Urinary Microparticles Research Articles

#2229 miR-186, a potential noninvasive diagnostic biomarker of Membranous nephropathy in urinary microparticles

Abstract Background and Aims Membranous nephropathy (MN) is one of the most common causes of nephrotic syndrome, and is associated with podocyte damage and proteinuria. Invasive biopsy is the gold-standard diagnostic method for this disease. The use of specific biomarkers, such as microparticles (MPs) originating from damaged podocytes released in a patient's urine, has been proposed as an early, noninvasive, and repetitive diagnostic method. According to the previous studies, MPs derived from podocytes are present in the urine of patients with different glomerulonephritis, such as diabetic nephropathy, lupus nephritis, renal injury in preeclampsia, and renovascular hypertensive disorders. The analysis of urinary microparticle-derived miRNAs from patients with kidney diseases can help detect diagnostic biomarkers. This study aimed to analyze podocyte damage-related miRNAs in MN, miR-30c, miR-135, and miR-18 in the urinary MP of MN patients to identify appropriate candidate biomarkers for MN Method Urine samples from 30 patients with membranous nephropathy and 16 healthy individuals were collected to extract podocyte MPs using ultracentrifugation. Characterization of these particles was determined using the specific protein marker of MPs, TSG-101, and the podocyte-specific marker Nephrin, by western blotting, and SEM was used to check the size and morphology. The expression levels of microRNAs extracted from podocyte MPs, miR-30c, miR-135, and miR-186, were also evaluated by real-time PCR. Results The evaluation of the characteristics of MPs showed that there were many particles with a size of more than 100 nm in the urine sample, and there were higher levels of the specific markers TSG-101 and Nephrin in the urine samples of MGN patients than in the control samples (P < 0.001). The expression level of miR-186 was compared between the three studied groups and based on the results of the expression of this miRNA in the group of membranous nephropathy patients compared to healthy people group, there was a significant increase in expression (P = 0.000) Conclusion This study showed that although the expression levels of miR-186 in podocyte MPs samples extracted from the urine of patients with MN were significantly changed compared to the studied controls, more studies should be performed to determine the diagnostic values.

ApoL1 in Podocyte-Derived Urinary Microparticles

ApoL1 in Podocyte-Derived Urinary Microparticles

Elevated Levels of Urinary Podocyte-Derived Microparticles in Nephrotic Syndrome

BACKGROUND: Nephrotic syndrome (NS) is the most common glomerular disease in childhood. The proposed hypothesis for the pathogenesis of this disease has changed over time, from immune dysregulation theory and systemic circulating factors theory, to the growing recognition of podocytopathies’ role. The existance of podocytopathies is usually examined by using podocyte-derived microparticles (MPs), such as nephrin, podocin, and podocalyxin (PCX). Therefore in this study, the difference between nephrin, podocin, and PCX expressions in NS children and healthy children was investigated.METHODS: An observational cross-sectional study was conducted, involving 33 children with NS and 22 age-matched healthy children as controls. Urine samples were collected from each subject in the early morning, before being processed and incubated with antibodies to detect nephrin, podocin, and PCX. The processed samples were then analyzed with flow cytometer methods.RESULTS: NS subjects had significantly higher expression of all three urinary podocyte-derived MPs compared to the control subjetcs. Nephrin, podocin, and PCX showed good discrimination in NS subjects with the area under curve (AUC) of 0.895, 0.849, and 0.728, respectively.CONCLUSION: This study revealed the differential expression of podocyte proteins in NS subjects compared to healthy controls. This supports the role of podocytopathies in the pathogenesis of NS. Therefore, nephrin, podocin, and PCX might have potentials to be future non-invasive diagnostic tools in glomerular disease.KEYWORDS: nephrin, nephrotic syndrome, podocalyxin, podocin, podocyte, urinary microparticle

Urinary levels of podocyte-derived microparticles are associated with the progression of chronic kidney disease

Podocyte-derived microparticles (MPs) could be secreted from activated or apoptotic podocytes. An increased number of podocyte-derived MPs in the urine might reflect podocyte injury in renal diseases. This study aimed to observe the change of urinary podocyte-derived MP levels in patients with chronic kidney disease (CKD) and to further explore its correlation with the progression of CKD. A prospective, longitudinal study was conducted in eighty patients with biopsy-proven CKD. Podocyte-derived MPs (annexin V and podocalyxin positive) were detected by flow cytometry. The number of urinary podocyte-derived MPs was analyzed to evaluate the association with biochemical measurements and pathological glomerulosclerosis assessment. Patients with idiopathic membranous nephropathy (IMN) were followed up after the six-month treatment of prednisone combined with tacrolimus to evaluate the association of urinary podocyte-derived MP levels and the remission of IMN. The CKD patients had higher urinary podocyte-derived MP levels compared with healthy controls (HCs). Baseline urinary levels of podocyte-derived MPs were positively correlated with 24-hour proteinuria, while were inversely correlated with the percentage of global glomerulosclerosis. The urinary podocyte-derived MPs levels had good discrimination for glomerulosclerosis [area under curve (AUC), 0.66]. The urinary podocyte-derived MPs levels in IMN patients were significantly decreased accompanied with the recovery of abnormal clinical parameters after six-month treatment. The urinary levels of podocyte-derived MPs were closely associated with podocyte injury and glomerulosclerosis, which could be useful for monitoring disease activity in CKD patients. Urinary podocyte-derived MPs might be a non-invasive biomarker for the evaluation of early CKD progression.

Urinary podocyte microparticles are associated with disease activity and renal injury in systemic lupus erythematosus

BackgroundNew non-invasive biomarkers are demanded to identify renal damage in various autoimmune-associated kidney diseases. Glomerular podocyte damage mediated by systemic lupus erythematosus (SLE) plays an important role in the pathogenesis and progression of lupus nephritis (LN). This study evaluated whether the podocyte-derived microparticles (MPs) were novel biomarkers of clinical and histological features in SLE patients with LN.MethodsA cross-sectional study, including 34 SLE patients and 16 healthy controls, was designed. Urinary annexin V+ podocalyxin+ MPs of all participants were quantified by flow cytometry. The correlation of podocyte-derived MPs with clinical and histological parameters of SLE patients was analysed.ResultsThe number of annexin V+ podocalyxin+ MPs from urine samples were markly increased in patients with SLE. Furthermore, the level of urinary podocyte-derived MPs was positively correlated with the SLE Disease Activity Index (SLEDAI) score, anti-dsDNA antibody titre, erythrocyte sedimentation rate, and proteinuria. Conversely, it was negatively correlated with the level of complement C3 and serum albumin. The number of urinary podocyte-derived MPs was significantly increased in SLE patients with high activity indices. Receiver operating characteristic (ROC) curves were calculated to assess the power for podocyte-derived MP levels in differentiating between SLE patients with and without LN. Podocyte-derived MP levels were able to differentiate between SLE patients with mild disease activity, as well as those with moderate and above disease activity. SLE patients showed increased podocyte-derived MP excretion into the urine.ConclusionsThese findings suggest that the change in urinary podocyte-derived MP levels could be useful for evaluating and monitoring SLE disease activity.

Assessment of urinary microparticles in normotensive patients with type 1 diabetes.

Assessment of urinary extracellular vesicles including exosomes and microparticles (MPs) is an emerging approach for non-invasive detection of renal injury. We have previously reported that podocyte-derived MPs are increased in diabetic mice in advance of albuminuria. Here, we hypothesised that type 1 diabetes and acute hyperglycaemia would increase urinary podocyte MP levels in uncomplicated diabetes. In this post hoc exploratory analysis, we examined archived urine samples from normoalbuminuric patients with uncomplicated type 1 diabetes studied under clamped euglycaemia and hyperglycaemia and compared with healthy controls. Urinary vesicles were assessed by electron microscopy and nanoparticle tracking while podocyte MPs were assessed by flow cytometry. Neither vesicle size nor total number were significantly altered in type 1 diabetes or acute hyperglycaemia. By contrast, urinary podocyte MP levels were higher in type 1 diabetes (0.47 [0.00-3.42] MPs/μmol creatinine [Cr]) compared with healthy controls (0.00 [0.00-0.00] MPs/μmol Cr, p < 0.05) and increased under hyperglycaemic clamp (0.36 [0.00-4.15] MPs/μmol Cr during euglycaemia vs 2.70 [0.00-15.91] MPs/μmol Cr during hyperglycaemia, p < 0.05). Levels of urinary albumin to creatinine ratio and nephrin (surrogates of podocyte injury) were unchanged by type 1 diabetes or acute hyperglycaemia. Taken together, our data show that urinary podocyte MP levels are higher in patients with type 1 diabetes in advance of changes in other biomarkers (albuminuria, nephrin). Examination of podocyte MPs may serve as an early biomarker of glomerular injury in uncomplicated type 1 diabetes.

Comparative Tissue Proteomics of Microdissected Specimens Reveals Novel Candidate Biomarkers of Bladder Cancer

More than 380,000 new cases of bladder cancer are diagnosed worldwide, accounting for ∼150,200 deaths each year. To discover potential biomarkers of bladder cancer, we employed a strategy combining laser microdissection, isobaric tags for relative and absolute quantitation labeling, and liquid chromatography-tandem MS (LC-MS/MS) analysis to profile proteomic changes in fresh-frozen bladder tumor specimens. Cellular proteins from four pairs of surgically resected primary bladder cancer tumor and adjacent nontumorous tissue were extracted for use in two batches of isobaric tags for relative and absolute quantitation experiments, which identified a total of 3220 proteins. A DAVID (database for annotation, visualization and integrated discovery) analysis of dysregulated proteins revealed that the three top-ranking biological processes were extracellular matrix organization, extracellular structure organization, and oxidation-reduction. Biological processes including response to organic substances, response to metal ions, and response to inorganic substances were highlighted by up-expressed proteins in bladder cancer. Seven differentially expressed proteins were selected as potential bladder cancer biomarkers for further verification. Immunohistochemical analyses showed significantly elevated levels of three proteins-SLC3A2, STMN1, and TAGLN2-in tumor cells compared with noncancerous bladder epithelial cells, and suggested that TAGLN2 could be a useful tumor tissue marker for diagnosis (AUC = 0.999) and evaluating lymph node metastasis in bladder cancer patients. ELISA results revealed significantly increased urinary levels of both STMN1 and TAGLN2 in bladder cancer subgroups compared with control groups. In comparisons with age-matched hernia urine specimens, urinary TAGLN2 in bladder cancer samples showed the largest fold change (7.13-fold), with an area-under-the-curve value of 0.70 (p < 0.001, n = 205). Overall, TAGLN2 showed the most significant overexpression in individual bladder cancer tissues and urine specimens, and thus represents a potential biomarker for noninvasive screening for bladder cancer. Our findings highlight the value of bladder tissue proteome in providing valuable information for future validation studies of potential biomarkers in urothelial carcinoma.

Abstract P150: Podocyte Derived Urinary Microparticles Are Elevated in Angiotensin II Induced Hypertension

Background: Early and non-invasive biomarkers of kidney damage are needed to identify hypertensive patients at risk for kidney damage. Urinary micropaticles (UMPs) have gained significant attention as potential novel biomarkers for kidney damage, and have already been identified in pre-albuminuric diabetic glomerular injury. These vesicles are less than 1 micron in size and carry markers of the parent cell. We hypothesized that podocyte derived UMPs are elevated in angiotensin II-induced hypertension (HTN) Methods: Primary podocytes were isolated and grown in culture. Wild-type mice were treated with AII (400ng/kg/min) via mini-osmotic pumps. Untreated WT mice served as controls. 24 hour urines were collected after 5 days of AII treatment. Enumeration and phenotyping of MPs was done of podocyte culture supernatant and urine. Podocalyxin (Pcal), podoplanin (Ppla) and annexin 5 (AV) were used as surface markers. Result: Pcal and Ppla positive MPs as well as AV positive and negative MPs were detectable in supernatant from primary podocyte cultures. Compared to untreated controls (n=3), AII treated mice (n=2) had an increase in systolic blood pressure (SBP) by 33 mmHG (p=0.02). Despite similar urinary albumin/creatinine ratios between groups, there was a trend of higher levels of total numbers of Ppla and Pcal positive MPs in hypertensive mice compared to untreated (Figure 1). In addition, Annexin negative but Ppla and Pcal positive MPs were also numerically higher in hypertensive mice. In conclusion, podocyte derived UMPs are detectable in AII HTN. These findings need to be confirmed in a larger group of animals. UMPs can be potential marker for kidney end-organ damage in HTN.

Urinary Podocyte Microparticles Identify Prealbuminuric Diabetic Glomerular Injury

Microparticles (MPs) are small (0.1-1.0 µm) vesicles shed from the surface of cells in response to stress. Whether podocytes produce MPs and whether this production reflects glomerular injury are unclear. We examined MP formation in cultured human podocytes (hPODs) and diabetic mice. hPODs were exposed to cyclical stretch, high glucose (HG; 25 mM), angiotensin II, or TGF-β. Urinary podocyte MPs were assessed in three mouse models of diabetic nephropathy: streptozotocin (STZ)-treated, OVE26, and Akita mice. Cyclic stretch and HG increased MP release as assessed by flow cytometry (P<0.01 and P<0.05, respectively, versus controls). Inhibition of Rho-kinase (ROCK) with fasudil blocked HG-induced podocyte MP formation. STZ-treated (8 weeks) mice exhibited increased urinary podocyte MPs compared with age-matched nondiabetic mice. Similarly, 16-week-old OVE26 mice had elevated levels of urinary podocyte MPs compared with wild-type littermates (P<0.01). In 1 week post-STZ-treated and 6- and 12-week-old Akita mice, urinary podocyte MPs increased significantly compared with those MPs in nondiabetic mice, despite normal urinary albumin levels. Our results indicate that podocytes produce MPs that are released into urine. Podocyte-derived MPs are generated by exposure to mechanical stretch and high glucose in vitro and could represent early markers of glomerular injury in diabetic nephropathy.

Abstract 28: Formation of Podocyte-Derived Microparticles in Diabetic Glomerular Injury

Hypertension is a significant cause of progressive kidney disease, particularly in the presence of diabetes. Under such conditions, increased glomerular capillary pressure subjects podocytes, specialized glomerular epithelial cells critical to filtration, to mechanical stress resulting in podocyte injury/dysfunction. Microparticles (MPs) are small (0.1-1.0 μm), membranous vesicles shed from the cell surface following injury. However, whether podocyte MP formation reflects glomerular injury is unknown. We examined MP formation by podocytes in vitro and in vivo. Conditionally immortalized human podocytes were exposed to 10% equibiaxial cyclic stretch (a mimic of increased intraglomerular pressure), high glucose (HG, 25 mM), mannitol (osmotic control), angiotensin II (Ang II, 500 nM) or transforming growth factor beta (TGF-β, 5 ng/mL). Additionally, urinary podocyte MPs were quantified in two mouse models of diabetic kidney disease: streptozotocin (STZ) and OVE26. MPs were characterized by nanoparticle tracking analysis and quantified by Annexin V (total MPs) or podocalyxin (podocyte MPs) labeling and flow cytometry. Podocyte-derived vesicles were identifiable in both media and urine samples with a mean size of 236 nm by nanoparticle tracking analysis. In vitro, cyclic stretch was associated with a 3-fold increase in MP release after 24 hours (P&lt;0.01, n=6). HG increased MP release 5-fold after 24 hours (P&lt;0.05, n=6). Mannitol had no effect on MP formation by either normal or stretched podocytes and neither Ang II, nor TGF-β altered podocyte MP formation over 24 hours. In vivo, both models of diabetes displayed typical hallmarks of renal injury (proteinuria, mesangial expansion). In OVE26 mice urinary podocyte MPs were elevated compared with their wild-type littermates (17479±8329 vs. 7 ±7, P&lt;0.05, n=5-7). Similarly, STZ-treated mice displayed increased urinary podocyte MPs as compared with untreated (18035±3813 vs. 43±34, P&lt;0.001, n=9-18) and urinary MPs levels were positively correlated with albuminuria (r2=0.74, P&lt;0.01). Our results suggest that podocytes produce MPs which are released into urine and are indicative of glomerular injury. Such processes may be mediated by intraglomerular capillary pressure and hyperglycemia.

Comparative and Targeted Proteomic Analyses of Urinary Microparticles from Bladder Cancer and Hernia Patients

Bladder cancer is a common urologic cancer whose incidence continues to rise annually. Urinary microparticles are an attractive material for noninvasive bladder cancer biomarker discovery. In this study, we applied isotopic dimethylation labeling coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to discover bladder cancer biomarkers in urinary microparticles isolated from hernia (control) and bladder cancer patients. This approach identified 2964 proteins based on more than two distinct peptides, of which 2058 had not previously been reported as constituents of human urine exosomes/microparticles. A total of 107 differentially expressed proteins were identified as candidate biomarkers. Differences in the concentrations of 29 proteins (41 signature peptides) were precisely quantified by LC-MRM/MS in 48 urine samples of bladder cancer, hernia, and urinary tract infection/hematuria. Concentrations of 24 proteins changed significantly (p<0.05) between bladder cancer (n=28) and hernia (n=12), with area-under-the-curve values ranging from 0.702 to 0.896. Finally, we quantified tumor-associated calcium-signal transducer 2 (TACSTD2) in raw urine specimens (n=221) using a commercial ELISA and confirmed its potential value for diagnosis of bladder cancer. Our study reveals a strong association of TACSTD2 with bladder cancer and highlights the potential of human urinary microparticles in the noninvasive diagnosis of bladder cancer.

Isolation and Identification of Potential Urinary Microparticle Biomarkers of Bladder Cancer

Bladder cancer leads to approximately 13,000 deaths annually in the United States. Early disease is often treated with minimal morbidity and has good prognosis, while the opposite is true for advanced disease. Currently, no tools exist for early detection of this cancer. Microparticles are small, subcellular particles released by essentially all cells upon activation and are known to be produced constitutively by cancer cells. Since most bladder cancers originate in the urothelial cells lining the lumen of the organ, we hypothesize that these cells will release microparticles into the urine. The goal of this study was to identify potential biomarkers in the urinary microparticles of individuals with bladder cancer. Urine microparticles from five healthy individuals and four individuals with bladder cancer were isolated. Samples were delipidated by PAGE and trypsin-digested, peptides were extracted, and the proteome was examined by LC-MS/MS using a Thermo Finnigan LTQ and LTQ-FT ion trap mass spectrometer. Protein identification was determined by SEQUEST and relative quantitation was assessed by comparing spectral counts. Eight proteins were elevated in the microparticles from individuals with bladder cancer. They include five proteins associated with the epidermal growth factor receptor pathway, the alpha subunit of GsGTP binding protein, resistin, and retinoic acid-induced protein 3. Further studies will be needed to validate these potential biomarkers.