomerular or interstitial diseases with or without DKD. The findings in nephrectomy specimens and the differential diagnoses are presented in detail.

VEGFR2 Blockade Improves Renal Damage in an Experimental Model of Type 2 Diabetic Nephropathy

The absence of optimal treatments for Diabetic Nephropathy (DN) highlights the importance of the search for novel therapeutic targets. The vascular endothelial growth factor receptor 2 (VEGFR2) pathway is activated in experimental and human DN, but the effects of its blockade in experimental models of DN is still controversial. Here, we test the effects of a therapeutic anti-VEGFR2 treatment, using a VEGFR2 kinase inhibitor, on the progression of renal damage in the BTBR ob/ob (leptin deficiency mutation) mice. This experimental diabetic model develops histological characteristics mimicking the key features of advanced human DN. A VEGFR2 pathway-activation blockade using the VEGFR2 kinase inhibitor SU5416, starting after kidney disease development, improves renal function, glomerular damage (mesangial matrix expansion and basement membrane thickening), tubulointerstitial inflammation and tubular atrophy, compared to untreated diabetic mice. The downstream mechanisms involved in these beneficial effects of VEGFR2 blockade include gene expression restoration of podocyte markers and downregulation of renal injury biomarkers and pro-inflammatory mediators. Several ligands can activate VEGFR2, including the canonical ligands VEGFs and GREMLIN. Activation of a GREMLIN/VEGFR2 pathway, but not other ligands, is correlated with renal damage progression in BTBR ob/ob diabetic mice. RNA sequencing analysis of GREMLIN-regulated genes confirm the modulation of proinflammatory genes and related-molecular pathways. Overall, these data show that a GREMLIN/VEGFR2 pathway activation is involved in diabetic kidney disease and could potentially be a novel therapeutic target in this clinical condition.

Prognostic nomogram and score to predict renal survival of patients with biopsy-proven diabetic nephropathy

AIMS

Both clinical and pathogenetic markers for accurate prediction of end-stage renal disease in diabetic nephropathy (DN) are lacking. This study aimed to establish an effective prognostic nomogram and a score for renal survival (RS) in biopsy-proven DN.

METHODS

Analyses were derived from 110 DN patients who underwent renal biopsy at China-Japan Friendship Hospital between January 2006 and May 2018 with DN as the only glomerular disease diagnosis. The prognostic ability of 34 baseline clinicopathologic parameters was evaluated using univariate and multivariate Cox regression analyses. The predictive accuracy and discriminative ability of the final model were measured using the calibration curve and concordance index (C-index). Internal validation of the model was assessed using bootstrap resampling.

RESULTS

Urinary proteinuria excretion, stages of chronic kidney disease, glomerular hyalinosis, and extracapillary hypercellularity were independent prognostic factors for RS, and all were selected into the nomogram. The calibration curve for the probability of survival showed good agreement between the prediction by nomogram and actual observation. The C-index for predicting survival was 0.79 (95% confidence interval (CI) 0.72-0.86). A high C-index value of 0.76 indicated good internal validation. The prognostic score had the potential to delineate two prognosis groups with median RS of 24 and 70 months, respectively.

CONCLUSIONS

The proposed nomogram and score provide a useful individualized risk estimate of renal prognosis in patients with DN.

Collapsing glomerulopathy in older adults

Collapsing glomerulopathy has been described in settings of viral infections, drug, genetic, ischemic, renal transplant, and idiopathic conditions. It has a worse prognosis than other morphologic variants of focal segmental glomerulosclerosis, and may be treated with aggressive immunosuppression. In this study, we sought to characterize the clinical and morphologic findings in older adults with collapsing glomerulopathy. Renal biopsies and associated clinical data from patients aged 65 or older with a diagnosis of collapsing glomerulopathy were retrospectively reviewed at 3 academic institutions. Patients (n = 41, 61% male, median age 71) usually had hypertension (88%), nephrotic range proteinuria (91%), and renal insufficiency (median serum creatinine 2.5 mg/dL). A likely precipitating drug (5%) or vascular procedure (5%) was identified in a minority of cases; viral infections were infrequent. Renal biopsies contained a median of 40% globally and 16% segmentally sclerotic glomeruli. Approximately 60% of cases had moderate or severe arteriosclerosis, arteriolar hyalinosis, and/or tubular atrophy and interstitial fibrosis; 7% had atheroembolic disease and 5% had thrombotic microangiopathy. In 28 patients with available follow-up information, eight (19%) were treated with immunosuppressives, which were not tolerated by 2. At a median interval of 14 months, 5 (18%) patients had died, 12 (43%) had end stage renal disease, and 12 were alive with renal insufficiency and proteinuria. Treatment with immunosuppressive therapy did not have a significant benefit with regard to the primary outcome of overall or renal survival. One steroid-treated patient with diabetes died 6 weeks after biopsy, with invasive rhinoorbital Rhizopus infection. In conclusion, collapsing glomerulopathy in older patients is usually not associated with viral infections, and is accompanied by significant chronic injury in glomeruli, vasculature, and tubulointerstitium. Aggressive immunosuppression likely contributed to one death in a patient with diabetes, and did not yield an overall or renal survival advantage in this cohort.

Collapsing Glomerulopathy Superimposed on Diabetic Nephropathy

Diabetic nephropathy (DN) is characterized by gradually progressive renal failure and proteinuria. Various types of nondiabetic kidney diseases may superimpose on DN, and affect the natural course, prognosis, and management. Collapsing glomerulopathy (CG) is a form of glomerular proliferative injury, characterized by rapid progression and associated with poor prognosis. CG may be idiopathic or secondary to other causes, and it has also been described with other forms of glomerular diseases. The association of CG with DN has not been reported widely. We report on a patient with DN who has undergone renal biopsy due to massive proteinuria and rapid loss of renal function. Renal biopsy was suggestive of CG superimposed on DN. He was treated conservatively, however, progressed to end-stage renal disease rapidly.

Aerobic Exercise Training Alleviates Renal Injury by Interfering with Mitochondrial Function in Type-1 Diabetic Mice

BACKGROUND Diabetic nephropathy was one of the most serious and harmful diabetic complications, characterized by progressive loss of renal function and renal fibrosis. Aerobic exercise training is an important non-pharmacologic method to prevent and treat diabetes mellitus and diabetic complications. MATERIAL AND METHODS Intraperitoneal (i.p.) injection of streptozocin (STZ) was used to construct a type 1 diabetic mouse model. Renal function and mitochondrial function were measured by urinary protein level, Masson staining and ATP, superoxide production, and membrane potential, respectively. The purpose of the research was to explore the effect of aerobic exercise training on renal and renal mitochondrial function, as well as the expression of Sirt1and PGC1α in type-1 diabetic mice. RESULTS Sedentary diabetic mice exhibited increased urinary protein level, blood glucose, and collagen deposition in renal tissues compared with sedentary control mice, which were significantly mitigated by aerobic exercise training. Diabetic mice displayed renal tissue mitochondrial dysfunction (decreased mitochondrial ATP production and membrane potential), as well as increased mitochondrial superoxide production, which were reversed by aerobic exercise. By using Western blot analysis, we identified the decreased expression of Sirt1 and PGC1α in the renal tissue of diabetic mice, which were partly reversed by aerobic exercise training. Data showed that silencing of Sirt1 abrogated the beneficial effect of aerobic exercise training against diabetes-induced mitochondrial abnormalities and renal damage in mice. CONCLUSIONS Aerobic exercise training alleviates diabetes-induced renal injury by improving mitochondrial function.

Collapsing glomerulopathy: update

Collapsing glomerulopathy (CG) is a rare entity as a glomerular disease. Although it has been considered as a variant of focal segmental glomerulosclerosis, the fact is that the podocyte lesions show different features with respect to the typical focal segmental glomerulosclerosis, an aspect that has been attributed to a type of podocytopathy. In CG, the podocyte lesion is typically characterised by a dysregulated podocyte phenotype, reflected by the loss of expression of mature podocyte markers. CG can be a primary disease or it can be associated with several causal factors that develop a common histopathological entity. The clinical expressiveness of CG is often characterised by the presence of a nephrotic syndrome and a rapid deterioration of the renal function than other variants of the focal segmental glomerulosclerosis. The prognosis of these patients is a rapid progression towards end-stage renal disease with poor response to treatment.

High glucose induces apoptosis via upregulation of Bim expression in proximal tubule epithelial cells

Diabetic nephropathy is the primary cause of end-stage renal disease. Apoptosis of tubule epithelial cells is a major feature of diabetic nephropathy. The mechanisms of high glucose (HG) induced apoptosis are not fully understood. Here we demonstrated that, HG induced apoptosis via upregulating the expression of proapoptotic Bcl-2 homology domain 3 (BH3)-only protein Bim protein, but not bring a significant change in the baseline level of autophagy in HK2 cells. The increase of Bim expression was caused by the ugregulation of transcription factors, FOXO1 and FOXO3a. Bim expression initiates BAX/BAK-mediated mitochondria-dependent apoptosis. Silence of Bim by siRNA in HK2 cells prevented HG-induced apoptosis and also sensitized HK2 cells to autophagy during HG treatment. The autophagy inhibitor 3-MA increased the injury in Bim knockdown HK2 cells by retriggering apoptosis. The above results suggest a Bim-independent apoptosis pathway in HK2 cells, which normally could be inhibited by autophagy. Overall, our results indicate that HG induces apoptosis via up-regulation of Bim expression in proximal tubule epithelial cells.

Segmental Sclerosis and Extracapillary Hypercellularity Predict Diabetic ESRD

Pathogenetic markers of diabetic kidney disease (DKD) progression to ESRD are lacking. We characterized the prognostic value of histologic findings in DKD for time to ESRD in native kidney specimens from biopsies performed from 1995 to 2011 with diabetic glomerulosclerosis as the only glomerular disease diagnosis (n=109). Biopsy specimens were analyzed according to standard methods, including determination of diabetic nephropathy class, as defined by the Renal Pathology Society. Clinical data were extracted from electronic medical records. We used competing risk models, with death as the competing risk, to estimate subdistribution hazard ratios (HRs) for ESRD. All multivariable models included age, sex, black race, baseline eGFR, and baseline proteinuria. Pathologic characteristics achieving P<0.1 were added into successively complex models. ESRD occurred in 56% of patients, and 26% of patients died before reaching ESRD. In univariate analyses, diabetic nephropathy class was not statistically significant in predicting time to ESRD. The final multivariable model (n=106) showed a borderline association between mild mesangial expansion and decreased risk for ESRD (subdistribution HR, 0.64; 95% confidence interval, 0.40 to 1.00). Poor prognostic factors in the final model included segmental sclerosis and extracapillary hypercellularity (subdistribution HR, 2.04; 95% confidence interval, 1.36 to 3.05; and subdistribution HR, 2.21; 95% confidence interval, 1.19 to 4.11, respectively). In conclusion, we identified segmental sclerosis and extracapillary hypercellularity as novel, poor prognostic indicators of time from DKD to ESRD. Whether these indicators represent a distinct pathogenetic phenotype of DKD will require a large study with a broad spectrum of disease severity.

Clinical and pathological characteristics of non-diabetic renal disease in type 2 diabetes patients

Background

Renal involvement in type 2 diabetes is mainly due to diabetic nephropathy (DN). Nevertheless, a sizable proportion of diabetic patients could actually have nondiabetic renal diseases (NDRDs) or DN plus NDRDs. This study aimed to explore the pathological features of NDRD in diabetic patients and to assess the predictability of diagnosing NDRD (±DN) versus isolated DN on the basis of clinical parameters.

Methods

Medical records of type 2 diabetes patients who underwent renal biopsy under suspicion of NDRD from January 2011 through November 2015 were analyzed retrospectively.

Results

A total of 101 patients were enrolled in this study. The most frequent indication for renal biopsy was recent onset of nephrotic syndrome (41%), followed by rapidly progressive renal failure (29%) and active urinary sediment (21%). On renal biopsy, 51% of patients had isolated DN, 20% had isolated NDRD and 29% had DN plus NDRD. IgA nephropathy was the most common cause of isolated NDRD, whereas acute tubular necrosis (39%) and acute interstitial nephritis (33%) were the main causes of NDRD superimposed on DN. Male gender, short-duration diabetes (<8 years), lower glycated hemoglobin and active urinary sediment (≥10 red and white blood cells per high-power field) were independent predictors of NDRD according to multiple logistic regression analysis.

Conclusions

Judicious use of renal biopsy revealed NDRD (±DN) in nearly half of type 2 diabetes patients with atypical renal presentation, especially in male patients with well-controlled diabetes, those who have had diabetes for a short duration and those with active urinary sediment.

Collapsing glomerulopathy: a 30-year perspective and single, large center experience

Collapsing glomerulopathy (CGP) is a pattern of kidney injury seen on renal biopsy with multiple associations and etiologies. It is most commonly described in African-Americans and others with recent African ancestry. The disease is rapidly progressive and often presents with abrupt onset of renal failure and nephrotic-range proteinuria. Since its description 30 years ago, this entity has transformed from a morphologic diagnosis typically seen in the setting of HIV infection to a complicated diagnosis with numerous etiologies, many of which are associated with underlying apolipoprotein L1 (APOL1)-risk variants or other genetic disorders. We review the evolution of CGP, and its history and proposed pathomechanisms. We also present the disease spectrum from our experience with emphasis on recognizing the lesion, distinguishing from mimics and linking the histopathological pattern to a specific cause. Our understanding continues to evolve as clinicians and scientists work toward a more complete understanding of the molecular pathways of injury in this disease and how these might be disrupted for therapeutic purposes. Much still remains to be discovered in CGP as the molecular underpinnings leading to disease are still not completely understood and no effective treatment exists despite the high morbidity. Based on this rapid evolution, CGP is a modern template of how we diagnose and think about kidney disease. The story of CGP represents the current shift in nephrology and nephropathology from morphology-alone-based diagnosis to a comprehensive approach including molecular diagnostics. We believe this new, holistic approach will lead to pathogenesis-centered diagnoses that will help to individualize risk stratification and treatment protocols.

Therapeutic angiogenesis by vascular endothelial growth factor supplementation for treatment of renal disease

PURPOSE OF REVIEW

Vascular endothelial growth factors (VEGFs) influence renal function through angiogenesis, with VEGF-A being the most potent inducer of vascular formation. In the normal glomerulus, tight homeostatic balance is maintained between the levels of VEGF-A isoforms produced by podocyte cells, and the VEGF receptors (VEGFRs) expressed by glomerular endothelial, mesangial, and podocyte cells. Renal disease occurs when this homeostatic balance is lost, manifesting in the abnormal autocrine and paracrine VEGF-A/VEGFR signaling, ultrastructural glomerular and tubular damage, and impaired filtration.

RECENT FINDINGS

Preclinical disease models of ischemic renal injury, including acute ischemia/reperfusion, thrombotic microangiopathy, and chronic renovascular disease, treated with exogenous VEGF supplementation demonstrated therapeutic efficacy. These results suggest a therapeutic VEGF-A paracrine effect on endothelial cells in the context of acute or chronic obstructive ischemia. Conversely, renal dysfunction in diabetic nephropathy appears to occur through an upregulated VEGF autocrine effect on podocyte cells, which is exacerbated by hyperglycemia. Therefore, VEGF supplementation therapy may be contraindicated for treatment of diabetic nephropathy, but specific results will depend on dose and on the specific site of VEGF delivery. A drug delivery system that demonstrates cell specificity for glomerular or peritubular capillaries could be employed to restore balance to VEGF-A/VEGFR2 signaling, and by doing so, prevent the progression to end-stage renal disease.

SUMMARY

The review discusses the preclinical data available for VEGF supplementation therapy in models of renal disease.

Collapsing glomerulopathy in a case of anti-neutrophil cytoplasmic antibody associated vasculitis

Collapsing glomerulopathy (CG) is a pathological entity characterized by collapse and wrinkling of glomerular tuft, podocyte dedifferentiation and hyperplasia. CG may be idiopathic or secondary to other diseases. CG has been described with IgA nephropathy, membranous glomerulopathy, diabetic nephropathy, and lupus nephritis. However, till date there is no report of CG in association with the anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV). Here, we present a case of CG that developed during follow-up in a case of AAV with biopsy proven pauci-immune glomerulonephritis.

Protective effects of adiponectin on uncoupling of glomerular VEGF-NO axis in early streptozotocin-induced type 2 diabetic rats

PURPOSE

To determine whether adiponectin could reduce microalbuminuria and provide renal protective effects by improving endothelial dysfunction and uncoupling of the glomerular vascular endothelial growth factor (VEGF)-nitric oxide (NO) axis in streptozotocin-induced type 2 diabetic rats.

METHODS

Wistar rats were randomly divided into normal control group, diabetic nephropathy (DN) group induced by high-fat feeding and streptozotocin, diabetic rats injected with adenovirus-expressed adiponectin (AD-AdipoQ), and diabetic rats injected with AD-IRES-EGFP as control. Blood and urine samples were collected. Endothelium-dependent vasodilatation (EDV) of the aorta was measured. Renal tissues were collected for CD34 immunohistochemistry. Glomerular NO and VEGF levels were measured by the Griess reaction and Western blot testing, respectively.

RESULTS

Injections of AD-AdipoQ significantly increased serum adiponectin levels and reduced the urinary albumin-to-creatinine ratio in diabetic rats (P < 0.05). The levels of plasma glucose, serum insulin, high-sensitivity C-reactive protein, and malondialdehyde were significantly reduced in diabetic rats after injections of AD-AdipoQ (P < 0.05). Severe EDV impairment was observed in the DN group, which was improved by AD-AdipoQ. CD34 expression in the glomeruli was also higher in diabetic rats, indicating increased proliferation of glomerular endothelial cells. However, AD-AdipoQ improved the increased proliferation of endothelial cells in the glomeruli. Diabetic rats showed increased glomerular VEGF levels and reduced NO levels. This uncoupling of the VEGF-NO axis was partially improved by AD-AdipoQ.

CONCLUSION

Adiponectin reduces the degree of microalbuminuria and has renal protective effects by improving endothelial dysfunction and uncoupling of the glomerular VEGF-NO axis in early diabetic nephropathy.