The phenotypes of podocytes and parietal epithelial cells may overlap in diabetic nephropathy

Reversal of diabetic nephropathy (DN) has been achieved in humans and mice, but only rarely and under special circumstances. Since progression of DN is related to podocyte loss, reversal of DN requires restoration of podocytes. Here we identified and quantified potential glomerular progenitor cells that could be a source for restored podocytes. DN was identified in 31 human renal biopsy cases and separated into morphologically early or advanced lesions. Markers of podocytes (WT-1, p57), parietal epithelial cells (claudin-1) and cell proliferation (Ki-67) were identified by immunohistochemistry. Podocyte density was progressively reduced with DN. Cells marking as podocytes (p57) were present infrequently on Bowman's capsule in controls, but significantly increased in histologically early DN. Ki-67 expressing cells were identified on the glomerular tuft and Bowman's capsule in DN, but rarely in controls. Cells marking as PECs were present on the glomerular tuft, particularly in morphologically advanced DN. These findings show evidence of phenotypic plasticity in podocyte and PEC populations and are consistent with studies in the BTBR ob/ob murine model in which reversibility of DN occurs with podocytes potentially regenerating from PEC precursors. Thus, our findings support, but do not prove, that podocytes may regenerate from PEC progenitors in human DN. If so, progression of DN may represent a modifiable net balance between podocyte loss and regeneration.

Collapsing focal segmental glomerulosclerosis following long-term treatment with oral ibandronate: case report and review of literature

Background

Renal toxicity has been reported with bisphosphonates such as pamidronate and zolidronate but not with ibandronate, in the treatment of breast cancer patients with bone metastasis. One of the patterns of bisphosphonate-induced nephrotoxicity is focal segmental glomerulosclerosis (FSGS) or its morphological variant, collapsing focal segmental glomerulosclerosis (CFSGS).

Case presentation

We describe a breast cancer patient who developed heavy proteinuria (protein/creatinine ratio 9.1) and nephrotic syndrome following treatment with oral ibandronate for 29 months. CFSGS was proven by biopsy. There was no improvement 1 month after ibandronate was discontinued. Prednisone and tacrolimus were started and she experienced a decreased in proteinuria.

Conclusion

In patient who develops ibandronate-associated CFSGS, proteinuria appears to be at least partially reversible with the treatment of prednisone and/or tacrolimus if the syndrome is recognized early and ibandronate is stopped.

Characterization of early disease status in treatment-naive male paediatric patients with Fabry disease enrolled in a randomized clinical trial

Trial Design

This analysis characterizes the degree of early organ involvement in a cohort of oligo-symptomatic untreated young patients with Fabry disease enrolled in an ongoing randomized, open-label, parallel-group, phase 3B clinical trial.

Methods

Males aged 5–18 years with complete α-galactosidase A deficiency, without symptoms of major organ damage, were enrolled in a phase 3B trial evaluating two doses of agalsidase beta. Baseline disease characteristics of 31 eligible patients (median age 12 years) were studied, including cellular globotriaosylceramide (GL-3) accumulation in skin (n = 31) and kidney biopsy (n = 6; median age 15 years; range 13–17 years), renal function, and glycolipid levels (plasma, urine).

Results

Plasma and urinary GL-3 levels were abnormal in 25 of 30 and 31 of 31 patients, respectively. Plasma lyso-GL-3 was elevated in all patients. GL-3 accumulation was documented in superficial skin capillary endothelial cells (23/31 patients) and deep vessel endothelial cells (23/29 patients). The mean glomerular filtration rate (GFR), measured by plasma disappearance of iohexol, was 118.1 mL/min/1.73 m² (range 90.4–161.0 mL/min/1.73 m²) and the median urinary albumin/creatinine ratio was 10 mg/g (range 4.0–27.0 mg/g). On electron microscopy, renal biopsy revealed GL-3 accumulation in all glomerular cell types (podocytes and parietal, endothelial, and mesangial cells), as well as in peritubular capillary and non-capillary endothelial, interstitial, vascular smooth muscle, and distal tubules/collecting duct cells. Lesions indicative of early Fabry arteriopathy and segmental effacement of podocyte foot processes were found in all 6 patients.

Conclusions

These data reveal that in this small cohort of children with Fabry disease, histological evidence of GL-3 accumulation, and cellular and vascular injury are present in renal tissues at very early stages of the disease, and are noted before onset of microalbuminuria and development of clinically significant renal events (e.g. reduced GFR). These data give additional support to the consideration of early initiation of enzyme replacement therapy, potentially improving long-term outcome.

Trial Registration

ClinicalTrials.gov NCT00701415

Interstitial eosinophilic aggregates in diabetic nephropathy: allergy or not?

BACKGROUND

Interstitial eosinophilic aggregates (IEA) in renal biopsies often suggest allergic tubulointerstitial nephritis, yet clear associations with drug reactions are often difficult to establish. IEA are also encountered in diabetic nephropathy (DN) and thought to be attributed to medication exposure.

METHODS

Native medical kidney biopsies performed at the University of Washington Medical Center were reviewed, including DN (n = 64), IgA nephropathy (IgAN, n = 28), membranous nephropathy (MN, n = 14), focal and segmental glomerulosclerosis (FSGS, n = 27) and membranoproliferative glomerulonephritis (MPGN, n = 28). IEA were defined as ≥5 eosinophils per high power field. The severity of interstitial fibrosis and tubular atrophy (IFTA) was scored semi-quantitatively as minimal, mild, moderate or severe.

RESULTS

IEA were remarkably more prevalent in DN (41%), when compared with IgAN (7%, P = 0.001), MN (8%, P = 0.017) or MPGN (14%, P = 0.013), but not FSGS (26%, P = 0.18). In DN cases, univariate analysis revealed that IEA were associated with greater IFTA severity, but not with the percentage of glomerulosclerosis, mesangial expansion, history of drug allergy, number of prescribed medications or particular class of medications (antibiotics, NSAIDs, aspirin, thiazide, loop diuretics, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, calcium channel blockers, beta blockers, insulin, sulfonylurea, metformin or allopurinol). Multivariate analysis showed that the severity of IFTA was the only significant predictor for IEA (P < 0.01) after stepwise adjustment for age, number of medications, drug allergy, diabetes type, % global glomerulosclerosis and mesangial expansion.

CONCLUSIONS

Our study shows that IEA are more common in DN, when compared with other types of glomerulopathy. In DN, IEA are associated with the severity of IFTA but not with prescribed medications or clinical history of allergy. This suggests that in DN IEA are often associated with chronic tubulointerstitial injury and are not diagnostic of an allergic interstitial nephritis.

Urinary elafin and kidney injury in hematopoietic cell transplant recipients

BACKGROUND AND OBJECTIVES

Graft-versus-host disease (GVHD) is associated with kidney injury after hematopoietic cell transplantation (HCT). Because plasma elafin levels correlate with skin GVHD, this study examined urinary elafin as a potential marker of renal inflammation and injury.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Urine was collected prospectively on 205 patients undergoing their first HCT from 2003 to 2010. Collections were done at baseline, weekly through day 100, and monthly through year 1 to measure elafin and urine albumin-to-creatinine ratio (ACR). Associations between urinary elafin levels and microalbuminuria, macroalbuminuria, AKI and CKD, and mortality were examined using Cox proportional hazards or linear regression models. Available kidney biopsy specimens were processed for immunohistochemistry.

RESULTS

Mean urinary elafin levels to day 100 were higher in patients with micro- or macroalbuminuria (adjusted mean difference, 529 pg/ml; P=0.03) at day 100 than in those with a normal ACR (adjusted mean difference, 1295 pg/ml; P<0.001). Mean urinary elafin levels were higher in patients with AKI compared with patients without AKI (adjusted mean difference, 558 pg/ml; P<0.01). The average urinary elafin levels within the first 100 days after HCT were higher in patients who developed CKD at 1 year than in patients without CKD (adjusted mean difference, 894 pg/ml; P=0.002). Among allogeneic recipients, a higher proportion of patients with micro- or macroalbuminuria at day 100 also had grade II-IV acute GVHD (80% and 86%, respectively) compared with patients with a normal ACR (58%; global P<0.01). Each increase in elafin of 500 pg/ml resulted in a 10% increase in risk of persistent macroalbuminuria (hazard ratio, 1.10; 95% confidence interval [95% CI], 1.06 to 1.13; P<0.001) and a 7% increase in the risk of overall mortality (95% CI, 1.02 to 1.13, P<0.01). Renal biopsy specimens from a separate cohort of HCT survivors demonstrated elafin staining in distal and collecting duct tubules.

CONCLUSION

Higher urinary elafin levels are associated with an increased risk of micro- and macroalbuminuria, AKI and CKD, and death after HCT.

Mosaicism of podocyte involvement is related to podocyte injury in females with Fabry disease

Background

Fabry disease. an X-linked deficiency of α-galactosidase A coded by the GLA gene, leads to intracellular globotriaosylceramide (GL-3) accumulation. Although less common than in males, chronic kidney disease, occurs in ∼15% of females. Recent studies highlight the importance of podocyte injury in Fabry nephropathy development and progression. We hypothesized that the greater the % of podocytes with active wild-type GLA gene (due to X-inactivation of the mutant copy) the less is the overall podocyte injury.

Methods

Kidney biopsies from 12 treatment-naive females with Fabry disease, ages 15 (8–63), median [range], years were studied by electron microscopy and compared with 4 treatment-naive male patients.

Results

In females, 51 (13–100)% of podocytes (PC) per glomerulus had no GL-3 inclusions, this consistent with a non-Fabry podocyte phenotype (NFPC). In PC with GL-3 inclusions [Fabry podocyte phenotype (FPC)], GL-3 volume density per podocyte was virtually identical in females and males, consistent with little or no cross-correction between FPC and NFPC. %NFPC per glomerulus (%NFPC/glom) correlated with age in females (r = 0.65, p = 0.02), suggesting a survival disadvantage for FPC over time. Age-adjusted %NFPC/glom was inversely related to foot process width (FPW) (r = −0.75, p = 0.007), an indicator of PC injury. GL-3 volume density in FPC in females correlated directly with FPW.

Conclusions

These findings support important relationships between podocyte mosaicism and podocyte injury in female Fabry patients. Kidney biopsy, by providing information about podocyte mosaicism, may help to stratify females with Fabry disease for kidney disease risk and to guide treatment decisions.

Glomerular structural-functional relationship models of diabetic nephropathy are robust in type 1 diabetic patients

Studies of structural-functional relationships have improved understanding of the natural history of diabetic nephropathy (DN). However, in order to consider structural end points for clinical trials, the robustness of the resultant models needs to be verified. This study examined whether structural-functional relationship models derived from a large cohort of type 1 diabetic (T1D) patients with a wide range of renal function are robust. The predictability of models derived from multiple regression analysis and piecewise linear regression analysis was also compared. T1D patients (n = 161) with research renal biopsies were divided into two equal groups matched for albumin excretion rate (AER). Models to explain AER and glomerular filtration rate (GFR) by classical DN lesions in one group (T1D-model, or T1D-M) were applied to the other group (T1D-test, or T1D-T) and regression analyses were performed. T1D-M-derived models explained 70 and 63% of AER variance and 32 and 21% of GFR variance in T1D-M and T1D-T, respectively, supporting the substantial robustness of the models. Piecewise linear regression analyses substantially improved predictability of the models with 83% of AER variance and 66% of GFR variance explained by classical DN glomerular lesions alone. These studies demonstrate that DN structural-functional relationship models are robust, and if appropriate models are used, glomerular lesions alone explain a major proportion of AER and GFR variance in T1D patients.

Predilection of segmental glomerulosclerosis lesions for the glomerulotubular junction area in type 1 diabetic patients: a novel mapping method

The location of segmental glomerular lesions in relation to the vascular or tubular pole may have diagnostic or prognostic significance. We have developed a model-based method to estimate the distance from a glomerular lesion to a given landmark (vascular or tubular pole) or the glomerular center and applied this to biopsies from 5 microalbuminuric, 5 normoalbuminuric and 7 proteinuric type 1 diabetic patients and 5 normal controls. The distance from each glomerular adhesion to the glomerulotubular junction was measured and divided by the glomerular radius, allowing comparability among different glomeruli, assuming a spherical shape for Bowman's capsule, an assumption which was validated. The frequency of adhesions in 6 glomerular zones with equal height (zone I adjacent to the glomerulotubular junction and zones II-VI progressively farther away) was determined: 59% of adhesions were in zone I, 15% in zone II, 16% in zone III, 7% in zone IV and 3% in zone VI (adjacent to the hilus). In glomeruli with only one adhesion, 82% of these were in zone I. This new method accurately localizes segmental lesions within glomeruli and revealed a marked predilection in type 1 diabetic patients for segmental sclerosis to develop at the glomerulotubular junction.

Temporal profile of diabetic nephropathy pathologic changes

Diabetic nephropathy, by far, is the most common cause of end stage renal disease in the US and many other countries. In type 1 diabetes, the natural history of diabetic nephropathy is tightly linked to evolution of classic lesions of the disease, namely glomerular basement membrane thickening, increased mesangial matrix, and reduced glomerular filtration surface density. These lesions progress in parallel and correlate with increased albumin excretion rate and reduced glomerular filtration rate across a wide range of renal function. In fact, the vast majority of the variances of albumin excretion and glomerular filtration rates can be explained by these glomerular lesions alone in type 1 diabetic patients. Although, classic lesions of diabetic nephropathy, indistinguishable from those of type 1 diabetes, also occur in type 2 diabetes, renal lesions are more heterogeneous in type 2 diabetic patients with some patients developing more advanced vascular or chronic tubulointerstitial lesions than diabetic glomerulopathy. More research biopsy longitudinal studies, especially in type 2 diabetic patients, are needed to better understand various pathways of renal injury in diabetic nephropathy.

Morphologic features of declining renal function in type 1 diabetes

Progressive renal dysfunction is a major complication of type 1 diabetes. Studying relationships between evolution of diabetic nephropathy lesions and renal functional alterations (structural-functional relationships) helps to better understand the natural history of diabetic nephropathy. The focus of this review is our current understanding of the interplay between morphologic changes of diabetic nephropathy and glomerular filtration rate (GFR) loss. These morphologic changes often may not progress in parallel to each other or to the decline in GFR or increase in albumin excretion rate (AER). Quantitative measures of renal (mainly glomerular) structural changes can predict a substantially larger fraction of AER variability compared with that of GFR, especially using linear correlation analyses. However, nonlinear models better fit the structural-functional relationships across a wide range of GFRs and AERs. Currently, there are insufficient longitudinal data to show which structural changes predict the slope of GFR decline in type 1 diabetic patients. Based on cross-sectional studies, however, such a predictor would be about 10% more robust in patients whose GFR was 45 mL/min/1.73 m(2) or greater if comprised of a composite of glomerular, tubular, and interstitial parameters versus glomerular changes alone. For a slowly progressive disease, such as diabetic nephropathy, in which, especially in the earlier stages, it takes a long time for GFR to decline substantially, such predictors are much needed and, if sufficiently precise, could potentially serve as a surrogate of renal functional decline in clinical trials.

The impact of C4d and microvascular inflammation before we knew them

It is important to identify prognostically important morphologic criteria in post-transplant management to tailor therapy and improve outcomes. Therefore, using biopsies carried out for cause <1-yr post-transplant, from an era when C4d staining and microvascular inflammation (MVI) were not clinically utilized, we studied the importance of C4d and MVI on graft survival. Snap-frozen first renal allograft biopsy specimens (done for cause) in the first post-transplant year from 1996 to 2001 were stained/examined for C4d, and pathology re-examined by a separate blinded pathologist. Graft outcomes in patients with and without MVI and/or C4d were compared. Of 128 patients, 39 (30.5%) biopsies were C4d+ and 89 (69.5%) were C4d-; 67 (52.3%) had no MVI (MVI-) while 61 (47.7%) had glomerulitis, peritubular capillaritis, or both (MVI+). There were no significant demographic differences between MVI+ and MVI- patients. A greater proportion of C4d+ biopsies was MVI+ (67%) than MVI- (33%; p = 0.004). C4d positivity had no impact on death-censored graft survival (DCGS). In contrast DCGS was worse in MVI+ than MVI- regardless of presence/absence of C4d (p = 0.005). In biopsies for cause carried out <1-yr post-transplant, MVI is associated with decreased DCGS, independent of the presence of C4d.

Effect of oral N-acetyl cysteine on eradication of Helicobacter pylori in patients with dyspepsia

AIM

Using mucolytic agents that decrease viscosity of the gastric mucous and therefore, increase the permeability of antibiotics through gastric membrane has been offered as an additive treatment to achieve a higher rate of eradication of Helicobacter pylori (H. Pylori) infection. The aim of this study was to determine the efficacy of oral N-acetyl cysteine (NAC) on eradication of H. pylori infections in patients suffering from dyspepsia.

METHODS

In this randomized double-blinded clinical trial, 60 H. pylori positive patients who were suffering from dyspepsia were included. They were divided into two groups. Both groups received three-drug regimen including pantoprazole 40 mg BD, ciprofloxacin 500 mg BD and bismuth subcitrate 120 mg two tablets BD. Experimental group (30 cases) received 600 mg of NAC besides three-drug regimen. Control group received placebo. The results of therapy were tested by 14C-UBT and were compared with each other two months after the first visit.

RESULTS

H. pylori infection was eradicated in 21 (70%) and 17 (60.7%) patients in experimental and control groups, respectively (P=0.526). Regarding clinical and endoscopic variables, no significant difference was observed between the two groups except for erosive gastritis (0.041) and erosive esophagitis (0.031).

CONCLUSION

Our findings offer that NAC has an additive effect on H. pylori triple therapy with pantoprazole, ciprofloxacin and bismuth subcitrate. Although NAC does not have any known activity against H. pylori, it can reduce the thickness of the mucus layer and increase the permeability of antibiotics at the site of infection. To evaluate this effect, more studies with larger sample size should be performed.

Angiotensin II blockade in kidney transplant recipients

Interstitial fibrosis/tubular atrophy (IF/TA) contributes to the loss of kidney allografts, and treatment or preventive options are lacking. We conducted a double-blind, randomized, placebo-controlled trial to determine whether angiotensin II blockade prevents the expansion of the cortical interstitial compartment, the precursor of fibrosis. We randomly assigned 153 transplant recipients to receive losartan, 100 mg (n=77), or matching placebo (n=76) within 3 months of transplantation, continuing treatment for 5 years. The primary outcome was a composite of doubling of the fraction of renal cortical volume occupied by interstitium from baseline to 5 years or ESRD from IF/TA. In the intention-to-treat analysis, using only patients with adequate structural data, the primary endpoint occurred in 6 of 47 patients who received losartan and 12 of 44 who received placebo (odds ratio [OR], 0.39; 95% confidence interval [CI], 0.13-1.15; P=0.08). We found no significant effect of losartan on time to a composite of ESRD, death, or doubling of creatinine level. In a secondary analysis, losartan seemed to reduce the risk of a composite of doubling of interstitial volume or all-cause ESRD (OR, 0.36; 95% CI, 0.13-0.99; P=0.05), but this finding requires validation. In conclusion, treatment with losartan did not lead to a statistically significant reduction in a composite of interstitial expansion or ESRD from IF/TA in kidney transplant recipients.

Prevention of acute kidney injury by tauroursodeoxycholic acid in rat and cell culture models

BACKGROUND

Acute kidney injury (AKI) has grave short- and long-term consequences. Often the onset of AKI is predictable, such as following surgery that compromises blood flow to the kidney. Even in such situations, present therapies cannot prevent AKI. As apoptosis is a major form of cell death following AKI, we determined the efficacy and mechanisms of action of tauroursodeoxycholic acid (TUDCA), a molecule with potent anti-apoptotic and pro-survival properties, in prevention of AKI in rat and cell culture models. TUDCA is particularly attractive from a translational standpoint, as it has a proven safety record in animals and humans.

METHODOLOGY/PRINCIPAL FINDINGS

We chose an ischemia-reperfusion model in rats to simulate AKI in native kidneys, and a human kidney cell culture model to simulate AKI associated with cryopreservation in transplanted kidneys. TUDCA significantly ameliorated AKI in the test models due to inhibition of the mitochondrial pathway of apoptosis and upregulation of survival pathways.

CONCLUSIONS

This study sets the stage for testing TUDCA in future clinical trials for prevention of AKI, an area that needs urgent attention due to lack of effective therapies.

Indolent systemic mastocytosis associated with light chain deposition disease

Systemic mastocytosis (SM) is characterized by infiltration of neoplastic mast cells in one or more organ systems. SM in association with plasma cell dyscrasia is very rare. We report a first case of indolent SM (ISM) associated with light chain deposition disease (LCDD) in a kidney biopsy from a 59-year-old female presenting with skin rash, elevated serum creatinine, hematuria and mild proteinuria. Subsequent workup demonstrated IgG kappa monoclonal protein in serum and urine. A bone marrow biopsy revealed neoplastic mast cells involving bone marrow without evidence of clonal myeloid or lymphoid proliferation. Kidney biopsy demonstrated modest mesangial expansion detected by light microscopy and unequivocal evidence of monoclonal kappa light chain deposition within glomerular capillaries, tubular basement membranes and vascular walls detected by immunofluorescence and/or electron microscopy, along with equivocal evidence of light chain cast nephropathy. Despite treatment with bortezomib and dexamethasone, her renal function was progressively declined over the next 6 months. This case is a reminder that SM can coincide with LCDD, which requires clinical suspicion and multimodality workup on a kidney biopsy including immunofluorescence and electron microscopy to reach the correct diagnosis.

Reduced elastogenesis: a clue to the arteriosclerosis and emphysematous changes in Schimke immuno-osseous dysplasia?

BACKGROUND

Arteriosclerosis and emphysema develop in individuals with Schimke immuno-osseous dysplasia (SIOD), a multisystem disorder caused by biallelic mutations in SMARCAL1 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a-like 1). However, the mechanism by which the vascular and pulmonary disease arises in SIOD remains unknown.

METHODS

We reviewed the records of 65 patients with SMARCAL1 mutations. Molecular and immunohistochemical analyses were conducted on autopsy tissue from 4 SIOD patients.

RESULTS

Thirty-two of 63 patients had signs of arteriosclerosis and 3 of 51 had signs of emphysema. The arteriosclerosis was characterized by intimal and medial hyperplasia, smooth muscle cell hyperplasia and fragmented and disorganized elastin fibers, and the pulmonary disease was characterized by panlobular enlargement of air spaces. Consistent with a cell autonomous disorder, SMARCAL1 was expressed in arterial and lung tissue, and both the aorta and lung of SIOD patients had reduced expression of elastin and alterations in the expression of regulators of elastin gene expression.

CONCLUSIONS

This first comprehensive study of the vascular and pulmonary complications of SIOD shows that these commonly cause morbidity and mortality and might arise from impaired elastogenesis. Additionally, the effect of SMARCAL1 deficiency on elastin expression provides a model for understanding other features of SIOD.

Quantitating glomerular endothelial fenestration: an unbiased stereological approach

BACKGROUND/AIMS

Glomerular endothelial cells are fenestrated, allowing for especially high transcellular hydraulic conductivity. Current knowledge about endothelial fenestration structural changes in disease conditions is limited, partly due to the absence of robust methodologies to quantitate these structures. Herein, we propose a novel method for estimating the percentage of endothelial fenestration.

METHODS

An unbiased stereological method based on contiguity of two phases and surface area density estimation using isotropic uniform random line probes was developed. A line grid for intercept counting and classifying endothelial coverage of fenestrated versus non-fenestrated areas was designed. The method was applied to renal biopsies from 15 patients with Fabry disease and 9 normal living kidney donor controls.

RESULTS

The percentage of glomerular capillary endothelial coverage which was fenestrated was lower in Fabry patients (43 ± 12%) versus controls (53 ± 9%; p = 0.047). The fraction of endothelial surface which was fenestrated was greater on the peripheral versus mesangial zones of the capillary walls in both Fabry patients (p = 0.00002) and controls (p = 0.0005).

CONCLUSION

The proposed method provides an unbiased tool to quantitate endothelial fenestration changes in glomeruli. The practical example introduced showed reduced glomerular endothelial fenestration in Fabry nephropathy.

Angiotensin II receptor blocker pretreatment of rats undergoing sudden renal ablation

BACKGROUND

Subtotal nephrectomy (N) in rats results in progressive hypertension, proteinuria and renal lesions. Renin-angiotensin system blockade initiated at N prevents these changes; treatments failing to reduce hypertension and proteinuria do not.

METHODS

Ten Munich-Wistar rats underwent 1&frac12; surgical N; eight littermates were pretreated with losartan (L) only for 6 weeks prior to 1&frac12; N (N + L). Pretreated (n = 8; C + L) and untreated controls (C; n = 8) had sham operations.

RESULTS

Over 6 months, N and N + L rats developed ∼80% increase in glomerular filtration rate per nephron over C and C + L, P < 0.001). Hypertension (intra-arterial mean blood pressure 116 ± 6.8 mmHg in N rats versus 102 ± 3.2 in C, 104 ± 8.4 in C + L, and 104 ± 8.4 in N + L rats, P < 0.001 for all) and proteinuria (120 ± 20 mg/day in N versus 39 ± 10 in C, 34 ± 8 in C + L and 35 ± 8 in N + L, P < 0.001 for all) developed only in N. Focal segmental glomerulosclerosis (FSGS) (%) at 6 months was 20 ± 8 in N and 17.5 ± 8 in N + L (ns) and <1 in C and C + L (P < 0.001 versus N and N + L). Interstitial fractional volume (Vv), 4.0 ± 1.7% in C and 4.4 ± 1.6% in C + L (ns), was similarly increased to 7.5 ± 2.5% in N and 9.0 ± 3.9% in N+L (P < 0.04 versus C and C + L). Atrophic tubule Vv was increased by >300% in N and N + L over C and C + L (P < 0.02 for all). Glomerular volume doubled in N and N + L (P < 0.001). Podocyte foot process effacement was greater in N and NL than in C or C + L (P ≤ 0.02 for all). Thus, L given for 6 weeks prior to 1&frac12; N prevented hypertension and proteinuria over the subsequent 6 months without reducing glomerular hypertrophy, hyperfiltration or interstitial, tubular or FSGS lesions or foot process effacement.

CONCLUSIONS

These studies dissociated systemic hypertension and proteinuria from the renal lesions in this model. Durable effects of losartan on blood pressure and proteinuria likely represent epigenetic processes.

Protective effects of PPARγ agonist in acute nephrotic syndrome

BACKGROUND

Peroxisome proliferator-activated receptor gamma (PPARγ) agonists have beneficial effects on renal structure and function in models of diabetes and chronic kidney diseases. However, the increased incidence of weight gain and edema potentially limits their usefulness. We studied an acute minimal-change disease-like nephrotic syndrome model to assess effects of PPARγ agonist on acute podocyte injury and effects on fluid homeostasis.

METHODS

Acute podocyte injury and nephrotic syndrome were induced by puromycin aminonucleoside (PAN) injection in rats.

RESULTS

PPARγ agonist, given at the time or after, but not before PAN, reduced proteinuria, restored synaptopodin, decreased desmin and trended to improve foot process effacement. There was no significant difference in glomerular filtration, effective circulating volume, blood pressure or fractional sodium excretion. PAN-injured podocytes had decreased PPARγ, less nephrin and α-actinin-4, more apoptosis and reduced phosphorylated Akt. In PAN-injured cultured podocytes, PPARγ agonist also reversed abnormalities only when given simultaneously or after injury.

CONCLUSIONS

These results show that PPARγ agonist has protective effects on podocytes in acute nephrotic syndrome without deleterious effects on fluid homeostasis. PPARγ agonist-induced decrease in proteinuria in acute nephrotic syndrome is dependent at least partially on regulation of peroxisome proliferator-response element-sensitive gene expression such as α-actinin-4 and nephrin and the restoration of podocyte structure.

Glomerulopathy in spontaneously obese rhesus monkeys with type 2 diabetes: a stereological study

BACKGROUND

Animal models could provide insights into the diabetic nephropathy pathogenesis; however, available rodent models do not mirror the heterogeneity of lesions in type 2 diabetic patients, and do not progress to end-stage renal disease. Previous studies showed that spontaneously obese type 2 diabetic rhesus monkeys develop many of the features of human diabetic glomerulopathy, and may progress to end-stage renal disease. Here, in order to further characterize diabetic glomerulopathy in this model, we used electron microscopic stereology.

METHODS

Renal biopsies from 17 diabetic, 17 pre-diabetic/metabolic syndrome and 11 non-diabetic monkeys were studied. Fractional volumes of mesangium [Vv(Mes/glom)], mesangial matrix [Vv(MM/glom)] and mesangial cells [Vv(MC/glom)], glomerular basement membrane width and peripheral glomerular basement membrane surface density per glomerulus [Sv(PGBM/glom)] were estimated. Glomerular filtration and albumin excretion rates were measured in a limited number of animals. Glomerular structural and biochemical/metabolic data were compared among the groups.

RESULTS

Compared to non-diabetic monkeys, diabetic rhesus monkeys showed classic diabetic nephropathy changes, including glomerular basement membrane thickening (p = 0.001), increased fractional volumes of mesangium (p = 0.02), and reduced peripheral glomerular basement membrane surface density per glomerulus (p = 0.03) compared to non-diabetic monkeys. Increased fractional volumes of mesangium was primarily due to increased mesangial matrix (p = 0.03). Glomerular structural parameter inter-relationships in diabetic monkeys mirrored those of human diabetic glomerulopathy. Albumin excretion rate was greater (p = 0.03) in diabetic vs. non-diabetic monkeys. There was trend for a positive correlation between albumin excretion rate and fractional volumes of mesangium.

CONCLUSIONS

This rhesus primate model shares many features of human diabetic glomerulopathy. Mesangial expansion in this model, similar to human diabetic nephropathy and different from available rodent models of the disease, is primarily due to increased mesangial matrix.

Progressive podocyte injury and globotriaosylceramide (GL-3) accumulation in young patients with Fabry disease

Progressive renal failure often complicates Fabry disease, the pathogenesis of which is not well understood. To further explore this we applied unbiased stereological quantitative methods to electron microscopic changes of Fabry nephropathy and the relationship between parameters of glomerular structure and renal function in 14 young Fabry patients (median age 12 years). Renal biopsies were obtained shortly before enzyme replacement therapy from these patients and from nine normal living kidney donors as controls. Podocyte globotriaosylceramide (GL-3) inclusion volume density increased progressively with age; however, there were no significant relationships between age and endothelial or mesangial inclusion volume densities. Foot process width, greater in male Fabry patients, also progressively increased with age compared with the controls, and correlated directly with proteinuria. In comparison to the biopsies of the controls, endothelial fenestration was reduced in Fabry patients. Thus, our study found relationships between quantitative parameters of glomerular structure in Fabry nephropathy and age, as well as urinary protein excretion. Hence, podocyte injury may play a pivotal role in the development and progression of Fabry nephropathy.

Tacrolimus and cyclosporine nephrotoxicity in native kidneys of pancreas transplant recipients

BACKGROUND AND OBJECTIVES

Calcineurin inhibitors, while representing advances for solid organ transplantation, have nephrotoxic potential that reduces their net benefit. Tacrolimus has been considered less nephrotoxic than cyclosporine, but direct quantitative comparisons of the changes in renal structure from baseline to follow-up biopsies have not been done. To avoid the pitfalls of renal allograft studies, including rejection and disease recurrence, we compared the development of calcineurin lesions in the native kidneys of 14 tacrolimus- and 12 calcineurin-treated pancreas transplant alone recipients cured of type 1 diabetes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Research renal biopsies obtained before and at 5 years after transplantation were studied using established morphometric methods.

RESULTS

The cyclosporine and tacrolimus groups had, respectively, on average, 33% versus 44% decline in GFR (ns), 27% versus 29% increase in cortical interstitial fractional volume (ns), 245% versus 347% increase in the fractional volume of cortical tubules that were atrophic (ns), and 291% versus 392% increase in the percent of globally sclerotic glomeruli (ns). Arteriolar hyalinosis did not change significantly in either group.

CONCLUSIONS

These studies indicate that the nephrotoxic potential of tacrolimus and cyclosporine are equivalent and support the development of strategies to reduce these negative effects.

Assessment of renal pathology and dysfunction in children with Fabry disease

Overt renal disease often first presents in male individuals with Fabry disease in early to middle adulthood, but proteinuria and reduced GFR may occur in adolescents and in young children. More recently, kidney biopsy data have shown early renal histologic changes in pediatric patients, and kidney dysfunction, primarily proteinuria, seems to be more common in girls. Renal investigations and their timing in children remain poorly defined. A consensus on renal investigations is necessary to understand the natural progression of the disease and to evaluate the efficacy of treatments such as enzyme replacement therapies. This article addresses three main categories: Use of GFRs, measuring albuminuria, and renal biopsies in children.

Effect of Notch activation on the regenerative response to acute renal failure

Episodes of acute renal failure (ARF) are not always fully reversible and may lead to chronic disease, due in part to an inadequate regenerative response. The Notch signaling pathway is involved in determining cell fate during development, and tissue maintenance and repair in adult organs. The purpose of this study was to examine the role of the Notch pathway in renal regeneration following ARF. Kidney injury, induced by ischemia-reperfusion, resulted in early activation of the Notch pathway, as evidenced by increased expression of Notch1 and Notch2 intracellular domain (cleaved Notch). The effect of exogenous administration of the Notch ligand Delta-like-4 (DLL4) on recovery from ARF was then studied. Rats were pretreated by intraperitoneal injection of DLL4 or vehicle control. Two days following the last DLL4 dose, ARF was induced by bilateral renal artery clamping for 45 min followed by reperfusion. The severity of renal injury was similar in DLL4 and control rats. Renal recovery was facilitated by DLL4 treatment, as evidenced by faster return of serum creatinine to baseline by 48 h in DLL4-treated rats as against 5 days in vehicle-treated control rats. Cell proliferation was higher in the DLL4-treated group. In conclusion, activation of the Notch pathway occurs following ARF. Pretreatment with the Notch ligand DLL4 enhanced recovery from ARF and represents a potential novel therapeutic option for regenerating the injured kidney.

Insulin resistance is an independent correlate of increased urine albumin excretion: a cross-sectional study in Iranian Type 2 diabetic patients

AIMS

To assess the association of insulin resistance with increased urinary albumin excretion (UAE) in a cohort of Iranian Type 2 diabetic patients.

METHODS

Three hundred and sixty-one men and 472 women with Type 2 diabetes were enrolled from three different outpatient clinics (Tehran, Iran) during the period 2005-2008. Patients with obstructive uropathy, severe heart failure, liver disease, cancer, autoimmune disease and macroalbuminuria were not included. Microalbuminuria (MA; defined as UAE >or= 30 mg/day) was found in 242 (29.1%) patients; 591 (70.9%) subjects had normoalbuminuria (UAE < 30 mg/day). Insulin resistance was assessed using homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

HOMA-IR index values were higher in subjects with MA than those with normoalbuminuria (P < 0.00001). Adjusted values (for age, sex and duration of diabetes) of UAE and HOMA-IR were 11.81 +/- 7.51 (mg/day) and 3.30 +/- 2.21 in normoalbuminuric and 75.36 +/- 55.57 (mg/day) and 4.98 +/- 3.22 in the MA group, respectively (P < 0.00001 for all). Multiple regression analysis showed that UAE was predicted by HOMA-IR, independently of age, duration of diagnosed diabetes, triglycerides, waist circumference, metabolic control, blood pressure and related treatments (P < 0.00001). When patients were categorized into quartiles of HOMA-IR, those of the fourth quartile (i.e. the most insulin resistant) were at a higher risk of increased UAE than other quartiles [odds ratio (OR) 3.7 (95% confidence intervals 2.7-6.2)].

CONCLUSIONS

In Iranian Type 2 diabetic patients, albuminuria was strongly associated with insulin resistance. HOMA-IR is an independent predictor of UAE.

Progression of diabetic nephropathy in type 1 diabetic patients

Understanding pathogenetic mechanisms of diabetic nephropathy progression risk factors is important. Structural-functional relationship studies have increased our understanding of the glomerular, vascular and tubulointerstitial lesions evolution at various stages of diabetic nephropathy. Classical and more recently described lesions of diabetic nephropathy are discussed. Structural changes associated with progression toward proteinuria and GFR loss are summarized. The relationships of renal structure and function in diabetic nephropathy are best described by non-linear models which mimic the natural history of the disease, i.e., renal pathology develops in clinical silence but, once established, leads to proteinuria and GFR decline.