The glomerular changes in children with reflux nephropathy

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.

Interplay between vesicoureteric reflux and kidney infection in the development of reflux nephropathy in mice

Vesicoureteric reflux (VUR) is a common congenital defect of the urinary tract that is usually discovered after a child develops a urinary tract infection. It is associated with reflux nephropathy, a renal lesion characterized by the presence of chronic tubulointersitial inflammation and fibrosis. Most patients are diagnosed with reflux nephropathy after one or more febrile urinary tract infections, suggesting a potential role for infection in its development. We have recently shown that the C3H mouse has a 100% incidence of VUR. Here, we evaluate the roles of VUR and uropathogenic Escherichia coli infection in the development of reflux nephropathy in the C3H mouse. We find that VUR in combination with sustained kidney infection is crucial to the development of reflux nephropathy, whereas sterile reflux alone fails to induce reflux nephropathy. A single bout of kidney infection without reflux fails to induce reflux nephropathy. The host immune response to infection was examined in two refluxing C3H substrains, HeN and HeJ. HeJ mice, which have a defect in innate immunity and bacterial clearance, demonstrate more significant renal inflammation and reflux nephropathy compared with HeN mice. These studies demonstrate the crucial synergy between VUR, sustained kidney infection and the host immune response in the development of reflux nephropathy in a mouse model of VUR.

Update on childhood urinary tract infection and vesicoureteral reflux

Urinary tract infection (UTI) is a leading cause of serious bacterial infection in young children. Vesicoureteral reflux (VUR), a common pediatric urologic disorder, is believed to predispose to UTI, and both are associated with renal scarring. The complex interaction of bacterial virulence factors and host defense mechanisms influence renal damage. However, some renal parenchymal abnormalities associated with VUR are noninfectious in origin. Long-term, renal parenchymal injury may be associated with hypertension, pregnancy complications, proteinuria, and renal insufficiency. Optimal management of VUR and UTI is controversial because of the paucity of appropriate randomized controlled trials; there is a need for well-designed studies. The recently launched Randomized Intervention for children with VesicoUreteral Reflux (RIVUR) study hopefully will provide insight into the role of antimicrobial prophylaxis of UTI in children with VUR.

TUMOR NECROSIS FACTOR-α GENE POLYMORPHISM IN REFLUX NEPHROPATHY

PURPOSE

Interstitial scarring contributes to the progression of renal failure in reflux nephropathy. The proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) has been implicated in the disease susceptibility and pathogenesis of several inflammatory diseases promoting interstitial infiltration of inflammatory cells. We evaluate the frequency of TNF-alpha gene polymorphism in patients with reflux nephropathy.

MATERIAL AND METHODS

Renal scarring was evaluated with technetium dimercapto-succinic acid renal scan. Genotyping was performed on 104 patients with reflux nephropathy and 30 controls for the TNF-alpha gene polymorphisms using polymerase chain reaction and restriction digest. This polymorphism involved a guanidine to adenosine transition at position -308 and was designated as TNF1 (-308G) and TNF2 (-308A).

RESULTS

The allele frequencies of TNF1 and TNF2 were 18.8% and 81.2% in patients with reflux nephropathy and 76.7% and 23.3% in controls, respectively. The genotype distribution of TNF-alpha-AA was significantly higher (66.4% vs 10%, p <0.05), while the TNF-alpha-GG was lower (13.4% vs 60%, p <0.05) in patients with reflux nephropathy compared to controls.

CONCLUSIONS

This study demonstrates for the first time the association of the cytokine TNF-alpha gene polymorphism in patients with reflux nephropathy. Our data suggest that patients with vesicoureteral reflux and TNF-alpha AA genotype may have increased susceptibility to reflux nephropathy.

Nitric oxide, enhanced by macrophage-colony stimulating factor, mediates renal damage in reflux nephropathy

BACKGROUND

Reflux nephropathy (RN) is a major cause of end-stage renal failure in children and young adults. Nitric oxide (NO) is an important mediator of tissue injury and inflammation. NO production is enhanced by hematopoietic growth factor including macrophage colony stimulating factor (M-CSF). M-CSF plays a pivotal role in the development of nephritis via macrophage activation. The aim of this study was to investigate the expression of inducible NO synthase (iNOS) and M-CSF in the refluxing kidney, in order to further understand the pathogenesis of RN.

METHODS

The kidney specimens from 6 patients with severe RN and 6 controls were examined by NADPH-diaphorase histochemistry and immunohistochemistry using ABC method with anti-M-CSF antibody. Double staining using NADPH-diaphorase histochemistry/M-CSF immunohistochemistry and M-CSF/iNOS fluorescence immunohistochemistry also was performed. In situ hybridization was performed using digoxigenin labeled M-CSF specific probe. RT-PCR was performed to evaluate the relative amount of iNOS mRNA expression. Apoptosis was determined using the in situ end-labeling technique.

RESULTS

The most striking difference between tissues from RN patients and controls was the marked increase in NADPH-d activity, iNOS immunoreactivity and mRNA and M-CSF immunoreactivity and mRNA expression in the kidneys of RN patients, particularly in the distal tubules, collecting system. Apoptotic cells were markedly increased in RN compared to controls.

CONCLUSIONS

Our findings suggest that the increase in M-CSF-stimulated local production of nitric oxide may be a major mediator in the development of reflux nephropathy.

Transferrin up-regulates chemokine synthesis by human proximal tubular epithelial cells: implication on mechanism of tubuloglomerular communication in glomerulopathic proteinura

BACKGROUND

The pathogenesis of glomerulosclerosis and tubulointerstitial fibrosis in proteinuric renal disease is obscure. We recently showed that transferrin, a key proteinuric component, mediates proximal tubular epithelial cell (PTEC) C3 synthesis. To further examine whether proteinuric tubular injury may induce glomerular inflammation and to characterize the role of transferrin in activating PTEC, glomerular mesangial cells (MC) were exposed to transferrin-activated PTEC culture supernatant and their proliferative and profibrotic responses analyzed.

METHODS

Human PTEC and MC were obtained by primary culture. Confluent, transferrin-stimulated PTEC were grown in serum-free medium to produce a "conditioned" medium that was incubated with quiescent MC. The proliferative response of MC was then assessed by thymidine uptake, and the expression of fibrogenic factors measured by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). The chemokine profile in PTEC after transferrin treatment was examined by RT-PCR and ELISA.

RESULTS

"Conditioned" supernatant from PTEC, which contained the highest amounts of platelet-derived growth factor (PDGF), stimulated MC proliferation compared with serum-free (P = 0.03) or transferrin-containing (P = 0.009) control media. This proliferative response was partially abrogated by treating MC with anti-PDGF. MC expression of PDGF, but not transforming growth factor-beta or intercellular cell adhesion molecule-1, was up-regulated by conditioned PTEC medium. Transferrin up-regulated monocyte chemoattractant peptide-1, interleukin-8, and macrophage migration inhibitory factor expression in a time- and dose-dependent fashion, but had no effect on RANTES expression by PTEC.

CONCLUSIONS

These results provide experimental evidence suggesting that there is a tubuloglomerular "cross-talk" mechanism in the proteinuric state. PTEC-secreted PDGF, which further induces mesangial PDGF, could partially account for the mesangial proliferation frequently observed in proteinuric renal disease. Transferrin is one of the culprit nephrotic proteins leading to tubular overexpression of various proinflammatory chemokines, which may explain the interstitial changes observed in proteinuric states.

Stress tolerance test and SDS-PAGE for the analysis of urinary proteins in children and youths

Excretion of urinary proteins (UP) is an important marker for the evaluation of patients with progressive renal disease. In order to analyze quantitative and qualitative variability of UP in relation to physical activity, we used standardized stress tolerance test and SDS-PAGE. Five urine samples were obtained from each patient at rest, during ordinary daily activity and after physical stress. Determination of total proteins was performed using Meulman's classic method with sulfosalicylic acid. UP were separated by ultrathin horizontal gradient SDS-PAGE according to Görg. There were 142 patients; 40 with poststreptococcal glomerulonephritis (PSGN), 11 with diabetes mellitus, 16 with chronic pyelonephritis and 75 who attended for investigation of asymptomatic proteinuria. Functional proteinuria was established in 42 subjects, who displayed maximal UP excretion during stress and the presence of apolipoprotein AI on SDS-PAGE. Children with PSGN showed no significant increase of UP during stress. Some children with diabetes mellitus (27%) and chronic pyelonephritis (47%) displayed microproteinuria or overt proteinuria after stress. Quantitative and qualitative changes in total UP excretion can be detected by stress tolerance test and SDS-PAGE. It remains to be seen whether stress tolerance test can identify children and youths who are at higher risk for disease progression.

[Parenchymatous cicatrix and urinary tract infection: physiopathology and clinical implications]

Renal scarring is the main long term complication of acute pyelonephritis in children. The prevalence rate is hazardous since data from the literature are confusing with respect to reflux nephropathy, chronic pyelonephritis and renal hypoplasia. The pathology of such lesions consists in focal interstitial fibrosis. When the first pyelonephritic attack occurs during infancy, renal growth may be compromised. The current approach of renal scar assessment is based on dimercaptosuccinic acid (DMSA) scan. Bilateral extensive lesions may be responsible for altered glomerular filtration rate (GFR) and/or arterial hypertension. The management of overt scarring is conservative and careful prevention must be based on early and aggressive treatment of acute pyelonephritis.

The late histologic findings in diarrhea-associated hemolytic uremic syndrome

Kidney biopsies were undertaken for persisting proteinuria 3.3 to 7 years (mean 5.4 years) from the onset of diarrhea-associated hemolytic uremic syndrome (D + HUS) in 5 boys and 2 girls (age at presentation mean 3.2 years, range 1.0 to 9.7 years). At 1 year the mean early morning urine protein/creatinine ratio was 100 mg/mmol, and the mean glomerular filtration rate was 65 mL/min/1.73 m2. At 5 years the mean early morning urine protein/creatinine ratio was 81 mg/mmol, and the mean glomerular filtration rate was 73 mL/min/1.73 m2. The biopsy specimens were compared with those of 7 age- and sex-matched children who were investigated for isolated persistent microscopic hematuria but in whom no abnormality was detected. Global glomerulosclerosis was noted in 6 patients with D + HUS, and 2 of these had segmental sclerosing lesions. Tubular atrophy and interstitial scarring were seen in all but 1 patients. The glomeruli in the D + HUS group were significantly larger than in the control group (P < .01). These findings are typically found in kidneys with reduced nephron numbers and are compatible with changes of hyperperfusion and hyperfiltration in surviving nephrons. Long-term follow-up of patients with D + HUS and proteinuria is advisable.

Postoperative medium-term follow-up of patients with bilateral, massive primary vesicorenal reflux and reduced renal function at presentation

We report the results of a medium-term follow-up study of 52 patients with bilateral, massive primary vesicorenal reflux (PVRR) with renal damage at presentation. Ten infants between 2 and 5 months of age, with a total of 19 renal units, had a temporary vesicostomy followed by ureteral reimplantation after 12-15 months; 42 patients with 81 renal units had primary ureteral reimplantation. The postoperative observation period covered 9.5 years on average (20 months - 21.5 years). The study showed that: (1) urinary specific gravity remained reduced in about 61% of patients; (2) proteinuria improved significantly, in a direct proportion to the favorable evolution of renal function; (3) the frequency of acute pyelonephritis decreased significantly from 98% to 23%. Postoperatively, 27 patients (51%) had one or more episodes of urinary tract infection (UTI) and 12 (23.0%) still had episodes of acute pyelonephritis. (4) At follow-up 7 patients (13.5%) had stable hypertension, while 3 others had unstable hypertension (19.2%); 8 had chronic renal insufficiency or end-stage renal disease. When only adolescents more than 12 years old were considered, the incidence of hypertension increased to 34.4% (10.29). (5) Some renal scarring developed despite successful antireflux surgery, and parenchymal growth, which was severely impaired prior to surgery, restarted although it remained below - 2 standard deviations from the mean. (6) In the overall series glomerular filtration rates (GFR) significantly improved after successful surgery. However, this improvement was much more evident in patients operated upon within the 1st year of life and in those who had had a temporary vesicostomy. In the subgroup of patients operated upon after 6 years of age, successful surgery had no effect on the further decline of renal function when this was already severely compromised. We conclude that early antireflux surgery or, in selected cases, temporary vesicostomy followed by ureteral reimplantation was effective in significantly improving GFR and sharply decreasing febrile UTIs in patients with massive bilateral PVRR and renal damage at presentation.

Glomerular morphometry in childhood reflux nephropathy, emphasizing the capillary changes

As a consequence of nephron loss, reflux nephropathy (RN) causes considerable glomerular hypertrophy. To examine the relative contributions of capillary dilatation and growth in producing hypertrophy, glomeruli contained in unscarred areas of renal biopsies from 19 children with RN were compared with those in 16 children with minimal change nephrotic syndrome and 16 with recurrent hematuria, who were used as controls representing normal childhood growth. Using computerized digitometry we measured the mean glomerular tuft area (GTA) in all complete, undistorted, nonsclerotic glomeruli in periodic acid-Schiff (PAS) stains. Measurements were repeated in four glomeruli of uniform size in periodic acid-silver methenamine stains, the results (GTA4) correlating significantly with GTA. In the same four glomeruli we measured the mean individual capillary luminal area (CLA) and counted the mean number of lumens per glomerulus (N). Mean mesangial area (MA) was calculated as GTA4 - (CLA x N). Cells per distal mesangial region were counted in PAS stains. GTA, GTA4, N, MA and mesangial cell counts were significantly greater in RN than controls, but CLA and fractional MA (MA/GTA%) did not differ. N correlated highly significantly with GTA4 in both RN and controls, but CLA did not do so. These findings are consistent with capillary growth by subdivision being the main mechanism of glomerular hypertrophy when nephron loss occurs during childhood, and the identity of the regressions of N versus GTA4 in RN and controls suggests that compensatory hypertrophy resembles the normal glomerular growth pattern in this age group.

Glomerular volume and renal function in children with different types of the nephrotic syndrome

Glomerular hypertrophy has been suggested to be an important factor in the pathogenesis of focal glomerular sclerosis. The aim of the present study was to analyse retrospectively the renal biopsies of 58 children (0.2-16.1 years of age) with different types of the nephrotic syndrome, minimal change nephrotic syndrome (MCNS), diffuse mesangial proliferation (DMP) and focal segmental glomerulosclerosis (FSGS). Glomerular surface area was measured and glomerular volume was calculated and related to steroid responsiveness and to renal function, measured by clearances of inulin and para-aminohippuric acid. Glomerular volume correlated with body surface area (BSA) and age. Because of this, patients with FSGS and DMP were matched according to BSA and age, with corresponding MCNS patients. Glomerular volumes of FSGS and DMP patients were significantly larger than those of MCNS patients. In the MCNS patients, significant correlations were found between glomerular volumes and glomerular filtration rate and effective renal plasma flow. Steroid-dependent and steroid-resistant patients showed larger glomeruli than the steroid-responsive children. We suggest that hyperfiltration and hyperperfusion, among other factors, may contribute to glomerular hypertrophy, mesangial proliferation and glomerulosclerosis.

Segmental sclerosing glomerular lesions

Segmental sclerosing glomerular lesions are usually all grouped together and called focal segmental glomerulosclerosis. This has meant that the term that was originally used for a defined clinical entity is now applied to a variety of conditions in man and experimental animals, with the assumption that the morphological changes are the same in all conditions. Studies of the position of segmental lesions within glomeruli, the size of glomeruli and the proportion of glomeruli affected have shown that this assumption is wrong. Such studies have identified a disease that corresponds to the original clinical concept of focal segmental glomerulosclerosis. This begins with the nephrotic syndrome in patients whose renal biopsies show large glomeruli with mesangial hypercellularity and segmental lesions at every tubular origin. Later the biopsies have segmental lesions throughout the glomerular tuft. This disease differs clinically and pathologically from other conditions that have segmental sclerosing lesions, such as in patients with reduced renal mass or patients with hypertension and proteinuria. The term focal segmental glomerulosclerosis is now too ambiguous and unsatisfactory to be used without qualification.

Reflux nephropathy: the glomerular lesion and progression of renal failure

Reflux nephropathy is the cause of 5%-10% of dialysed end-stage renal failure. Once scarring has occurred, the prognosis depends on the severity of initial damage and the presence of proteinuria, which reflects the development of glomerulosclerosis. It is independent of ongoing reflux or infection. Histological appearances highly suggestive of reflux nephropathy can occur in radiologically normal kidneys. Duplex Doppler scans of ureteric orifices suggest these patients may have lateral insertion, suggesting past reflux. Glomerular hypertrophy correlates well with reduced renal function and severe renal scarring, but poorly with focal and segmental glomerulosclerosis, which correlates with proteinuria. Increasing attention is being paid to the tubulo-interstitium and the relationships between the cellular infiltrates (mainly T4 cells) and glomerular, tubular and vascular damage. Control of hypertension, hyperphosphataemia and a low-protein diet are the only currently widely accepted treatments for slowing progression.

Glomerular morphometry in reflux nephropathy: functional and radiological correlations

Using computerized digitometry, we investigated the relationships between renal size, glomerular filtration rate (GFR), proteinuria, incidence of segmental and global glomerulosclerosis, glomerular size, hilar arteriolar wall thickness and hyaline deposition in renal biopsies obtained from 24 children and adolescents with reflux nephropathy, of whom only 4 were hypertensive. Age-matched controls comprised minimal-change nephrotic syndrome (6) and recurrent haematuria with normal biopsy (13). The mean sectional area of patients' glomeruli was double that of controls. Glomerular size correlated with the amount of proteinuria (measured as protein/creatinine ratios in early morning urine) and inversely with renal size and GFR. Segmental sclerosis, invariably of hilar origin, was observed in 8 patients and the percentage of glomeruli affected correlated strongly with glomerular size and proteinuria. Global sclerosis was found equally in patients and controls, and showed no similar correlations. Compared with controls, patients' hilar arterioles showed increased wall thickness, more intramural hyaline deposits and decreased luminal diameter when related to glomerular size. The proteinuria and glomerular changes are consistent with hyperfiltration, while the previously undescribed hilar vascular changes, which both precede and accompany sclerosis, resemble abnormalities reported experimentally following renal ablation.

Urinary protein/creatinine index in follow up of patients with Wilms' tumour after nephrectomy

The protein/creatinine index (p/c) was determined in early morning urine (EMU) samples from available patients with Wilms' tumour who had had a nephrectomy and whose diagnosis had been made between January 1970 and December 1989. Clinical details were obtained by case note review. Results were obtained from 36 boys and 40 girls. The mean interval between nephrectomy and measurement of the EMUp/c was 9.0 years (2-23). Eleven patients had a EMUp/c greater than 20 mg/mmol (normal range less than 20). Of the 11 patients with proteinuria, there were in addition to nephrectomy other adverse features including bilateral tumours, treatment with nephrotoxic drugs, and dysplastic kidneys. Renal dysfunction seems most likely to occur where there are adverse factors in addition to unilateral nephrectomy. There was a significant correlation between the glomerular filtration rate and the EMUp/c, and it is thought that this is a simple tool which can be used for the regular monitoring of renal function in these patients.

Effect of cholesterol on the position of segmental lesions in unilaterally nephrectomized rats

Different positions of segmental lesions within glomeruli may correspond to different pathogenetic mechanisms. The effect of a high cholesterol diet on the position of lesions had not previously been investigated. This was studied in rats following unilateral nephrectomy, as a change in position would suggest a different mechanism of damage. Thirty-two female WAG/ola rats had unilateral nephrectomy. Half the rats were given a diet supplemented with 4 per cent cholesterol and 1 per cent cholic acid. At death, six at 10 weeks after nephrectomy and the rest at 24 weeks, kidney sections were examined microscopically. There were significantly more segmental lesions in the cholesterol-fed rats than in the controls, and these lesions were almost entirely at the glomerular hilum in both groups. Significantly more glomeruli contained foamy cells in the cholesterol-fed group, both within lesions and away from them. These findings confirmed that in reduced renal mass, segmental lesions are mainly hilar. The diet increases the number of glomeruli affected by lesions, but these are still mainly hilar. Therefore one possibility is that hypercholesterolaemia worsens the hyperfiltration effect on glomeruli. The diet also produces foamy cells scattered throughout the glomeruli but these do not appear to develop into segmental lesions.