Fabry Nephropathy Research Articles

Podocyturia: why it may have added value in rare diseases.

Fabry disease is an inherited lysosomal disease in which defects in the GLA gene lead to α-galactosidase-A deficiency, and accumulation of glycosphingolipids, including lyso-Gb3, a podocyte stressor. Therapy is available as enzyme replacement therapy and, for some patients, the chaperone migalastat. A key decision is when to start therapy, given its costs and potential impact on some aspects of quality of life. The decision is especially difficult in otherwise asymptomatic patients. A delayed start of therapy may allow kidney injury to progress subclinically up to the development of irreversible lesions. Non-invasive tools to monitor subclinical kidney injury are needed. One such tool may be assessment of podocyturia. In this issue of CKJ, [Trimarchi H, Canzonieri R, Costales-Collaguazo C et al. Early decrease in the podocalyxin to synaptopodin ratio in urinary Fabry podocytes. Clin Kidney J 2019; doi.org/10.1093/ckj/sfy053] report on podocyturia assessment in Fabry nephropathy. Specifically, they report that podocalyxin may be lost from detached urinary podocytes.

Clinic-Pathologic Features and Renal Outcome of Fabry Disease: Data from a Chinese Cohort

Background: Fabry disease (FD) with life-threatening complications occurs as a result of organ damage in kidneys, heart, and brain. Only a few studies, especially from Asia, report their long-term outcome. Methods: In this monocentric study, patients with Fabry nephropathy confirmed by renal biopsy were clinically investigated in a comprehensive manner. The clinic-pathological features, progression, and risk factors for the outcome were analyzed. Results: Thirty-one patients were recruited, after median 62 months (range 8–156 months) follow-up, 23 of them had stable renal function while 8 underwent renal function deterioration. Frequent presenting symptoms included acroparesthesia (58.1%), edema (51.6%), hypo- or anhidrosis (38.7%), and angiokeratoma (32.3%). Left ventricular hypertrophy was present in 62.5% patients with renal function deterioration and 17.4% patients with stable renal function (p = 0.03). The renal cumulative survival rate of all patients was 64.5% in 10 years. Mainz Severity Score Index (MSSI) and segmental sclerosis are independent predictive factors for a more rapid progression of Fabry nephropathy. The receiver operating characteristic analysis demonstrated that the area under the curve for the prediction of renal function progression on the basis of MSSI and segmental sclerosis levels in patients with FD was 0.845 and 0.780, respectively. MSSI score ≥18 or segmental sclerosis ≥3.9% in patients with FD positively correlated with poor renal prognosis. Conclusions: FD’s clinical manifestations are heterogeneous and nonspecific. The ­10-year cumulative renal survival rate was low in Chinese patients. MSSI score and segmental sclerosis levels predict the renal prognosis of patients with FD sensitively.

Early decrease in the podocalyxin to synaptopodin ratio in urinary Fabry podocytes.

BackgroundIn Fabry nephropathy, podocyturia is an early event that may lead to glomerulosclerosis and chronic kidney disease. The glycocalyx is a potential podocyte damaged compartment in glomerulopathies. We investigated glycocalyx podocalyxin in urinary detached podocytes compared with cytoplasmic synaptopodin.MethodsThis was a cross-sectional study including 68 individuals: Controls (n = 20) and Fabry patients (n = 48), 15 untreated and 33 treated. Variables included age, gender, urinary protein/creatinine ratio (UPCR), estimated glomerular filtration rate (eGFR), lyso-triasocylsphingosine (lyso-Gb3) levels and enzyme replacement therapy (ERT). Podocyturia was assessed by immunofluorescence and podocyte subpopulations were analyzed.ResultsFabry patients displayed higher podocyturia than controls. Fabry treated subjects (n = 33) presented significantly higher UPCR compared with untreated ones (n = 15); podocyturia, eGFR and lyso-Gb3 levels were not different. All control podocytes colocalized synaptopodin and podocalyxin; 13 Fabry patients (27%) colocalized these proteins, while 35 (73%) were only synaptopodin positive. No podocalyxin-positive/synaptopodin-negative cells were encountered. In Fabry patients, podocyturia was significantly higher and proteinuria lower in those that colocalized.ConclusionFabry patients present higher podocyturia and a presumably more damaged glycocalyx assessed by podocalyxin. Treated patients had significant higher proteinuria suggesting ERT is initiated late, at advanced stages. The degree of podocalyxin-negative podocytes was similar in both groups, but colocalization was associated with lower proteinuria. Podocyturia assessed by podocalyxin alone may be underestimated. The implications of podocyte glycocalyx damage deserve further investigations.

Enzyme replacement therapy dose and Fabry nephropathy.

Enzyme replacement therapy dose and Fabry nephropathy.

A Novel Missense GLA Mutation (p.G35V) Detected in Hemodialysis Screening Leads to Severe Systemic Manifestations of Fabry Disease in Men and Women

Background/Aims: Fabry disease (FD), an X-linked lysosomal storage disorder, leads to accumulation of globotriaosylceramide. Screening in dialysis patients may identify genetic variants of unknown clinical significance. We aimed to characterize the pathogenicity of a novel GLA gene mutation identified during hemodialysis screening and the histologic findings of early Fabry nephropathy. Methods: One out of 108 male hemodialysis patients screened for FD presented low α-galactosidase A activity. A novel missense mutation (p.G35V) in the GLA gene was detected. Family screening identified 11 additional cases (8 women). Clinical investigation was conducted in 10 patients (index case and 9 relatives). Pathogenicity of the new mutation was investigated by clinical and laboratory tests, cardiac and cranial magnetic resonance imaging, and kidney biopsy. Results: Cardiac manifestations were detected in most patient from both genders, such as left ventricular hypertrophy and short PR interval. White matter lesion was present in 3 women. Pulvinar lesion of the thalamus and ischemic stroke were detected in male patients. Abnormal glomerular filtration rate (GFR) and/or albuminuria were present in 5 patients (3 women). Renal biopsies (n = 7) revealed globotriaosylceramide deposits in different cell types and foot processes effacement in all patients, including women with normal albuminuria. Despite a normal GFR, tubulointerstitial fibrosis ranging from 5 to 20% was present in young women and men with normal or high albuminuria, respectively. Conclusion: The novel missense mutation p.G35V leads to severe systemic manifestations of FD in men and women. Kidney histological changes, including tubulointerstitial fibrosis, may predate albuminuria and GFR changes in adult women. Novel non-invasive markers are required for early detection of Fabry nephropathy.

Fabry Nephropathy.

Fabry disease is a rare X-linked recessive lysosomal storage disease. Multiple mutations of the GLA gene lead to a deficient or absent activity of the lysosomal enzyme α-galactosidase A, resulting in progressive glycotriaosylceramide accumulation in many organs. Low α-galactosidase A activity and mutations in the GLA gene confirm the diagnosis. Clinical signs are multisystemic, heterogeneous, and progressive. Renal, cardiac, and neurovascular involvements are the main life-threatening complications, highlighting the importance of an early initiation of enzyme replacement therapy improving long-term outcome. Fabry nephropathy lesions are characterized by a cell vacuolization of glomeruli, tubules, interstitium, and arteries and by ultrastructural myelin bodies. The main histologic differential diagnoses are toxicity of lysosomal inhibitors and other renal lipidoses. Renal biopsies are not necessary for diagnosis but have an important role in the evaluation of disease evolution and treatment efficiency, which is a major challenge for improving outcome and quality of life.

Long-Term Dose-Dependent Agalsidase Effects on Kidney Histology in Fabry Disease.

Dose-dependent clearing of podocyte globotriaosylceramide has previously been shown in patients with classic Fabry disease treated with enzyme replacement. Our study evaluates the dose-dependent effects of agalsidase therapy in serial kidney biopsies of patients treated for up to 14 years. Twenty patients with classic Fabry disease (12 men) started enzyme replacement therapy at a median age of 21 (range =7-62) years old. Agalsidase-α or -β was prescribed for a median of 9.4 (range =5-14) years. The lower fixed dose group received agalsidase 0.2 mg/kg every other week throughout the follow-up period. The higher dose group received a range of agalsidase doses (0.2-1.0 mg/kg every other week). Dose changes were made due to disease progression, suboptimal effect, or agalsidase-β shortage. Serial kidney biopsies were performed along with clinical assessment and biomarkers and scored according to recommendations from the International Study Group of Fabry Nephropathy. No statistical differences were found in baseline or final GFR or albuminuria. Kidney biopsies showed significant reduction of podocyte globotriaosylceramide in both the lower fixed dose group (-1.39 [SD=1.04]; P=0.004) and the higher dose group (-3.16 [SD=2.39]; P=0.002). Podocyte globotriaosylceramide (Gb3) reduction correlated with cumulative agalsidase dose (r=0.69; P=0.001). Arterial/arteriolar intima Gb3 cleared significantly in the higher dose group, all seven patients with baseline intimal Gb3 cleared the intima, one patient gained intimal Gb3 inclusions (P=0.03), and medial Gb3 did not change statistically in either group. Residual plasma globotriaosylsphingosine levels remained higher in the lower fixed dose group (20.1 nmol/L [SD=11.9]) compared with the higher dose group (10.4 nmol/L [SD=8.4]) and correlated with cumulative agalsidase dose in men (r=0.71; P=0.01). Reduction of podocyte globotriaosylceramide was found in patients with classic Fabry disease treated with long-term agalsidase on different dosing regimens, correlating with cumulative dose. Limited clearing of arterial/arteriolar globotriaosylceramide raises concerns regarding long-term vascular effects of current therapy. Residual plasma globotriaosylsphingosine correlated with cumulative dose in men.

Urinary mulberry cells and mulberry bodies are useful tool to detect late-onset Fabry disease.

Fabry disease is an X-linked lysosomal storage disorder caused by a lack of α-galactosidase A activity, which leads to the accumulation of globotriaosylceramide in various organs. A complete lack of α-galactosidase A activity in a hemizygous male is the classical phenotype, and some hemizygous males show primarily cardiac and/or renal symptoms that appear in adulthood; this is called the variant type or the late-onset type. The kidney and heart are the major target organs, with damage to these organs related to mortality. Thus, in Fabry patients, early detection and early treatment are critical to longevity. Here, we present a 55-year-old Japanese male patient who was diagnosed with late-onset Fabry nephropathy with cardiomyopathy but with no abnormal urinary findings except for urinary mulberry cells and mulberry bodies. In spite of the absence of abnormal urinary findings, the light microscopic and electron microscopic pathological findings showed extensive deposition of globotriaosylceramide to podocytes. In this paper, we propose that the presence of mulberry cells and mulberry bodies can be used for the earlier detection of Fabry nephropathy, especially the late-onset type.

New biomarkers defining a novel early stage of Fabry nephropathy: A diagnostic test study.

Renal involvement in Fabry disease is a major determinant of overall disease prognosis and early enzyme replacement therapy seems effective in preventing progression of kidney injury. Gb3 storage, glomerular sclerosis and tubulo-interstitial fibrosis may occur with minimal or no changes on standard renal tests, hence alternative markers of renal dysfunction are crucial. In this study we compared several biomarkers with albuminuria in the identification of incipient Fabry nephropathy and their diagnostic accuracy to identify chronic kidney disease (CKD) stage≥2. In this multicentre, prospective, cross-sectional and diagnostic test study, a cohort of 78 Fabry patients and 25 healthy controls was consecutively recruited. Patients were grouped by severity of nephropathy: 1) albuminuria<30mg/g; 2) albuminuria 30-299mg/g; 3) albuminuria>300mg/g; 4) glomerular filtration rate (GFR)<60mL/min/1.73m2. Several index tests, namely biomarkers of glomerular (transferrin and type IV collagen) and tubular (α1-microglobulin, N-acetyl-β-glucosaminidase and alanine aminopeptidase) dysfunction were compared with the reference standard (albuminuria). Significant increase of all tested biomarkers in Fabry patients, even in the subgroup of patients without evidence of nephropathy. We also found inverse significant correlations between estimated GFR and collagen type IV (ρ=-0.289; p=0.003) or N-acetyl-β-glucosaminidase (ρ=-0.448; p<0.001), which were stronger than with albumin (ρ=-0.274; p=0.019). There was also better diagnostic accuracy of N-acetyl-β-glucosaminidase to predict CKD stage≥2. These results suggest that studied biomarkers may overcome the limitations of albuminuria as sensitive marker of early renal dysfunction and as marker for CKD progression risk. These biomarkers may also define novel early stages of nephropathy characterized by mesangial expansion and/or tubular damage.

Expression of uPAR in Urinary Podocytes of Patients with Fabry Disease.

Background. Despite enzyme replacement therapy, Fabry nephropathy still progresses. Podocyturia is an irreversible event that antedates proteinuria and leads to chronic renal failure. We evaluated a potential mechanism of podocyte detachment via the expression of the urokinase-type Plasminogen Activator Receptor (uPAR) in urinary podocytes of Fabry patients. Methods. This is a cross-sectional study that included controls (n = 20) and Fabry patients (n = 44) either untreated (n = 23) or treated with agalsidase-β (n = 21). Variables. Variables are estimated glomerular filtration rate (eGFR), urinary protein : creatinine ratio, and urinary uPAR+ podocyte : creatinine ratio. uPAR mRNA expression in response to lyso-Gb3, a bioactive glycolipid accumulated in Fabry disease, was studied in cultured human podocytes. Results. Controls and Fabry patients had similar age, gender, and renal function. Urinary uPAR+ podocytes were higher in patients than in controls. Untreated patients were significantly younger; had more females, and presented lower urinary protein : creatinine ratios and significantly higher urinary uPAR+ podocytes than treated subjects. In treated patients, urinary uPAR+ podocytes correlated with urinary protein : creatinine ratio (ρ = 0.5; p = 0.02). Lyso-Gb3 at concentrations found in the circulation of Fabry patients increased uPAR expression in cultured podocytes. Conclusions. Urinary podocytes expressing uPAR are increased in Fabry patients, especially in untreated patients. The potential contribution of uPAR expression to podocyte detachment merits further studies.

Improving the detection of heterozygous females for Fabry disease

Renal involvement in Fabry disease is a major determinant of overall disease prognosis and early enzyme replacement therapy seems effective in preventing progression of kidney injury. Gb3 storage, glomerular sclerosis and tubulo-interstitial fibrosis may occur with minimal or no changes on standard renal tests, hence alternative markers of renal dysfunction are crucial. In this study we compared several biomarkers with albuminuria in the identification of incipient Fabry nephropathy and their diagnostic accuracy to identify chronic kidney disease (CKD) stage ≥ 2.In this multicentre, prospective, cross-sectional and diagnostic test study, a cohort of 78 Fabry patients and 25 healthy controls was consecutively recruited. Patients were grouped by severity of nephropathy: 1) albuminuria < 30 mg/g; 2) albuminuria 30–299 mg/g; 3) albuminuria > 300 mg/g; 4) glomerular filtration rate (GFR) < 60 mL/min/1.73 m2. Several index tests, namely biomarkers of glomerular (transferrin and type IV collagen) and tubular (α1-microglobulin, N-acetyl-β-glucosaminidase and alanine aminopeptidase) dysfunction were compared with the reference standard (albuminuria).Significant increase of all tested biomarkers in Fabry patients, even in the subgroup of patients without evidence of nephropathy. We also found inverse significant correlations between estimated GFR and collagen type IV (ρ = − 0.289; p = 0.003) or N-acetyl-β-glucosaminidase (ρ = − 0.448; p < 0.001), which were stronger than with albumin (ρ = − 0.274; p = 0.019). There was also better diagnostic accuracy of N-acetyl-β-glucosaminidase to predict CKD stage ≥ 2.These results suggest that studied biomarkers may overcome the limitations of albuminuria as sensitive marker of early renal dysfunction and as marker for CKD progression risk. These biomarkers may also define novel early stages of nephropathy characterized by mesangial expansion and/or tubular damage.

Urinary Podocyte Loss Is Increased in Patients with Fabry Disease and Correlates with Clinical Severity of Fabry Nephropathy.

Chronic kidney disease is a major complication of Fabry disease. Podocytes accumulate globotriaosylceramide inclusions more than other kidney cell types in Fabry patients. Podocyte injury occurs early in age, and is progressive. Since injured podocytes detach into the urine (podocyturia), we hypothesized that podocyturia would increase in Fabry patients and correlate with clinical severity of Fabry nephropathy. Urine specimens from 39 Fabry patients and 24 healthy subjects were evaluated for podocyturia. Most of the Fabry patients and many healthy subjects had podocyturia. The number of podocytes per gram of urine creatinine (UPodo/g Cr) was 3.6 fold greater in Fabry patients (3,741 ± 2796; p = 0.001) than healthy subjects (1,040 ± 972). Fabry patients with normoalbuminuria and normoproteinuria had over 2-fold greater UPodo/g Cr than healthy subjects (p = 0.048). UPodo/gCr was inversely related to eGFR in male patients (r = -0.69, p = 0.003). UPodo/gCr was directly related to urine protein creatinine ratio (r = 0.33; p = 0.04) in all Fabry patients. These studies confirm increased podocyturia in Fabry disease, even when proteinuria and albuminuria are absent. Podocyturia correlates with clinical severity of Fabry nephropathy, and potentially may be of prognostic value.

A case of rapid progression of Fabry nephropathy with remarkable glomerulomegaly: a case report and mini literature review of weak response to enzyme replacement therapy (ERT)

Fabry disease is a rare X-linked hereditary disorder (Xq22) caused by a deficiency in alpha-galactosidase (α-GAL) activity. This enzyme deficit results in the systemic accumulation of glycophospholipids, leading to multi-organ failure including the heart, kidneys, and brain. Enzyme replacement therapy (ERT) improves the prognosis of patients with Fabry disease. We describe a case showing progressive renal failure despite ERT. An 18-year-old obese male patient (body mass index (BMI) 29.9 kg/m2) was admitted for detailed examination of mild degree hypertension (150/65 mmHg) and proteinuria occurring for 2 years prior to admittance. Laboratory tests revealed mostly normal kidney function (serum creatinine 0.5 mg/dL, estimated glomerular filtration rate 181 mL/min/m2) with low α-GAL activity, a significant level of proteinuria (0.5–1.0 g/day), and the presence of mulberry cells in the urinary sediment. Renal biopsy demonstrated marked glomerulomegaly with diffuse vacuolization of the glomerular epithelial cells and focal segmental glomerulosclerosis. Electron microscopy revealed typical zebra bodies in the glomerular epithelial cells and effacement of foot processes of the epithelium. We could not find any cause of glomerulomegaly except for obesity. α-GAL gene analysis revealed a missense mutation in R301Q. Although ERT with agalsidase α was initiated, his renal function declined, and hemodialysis was initiated at 22 years of age. We present a case of rapid progression of Fabry nephropathy despite ERT. As with other renal diseases, obesity may aggravate the progression of Fabry nephropathy.

Identification of a novel GLA mutation (Y88C) in a Korean family with Fabry nephropathy: a case report

BackgroundFabry disease is a rare X-linked lysosomal storage disorder caused by α-galactosidase A deficiency. With the advancement of molecular diagnostic tools, more disease-causing mutations in α-galactosidase A (GLA) have been identified in Fabry disease. We found a novel mutation in a Korean family with predominant renal manifestations of the disease.Case presentationA 24-year-old man who wanted to donate a kidney to his 28-year-old brother with end-stage renal disease of unknown cause was evaluated. The 24-year-old man underwent percutaneous renal biopsy because of an accidentally found proteinuria. Electron microscopy of his renal biopsy showed numerous electron-dense multi-lamellar inclusions in the epithelial cytoplasm, typical for Fabry disease. Clinical and laboratory evaluation including the assessment of GLA enzyme activity and direct DNA sequencing in four members of the family were performed. Renal biopsy findings in the two affected male patients were described. Re-evaluation of a renal biopsy specimen of his 28-year-old brother obtained when he was diagnosed with renal failure revealed a very focal area of suspicious multilamellated structures in the Bowman’s space. DNA sequencing on the young man, his brother, and his mother revealed a novel GLA gene mutation, c.263A > G (p.Tyr88Cys). The three all showed decreased α-galactosidase A activity.ConclusionA novel GLA mutation, c.263A > G (p.Tyr88Cys), was found in a Korean family with predominant renal manifestations of Fabry disease.

Podocyturia as a biomarker of early kidney damage in fabry nephropathy

Podocyturia as a biomarker of early kidney damage in fabry nephropathy

Characterization and phosphoproteomic analysis of a human immortalized podocyte model of Fabry disease generated using CRISPR/Cas9 technology.

Fabry nephropathy is a major cause of morbidity and premature death in patients with Fabry disease (FD), a rare X-linked lysosomal storage disorder. Gb3, the main substrate of α-galactosidase A (α-Gal A), progressively accumulates within cells in a variety of tissues. Establishment of cell models has been useful as a tool for testing hypotheses of disease pathogenesis. We applied CRISPR/Cas9 genome editing technology to the GLA gene to develop human kidney cell models of FD in human immortalized podocytes, which are the main affected renal cell type. Our podocytes lack detectable α-Gal A activity and have increased levels of Gb3. To explore different pathways that could have distinct patterns of activation under conditions of α-gal A deficiency, we used a high-throughput antibody array to perform phosphorylation profiling of CRISPR/Cas9-edited and control podocytes. Changes in both total protein levels and in phosphorylation status per site were observed. Analysis of our candidate proteins suggests that multiple signaling pathways are impaired in FD.

Reaccumulation of globotriaosylceramide in podocytes after agalsidase dose reduction in young Fabry patients

Agalsidase-α 0.2 mg/kg every other week (eow) and agalsidase-β 1.0 mg/kg/eow are licensed in Europe as equipotent treatment of the α-galactosidase deficiency in Fabry disease. This case series describes the effects of agalsidase dose adjustments in serial kidney biopsies in switch patients. All treatment-naïve patients with classical Fabry disease in our centre started on agalsidase-β 1.0 mg/kg/eow and subsequently switched to agalsidase-α 0.2 mg/kg/eow were included ( n = 3). The median age at enzyme replacement therapy start was 11 (range 7-18) years. Kidney biopsies were performed at baseline, after 5 years of agalsidase-β 1.0 mg/kg/eow and after 3 subsequent years of agalsidase-α 0.2 mg/kg/eow. One patient was re-biopsied 2 years after reswitch to agalsidase-β 1.0 mg/kg/eow. The scoring system of the International Scoring Group of Fabry Nephropathy was used. The patients completely cleared globotriaosylceramide (GL3) from mesangial and endothelial cells and partly cleared podocytes on agalsidase-β 1.0 mg/kg/eow. Reaccumulation of GL3 in podocytes, but not in the mesangium or endothelium, occurred after 3 years of agalsidase-α 0.2 mg/kg/eow. Subsequent reduction of podocyte GL3 was observed in the single patient rebiopsied 2 years after reswitch to agalsidase-β 1.0 mg/kg/eow. Partial clearance, reaccumulation and renewed partial clearance of podocyte GL3 deposits in serial kidney biopsies over 8-10 years were seen in parallel with agalsidase dose adjustments. Repeated kidney biopsies may impact therapeutic choices in Fabry disease.

Anti-proteinuric therapy and Fabry nephropathy; factors associated with preserved kidney function during agalsidase-beta therapy

Anti-proteinuric therapy and Fabry nephropathy; factors associated with preserved kidney function during agalsidase-beta therapy

Clinical-pathological correlation in Fabry nephropathy in Mexican children based on ISGFN

Clinical-pathological correlation in Fabry nephropathy in Mexican children based on ISGFN

Differential response of glomerular parietal epithelial cells and podocytes to enzyme replacement therapy in Fabry nephropathy

Differential response of glomerular parietal epithelial cells and podocytes to enzyme replacement therapy in Fabry nephropathy