Diagnosis of Alport syndrome—search for proteomic biomarkers in body fluids (original) (raw)
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The Journal of physiology, 2014
The glomerular filtration barrier comprises a fenestrated capillary endothelium, glomerular basement membrane and podocyte slit diaphragm. Over the past decade we have come to realise that permselectivity depends on size and not necessarily charge, that the molecular sieve depends on the podocyte contractile apparatus and is highly dynamic, and that protein uptake by proximal tubular epithelial cells stimulates signalling and the production of transcription factors and inflammatory mediators. Alport syndrome is the second commonest monogenic cause of renal failure after autosomal dominant polycystic kidney disease. Eighty per cent of patients have X-linked disease caused by mutations in the COL4A5 gene. Most of these result in the replacement of the collagen IV α3α4α5 network with the α1α1α2 heterotrimer. Affected membranes also have ectopic laminin and increased matrix metalloproteinase levels, which makes them more susceptible to proteolysis. Mechanical stress, due to the less ela...
Urine-derived podocytes-lineage cells: A promising tool for precision medicine in Alport Syndrome
Human mutation, 2018
Alport Syndrome (ATS) is a rare genetic disorder caused by collagen IV genes mutations, leading to glomerular basement membrane damage up to end-stage renal disease. Podocytes, the main component of the glomerular structure, are the only cells able to produce all the three collagens IV alpha chains associated with ATS and thus, they are key players in ATS pathogenesis. However, podocytes-targeted therapeutic strategies have been hampered by the difficulty of non-invasively isolating them and transcripts-based diagnostic approaches are complicated by the inaccessibility of other COL4 chains-expressing cells. We firstly isolated podocyte-lineage cells from ATS patients' urine samples, in a non-invasive way. RT-PCR analysis revealed COL4A3, COL4A4, and COL4A5 expression. Transcripts analysis on RNA extracted from patient's urine derived podocyte-lineage cells allowed defining the pathogenic role of intronic variants, namely one mutation in COL4A3 (c.3882+5G>A), three mutatio...
Matrix metalloproteinases in nephrotic syndrome; a vital but obscure field of research
Journal of Nephropathology, 2019
Context: Matrix metalloproteinases (MMPs) are involved in the remodelling of the glomerular basement membrane (GBM) by tightly regulating the metabolism of extracellular matrix (ECM) of the GBM. Evidence Acquisitions: Directory of Open Access Journals (DOAJ), Google Scholar, PubMed, EBSCO, Scopus and Web of Science have been searched. Results: Gelatinases (MMP-2 and MMP-9) are mainly found involved in the remodelling of GBM and therefore this review focuses on these two MMPs and their action in nephrotic syndrome (NS), which is a protein losing enteropathy occurring due to the loss of integrity of GBM. In addition to the blood corpuscles, glomerular epithelial cells and mesangium are also expressing MMPs, and various cytokines and growth factors are involved in addition to tissue inhibitors of metalloproteinases (TIMPs) in regulating the metabolism of ECM via MMPs. While examining the results of MMP activity and expression in NS, except diabetic nephropathy (DN), membranoproliferative glomerulonephritis (MPGN) and hereditary NS where there was a clear down-regulation of MMP, all the other types of NS showed conflicting results. Both suppression and induction of MMPs are finally leading to GBM thickening, loss of integrity and proteinuria. Enhanced MMP activity leads to increase in matrix turnover and accumulation of ECM remnants and apoptotic cells leading to fibrosis. On the other hand, diminished expression of MMPs prevents the normal ECM turnover and matrix accumulation. The review compiled the mechanisms of action of both downregulation and upregulation of MMPs. Conclusions: Imbalance of ECM metabolism due to varied expression levels and activities of MMPs in different types of primary NS might contribute to the progression of nephropathies. Further studies are required to identify the potential and usage of MMPs as a diagnostic/prognostic/ therapeutic tool.
Alport syndrome--insights from basic and clinical research
Nature reviews. Nephrology, 2013
In 1927, Arthur C. Alport first published his description of a triad of symptoms in a family with hereditary congenital haemorrhagic nephritis, deafness and ocular changes. A few years after his death, this group of symptoms was renamed Alport syndrome. To this day, Alport syndrome still inevitably leads to end-stage renal disease and the need for renal replacement therapy, starting in young adulthood. During the past two decades, research into this rare disease has focused on the effects of mutations in collagen type IV and the role of changes in podocytes and the glomerular basement membrane that lead to early kidney fibrosis. Animal models of Alport syndrome also demonstrate the pathogenetic importance of interactions between podocytes and the extracellular matrix. Such models might also help researchers to answer basic questions about podocyte function and the development of fibrosis, and to develop new therapeutic approaches that might be of use in other kidney diseases. In thi...
Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association, 2016
Alport syndrome (AS) is a genetic disease characterized by haematuric glomerulopathy variably associated with hearing loss and anterior lenticonus. It is caused by mutations in the COL4A3, COL4A4 or COL4A5 genes encoding the α3α4α5(IV) collagen heterotrimer. AS is rare, but it accounts for >1% of patients receiving renal replacement therapy. Angiotensin-converting enzyme inhibition slows, but does not stop, the progression to renal failure; therefore, there is an urgent requirement to expand and intensify research towards discovering new therapeutic targets and new therapies. The 2015 International Workshop on Alport Syndrome targeted unmet needs in basic science, genetics and diagnosis, clinical research and current clinical care. In three intensive days, more than 100 international experts including physicians, geneticists, researchers from academia and industry, and patient representatives from all over the world participated in panel discussions and breakout groups. This repo...
A review of clinical characteristics and genetic backgrounds in Alport syndrome
Clinical and Experimental Nephrology, 2018
Alport syndrome (AS) is a progressive hereditary renal disease that is characterized by sensorineural hearing loss and ocular abnormalities. It is divided into three modes of inheritance, namely, X-linked Alport syndrome (XLAS), autosomal recessive AS (ARAS), and autosomal dominant AS (ADAS). XLAS is caused by pathogenic variants in COL4A5, while ADAS and ARAS are caused by those in COL4A3/COL4A4. Diagnosis is conventionally made pathologically, but recent advances in comprehensive genetic analysis have enabled genetic testing to be performed for the diagnosis of AS as first-line diagnosis. Because of these advances, substantial information about the genetics of AS has been obtained and the genetic background of this disease has been revealed, including genotype-phenotype correlations and mechanisms of onset in some male XLAS cases that lead to milder phenotypes of late-onset end-stage renal disease (ESRD). There is currently no radical therapy for AS and treatment is only performed to delay progression to ESRD using nephron-protective drugs. Angiotensin-converting enzyme inhibitors can remarkably delay the development of ESRD. Recently, some new drugs for this disease have entered clinical trials or been developed in laboratories. In this article, we review the diagnostic strategy, genotype-phenotype correlation, mechanisms of onset of milder phenotypes, and treatment of AS, among others. Keywords Genotype-phenotype correlation • Thin basement membrane • ACE inhibitor • Bardoxolone This article was presented as the Clinical Scientist Award memorial lecture at the 60th annual meeting of the Japanese Society of Nephrology, held at Sendai, Japan in 2017.
The Alport nephropathy: clinicopathological correlations
Pediatric Nephrology, 2005
The alleged dominance of diffuse attenuation of the glomerular basement membrane (GBM) in young children and females with Alport's Syndrome (AS) suggests that it might be the initial ultrastructural manifestation of type IV collagen defects. We carried out a 'blind' review of 130 renal biopsies obtained from 100 patients with AS, emphasizing the electron microscopy changes, and related the findings to the clinical presentation and outcome. The intracapillary distribution of (1) thickened, (2) attenuated and (3) normal GBM was assessed individually as: none (grade 0), <25% (grade 1), 25-50% (grade 2) and >50% (grade 3). Deafness was defined as persistent loss of > or =30 dBs. Proteinuria was measured as protein/creatinine ratios in early morning urine. Heavy proteinuria (> or =200 mg/mmol) correlated significantly with the presence of segmental and global glomerulosclerosis and foam cells. Comparing grades 0+1 vs. 3 GBM changes, using a 2x2 chi(2) test, there were significant correlations between grade 3 GBM thickening and male sex (P =0.005), heavy proteinuria (P =0.02) and deafness (P <0.001). GBM thickening did not correlate with age at the initial biopsy, but repeat biopsies demonstrated increasing thickening with age. The grades of GBM attenuation did not correlate with either age at biopsy or sex. In 11 biopsies with atypical lamina densa changes in thickened GBM segments, there were no differences in clinicopathological correlations compared with classical biopsies. Our data indicate that diffuse GBM attenuation can be an ultrastructural variant of the Alport nephropathy, but do not support the contention that it is the initial lesion.