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Aim MMP-12 (macrophage elastase) is an enzyme that can cleave various extracellular matrix proteins and is required for macrophage infiltration and pulmonary fibrosis in experimental emphysema. We have shown previously that MMP-12 is highly up-regulated in experimental anti-glomerular basement membrane (GBM) disease. The aim of this study was to determine whether MMP-12 is required for glomerular macrophage infiltration and crescent formation in anti-GBM glomerulonephritis. Methods Accelerated anti-GBM disease was induced in groups of MMP-12 gene deficient mice (MMP-12-/-) and wild type C57BL/6 J (WT) controls, which were killed 12 days after injection of anti-GBM serum. Results WT and MMP-12-/- mice developed glomerular damage and glomerular tuft adhesions to Bowman's capsule. Both groups developed severe proteinuria. WT mice also developed significant loss of renal function and crescents in 22% of glomeruli, which were associated with macrophage infiltration and Bowman's capsule rupture. In contrast, MMP-12-/- mice were partially protected from renal function decline, crescent formation and Bowman's capsule rupture. This was associated with reduced macrophage infiltration in both glomeruli and the interstitium, and with reduced expression of CCL2, TNF-α and iNOS mRNA in MMP12-/- kidneys. In addition, KIM-1 mRNA levels were reduced in MMP-12-/- mice indicating less tubular damage. Conclusions These data demonstrate that endogenous MMP-12 facilitates macrophage accumulation and activation in anti-GBM glomerulonephritis which is required for glomerular crescent formation, Bowman's capsule rupture, tubular damage and renal function decline.

Aim The current study was designed to observe the ultrastructural changes of podocyte foot processes during the remission phase and its relationship with the amount of the proteinuria in patients with minimal change disease (MCD). Methods Electron micrographs of glomerular capillaries were taken from 33 adult cases with MCD, including 12 cases with nephrotic syndrome, 15 cases in partial remission and six cases in complete remission. The foot processes were classified into three grades by the ratio of the height to basal width: 0.5–1, 1–2 and ≥2. The foot process width (FPW) and the number of foot processes in different grades per 10 μm of glomerular basement membrane (GBM) were measured. Normal renal tissues from 12 nephrectomies for renal carcinoma were selected as controls. Results There were statistical differences (P = 0.001) in the mean FPW among the nephrotic group (1566.4 ± 429.4 nm), partial remission group (1007.8 ± 234.9 nm), complete remission group (949.8 ± 168.2 nm) and normal controls (471.9 ± 51.8 nm). For the height-to-width ratio ≥2, the number of foot process per 10 μm GBM was significantly greater in the normal group than that in the complete remission group (0.84 ± 0.24 vs. 3.84 ± 1.80, P = 0.016). Taking all three groups of patients together, the mean FPW showed correlation with the level of proteinuria (r = 0.506, P = 0.003). Conclusion There may be no causal relationship between proteinuria and foot process effacement. In complete remission phase, both FPW and shape of foot process had not returned to normal while proteinuria disappeared.

Aim: Cases with anti-glomerular basement membrane (GBM) disease have been reported with linear deposit of immunoglobulin G (IgG) along GBM, but have undetectable anti-GBM antibodies in circulation by enzyme linked immunosorbent assays (ELISA). We speculated that the structure of the antigens recognized by these antibodies may contribute to the negative results of ELISA. Methods: Sera from four patients were collected, with typical linear deposit of IgG along GBM but no anti-GBM reactivity by commercial ELISA kits. Circulating anti-GBM antibodies were detected by indirect immunofluorescence. Antigen specificity and its conformational structure was investigated by western-blot analysis, using recombinant human α1–α5(IV)NC1 and chimeric proteins EA and EB as antigens. Results: The presence of circulating anti-GBM antibodies were confirmed by indirect immunofluorescence with linear deposit of IgG towards cryptic epitopes along GBM on normal kidney sections. These antibodies did not recognize recombinant human α1, α2, α4 or α5(IV)NC1, but could blot α3(IV)NC1 under non-reducing non-boiling conditions on western-blot analysis, when the conformational epitope(s) on α3(IV)NC1 were thought to be preserved. When α3(IV)NC1 was prepared under reducing conditions with β-mercaptoethanol and/or boiled to destroy the disulfide bonds, the binding with the antibodies disappeared. Moreover, these antibodies recognized neither EA nor EB, indicating their distinct epitope repertoire. Conclusion: Circulating anti-GBM antibodies undetectable by ELISA could recognize cryptic and conformation-dependent epitopes restricted on α3(IV)NC1, distinct from EA and EB. Indirect immunofluorescence was necessary for antibody detection and treatment monitoring under such circumstances.

SUMMARY: Aim: Statins are widely used for their cholesterol-lowering effects and for prevention of cardiovascular disease. Evidence indicates that these drugs also have immunomodulatory and other non-lipid lowering effects, with studies suggesting benefit in some animal models of immune (particularly T helper (Th)1)-mediated inflammatory disease and their corresponding human disease counterparts. We sought to evaluate the immunomodulatory effects and therapeutic potential of atorvastatin in experimental crescentic glomerulonephritis, a Th1-predominant animal model of glomerulonephritis. Methods: Autologous phase, anti-glomerular basement membrane glomerulonephritis was induced in C57BL/6 mice by intravenous injection of sheep anti-mouse glomerular basement membrane globulin. Mice were administered atorvastatin (10 or 100 mg/kg) or control (phosphate-buffered saline) daily by oral gavage. Immune responses and renal injury were assessed after 21 days. Results: Compared with control-treated mice, treatment with atorvastatin did not alter renal injury (serum creatinine, proteinuria, glomerular crescent formation) or glomerular leukocytic infiltration (CD4+ T cells or macrophages). Atorvastatin resulted in a dose-related increase in circulating serum antibody to the disease-inducing antigen but no differences in antigen-stimulated splenocyte production of Th1/Th2 cytokines. At the higher dose, atorvastatin also led to a significant reduction in apoptosis of splenic CD4+ T lymphocytes. Conclusion: This study demonstrates that statins modulate humoral responses and alter splenic CD4+ T cell apoptosis. However, atorvastatin does not lead to significant changes in T helper cell polarization or renal injury in experimental crescentic glomerulonephritis.

Minimal change nephrotic syndrome (MCNS) is the most common cause of the nephrotic syndrome in children, accounting for 90% of cases under the age of 10 years and more than 50% in older children. It has been proposed that MCNS reflects a disorder of T-lymphocytes. These T cells are thought to release a cytokine - so-called permeability factor - that injures the glomerular epithelial cells. The identity of this permeability factor is still uncertain. Epithelial cell damage may lead to albuminuria in MCNS by altering the metabolism of polyanions, such as heparan sulphates, that constitute most of the normal charge barrier to the glomerular filtration of macromolecules such as albumin. In contrast, in focal segmental glomerulosclerosis (FSGS) the proteinuria is primarily due to an increased number of large pores in the glomerular basement membrane, leading to an impairment in size selectivity. It has been documented by repeated renal biopsies that some patients with apparent MCNS at the initial biopsy progress to FSGS. Morphological signs which have been proposed to identify the high-risk subset of MCNS include widespread IgM deposits (IgM nephropathy) and diffuse mesangial hypercellularity. It has been also documented that the initial biopsy of paediatric patients who subsequently showed FSGS had larger glomeruli from children with MCNS and healthy controls. Therefore, the presence of glomerular hypertrophy in biopsies of apparent MCNS appeared to be a high specific indicator of increased risk for progression to FSGS. In comparison with MCNS, a higher proportion of patients with mild mesangial hypercellularity are initial non-responder. More severe degree of mesangial hypercellularity, as seen in patients with diffuse mesangial hypercellularity, was associated with an even poorer initial response to steroid. Accordingly, it appears that mesangial proliferative glomerulonephritis is a more severe form of MCNS in which the initial injury is greater, leading to mesangial dysfunction and a slower rate of recovery, and this disorder is a part of the MCNS-FSGS spectrum. In this viewpoint, it can also be said that FSGS is the most severe form of MCNS in which the initial injury is the greatest, so the majority of patients with FSGS are non-responders to steroid and progress to chronic renal failure. In summary, documents define the risk for progressive renal disease based on the presence of mesangial hypercellularity and glomerular hypertrophy in renal biopsies of patients with MCNS, thus directing vigilant follow up and more aggressive treatment of high-risk patients.

SUMMARY: Background: Thin basement membrane nephropathy (TBMN) and IgA glomerulonephritis (IgA gn) are the most common primary glomerular conditions diagnosed on renal biopsy, performed for microscopic haematuria or microscopic haematuria with proteinuria. While up to 50% of patients with IgA gn will develop chronic renal failure, most patients with TBMN enjoy an excellent prognosis. Because TBMN is estimated to occur in up to 1% of the general population, differentiation between the two conditions without resort to renal biopsy is desirable. Methods: This retrospective analysis of 248 patients diagnosed on renal biopsy as having either TBMN or IgA gn, sought to identify clinical or biochemical factors which would have enabled confident differentiation between the two conditions to be made without resort to renal biopsy. Results: No single clinical or pathological variable adequately discriminated between the two conditions. Impaired renal function and heavy proteinuria were highly specific for IgA gn but lacked sensitivity in differentiating from TBMN. Isolated microscopic haematuria (IMH) was a more common finding in patients diagnosed with TBMN but, as a discriminator between TBMN and IgA gn, lacked sufficient specificity. However, if assumptions were made based on the differing incidence of a positive family history between IgA gn and TBMN, then specificity of >99% could be achieved. Conclusion: TBMN and IgA gn cannot be distinguished on the basis of clinical or pathological variables alone. However, in patients with IMH and a positive family history of either IMH or biopsy-proven TBMN, there is usually no need for renal biopsy.

SUMMARY: Although the role of glomerular basement membrane has been emphasised as the barrier for retaining plasma proteins in the past three decades, some recent studies have demonstrated that the slit diaphragm of the glomerular epithelial cell (podocyte) is the structure likely to be the barrier in the glomerular capillary wall. Nephrin and podocin were identified as gene products mutated in Finnish-type congenital nephrotic syndrome and autosomal recessive steroid-resistant nephrotic syndrome, respectively. Nephrin s located at the outer leaflet of plasma membranes of the slit diaphragm. Podocin is reported to have an interaction with nephrin. The anti-nephrin antibody is capable of inducing massive proteinuria, which indicates that nephrin is a key functional molecule in the slit diaphragm. The expression of nephrin and podocin was reduced in glomeruli of minimal change nephrotic syndrome, which suggested that the altered expression of these molecules contributes to the development of proteinuria also in acquired diseases. Some recent studies demonstrated that CD2-associated protein (CD2AP) is also a functional molecule in the slit diaphragm, and its expression is altered in membranous nephropathy. These observations suggested that alteration of the molecular arrangement in the slit diaphragm is involved in the development of proteinuria in several kinds of glomerular diseases.

SUMMARY: Background: Thin basement membrane disease (TBMD) occurs in 5–11% of renal biopsy series, and can be associated with other glomerulopathies (GNs). Data on the prevalence, clinical features, and prognosis of TBMD with other GNs are limited. Methods and Results: From June 1990 to May 2001, findings from 658 native kidney biopsies were retrospectively studied. The overall prevalence of TBMD was 7.9% (52 of 658). The mean glomerular basement membrane (GBM) thickness was 206 ± 30 nm. Clinicopathological features were compared for patients with TBMD only (n = 14) and in those with TBMD and GN (n = 38). Focal segmental glomerulosclerosis, mesangial proliferative GN, and minimal change disease were the most common GNs associated with TBMD. After a mean follow-up period of 44.9 ± 42.5 months, the group who only had TBMD revealed a relatively benign disease with microscopic haematuria and trivial proteinuria, a low prevalence of hypertension, and no renal progression. In the group who had both TBMD and GN, heavy proteinuria (6.1 ± 5.2 g/day), hypoalbuminaemia (26 ± 12 g/L) and renal insufficiency (76 ± 25 mL/min) might develop. Conclusion: We suggested that the TBMD is a developmental abnormality of little or no significance and that it is the underlying associated GN rather than TBMD, which has the relevance to the outcome of renal disease.

SUMMARY: In diabetic nephropathy, a decrease in the activity of matrix metalloproteinase (MMP) might contribute to the build-up of extracellular matrix protein in the mesangium and the glomerular basement membrane (GBM). Levels of MMP activity were measured as gelatinolytic activity in glomerular homogenates isolated from rats 1, 4, 12, 24 and 48 weeks after inducing diabetes mellitus (DM) with streptozotocin. The level of glomerular gelatinolytic activity after 1 week in DM rats was significantly increased compared with that in controls (224.8% of control; DM vs. control, 13.58 vs. 6.04 mU/glomerulus; P < 0.05), then decreased by 48 weeks (week 4, 92.8% of control; week 12, 81.9% of control; week 24, 31.8% of control; week 48, 47.3% of control). Glomerular metalloproteinase migrated on gelatin zymography at positions representing molecular weights of approximately 97, 80, 70 and 65 kDa. The intensity of these lytic bands was increased at 1 week but decreased at 24 and 48 weeks. Light microscopy revealed hypercellularity in the mesangial area at 1 week, followed by mild and marked mesangial expansion with GBM thickening at 12 and 48 weeks respectively. These data suggest that the persistent decrease in glomerular gelatinolytic activity during the chronic phase contributes to mesangial expansion and GBM thickening in DM rats. Moreover, the activity may play different roles at the time of onset and during the progression of diabetic nephropathy.

SUMMARY: Studies in experimental models have established that blockade of either interleukin 1 (IL-1) or tumour necrosis factor α (TNF-α) is effective in suppressing crescentic glomerulonephritis. However, it is not known whether simultaneous blockade of both cytokines will provide additional disease suppression compared with that produced by single cytokine blockade. We have addressed this question in a study of accelerated crescentic anti-glomerular basement membrane (GBM) glomerulonephritis in the rat. Groups of six animals were treated with an IL-1 receptor antagonist (IL-1ra), TNF-α-binding protein (TNFbp), IL-1ra + TNFbp (combined) or saline (control) from the time of anti-GBM serum injection until being killed, 10 days later. Saline-treated animals developed crescentic glomerulonephritis with tubulointerstitial damage, heavy proteinuria and renal impairment. Compared with saline, treatment with either IL-1ra or TNFbp alone resulted in significant suppression of crescent formation (3.0% and 3.3%, respectively, vs. 21.0%; both P < 0.001 vs. control), tubulointerstitial leucocytic infiltration (262 ± 31 and 282 ± 32 cells/mm2 vs. 481 ± 71 cells/mm2; both P < 0.001 vs. control) and proteinuria (167 ± 44 and 164 ± 23 mg/24 h vs. 279 ± 36 mg/24 h; both P < 0.001 vs. control) and prevented the loss of renal function. Combined IL-1ra and TNFbp treatment resulted in a virtually identical degree of disease suppression as individual cytokine blockade in terms of crescent formation (2.7%), interstitial leucocytic infiltration (274 ± 45 cells/mm2), proteinuria (190 ± 18 mg/24 h) and renal function preservation. In conclusion, this study has demonstrated that blockade of either IL-1 or TNF-α alone substantial suppresses experimental crescentic glomerulonephritis to a similar extent to that achieved by simultaneous blockade of both cytokines. These findings provide a rationale for the use of cytokine monotherapy, rather than multiple cytokine blockade, in the treatment of human crescentic glomerulonephritis.

SUMMARY: We have previously demonstrated the presence of detached podocytes in the urine in various glomerular diseases. In this study, we investigated the pathological significance of detachment of urinary podocytes (u-podocytes) in childhood IgA nephropathy. We investigated 28 children with IgA nephropathy. U-podocytes were detected in the urinary sediment by immunofluorescence. Renal pathological changes and urinalysis, including the u-podocyte test, were analysed. The expression of glomerular basement membrane (GBM) components, integrins and cytoskeleton components on urinary podocytes was investigated using dual immunofluorescence in 12 patients. The u-podocyte score paralleled the acute glomerular changes in renal biopsy samples. The infiltration of glomerular macrophages and polymorphonuclear leucocytes, and the number of urinary leucocytes, correlated highly with the u-podocyte score. Some of the u-podocytes expressed integrins and also components of the GBM. Detachment of podocytes reflects the presence of acute glomerular lesions. Infiltration of glomerular leucocytes is considered to be the cause of the detachment, partly because of the destruction of the GBM.

Summary: Recent in vitro studies have shown the synthesis of interleukin-6 (IL-6) in glomerular mesangial and epithelial cells, and suggested the involvement of IL-6 in mesangial proliferative glomerulonephritis. However, the expression site of IL-6 mRNA in renal tissue of IgA nephropathy (IgAN), the most common chronic mesangial proliferative glomerulonephritis, remains obscure. to localize IL-6 mRNA in renal biopsy specimens of IgAN, we used nonradioactive in situ hybridization (ISH) developed in our laboratory, sensitive in detecting individual cells positive for a specific mRNA. In some sections, periodic acid-Schiff staining was performed after ISH in order to identify the topographical relation between IL-6 mRNA positive cells and glomerular basement membrane and mesangial area. In situ hybridization for IL-6 mRNA and immunohistochemistry for CD3 and CD68, markers for lymphocytes and monocytes, respectively, were also performed on serial sections to examine the contribution of infiltrated mononuclear cells to cells positive for IL-6 mRNA in glomeruli. Glomerular resident cells, including glomerular mesangial and epithelial cells and cells of Bowman's capsule, as well as tubular epithelial cells and infiltrated mononuclear cells expressed IL-6 mRNA. We also compared the localization of IL-6 mRNA and protein and showed different distribution between the gene product and protein. the expression of IL-6 mRNA correlated with the degree of mesangial cell proliferation and tubulointerstitial changes. Our results indicate that IL-6 is synthesized in renal tissues of IgAN and suggest that the increased IL-6 expression may be important in the pathogenesis of IgAN.

Summary: Transporter-associated with antigen processing (TAP1 and TAP2) gene products are involved in the transport/processing of self-peptides from cytosol into endoplasmic reticulum (ER). In ER, these peptides associate with human leucocyte antigen (HLA)-class I molecules for further presentation at cell surface. Deficient processing and/or presentation could lead to altered self-tolerance resulting in autoimmunity. We studied TAP1 and TAP2 genes and genotypes frequencies in 49 controls and in 101 patients with primary IgA nephritis (IgAN). the patients were divided into two groups: 45 patients with end-stage renal failure (ESRF) and 56 patients with normal kidney function (NKF). DNA was extracted from peripheral blood and amplified by double amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) using appropriate primers for the two point-mutations on TAP1 genes and for the three point-mutations on TAP2 genes, which are the basis of TAP polymorphism. We have found a weak association between TAP2-p379-VAL/ILE genotype and total-IgAN (24%vs 12% in controls; P= 0.05). However, the analysis of a subgroup of IgAN patients bearing HLA-B35 antigen, a former poor prognosis marker, disclosed an association between the TAP2-1993Ntd-Guanine variant (coding for TAP2-p665-ALA): 31% in B35-ESRF-IgAN subgroup vs 6% in controls (P=0.04) and 13% in B35-NKF-IgAN (P=NS). the complexity of immunogenetic studies in IgAN is further increased by the existence of two opposite pathological subgroups: normal glomerular basement membrane (GBM) thickness vs thin-GBM. There was a complex relation in IgAN between this TAP2 variant and the following parameters: ESRF, HLA-B35, and normal-GBM. Further investigations are therefore needed.

Summary: Serum sickness nephritis was induced in young (3 weeks old) and old (50 weeks old) Fischer rats by immunization with egg albumin, and the age-related clinicopathological differences were analyzed. At least four differences were recognized between the young and old nephritis rats. First, the induced proteinuria was transient in the young group, but persistent in the old group and second, intramembranous electron dense deposits (IMEDD) in the thickened glomerular basement membrane were characteristic in the old group by electron microscopic observation. Third, the peripheral distribution of immune complexes in glomemlus was much more dominant in the young group. Fourth, the accumulation of monocytes was more prominent in the young group. These findings support the following suggestions: (i) in the ageing rats, there may be lowered efficiency of turnover of the extracellular matrix and the decreased ability of the mononuclear phagocyte system function; (ii) these changes may be responsible for the delayed clearance of the immune complexes from the glomerulus, and (iii) the longstanding presence of IMEDD observed in the ageing rats may play a role in persistent proteinuria.

Summary: We examined the activity and the characteristics of gelatinolytic enzymes in the urine from normal subjects and the patients with glomerulonephritis (GN). Gelatinolytic activity was assayed by using [3H]gelatin (heat-denatured type I collagen) as a substrate. the activity found to be 2463 ± 204 U/day (mean ± SEM, n = 17) in the urine from the healthy individuals, but was negligible in plasma samples. In GN patients (n=24) urinary gelatinolytic activity (724± 149 U/day, P < 0.001) was significantly lower compared with the healthy individuals. Partial purification (anion exchange column chromatography followed by gel filtration) revealed that two active gelatinolytic enzymes (molecular weight [Mr]92 kDa; high molecular weight [HMW] gelatinase, Mr 40 kDa; low molecular weight [LMW] gelatinase) were present in the urine obtained from the healthy individuals. the activity of these enzymes was inhibited by EDTA, 1,10-phenanthroline and α2-macroglobulin, but not by inhibitors for serine, cystein and aspartic proteinase. As the optimum pH was in the neutral range (pH 6–9), these gelatinases were considered to be neutral endometalloproteinases. These enzymes could degrade acid soluble type IV collagen and native rat glomerular basement membrane (GBM) in addition to gelatin, but not type I collagen. Immunoblotting with antibodies against human metalloproteinases (MP) identified HMW gelatinase with matrix metalloproteinase (MMP)-9 (gelatinase B) and LMW gelatinase with MMP-2 (gelatinase A), respectively. As these enzymes are metalloproteinase (MP) capable of degrading GBM and its component, urinary MP may be a useful subject as a tool searching the metabolic alteration of glomerular extracellular matrix in renal diseases.

Summary: The effects of enalapril and verapamil on glomerular protein content, fractional mesangial area and glomerular basement membrane (GBM) thickness were examined in spontaneously hypertensive rats with streptozotocin-induced diabetes. Two groups of 16 animals received enalapril maleate or verapamil to achieve normal blood pressure while a third untreated group remained hypertensive throughout the 3 month experimental period. Blood glucose levels were maintained at 6–10 mmol/L in each group. Creatinine clearance and 24 h urine protein were measured at second weekly intervals. Glomerular protein and other structural parameters were measured at the end of the experiment. Plasma angiotensin II (AII) and glomerular All receptors were also quantitated at the end of the experiment. At 3 months, proteinuria was lowest in the enalapril-treated animals while creatinine clearance was lower in the treated groups than controls. Glomerular protein content (μg/glomerulus) was lower in the enalapril-treated group than verapamil-treated (P

Summary: The aim of this study was to examine the relationship of basic fibroblast growth factor (FGF-2) and its receptor (FGF-R) to tubular proliferation, interstitial fibrosis, glomerular cell proliferation and crescent formation in the development of anti glomerular basement membrane (GBM) glomerulonephrids in the rat. Using new microwave-based histochemistry techniques, weak constitutive expression of mRNA and protein for FGF-2 and FGF-R was evident in tubules and glomeruli of normal rat kidney. Double and triple staining with the proliferating cell nuclear antigen (PCNA) demonstrated that in disease there was focal up-regulation of FGF-2 and FGF-R mRNA and protein expression within proliferating tubules and fibroblast-like cells in areas of interstitial fibrosis. In contrast, tubules in non-inflamed areas of kidney showed no change in FGF-2 and FGF-R expression or cellular proliferation. In addition, many FGF-2+PCNA+ and FGF-R+PCNA+ cells, probably mesangial cells and podocytes, were evident within glomerular segmental proliferative lesions. of particular interest was the observation that many epithelial cells within cellular crescents, inculding proliferating (PCNA+) epithelial cells, strongly expressed both FGF-2 and FGF-R. Furthermore, there was strong FGF-2 and FGF-R expression by proliferating fibroblast-like cells within fibrocellular crescents suggesting that FGF-2 is involved in the formation and fibrotic progression of glomerular crescents. In conclusion, this study provides evidence that increased expression of FGF-2 and its receptor may participate in the proliferative/fibrotic response in progressive crescentic glomerulonephritis.

Summary: Patients with thin basement membrane disease (TBMD) exhibit persistent haematuria with a diffuse thinning of the glomerular basement membrane (GBM), especially of the lamina densa. It appears to be an autosomal dominant trait. It has been reported that the Goodpasture epitope, which is located in the non-collagenous domain of type IV collagen α 3 chain, may be reduced in patients with TBMD. We speculated that the candidate gene for TBMD could be the type IV collagen α 3 chain gene (COL4A3), which is present closely to type IV collagen α 4 chain gene (COL4A4) on chromosome 2q35–37. We conducted a linkage analysis to investigate the relationship between familial TBMD and COL4A3 gene, using COL4A3 cDNA polymorphism and a (CA)n microsatellite marker located in the COL4A3 gene. We examined 32 individuals from four Japanese families with TBMD. There were no associations between the patients with haematuria and certain alleles of the two markers in the pedigrees of three families. It has been reported that type IV collagen α 1 chain gene (COL4A1) and α 2 chain gene (COL4A2) are not involved in TBMD, and that α 5 chain gene (COL4A5) and a 6 chain gene (COL4A6) map to chromosome X. In conclusion, our findings suggested that familial TBMD is not caused by the genetic abnormalities of type IV collagen genes isolated thus far.

Summary: Glomerular permselectivity is determined by complex interactions of the glomerular basement membrane (GBM) and the endothelial and epithelial cells of the glomerular capillary wall. Proteinuria may result acutely from functional changes in filtration, and be quickly reversible. Chronic structural changes may also contribute to proteinuria in many disease settings by affecting the components of the glomerular capillary wall (GCW). Thus, glomerular epithelial cell abnormalities are prominent in both minimal change disease and focal segmental glomerulosclerosis, whereas altered GBM thickness and composition are major features in diabetic nephropathy and Alport syndrome. A multitude of pathologic stimuli appear to influence proteinuria, including the renin-angiotensin system and numerous other cytokines. Human and experimental data indicate a heterogeneity of mechanisms in different diseases manifesting proteinuria which are associated with a range of structural appearances from normal morphology to a severely damaged GCW. Current therapeutic trials in progressive human renal diseases have focused on the potential benefits of angiotensin converting enzyme inhibitor (ACEI). Encouraging results indicate amelioration of both functional and structural components of proteinuria, as well as a benefit on sclerosis, although the latter effect has so far only been documented in animal studies. Advances in molecular technologies may allow identification of more specific abnormalities in the GCW which underlie proteinuria. Further understanding of these abnormalities will direct future therapy at the specific defect in each disease setting.