Urinary epidermal growth factor as a prognostic marker for the progression of Alport syndrome in children.

BACKGROUND: Alport syndrome is a rare hereditary kidney disease manifested with progressive renal failure. Considerable variation exists in terms of disease progression among patients with Alport syndrome. Identification of patients at high risk of rapid progression remains an unmet need. Urinary epidermal growth factor (uEGF) has been shown to be independently associated with risk of progression to adverse kidney outcome in multiple independent adult chronic kidney disease (CKD) cohorts. In this study, we aim to assess if uEGF is associated with kidney impairment and its prognostic value for children with Alport syndrome. METHODS: One hundred and seventeen pediatric patients with Alport syndrome and 146 healthy children (3-18 years old) were included in this study. uEGF was measured in duplicates in baseline urine samples using ELISA (R&D) and concentration was normalized by urine creatinine (uEGF/Cr). In patients with longitudinal follow-up data (n = 38), progression was defined as deteriorated kidney function (CKD stage increase) during follow-up period (follow-up length is about 31 months in average). The association of baseline uEGF/Cr level with estimated glomerular filtration rate (eGFR) slope and Alport syndrome patients' progression to a more advanced CKD stage during the follow-up period was used to evaluate the prognostic value of the marker. RESULTS: We found that uEGF/creatinine (uEGF/Cr) decreases with age in pediatric patients with Alport syndrome with a significantly faster rate than in healthy children of the same age group. uEGF/Cr is significantly correlated with eGFR (r = 0.75, p < 0.001), after adjustment for age. In 38 patients with longitudinal follow-up, we observed a significant correlation between uEGF/Cr and eGFR slope (r = 0.58, p < 0.001). Patients with lower uEGF/Cr level were at increased risk of progression to a higher CKD stage. uEGF/Cr was able to distinguish progressors from non-progressors with an AUC of 0.88, versus 0.77 by eGFR and 0.81 by 24-h urinary protein (24-h UP). CONCLUSIONS: Our study suggests that uEGF/Cr is a promising biomarker for accelerated kidney function decline in pediatric patients with Alport syndrome. It may help to identify patients at high risk of progression for targeted clinical care and improve the patients' stratification in interventional trials.

Renal, auricular, and ocular outcomes of Alport syndrome and their current management.

Alport syndrome is a hereditary glomerular basement membrane disease caused by mutations in the COL4A3/4/5 genes encoding the type IV collagen alpha 3-5 chains. Most cases of Alport syndrome are inherited as X-linked dominant, and some as autosomal recessive or autosomal dominant. The primary manifestations are hematuria, proteinuria, and progressive renal failure, whereas some patients present with sensorineural hearing loss and ocular abnormalities. Renin-angiotensin-aldosterone system blockade is proven to delay the onset of renal failure by reducing proteinuria. Renal transplantation is a curative treatment for patients who have progressed to end-stage renal disease. However, only supportive measures can be used to improve hearing loss and visual loss. Although both stem cell therapy and gene therapy aim to repair the basement membrane defects, technical difficulties require more research in Alport mice before clinical studies. Here, we review the renal, auricular, and ocular manifestations and outcomes of Alport syndrome and their current management.

Accelerated podocyte detachment and progressive podocyte loss from glomeruli with age in Alport Syndrome.

Podocyte depletion is a common mechanism driving progression in glomerular diseases. Alport Syndrome glomerulopathy, caused by defective α3α4α5 (IV) collagen heterotrimer production by podocytes, is associated with an increased rate of podocyte detachment detectable in urine and reduced glomerular podocyte number suggesting that defective podocyte adherence to the glomerular basement membrane might play a role in driving progression. Here a genetically phenotyped Alport Syndrome cohort of 95 individuals [urine study] and 41 archived biopsies [biopsy study] were used to test this hypothesis. Podocyte detachment rate (measured by podocin mRNA in urine pellets expressed either per creatinine or 24-hour excretion) was significantly increased 11-fold above control, and prior to a detectably increased proteinuria or microalbuminuria. In parallel, Alport Syndrome glomeruli lose an average 26 podocytes per year versus control glomeruli that lose 2.3 podocytes per year, an 11-fold difference corresponding to the increased urine podocyte detachment rate. Podocyte number per glomerulus in Alport Syndrome biopsies is projected to be normal at birth (558/glomerulus) but accelerated podocyte loss was projected to cause end-stage kidney disease by about 22 years. Biopsy data from two independent cohorts showed a similar estimated glomerular podocyte loss rate comparable to the measured 11-fold increase in podocyte detachment rate. Reduction in podocyte number and density in biopsies correlated with proteinuria, glomerulosclerosis, and reduced renal function. Thus, the podocyte detachment rate appears to be increased from birth in Alport Syndrome, drives the progression process, and could potentially help predict time to end-stage kidney disease and response to treatment.

Somatic mosaicism and variant frequency detected by next-generation sequencing in X-linked Alport syndrome.

X-linked Alport syndrome (XLAS) is a progressive, hereditary nephropathy. Although men with XLAS usually develop end-stage renal disease before 30 years of age, some men show a milder phenotype and develop end-stage renal disease later in life. However, the molecular mechanisms associated with this milder phenotype have not been fully identified. We genetically diagnosed 186 patients with suspected XLAS between January 2006 and August 2014. Genetic examination involved: (1) extraction and analysis of genomic DNA using PCR and direct sequencing using Sanger's method and (2) next-generation sequencing to detect variant allele frequencies. We identified somatic mosaic variants in the type VI collagen, α5 gene (COL4A5) in four patients. Interestingly, two of these four patients with variant frequencies in kidney biopsies or urinary sediment cells of ≥50% showed hematuria and moderate proteinuria, whereas the other two with variant frequencies of <50% were asymptomatic or only had hematuria. De novo variants can occur even in asymptomatic male cases of XLAS resulting in mosaicism, with important implications for genetic counseling. This is the first study to show a tendency between the variant allele frequency and disease severity in male XLAS patients with somatic mosaic variants in COL4A5. Although this is a very rare status of somatic mosaicism, further analysis is needed to show this correlation in a larger population.

Alport syndrome: the effects of spironolactone on proteinuria and urinary TGF-ß1.

BACKGROUND: Alport syndrome (AS) is a progressive hereditary glomerular disease. Recent data indicate that aldosterone promotes fibrosis mediated by the transforming growth factor-ß1 (TGF-ß1) pathway, which may worsen proteinuria. Spironolactone (SP) antagonizes aldosterone and this study aimed to evaluate the efficacy of SP in reducing proteinuria and urinary TGF-ß1 excretion in proteinuric AS patients. METHODS: The study involved ten children with AS, normal renal function, and persistent proteinuria (>6 months; uPr/uCr ratio >1). SP 25 mg once a day for 6 months was added to existing ACE inhibitor treatment with or without angiotensin-II receptor blockade. Urine and blood samples were examined monthly. Urinary TGF-ß1 levels were measured twice before and three times during SP treatment. Plasma renin activity (PRA) and serum aldosterone levels were also measured. In eight patients, uProt/uCreat was also assessed after 9 months and 12 months of SP treatment. RESULTS: After beginning SP therapy, all patients showed significant decrease in mean uProt/uCreat ratio (1.77 ± 0.8 to 0.86 ± 0.6; p < 0.001) and mean urinary TGF-ß1 levels (104 ± 54 to 41 ± 20 pg/mgCreatinine; p < 0.01), beginning after 30 days of treatment and remaining stable throughout SP administration. PRA remain unchanged, and mean serum aldosterone increased from 105 ± 72 pg/ml to 303 ± 156 pg/ml (p < 0.001). The only side effect was gynecomastia in an obese boy. After 1 year of therapy, mean uProt/uCreat remains low (0.82 ± 0.48). CONCLUSIONS: Addition of SP to ACE-I treatment with or without angiotensin II receptor blokers (ARB) significantly reduced proteinuria. This was mediated by decreased urinary TGF-ß1 levels and not associated with major side effects.

Losartan and enalapril are comparable in reducing proteinuria in children with Alport syndrome.

BACKGROUND: A previous subgroup analysis of a 12-week, double-blind study demonstrated that losartan significantly lowered proteinuria versus placebo and amlodipine and was well tolerated in children (1-17 years old) with proteinuria secondary to Alport syndrome. The present subgroup analysis of the open-label, extension phase of this study assessed the long-term efficacy and tolerability of losartan versus enalapril. METHODS: Patients who had completed the double-blind study were re-randomized to losartan or enalapril and followed for proteinuria and renal function for up to 3 years. RESULTS: Twenty-seven patients with Alport syndrome were randomized to losartan (0.44-2.23 mg/kg/day; n = 15) or enalapril (0.07-0.72 mg/kg/day; n = 12). The least-squares (LS) mean percent change from week 12 in urinary protein to creatinine ratio (UPr/Cr was +1.1 % in the losartan group versus a further 13.9 % reduction in the enalapril group (GMR [95 % CI] = 1.2 [0.7, 2.0]); the LS mean change from week 12 in estimated glomerular filtration rate (eGFR) was -6.4 ml/min/1.73 m(2) in the losartan group versus -9.1 ml/min/1.73 m(2) in the enalapril group. The adverse event incidence was low and comparable in both treatment groups. CONCLUSIONS: In children with proteinuria secondary to Alport syndrome, losartan maintained proteinuria reduction, and enalapril produced a further proteinuria reduction over the 3-year study period. Both agents were generally well tolerated.

[Features of proteinuria in Chinese male patients with Alport syndrome].

OBJECTIVE: To explore the timing and course of proteinuria in Chinese patients with Alport syndrome (AS). METHODS: This retrospectively study included 118 unrelated male AS patients at Department of Pediatrics, Peking University First Hospital between 1994 and 2009. The clinical data of the onset age of proteinuria, the degree of proteinuria and the prevalence of microalbuminuria were analyzed. Urinary total protein was detected by the pyrogallol red protein dye-binding assay, urinary microalbumin by immunoturbidimetric assay and urinary creatinine level by alkaline kinetics. Microalbuminuria was detected when the microalbumin: creatinine ratio was > 30 mg/g on a single random midstream first morning urine sample. RESULTS: A total of 106 patients had proteinuria. The occurring or detecting age of proteinuria varied from 1 month to 27 years. Five patients (4.7%) were under 1 year of age and 15 patients (14.2%) at toddler's age. Among 43 cases with nephrotic-level proteinuria, 21 cases (48.8%) presented with nephrotic-level proteinuria at age 6 - 12 year. Both urine total protein and morning urine microalbumin measurements within 7 days were made in 53 patients. Microalbuminuria occurred in 4 of 5 patients with normal daily urinary protein excretion. All 48 patients had daily proteinuria > 0.15 g. Increased urinary microalbumin was detected in 4 of 5 patients with normal daily urinary protein excretion and 46 patients with daily proteinuria > 0.15 g. The consistency of urine microalbumin concentration and urine microalbumin-to-creatinine ratio was excellent in 51 patients. However, in 2 patients with slightly increased daily urine total protein, urine microalbumin concentration was normal while the urine microalbumin-to-creatinine ratio abnormal (> 30 mg/g). CONCLUSIONS: In AS males, proteinuria occurs earlier and progresses rapidly. Since microalbuminuria precedes the onset of proteinuria, either urine microalbumin concentration or urine microalbumin-to-creatinine ratio in morning specimens should be used for detecting microalbuminuria. And microalbuminuria may serve as an early endpoint in intervention trials.

Urinary biomarkers of renal disease in dogs with X-linked hereditary nephropathy.

BACKGROUND: Sensitive and specific biomarkers for early tubulointerstitial injury are lacking. HYPOTHESIS: The excretion of certain urinary proteins will correlate with the state of renal injury in dogs with chronic kidney disease. ANIMALS: Twenty-five male colony dogs affected with X-linked hereditary nephropathy (XLHN) and 19 unaffected male littermates were evaluated. METHODS: Retrospective analysis of urine samples collected every 2-4 weeks was performed. Urine proteins evaluated were retinol binding protein (uRBP/c), ß2-microglobulin (uB2M), N-acetyl-ß-D-glucosaminidase (uNAG/c), neutrophil gelatinase-associated lipocalin (uNGAL/c), and immunoglobulin G (uIgG/c). Results were correlated with serum creatinine concentration (sCr), glomerular filtration rate (GFR), urine protein : creatinine ratio, and histopathologic analysis of serial renal biopsies. Analytical validation was performed for all assays; uNAG stability was evaluated. RESULTS: All urinary biomarkers distinguished affected dogs from unaffected dogs early in their disease process, increasing during early and midstages of disease. uRBP/c correlated most strongly with conventional measures of disease severity, including increasing sCr (r = 0.89), decreasing GFR (r = -0.77), and interstitial fibrosis (r = 0.80), P < .001. However, multivariate analysis revealed age, sCr, uIgG/c, and uB2M, but not uRBP/c, as significant independent predictors of GFR (P < .05). CONCLUSIONS AND CLINICAL IMPORTANCE: All urinary biomarkers were elevated before sCr increased, but typically after proteinuria developed in dogs with progressive glomerular disease because of XLHN. uRBP/c measurement might be promising as a noninvasive tool for diagnosis and monitoring of tubular injury and dysfunction in dogs.

The renal allograft donor with isolated microhematuria.

Recently, there has been extensive debate about extending the criteria for accepting living donors to include the presence of mild renal abnormalities such as isolated microhematuria. Hematuria defined as the detection of greater than five red blood cells per high power field can be associated with abnormalities throughout the urinary tract. Detection of casts or dysmorphic red blood cells in the urine sediment with or without proteinuria could indicate underlying intrinsic renal disease. Anatomic causes, such as stones and tumors, should be excluded; cystoscopy may be indicated to exclude bladder pathology. Obviously, urinary tract infection, uncontrolled hypertension and latent diabetes mellitus must be excluded. Microscopic hematuria could be associated with mesangial IgA deposits; as 10% of first-degree relatives of patients with IgA glomerulonephritis suffer from microhematuria and/or proteinuria that may require consideration of renal biopsy. Microhematuria could also be associated with other known hereditary renal diseases such as C3 deposits disease, IgM nephropathy, autosomal dominant polycystic kidney disease, Alport's syndrome or thin basement membrane disease. In conclusion, careful assessment of isolated microhematuria, in the context of living kidney donation, is mandatory as results may reveal occult renal disease that may contraindicate kidney donation.

Angiotensin converting enzyme inhibitor therapy in children with Alport syndrome: effect on urinary albumin, TGF-beta, and nitrite excretion.

BACKGROUND: Angiotensin converting enzyme inhibitors are routinely prescribed to patients with chronic kidney disease because of their known renoprotective effects. We evaluated the effect of short-term therapy with the angiotensin converting enzyme inhibitor, enalapril, in early Alport syndrome, defined as disease duration less than 10 years and a normal glomerular filtration rate. METHODS: 11 children with early Alport syndrome were investigated. Two consecutive early morning urine specimens were collected at the start of the study for measurement of urinary creatinine, total protein, albumin, TGF-beta, and nitrite excretion. Patients were treated with enalapril, congruent with 0.2 mg/kg/day, once a day for 14 days. Two early morning urine specimens were collected on days 13 and 14 of enalapril treatment and two weeks later for measurement of urinary creatinine, total protein, albumin, TGF-beta, and nitrite excretion. RESULTS: Prior to treatment, urinary excretion of transforming growth factor-beta and nitrite, the major metabolite of nitric oxide, was within normal limits in all patients. Administration of enalapril for 2 weeks did not alter urinary albumin, transforming growth factor-beta, or nitrite excretion. CONCLUSION: These findings suggest that early Alport syndrome represents a disease involving exclusively intrinsic glomerular barrier dysfunction. At this stage of the illness, there is no evidence of angiotensin II-mediated proteinuria or increased production of transforming growth factor-beta and, therefore, routine treatment with an angiotensin converting enzyme inhibitor may not be warranted.

Importance of mechanical damage to urinary red blood cells by the glomerular basement membrane.

The reasons for morphological changes of urinary red blood cells (RBC) in patients with glomerulonephritis are still controversial. In order to evaluate the importance of mechanical damage by the glomerular basement membrane (GBM), we examined urinary RBC taken from the patients with two different diseases which have characteristic GBM changes. Urinary RBC taken from 20 patients with Alport syndrome and nine with thin GBM disease were examined using a scanning electron microscope. Nineteen out of the 20 patients (95.0%) with Alport syndrome showed 'glomerular type', while five of the nine patients (55.6%) with thin GBM disease showed 'glomerular type'. These results suggest that more complicated GBM abnormalities cause more severe RBC distortion. Therefore, we conclude that mechanical damage by the GBM may be the major factor in dysmorphism of urinary RBC.

Determination of the urinary D/L trans-3-hydroxyproline ratio: a noninvasive screening test for Alport syndrome.

Because disturbed conformation of connective tissue proteins can be accompanied by increased racemization (i.e., an increased ratio of dextrorotatory (D) to levorotatory (L) amino acid molecules), we studied by high-performance liquid chromatography the renal excretion of the D-form of the basement membrane-specific trans-3-hydroxyproline in patients with Alport syndrome. The D/L ratio was significantly higher in patients with Alport syndrome than in patients with other renal diseases or in healthy control subjects. We therefore suggest that this factor may be a simple noninvasive (screening) test for Alport syndrome.

High-density genetic and physical mapping of DNA markers near the X-linked Alport syndrome locus: definition and use of flanking polymorphic markers.

To refine the genetic and physical mapping of the locus for Alport syndrome (ATS), 22 X-chromosome restriction fragment length polymorphism (RFLP) markers that fall between Xq21.3 and Xq25 were tested for genetic linkage with the disease and also mapped with respect to a series of physical breakpoints in this region. The location of the COL4A5 gene, which has recently been shown to be mutated in at least some families with Alport syndrome, was determined with respect to the same physical breakpoints. Two large Utah kindreds were included in the genetic studies, kindreds P and C, with 125 and 63 potentially informative meioses, respectively. Both kindreds have essentially identical nephritis; however, kindred P has sensorineural hearing loss associated with the nephritis, while kindred C does not. A mutation in COL4A5 has been demonstrated for kindred P, but no change in this gene has yet been detected for kindred C. Twelve informative probes did not recombine with the disease locus in either kindred (theta = 0.0, with combined lod scores for the two kindreds ranging from 7.7 to 30.0). The closest markers that could be demonstrated to flank the disease locus were the same for each kindred and thus the locations of the mutations causing the two disease phenotypes are not distinguishable at the current level of genetic resolution. The flanking markers are also useful for the resolution of questionable diagnoses and allow accurate estimates for these families of the rate of sporadic hematuria in noncarrier females (7%) and the penetrance of hematuria for carrier females (93%).

Urinary 3-hydroxyproline excretion in Alport's syndrome: a non-invasive screening test?

Alport's syndrome is characterised by morphological and structural changes of the renal basement membranes. As the hydroxyproline content of isolated glomerular basement membranes is reduced in patients with Alport's syndrome, it is possible that the renal excretion of 3-hydroxproline (3-OHP), a key substrate of basement membrane collagen, may be altered in such patients. The urinary excretion of 3-OHP was determined by thin layer chromatography in 20 patients with Alport's syndrome, in healthy control subjects, and in patients with other renal diseases. These included patients with poststreptococcal glomerulonephritis, lower urinary tract infection, severe reflux nephropathy, lithium induced nephropathy, polycystic kidney disease, familiar benign haematuria, and renal graft rejection. Urinary excretion of 3-OHP was significantly higher in patients with Alport's syndrome compared with the patients with other renal diseases and the healthy control subjects. All other renal diseases investigated had 3-OHP values within the normal range. Urinary 3-OHP determination detected patients with Alport's syndrome with a high sensitivity (95.2%) and specificity (97.2%). We therefore suggest using urinary 3-OHP determinations as a simple non-invasive screening test for Alport's syndrome.

Nonfamilial hematuria associated with glomerular basement membrane alterations characteristic of hereditary nephritis: comparison with hereditary nephritis.

Characteristic ultrastructural alterations of the glomerular basement membrane (GBM) have been reported in hereditary nephritis and in children without a family history of renal disease. The clinical features, renal biopsy findings, and subsequent course were studied retrospectively in 48 children with such GBM changes to compare findings in those with and without a family history of nephritis and to determine the significance of the GBM changes in patients with nonfamilial disease. All 48 patients had hematuria. For 30, there was hematuria in at least one other member of the family (familial hematuria group); for 18, there was no familial incidence. There were no differences between the two groups with regard to clinical and pathologic findings. At the latest follow-up six boys with familial hematuria and three boys with nonfamilial hematuria had reduced renal function, and nine boys with familial hematuria and four boys and one girl with nonfamilial hematuria had neurosensory deafness. Our study results show that children with these GBM changes, with or without a family history of hematuria, tend to have a progressive course, with frequent occurrence of neurosensory deafness, and that the prognosis is more severe in boys. These observations suggest that such GBM changes in patients with nonfamilial hematuria may represent new mutations for hereditary nephritis.

The urinary excretion of total hydroxylysine and its glycosides in normal persons, and in patients suffering from Alport's syndrome--contribution of the peptide-bound fraction.

As Alport's syndrome is probably a molecular disorder of basement membrane composition, investigation of the urine on basement membrane components might be a diagnostic aid. It was shown previously that measurement of the excretion of free hydroxylysine and its glycosides, glucosylgalactosylhydroxylysine and galactosylhydroxylysine, was not useful for this purpose. Because the urinary peptide-bound fraction may be more basement membrane specific, a subsequent study was performed with respect to the total (= free and peptide-bound) concentrations and fractions. To establish reference values, urinary specimens of 38 normal subjects of different ages were investigated. These values were used for comparison with data on 30 Alport patients, and 10 Alport siblings. 10 patients with benign recurrent hematuria were also investigated. No marked differences were observed in the excretory rates between normals and patients.

Urinary excretion of hydroxylysine and its glycosides in Alport's syndrome and several other glomerulopathies.

Alport's syndrome probably is a molecular disorder of basement membrane composition. Investigation of urine on basement membrane components such as hydroxylysine and its glycosides, glucosylgalactosylhydroxylysine and galactosylhydroxylysine, may be helpful for diagnosis of the disease. Urinary specimens of 33 patients and 12 siblings were investigated, and the results were compared with those of 14 healthy adults and of 29 healthy children. The urine of patients with glomerulopathies, occurring during childhood (IgA nephropathy, benign recurrent hematuria, poststreptococcal glomerulonephritis, Henoch-Schönlein nephropathy, membranoproliferative glomerulonephritis, and nephrotic syndrome due to minimal lesions), was also investigated. No marked differences between normal and diseased subjects could be demonstrated, with respect to excretion of hydroxylysine and its glycosides, in contrast to data reported in the literature.