Focal segmental glomerulosclerosis (FSGS) is characterized by focal and segmental obliteration of glomerular capillary tufts with increased matrix. FSGS is classified as collapsing, tip, cellular, perihilar and not otherwise specified variants according to the location and character of the sclerotic lesion. Primary or idiopathic FSGS is considered to be related to podocyte injury, and the pathogenesis of podocyte injury has been actively investigated. Several circulating factors affecting podocyte permeability barrier have been proposed, but not proven to cause FSGS. FSGS may also be caused by genetic alterations. These genes are mainly those regulating slit diaphragm structure, actin cytoskeleton of podocytes, and foot process structure. The mode of inheritance and age of onset are different according to the gene involved. Recently, the role of parietal epithelial cells (PECs) has been highlighted. Podocytes and PECs have common mesenchymal progenitors, therefore, PECs could be a source of podocyte repopulation after podocyte injury. Activated PECs migrate along adhesion to the glomerular tuft and may also contribute to the progression of sclerosis. Markers of activated PECs, including CD44, could be used to distinguish FSGS from minimal change disease. The pathogenesis of FSGS is very complex; however, understanding basic mechanisms of podocyte injury is important not only for basic research, but also for daily diagnostic pathology practice.
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Background Segmental glomerulosclerosis without significant mesangial or endocapillary proliferation is rarely seen in IgA nephropathy (IgAN), which simulates idiopathic focal segmental glomerulosclerosis (FSGS). We recently recognized aberrant blood vessels running through the adhesion sites of sclerosed tufts and Bowman’s capsule in IgAN cases with mild glomerular histologic change.
Methods To characterize aberrant blood vessels in relation to segmental sclerosis, we retrospectively reviewed the clinical and histologic features of 51 cases of FSGS-like IgAN and compared them with 51 age and gender-matched idiopathic FSGS cases.
Results In FSGS-like IgAN, aberrant blood vessel formation was observed in 15.7% of cases, 1.0% of the total glomeruli, and 7.3% of the segmentally sclerosed glomeruli, significantly more frequently than in the idiopathic FSGS cases (p = .009). Aberrant blood vessels occasionally accompanied mild cellular proliferation surrounding penetrating neovessels. Clinically, all FSGS-like IgAN cases had hematuria; however, nephrotic range proteinuria was significantly less frequent than idiopathic FSGS.
Conclusions Aberrant blood vessels in IgAN are related to glomerular capillary injury and may indicate abnormal repair processes in IgAN.
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IgA nephropathy Maria F. Soares, Ian S.D. Roberts Current Opinion in Nephrology and Hypertension.2017; 26(3): 165. CrossRef
BACKGROUND The histological subtypes of focal segmental glomerulosclerosis (FSGS) have different significance and influence clinical presentations and outcomes in patients with FSGS. However, no such data has been reported in Korea. METHODS We reviewed renal biopsy specimens of 69 adult patients who were diagnosed with idiopathic FSGS between 2000 and 2008, subclassified them according to the Columbia classification and correlated the results with clinical findings. RESULTS The frequencies of the FSGS subtypes were not otherwise specified (NOS) (n = 28), tip (n = 21), perihilar (n = 11), collapsing (n = 5) and cellular types (n = 4) in descending order. Nephrotic syndrome was more common in patients with the tip and collapsing types than the perihilar type. The prevalence of chronic kidney disease stage 4/5 at the time of renal biopsy was significantly higher in patients with the cellular type than the NOS or the tip type. The remission rate after treatment tended to be higher in patients with the NOS type (22.0%) and the tip type (15.2%) than the perihilar (6.8%) and collapsing types (3.4%). CONCLUSIONS Classifying FSGS subtypes may be helpful to predict of clinical features and renal outcomes.
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Podocytopathy and Morphologic Changes in Focal Segmental Glomerulosclerosis Hyeon Joo Jeong Journal of the Korean Society of Pediatric Nephrology.2013; 17(1): 13. CrossRef
Pathology and Classification of Focal Segmental Glomerulosclerosis Yong-Jin Kim Journal of the Korean Society of Pediatric Nephrology.2012; 16(1): 21. CrossRef
BACKGROUND Osteopontin (OPN) is a cytokine related to cell-matrix adhesion and cell survival and is expressed in the distal convoluted tubules in normal adult kidneys. Only one in vitro study has investigated the role of OPN in mechanically stretched podocytes and their actin cytoskeleton rearrangement. METHODS Glomerular OPN expression was investigated in biopsies from patients with human idiopathic focal segmental glomerulosclerosis (FSGS) (n = 25) and in normal renal biopsies (n = 16) by immunohistochemistry. RESULTS OPN was expressed in the podocytes from patients with FSGS. OPN expression increased in podocytes from both non-sclerotic hypertrophic and sclerotic glomerular tufts in patients with FSGS compared to the podocytes in normal controls. CONCLUSIONS The results suggest that OPN plays a role in the early adaptive response of podocytes to the increased mechanical load caused by glomerular hypertrophy preceding FSGS. OPN was involved in cell-matrix adhesion and influenced the detachment delay of podocytes from the glomerular basement membrane and apoptosis.
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Podocyte Expression of Osteopontin and FSP-1/S100A4 in Human Crescentic Glomerulonephritis Ghil Suk Yoon, Tae Sook Kim The Korean Journal of Pathology.2011; 45(3): 237. CrossRef
BACKGROUND C1q nephropathy (C1qN) is a controversial diagnostic entity defined by Jennette and Hipp in 1985. The prevalence is very low and a few large scale studies have been reported. Application of the criteria for clinical diagnostics of C1qN may cause confusion with other glomerulonephropathies, such as minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS). In order to clarify the confusion with glomerulonephropathies, we did this study to identify the clinicopathological characteristics and the exact disease entity of C1qN. METHODS A total of 5,258 kidney biopsies at Kangnam St Mary's Hospital were reviewed. Twenty three cases (0.44%) met the criteria of C1qN. Twenty eight cases showing dominant C1q deposits without electron dense depostis (EDD) grouped as C1q+EDD-, and previously diagnosed typical cases of MCD and FSGS were selected for this study. Four groups were compared to each other with regard to the clinical and pathological aspects of the disease. RESULTS: C1qN patients had an average age of 30.4 years. Eighteen were males and 5 were females. Eighty seven percent had proteinuria and 18% had hematuria. By electron microscopy analysis, 100% had mesangial EDD and 47.8% showed foot process effacement. C1qN had some significant differences compared with C1q+EDD-, MCD and FSGS. CONCLUSIONS: C1qN is clinically and morphologically different from MCD and FSGS. However, additional long term studies are needed to fully define C1qN from other glomerulonephritis with C1q deposits.
It is not clear whether glomerular hypertrophy is related to the pathogenesis of focal segmental glomerulosclerosis (FSGS). We analyzed renal biopsies from 20 adults with FSGS by morphometry, and the data were compared with those from age- and sex-matched patients with minimal lesion. Mean glomerular volume in the FSGS group was significantly larger than that in the minimal lesion group[(3.4 + 1.1 vs 2.5 0.5)x10(6) micrometer3, P<0.01]. The percentage of glomeruli with global and segmental sclerosis in FSGS group was significantly correlated with the mean glomerular volume (r=+0.66, P<0.001). Relative interstitial volume of renal cortex in the FSGS group was correlated with the serum creatinine concentration(r=+0.5, P<0.05). These results suggest that glomerular hypertrophy observed in our patients with FSGS was related to nephron loss caused by glomerulosclerosis. The interstitial fibrosis may lead to obliteration of postglomerular interstitial capillary network with secondary elevation of glomerular capillary pressure resulting in progressive loss of renal function.
To evaluate the structural characteristics that might be related to the clinical features noted in preeclamptic patients with focal segmental glomerulosclerosis(FSGS), we analyzed post-partum renal biopsies of 8 preeclamptic patients with FSGS (group 1) by morphometry and glomerular studied the structural-functional relationships. These findings were also compared with those from three postpartum cases with minimal change lesion(group 2) and normal age-matched women(group 3). Mean glomerular volume (MGV) in group 1 and group 2 was (2.64 +/- 0.49) x 10(6) micrometer3 and (2.56+/-0.25)x 10(6) micrometer3, respectively. MGV in both groups was significantly increased compared with that of the control group [(1.11+/-0.22)x10(6) micrometer3](p<0.0005). The volume density of the mesangium/glomerulus [Vv(mes/glom)] in the group 1 patients was significantly increased (p<0.0001) when compared with that of the group 2 and the control group patients. The increment of Vv(mes/glom) was related to both the mesangial cell proliferation and expansion of mesangial matrix. The volume density of the capillary lumen/glomerulus [Vv(cap/glom)] in group I was significantly decreased(p<0.0001) when compared with that of group 2 and the control group. Vv(cap/glom) was directly related to Ccr in group l(r=0.70, p=0.05). These results suggest that reduced capillary luminal area caused by mesangial interposition is related to the decreased glomerular filtration rate in preeclamptic FSGS.
The pathogenetic mechanism of focal segmental glomerulosclerosis (FSGS) is not known. Some authors suggest glomerular hypertrophy may precede the development of FSGS in patients with minimal lesion. It was recently reported that the size of nonsclerotic glomeruli in adults with FSGS is significantly larger than that of cases with minimal lesion. It is not clear whether glomerular hypertrophy observed in adults with FSGS is also seen in children with FSGS. Thus, we have analyzed 37 renal biopsies from children with FSGS by morphometry and the data were compared with 37 renal biopsies from age- and sex-matched patients with minimal lesion. The number of glomeruli submitted for morphometric analysis was 22.6+/-14.2 in cases with FSGS and 30.9+/-11.4 in cases with minimal lesion. Mean glomerular volume (MGV) in FSGS group was significantly larger than that of minimal lesion [(13.1+/-3.9) x10(5) microm3 vs.
(10.1+/-1.9) x10(5) microm3, p<0.001]. The relative interstitial volume of renal cortex in patients with FSGS was significantly larger than that of minimal lesion [(0.106+/-0.051) microm3/microm3 vs. (0.029+/-0.012) microm3/microm3, p<0.0001]. In FSGS, the percentage of glomeruli with FSGS was significantly correlated with relative interstitial volume of renal cortex (r=0.79, p<0.0001). As is the case for adult FSGS, MGV of children with FSGS is significantly larger than that of minimal lesion. Thus, the presence of glomerular hypertrophy observed in biopsies with minimal lesion nephropathy seems to be an indication that the coexistent FSGS lesions are undetected due to sampling problems.
Cyclosporine A(CsA) is known as a potent immunosupressive agent, and recently its supressive effects of proteinuria in minimal change nephrotic syndrome, and other glomerular diseases have been demonstrated. But the mechanism of supression of proteinuria is not clear. This study aimed to investigate the mechanism of supression of proteinuria in puromycin aminonucleoside (PAN) induced minimal change nephrosis(MCN), by a single dose of PAN, and focal segmental glomerulosclerosis(FSG) by long term repeated administration of PAN with unilateral nephrectomy in Sprague-Dawley rats, using transmission electron microscopy. We also analysed the effects of CsA on the histopathologic changes such as glomerular sclerosis, and subtypes of infiltrated mononuclear cells in glomeruli and renal interstitium. The results are as follows: Marked proteinuria was developed in MCN and FSG groups. It was significantly reduced by administration of CsA. BUN and creatinine were significantly increased in FSG with the administration of CsA, compared with FSG without CsA. On ultrastructural examination, MCN group showed effacement of foot processes, and microvillous transformation. Occasional focal detatchment of podocytes from the GBM, vacuolar degeneration, and electron dense droplets in the podocytes were also seen. The latter findings were remarkably reduced by CsA. The Above ultrastructural findings, seen in the MCN group, were more severe in the FSG groups. On comparison of ultrastructural fingings of FSG with or without CsA groups, severe vacuolar degeneration, abundant electron dense granules, and focal detatchment of foot processes were more frequently seen in FSG groups and they were significantly reduced by CsA. But irregularity and thickening of GBM were deepend in FSG with CsA group. There were no significant differences of glomerular sclerosis, adhesion to the Bowman's capsules in both the MCN and the FSG groups by administration of CsA.
Foamy degeneration of endothelial and mesangial cells, epithelial proliferation, hyalinosis and mononuclear infiltration were significantly reduced by CsA in FSG groups. Microcalcification was commonly seen in CsA administrated groups. The main sutype of infiltrated mononuclear cells in glomeruli and interstitium were monocytes in FSG groups. The proportion of T cells were higher in interstitium by disease progression and it was significantly decreased by CsA. On conclusion the most important ultrastructural changes, regarded as the main mechanism of supression of proteinuria is that the CsA stabilize the podocytes, by preventing vacuolar degeneration and focal detatchment. But CsA does not influence the progression of glomerular sclerosis in PAN induced nephrosis.
Almost all advanced glomerular diseases have glomerular sclerotic changes to varying degrees whatever causes their primary glomerular disease are. Pathogenesis of these sclerosis has been thought of as the hyperfiltration in the primary glomerulosclerosis due to development of glomerular hypertension in each insulted glomeruli. This background gave the theoretical bases for antihypertensive therapies for supporting chronic renal insufficient patients.
Angiotensin converting enzyme (ACE) inhibitor, one of the antihypertensive drugs, has received attention recently for its effectiveness. The aims of this study determined the effects and mechanism of the ACE inhibitor, enalapril, on the glomerulosclerosis in FGS/NgaKist mice, which was an animal model of chronic renal failure by generating spontaneously heavy proteinuria and progressive glomerulosclerosis. Five-week-old FGS/NgaKist mice (n=38) were assigned to four groups. Group 1a (n=6) and group 2a (n=8) fed with a vehicle, were sacrificed at the end of 10 weeks and 15 weeks, respectively. Group 1b (n=12) and 2b (n=12) received enalapril (100 mg/L) in drinking water for 5 weeks and 10 weeks from 6th week of age respectively, and were sacrified on the same day as the control groups. Doses of enanapril were maintained to 2 mg/kg/day by measuring the amount of water consumption. In enalapril groups 1b and 2b, systemic blood pressure (74.7 14.0 mm Hg, 74.3 15.9 mmHg) were significantly lower than control group 2a (116.1 4.6 mmHg, P<0.001). Similarly, degree of proteinuria lowered in enalapril group 2b versus control group 2a (0% and 50.0%, P<0.001). Glomerulosclerosis percentage significantly decreased (P<0.001) (group 1b and 2b; 1.9 6.5, 5.6 7.0 vs control 1a and 2a; 32.8 15.5, 31.4 13.8). Glomerulosclerosis score also decreased (P<0.001) (group 1b and 2b; 0.02 0.08 vs control 1a and 2a; 0.48 0.12, 0.30 0.14). The immunofluorescent staining of enalapril groups showed negative for mesangial deposition of IgG, IgA, IgM, and C3 which were positive in control groups. Immunohistochemical staining with TGF-beta1 was negative in enalapril groups and sclerotic glomeruli both enalapril groups and control groups. These results support that the ACE inhibitor has a renoprotective effect on glomerulosclerosis not only by decreasing the blood pressure but also by suppressing the immune deposits on glomeruli.
Pathogenetic mechanisms of progressive glomerulosclerosis are not clear. We studied the long-term(10 weeks) effects of puromycin aminonucleoside(PAN) in Sprague-Dawley rats with or without uninephrectomy(UN). Compared to rats with PAN injections only, rats with uninephrectomy and PAN injections showed significantly higher serum levels of urea nitrogen(153 +/- 155 mg/dl vs. 16 +/- 4 mg/dl, p<0.01), ceatinine(2.96 +/- 1.21 mg/dl vs. 0.92 +/- 0.36 mg/dl, p<0.01), cholesterol(466 +/- 125 mg/dl vs. 94 +/- 27 mg/dl, p<0.01), and triglyceride(337 +/- 237 mg/dl vs. 111 +/- 36 mg/dl, p<0.05) as well as increased amounts of proteinuria(428 +/- 90 mg/day vs. 136 +/- 130 mg/day, p<0.01). Lesions of focal segmental glomerulosclerosis(FSGS) were more frequently observed in rats with UN and PAN injections than rats with PAN infections only(39.5 +/- 17.2% vs. 4.3 +/- 4.7%, p<0.01). Ultrastructural examination of the glomeruli from rats with UN and PAN injections revealed severe epithelial cell changes including foot process effacement, vaculoar change or pseudocyst formation and focal detachment of epithelial cells from the underlying basement membrane. The results suggest that chronic nephrosis induced by PAN showed functional and morphologic features similar to those of human FSGS. Cytotoxic effect of PAN on the glomerular epithelial cells may be an initiating factor for the development of FSGS. which may be aggravated by some hemodynamic changes induced by uninephrectomy.