Normal Glomerular Basement Membrane Research Articles

IPSC-derived type IV collagen α5-expressing kidney organoids model Alport syndrome

Alport syndrome (AS) is a hereditary glomerulonephritis caused by COL4A3, COL4A4 or COL4A5 gene mutations and characterized by abnormalities of glomerular basement membranes (GBMs). Due to a lack of curative treatments, the condition proceeds to end-stage renal disease even in adolescents. Hampering drug discovery is the absence of effective in vitro methods for testing the restoration of normal GBMs. Here, we aimed to develop kidney organoid models from AS patient iPSCs for this purpose. We established iPSC-derived collagen α5(IV)-expressing kidney organoids and confirmed that kidney organoids from COL4A5 mutation-corrected iPSCs restore collagen α5(IV) protein expression. Importantly, our model recapitulates the differences in collagen composition between iPSC-derived kidney organoids from mild and severe AS cases. Furthermore, we demonstrate that a chemical chaperone, 4-phenyl butyric acid, has the potential to correct GBM abnormalities in kidney organoids showing mild AS phenotypes. This iPSC-derived kidney organoid model will contribute to drug discovery for AS.

Correlation of TB LAM Ag (Tuberculosis Lipoarabinomannan Antigen) Results from Urine with Adenosine Deaminase Levels from Pleural Fluid Patients with Pulmonary TB Accompanied by Pleural Effusion

Background: One of the newest testing methods for active TB uses TB LAM Antigen, in which lipoarabinomannan (LAM) as the examined substance serves as the main component of the cell wall of M. tuberculosis (MTB) and the degradation product of MTB by macrophages in the human body. Patients with active TB with or without HIV infection may experience a decreased antibody response, which causes LAM not to bind to antibodies so that it can pass through the normal glomerular basement membrane and can be detected in the urine. Lateral flow urine lipoarabinomannan assay (LF-LAM) can detect this material with urine samples from active TB patients. Another TB screening method uses the measurement of adenosine deaminase (ADA) activity. ADA has a very important function for the proliferation and differentiation of lymphoid cells, especially T cells, and assists in the maturation of monocytes into macrophages. Objective: This study aims to qualitatively prove the correlation between the pleural fluid ADA levels of pulmonary TB patients with pleural effusion using the LF-LAM test results and examine the potential of TB LAM Ag, which correlates with increased pleural fluid ADA levels, as a diagnostic tool for diagnosing pulmonary TB. Method: It is an observational analytic study with a crosssectional design. Materials for this study included temporary urine from active TB patients at Dr. Soetomo Regional Public Hospital collected in May-August 2022. The descriptive analysis was conducted using SPSS 25.0. The data were tested for normal distribution and with the homogeneity test of Shapiro-Wilk's data. The statistical analysis was performed using the Mann-Whitney test, while the kappa suitability test was carried out to determine the correlation and level of concordance between the ADA cut-off value of pleural fluid and the TB LAM Ag test results. Results: This study involved 50 subjects consisting of 22 (44%) subjects with ADA test results between 40-100 IU/L compared to 28 subjects (56%) with ADA test results below 40 IU/L. There were 14 (28%) subjects with positive TB LAM Ag test results, consisting of 10 (45%) active TB subjects with a high ADA test cut-off of 40-100 IU/L and 4 (14%) active TB subjects with a low ADA test cut-off below 40 IU/L, with a p-value = 0.012. Conclusions: There is a correlation between TB Lipoarabinomannan antigen test results of TB patients with pleural effusion. TB LAM Ag can be detected positive on ADA test results of < 40 IU/L and more positive in active TB patients with high ADA test results of > 40-100 IU/L. Therefore, the TB LAM Ag test is more sensitive than the ADA test. The cut-off value of the ADA test reached 76.4 U/L, and a positive TB LAM was found.

MO058: Do Renal Biopsies Assist Understanding of Loin Pain Hematuria Syndrome?

Abstract BACKGROUND AND AIMS Loin pain-hematuria syndrome (LPHS) first described in 1967 is a complex and poorly understood rare disease, with a prevalence of 0.012%. It predominantly affects young women in their late 20s and early 30s2. Patients with LPHS experience extreme flank (loin) pain that can be unilateral or bilateral, along with gross or microscopic hematuria. In most cases, the pain is so severe that the patients are forced to quit their jobs, become opiate dependent, need antidepressants, require long term disability and a proportion contemplate committing suicide. Due to inadequate understanding of the pathophysiology of LPHS, the goal of management has been limited to symptomatic relief and pain management. As there are still gaps in our understanding of glomerular hematuria, we opted to assess the histopathological features of kidney biopsies of 14 LPHS patients to evaluate the correlation of glomerular basement membrane (GBM) alterations with hematuria and pain. METHOD In this cross-sectional study, 14 patients with LPHS underwent kidney biopsies. Demographic data (sex, age, ethnicity, weight and height), renal biomarkers (urine blood, urine protein and serum creatinine) and comorbidities were obtained prior to the procedure. The kidney biopsies were investigated under light microscopy, immunofluorescence microscopy and electron microscopy. Descriptive statistics were used to report baseline characteristics and histology findings. RESULTS All 14 patients were female, with median age 37 years. About 78.6% of the patients were Caucasian. None of the 14 patients had an abnormal glomerular filtration rate or an elevated albumin creatinine ratio (&amp;gt;3 mg/mmoL). 11/14 patients had macroscopic hematuria with 7/11 reporting gross hematuria with exacerbations of loin pain. 5/14 patients showed evidence of endothelial injury. Of the 14 patients, 1/14 had an insufficient sample, 1/13 had thick glomerular basement membrane, 1/13 had IgA nephropathy and 11/13 had normal GBM (Table 1). Regardless of GBM thickness, most patients had RBC cells ± casts implying glomerular leak. There was no evidence of podocyte injury. The presence of endothelial cell injury by electron microscopy may suggest a role for vascular damage in the pathogenesis of at least a subgroup of LPHS patients. CONCLUSION The array of histological changes identified in our study offers some understanding of the hematuria component but cannot explain pain as most patients did not have histological evidence of interstitial edema. In conclusion, our findings indicate that there is an urgent need for advanced understanding of molecular mechanisms underlying the heterogeneity of this disease. In our next phase of the study, we intend to compare gene signatures of LPHS patients with patients with isolated hematuria (without pain) to help enhance our understanding of unique genetic predisposing factors to this disease.

Positive Lateral Flow Urine Lipoarabinomannan Assay (LF-LAM) Result in Detection of Active Tuberculosis

Lipoarabinomannan (LAM) is the main component of M. tuberculosis (MTB) wall as result of MTB degradation by macrophages in the human body. In patients with active TB and HIV co-infection, a decrease in antibody responses may be apparent that some of LAM may not be bound with antibodies. In this condition, LAM can pass through the normal glomerular basement membrane and can be detected in the urine. One laboratory examination for detecting LAM is the Lateral Flow Urine Lipoarabinomannan (LF-LAM) assay that uses urine as the sample. The purpose of this cross-sectional observational descriptive comparative study was to compare the positivity rate of LF-LAM examination results in active TB patients with and without HIV infection. Random urine samples were collected from patients diagnosed with active TB with and without HIV infection who visited Dr. Hasan Sadikin General Hospital Bandung from August to October 2020. The proportion between the group with HIV and group without HIV was analyzed with the Chi-Square test. Subjects were 52 patients, consisting of 25 (48%) subjects with HIV infection and 27 (52%) subjects without HIV infection. The positive LF-LAM results were found in 11 (21%) subjects, consisting of 9 (36%) subjects with HIV infection and 2 (7%) subjects without HIV infection, with p=0.012. In conclusion, the positivity rate of LF-LAM results is higher in active TB patients with HIV infection compared to those without HIV infection.

Genetic Basis of Type IV Collagen Disorders of the Kidney.

The glomerular basement membrane is a vital component of the filtration barrier of the kidney and is primarily composed of a highly structured matrix of type IV collagen. Specific isoforms of type IV collagen, the α3(IV), α4(IV), and α5(IV) isoforms, assemble into trimers that are required for normal glomerular basement membrane function. Disruption or alteration in these isoforms leads to breakdown of the glomerular basement membrane structure and function and can lead to progressive CKD known as Alport syndrome. However, there is wide variability in phenotype among patients with mutations affecting type IV collagen that depends on a complex interplay of sex, genotype, and X-chromosome inactivation. This article reviews the genetic basis of collagen disorders of the kidney as well as potential treatments for these conditions, including direct alteration of the DNA, RNA therapies, and manipulation of collagen proteins.

Pediatric glomerular hematuria: a clinicopathological study.

Hematuria is a common problem in pediatric practice and necessitates exhausting studies to detect etiology and establish proper management and counselling. We reviewed the clinical and pathological findings in 95 children presented between 2013 and 2019 with gross or microscopic hematuria with or without proteinuria in whom non-glomerular causes were excluded. In addition, a reference range for normal glomerular basement membrane thickness (GBMT) is introduced based on the assessment of biopsies of 20 steroid-resistant nephrotic syndrome cases aged 3-15years, and with minimal change pathology. Fifty-seven males and 38 females with a mean age of 7.72 ± 3.27years were included. Recurrent gross hematuria was the most frequent presentation (42%) while accidentally discovered hematuria wasreported in 34.7% of patients. Alport syndrome (AS) was the most frequent diagnosis(66.3%) followed by thin basement membrane disease (TBMD) (29.5%) and Immunoglobulin A nephropathy (IgAN) (4%). A reference for normal GBMT was 360.3 ± 87.5nm which is comparable to published references. Males with AS had a higher incidence of progression to renal failure and requirement for dialysis (p = 0.006 and 0.03, respectively) compared to females. Persistent proteinuria and lower glomerular filtration rate at diagnosis were associated with poor outcomes (p < 0.001 each). Alport Syndrome is the most common cause of glomerular hematuria in Egyptian children. Persistence of proteinuria and lower GFR at initial presentation were the main predictors of poor outcomes. The establishment of GBMT reference range for each locality is mandatory for the proper diagnosis of such cases.

Rethinking glomerular basement membrane thickening in diabetic nephropathy: adaptive or pathogenic?

Diabetic nephropathy (DN) is the leading cause of chronic kidney disease in the United States and is a major cause of cardiovascular disease and death. DN develops insidiously over a span of years before clinical manifestations, including microalbuminuria and declining glomerular filtration rate (GFR), are evident. During the clinically silent period, structural lesions develop, including glomerular basement membrane (GBM) thickening, mesangial expansion, and glomerulosclerosis. Once microalbuminuria is clinically apparent, structural lesions are often considerably advanced, and GFR decline may then proceed rapidly toward end-stage kidney disease. Given the current lack of sensitive biomarkers for detecting early DN, a shift in focus toward examining the cellular and molecular basis for the earliest structural change in DN, i.e., GBM thickening, may be warranted. Observed within one to two years following the onset of diabetes, GBM thickening precedes clinically evident albuminuria. In the mature glomerulus, the podocyte is likely key in modifying the GBM, synthesizing and assembling matrix components, both in physiological and pathological states. Podocytes also secrete matrix metalloproteinases, crucial mediators in extracellular matrix turnover. Studies have shown that the critical podocyte-GBM interface is disrupted in the diabetic milieu. Just as healthy podocytes are essential for maintaining the normal GBM structure and function, injured podocytes likely have a fundamental role in upsetting the balance between the GBM's synthetic and degradative pathways. This article will explore the biological significance of GBM thickening in DN by reviewing what is known about the GBM's formation, its maintenance during health, and its disruption in DN.

Alternative Pathway Dysregulation and the Conundrum of Complement Activation by IgG4 Immune Complexes in Membranous Nephropathy.

Membranous nephropathy (MN), a major cause of nephrotic syndrome, is a non-inflammatory immune kidney disease mediated by IgG antibodies that form glomerular subepithelial immune complexes. In primary MN, autoantibodies target proteins expressed on the podocyte surface, often phospholipase A2 receptor (PLA2R1). Pathology is driven by complement activation, leading to podocyte injury and proteinuria. This article overviews the mechanisms of complement activation and regulation in MN, addressing the paradox that anti-PLA2R1 and other antibodies causing primary MN are predominantly (but not exclusively) IgG4, an IgG subclass that does not fix complement. Besides immune complexes, alterations of the glomerular basement membrane (GBM) in MN may lead to impaired regulation of the alternative pathway (AP). The AP amplifies complement activation on surfaces insufficiently protected by complement regulatory proteins. Whereas podocytes are protected by cell-bound regulators, the GBM must recruit plasma factor H, which inhibits the AP on host surfaces carrying certain polyanions, such as heparan sulfate (HS) chains. Because HS chains present in the normal GBM are lost in MN, we posit that the local complement regulation by factor H may be impaired as a result. Thus, the loss of GBM HS in MN creates a micro-environment that promotes local amplification of complement activation, which in turn may be initiated via the classical or lectin pathways by subsets of IgG in immune complexes. A detailed understanding of the mechanisms of complement activation and dysregulation in MN is important for designing more effective therapies.

Podocyte Detachment Is Associated with Renal Prognosis in ANCA-Associated Glomerulonephritis: A Retrospective Cohort Study.

The prognosis of antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (ANCA-GN) is unfavorable despite immunosuppressive therapy. It has been suggested that the loss of podocytes is a hallmark of progressive kidney disease. However, it is unclear about podocyte injuries and their predictive values on the prognosis in ANCA-GN. Therefore, the current study aimed to investigate the podocyte injury in renal histopathology and its association with renal prognosis of patients with ANCA-GN.A total of 170 patients with ANCA-GN were recruited in this study. Morphometric investigation of podocytes by electron microscopy including foot process width (FPW), podocyte density per glomerulus (Nv), and glomerular basement membrane (GBM) width were measured and calculated in ANCA-GN patients. Cox regression analysis was used to analyze the association between podocyte injuries and prognosis of patients with ANCA-GN.Foot processes broadening, podocyte detachment, and GBM thickening could be observed in electron micrographs in the specimens of 158/170 (92.9%), 142/170 (83.5%), and 150/170 (88.2%) patients, respectively. Compared with normal controls, FPW and GBM width in ANCA-GN patients was significantly higher (1269.39 ± 680.19 vs 585.81 ± 77.16, P = 0.004; 668.23 ± 208.73 vs 354.23 ± 52.70, P = 0.000, respectively), while the podocyte density was significantly lower (55.90 ± 36.32 vs 255.23 ± 47.29, P = 0.000). The podocyte density was independently associated with the recovery of renal function in logistic regression analysis (OR, 1.083; 95% CI, 1.025–1.440; P = 0.005). Furthermore, multivariate analysis revealed that podocyte density was an independent predictor of end-stage renal disease (ESRD) (model A: HR, 0.950; 95% CI, 0.919–1.982; P = 0.002; model B: HR, 0.953; 95% CI, 0.922–0.985; P = 0.004).Podocyte structural damage and detachment occurred frequently in patients with ANCA-GN. Moreover, podocyte detachment was an independent predictor of renal outcomes.

A mouse Col4a4 mutation causing Alport glomerulosclerosis with abnormal collagen α3α4α5(IV) trimers

A spontaneous mutation termed bilateral wasting kidneys (bwk) was identified in a colony of NONcNZO recombinant inbred mice. These mice exhibit a rapid increase of urinary albumin at an early age associated with glomerulosclerosis, interstitial nephritis, and tubular atrophy. The mutation was mapped to a location on Chromosome 1 containing the Col4a3 and Col4a4 genes, for which mutations in the human orthologs cause the hereditary nephritis Alport syndrome. DNA sequencing identified a G to A mutation in the conserved GT splice donor of Col4a4 intron 30, resulting in skipping of exon 30 but maintaining the mRNA reading frame. Protein analyses showed that mutant collagen α3α4α5(IV) trimers were secreted and incorporated into the glomerular basement membrane (GBM), but levels were low, and GBM lesions typical of Alport syndrome were observed. Moving the mutation into the more renal damage-prone DBA/2J and 129S1/SvImJ backgrounds revealed differences in albuminuria and its rate of increase, suggesting an interaction between the Col4a4 mutation and modifier genes. This novel mouse model of Alport syndrome is the only one shown to accumulate abnormal collagen α3α4α5(IV) in the GBM, as also found in a subset of Alport patients. These mice will be valuable for testing potential therapies, for understanding abnormal collagen IV structure and assembly, for gaining better insights into the mechanisms leading to Alport syndrome and to the variability in the age of onset and associated phenotypes.

Proteinuria: pathophysiology, diagnostic and therapeutic approach

Normal urine contains minute amounts of protein. The normal glomerular basement membrane imposes a barrier to large plasma proteins. This effect depends mainly on basement membrane pore size and electrostatic charge. However, a relevant role is also played by podocytes. Smaller proteins are filtered freely. Most of the proteins normally entering the urine are catabolized by the proximal tubules. The most frequent cause of major proteinuria is the functional failure of the glomerular barrier (glomerular proteinuria). In tubular proteinuria functional disturbances of the tubules result in a lack of catabolization of smaller proteins that can readily cross the glomerular barrier. The overflow proteinuria is caused by the glomerular filtration of compounds that are present in the plasma at higher concentrations in certain diseases; for example: light chain of immunoglobulins in multiple myeloma. Proteinuria may occur as a consequence of resistance to venous outflow, as in orthostatic proteinuria. This is asymptomatic and occurs mainly in young, slim and tall males, and it is generally benign. Proteinuria should be monitored regularly in any disease that is potentially related to glomerular damage, such as diabetes mellitus, autoimmune disorders, and hypertension. The correct diagnosis in a patient with proteinuria can only be obtained by renal biopsy. The presence of proteinuria is a well-known major independent risk factor for progressive renal damage, and for cardiovascular morbidity and mortality. The interaction of albumin with proximal tubules leads to renal damage through an increased expression of a variety of inflammatory and fibrogenic cytokines. This progression seems to be largely independent of the initial insult, and it is the final common pathway for chronic, proteinuric nephropathies in animals and humans. Both interstitial inflammation and progression of disease can be controlled by drugs that interfer with the renin angiotensin system, such as the angiotensin-converting enzyme inhibitors (ACEI), the angiotensin receptor blockers (ARB), and the aldosterone receptor blockers. These agents strengthen the glomerular permeability barrier to protein, limit proteinuria and filtered protein-dependent inflammatory indicators.

Differential expression of laminin isoforms in diabetic nephropathy and other renal diseases

AbstractLaminin a non-collagenous glycoprotein is a major component of the renal glomerular basement membrane and mesangium. Thus far eleven distinct chains have been described, permutations of which make up 15 laminin isoforms. Laminin molecules interact with cells and other matrix molecules during organ development and differentiation. We studied the distribution of laminin isoforms in patients with type 1 diabetic nephropathy, membranous nephropathy, membranoproliferative glomerulonephritis and IgA nephropathy/ Henoch–Schönlein purpura. Immunofluorescence microscopic studies with laminin-chain-specific antibodies to the α1, α2, α5, β1, β2 and γ1 chains detected α2, β1 and γ1 chain expression in the normal mesangium and α5, β2 and γ1 in normal glomerular basement membrane. Significantly, constituents of the glomerular basement membrane, α5, β2 and γ1 chains were overexpressed in kidneys with diabetic nephropathy. Initially the constituents of the mesangium increased commensurate with the degree of mesangial expansion and degree of diabetic nephropathy. Reduction in α2 chain intensity was observed with severe mesangial expansion and in the areas of nodular glomerulosclerosis. In addition, with late disease aberrant expression of α2 and β2 chains was observed in the mesangium. Glomerular basement membrane in renal disease overexpressed molecules normally present in that location. In summary, the alterations in basement membrane composition in various renal diseases seem to not only reflect the balance between synthesis and degradation of normal basement membrane constituents, but also their aberrant expression.

Thin Basement Membrane Disease (TBMD)の臨床的ならびに超微形態学的検討

Among patients with minor glomerular abnormality detected by light microscopy, but without significant finding by immunofluorescent study, fifteen cases showing global thinning of the glomerular basement membrane (GBM) when examined by electron microscopy were investigated as thin basement membrane disease (TBMD). Fourteen cases with a normal GBM thickness were selected as the control group. In the TBMD group, the mean width of the GBM, the distance between the cell membranes of the epithelial and endothelial cells, was 225 +/- 20 nm, whereas it was 354 +/- 42 nm in the control group. Some cases in the control group revealed a thinner GBM than other cases, which suggested the existence of an intermediate type between the TBMD and normal groups. The mean thickness of GBM in the intermediate and other control cases were 299 +/- 6 nm and 388 +/- 9 nm, respectively. In addition to global thinning of the GBM, the characteristic lesions of TBMD, a lucent appearance of the mesangial area (6 cases), widening of the subendothelial space (8 cases), splitting of the GBM (2 cases) and rupture of the GBM (one case) were observed in the TBMD cases, although these changes were mild in degree. A lucent appearance of the mesangium and widening of the subendothelial space were noticed more frequently in the TBMD group, compared with the control group. A common urinary abnormality in the TBMD patients was microscopic hematuria, which was occasionally associated with mild to moderate proteinuria. The renal function remained within the normal range in thirteen cases. Five cases of the TBMD group had members with renal abnormality in their family, of whom two showed renal failure and were undergoing hemodialysis.

Integrin α2-deficient mice provide insights into specific functions of collagen receptors in the kidney

BackgroundIntegrins are important cellular receptors for collagens. Within the glomerulus, podocytes regulate the integrity of the glomerular basement membrane (GBM) by sensing the presence of collagen and regulating collagen IV synthesis. The present study evaluates the role of integrin α2 (ITGA2) in cell-matrix interaction.Methods and ResultsITGA2-deficient mice had normal renal function but moderate proteinuria and enhanced glomerular and tubulointerstitial matrix deposition. Electron microscopy demonstrated irregular podocyte-matrix interaction, causing pathological protrusions towards the urinary (podocyte) side of the GBM. These characteristic subepithelial bulges mimic the renal phenotype of mice, which are deficient in another collagen receptor, discoidin domain receptor (DDR)1. Using immunogold staining, ITGA2 expression was found to localize to the basolateral site of the podocyte foot processes. ITGA2-deficient mice overexpressed transforming growth factor (TGF)β and connective tissue growth factor (CTGF) compared with wild-type mice. Using in situ hybridization, tubular cells were found to be the primary site of TGFβ synthesis and podocytes the source of CTGF in ITGA2-deficient mice.ConclusionThese findings support our hypothesis that both these collagen receptors (ITGA2 and DDR1) play a similar role within the kidney. Further, cell-matrix interaction via collagen receptors seems to be crucial for maintenance of normal GBM architecture and function. Targeting collagen receptors such as ITGA2 might be a new form of treatment for progressive fibrotic diseases.

Maintenance of Glomerular Filtration Barrier Integrity Requires Laminin α5

Mutation of the mouse laminin alpha5 gene results in a variety of developmental defects, including defects in kidney structure and function. Whereas the total absence of laminin alpha5 results in breakdown of the glomerular basement membrane (GBM) and failed glomerular vascularization, a hypomorphic Lama5 mutation (the Lama5(neo) allele) results in proteinuria, hematuria, polycystic kidney disease (PKD), and death 3 to 4 weeks after birth. Here, we examined the role of podocyte-derived laminin alpha5 via podocyte-specific inactivation of Lama5 and podocyte-specific rescue of the Lama5(neo) mutation. Podocyte-specific inactivation of Lama5 resulted in varying degrees of proteinuria and rates of progression to nephrotic syndrome. The GBM of proteinuric mice appeared thickened and "moth-eaten," and podocyte foot processes became effaced. Podocyte-specific restoration of laminin alpha5 production using two distinct strategies in Lama5(neo/neo) mice resulted in the resolution of proteinuria, hematuria, and PKD. These results suggest that the development of normal GBM structure and function requires podocyte-derived laminin alpha5 during and after glomerulogenesis and present a unique mechanism for the pathogenesis of PKD in these mice.

Banded Collagen in the Kidney with Special Reference to Collagenofibrotic Glomerulopathy

Background: The normal glomerular basement membrane, composed of type IV collagen, plays an important function in the process of filtration. Rarely, type III, type I, or type V collagen is seen in the glomerulus, resulting in three different types of non-immune mediated glomerulopathies recognized thus far. These are characterized by deposition of banded collagen fibers in the glomerulus. Methods: The authors reviewed 4934 kidney biopsies submitted over the past 5 years. Five of these revealed the presence of banded collagen in the glomeruli. Conclusion: Combined clinical and ultrastructural examination has led to a definitive diagnosis. These diseases exhibit indolent progression and as yet do not have specific treatment.

Analysis of the Glomerular Basement Membrane in Images of Renal Biopsies Using the Split-and-Merge Method: A Pilot Study

Abnormal thinning, thickening, or variation in the thickness of the glomerular basement membrane (GBM) are caused by familial hematuria, diabetes mellitus, and Alport syndrome, respectively. We propose a semi-automated procedure for the segmentation and analysis of the thickness of the GBM in images of renal biopsy samples obtained by using a transmission electron microscope (TEM). The procedure includes the split-and-merge algorithm, morphological image processing, skeletonization, and statistical analysis of the width of the GBM. The procedure was tested with 34 TEM images of six patients. The mean and standard deviation of the GBM width for a patient with normal GBM were estimated to be 368 +/- 177 nm, those for a patient with thin GBM associated with familial hematuria were 216 +/- 95 nm, and those for a patient with thick GBM due to diabetic nephropathy were 1,094 +/- 361 nm. Comparative analysis of the results of image processing with manual measurements by an experienced renal pathologist indicated low error in the range of 12 +/- 9 nm.

Development of lupus nephritis is associated with qualitative changes in the glomerular collagen IV matrix composition

Lupus nephritis is associated with thickening of the glomerular extracellular membranes. Distribution of collagen IV alpha-chains in the glomerular basement membrane in kidneys of lupus-prone B/W mice has been examined in this study. The results are indicative of a qualitative change in the collagen IV matrix occurring around the time of development of proteinuria, with an embryonic alpha1/alpha2 isoform replacing the normal glomerular basement membrane (GBM). These changes mimic alterations seen in Alport syndrome and coincide with an increase in collagenolytic activity within the glomerulus. It has been hypothesized that alterations in collagen matrix synthesis represent compensatory responses to an increase in GBM proteolysis and could represent an important step in the pathogenesis of nephritis through the formation of a dysfunctional glomerular filter. Also, aberrations in the collagen matrix composition could contribute to the deposition of autoantibodies within the glomerulus.

Segmentation and Analysis of the Glomerular Basement Membrane in Renal Biopsy Samples Using Active Contours: A Pilot Study

Some renal diseases cause changes in the structure of the glomerular basement membranes (GBM). Measurement of the thickness of the GBM can be performed on transmission electron microscopy (TEM) images of renal biopsy samples. Increased thickness of the GBM is observed in patients with diabetic nephropathy. Abnormally thin GBMs are associated with hematuria. We propose image processing methods for the detection and measurement of the GBM. The methods include edge detection, morphological image processing, active contour modeling, skeletonization, and statistical analysis of the width of the GBM. In the present pilot study, the methods were tested with 34 TEM images of six patients. The estimated mean and standard deviation of the GBM width for a patient with normal GBM were 348 +/- 135 nm; those for a patient with thin GBMs due to hematuria were 227 +/- 94 nm; and those for a patient with diabetic nephropathy were 1,152 +/- 411 nm. Comparison with manual measurements by an experienced renal pathologist indicated low error in the range of 36 +/- 11 nm.

IgA Nephropathy Associated with Thin Basement Membrane with or without Inflammatory Disease: Getting a Different Prognosis?

Background. Thin basement membrane nephropathy (TBMN) patients with additional inflammatory diseases and IgA nephropathy (IgAN) have not been reported before. It was unclear that if the prognosis of these patients is better or worse than patients with IgAN and TBMN, or IgAN patients with normal glomerular basement membrane (GBM). Methods. We first reported five TBMN patients with additional inflammatory diseases and IgAN: three were with rheumatoid arthritis, and two had Crohn's disease. Clinical and laboratory features were analyzed between this group (group 3), IgAN patients with normal GBM (group 1), and patients with TBMN and IgAN (group 2). Results. Significant differences were observed in serum levels of IgG, IgA, and IgM between groups 1 and 3, p < 0.001, and between groups 2 and 3, p < 0.001. Glomerular filtration rate (GFR) in group 3 was significantly lower than that of groups 1 and 2, p < 0.01, respectively. Conclusion. The prognosis of these patients is worse than patients with IgAN and TBMN or IgAN patients with normal GBM. Serum immunoglobulin levels and GFR in these patients were different from patients with IgAN and TBMN, or IgAN patients with normal GBM.