Cyclosporine A-Induced Kidney Alterations Are Limited by Melatonin in Rats: An Electron Microscope Study

The effect of melatonin on experimental prolonged cyclosporine A (CsA) nephrotoxicity was analyzed by electron microscopy and morphometry. Twenty female Wistar rats were divided into groups that received (1) CsA at a therapeutic dose (15 mg/kg/day) sc for 40 days; (2) olive oil, CsA vehicle, as controls; (3) CsA plus melaton (1 mg/kg) ip for the same time; (4) melatonin alone, as additional controls. All controls had normal renal ultrastructure. However, in CsA group, both tubular and glomerular alterations were observed. The authors found apoptotic and necrotic proximal tubules with disrupted brush border, swollen mitochondria, abundant lysosomes; in the glomerulus, amorphous basement membrane, and abnormal mesangial matrix. CsA plus melatonin administration partly prevented these changes. Nevertheless, fibrillar deposits in podocytes and basolateral membrane dilatations in proximal tubules were observed. Histopathological analysis on semithin sections and ultrastructural morphometry were also performed. CsA induced interstitial fibrosis, atrophy, and PAS positive inclusions in the proximal tubules. Moreover, CsA reduced glomerular and mesangial volume but enhanced mesangial matrix volume and basement membrane thickness. After CsA plus melatonin, these parameters were reduced in the proximal tubules and restored in the glomerulus. In conclusion, melatonin attenuated morpho-quantitative alterations induced by CsA in the rat kidney.     

Tubulointerstitial nephritis and glomerulonephritis in Brown-Norway rats immunized with heterologous glomerular basement membrane.

Tubulointerstitial nephritis and glomerulonephritis were produced in Brown-Norway rats (BN) by a single immunization with 2 mg of lyophilized bovine glomerular basement membrane. Tubulointerstitial nephritis was evident before glomerulonephritis. Antibody first bound to tubular basement membranes (TBM), and then the renal cortex was infiltrated with inflammatory cells. The TBM was split, and many renal tubules, especially proximal tubules, were destroyed. Approximately 14 days after the beginning of the tubular phase, antibody was observed to be bound to glomerular basement membranes (GBM) in linear fashion. There was epithelial and mesangial cell proliferation, splitting and reduplication of GBM, crescent formation, and glomerular scarring and atrophy.     

Glomerulopathy and arteriolopathy in congenital nephrotic syndrome: Light,electron, and fluorescence microscopy studies

This report describes the light, electron, and fluorescence microscopy studies of the kidney from a one mouth old, prematurely born infant with the nephrotic syndrome. Light microscopy revealed enlargement of Bowman's space, an excessive number of glomerular epithelial cell nuclei, and cystic dilatation of cortical tubules. By electron microscopy two disparate types of glomerular lesions were found: a thin basement membrane with fusion of foot processes suggestive of lipoid nephrosis and linear electron-density in the basement membrane with excessive mesangial matrix and capillary collapse suggesting an antibasement membrane type of glomerulonephritis or mesangial sclerosis. Conspicuous cystic spaces were found in the proximal tubules only. In the arterioles there were cystic spaces in the endothelial cells and smooth muscle cells, thickening of the basement membranes of endothelial cells and smooth muscle cells, and excessive amounts of nonstriated fibrils in the subendothelial basement membrane. Masses of fibrin were noted in the lumina of veins, peritubular capillaries, and interstitium between veins and peritubular capillaries. Such multiple glomerular and arteriolar lesions have not been reported previously in congenital nephrotic syndrome. These lesions suggest an antigen-antibody reaction in the mother that might have been directed toward the glomerular basement membrane in the fetus, producing these lesions.     

Heterogeneous distribution of monomeric elements from the globular domain (NC1) of type IV collagen in renal basement membranes as revealed by high resolution quantitative immunocytochemistry.

Heterogeneity in the distribution of major components, namely laminin, entactin/nidogen, heparan sulfate proteoglycan and type IV collagen among renal basement membranes, was previously demonstrated (Desjardins and Bendayan, J Histochem Cytochem 37:885-897, 1989). To further investigate the nature of basement membranes, we applied high resolution immunocytochemistry to reveal monomers M1, M2* and M3 composing the NC1 domain of type IV collagen of various rat renal basement membranes. Labeling for the three monomers was confined to basement membranes. Quantitative morphometrical analysis demonstrated that the labeling for each monomer was not evenly distributed among the various basement membranes. Labeling for M1 was intense over the proximal tubule and the Bowman's capsule basement membranes. In the glomerulus, the mesangial matrix was highly labeled, whereas the glomerular basement membrane was labeled with a lower intensity. In contrast, labeling for M2* and M3 were high in the glomerular basement membrane, while very low in the mesangial matrix. Labeling intensities were intermediate in the other renal basement membranes. The ultrastructural distribution analysis made over the glomerular basement membrane showed a preferential subendothelial localization of M1 monomers. M2 and M3 on the other hand, were found throughout the entire thickness of the basement membrane. M1 monomers being associated to alpha 1(IV) and alpha 2(IV) chains of type IV collagen, and M2* and M3 to alpha 3(IV) and alpha 4(IV) chains respectively, our results thus demonstrate the existence of an heterogeneity in the collagenous nature of renal basement membranes, particularly the glomerular one. This heterogeneity must reflect variations in the structural arrangement of basement membranes and therefore in their functional properties.     

Glomerular basement membrane alterations induced by gentamicin administration in rats

The widespread therapeutic use of the aminoglycoside antibiotic gentamicin (GM) is limited by its nephrotoxic side effect, which can lead to acute renal failure. This study aimed at examining effects of high, supratherapeutic doses of gentamicin on morphological, structural and functional alterations of the glomerular basement membrane in adult rats. Experiments were done on 30 male Wistar rats, divided into two experimental groups. GM-group (20 rats) received gentamicin at a dose of 100mg/kg intraperitoneally during eight consecutive days. Control or C-group (10 rats) received 1 ml/day saline intraperitoneally. For histological analysis, 5 microm thick sections were stained with hematoxylin and eosin (HE), periodic acid Schiff (PAS), and Jones methenamine silver. Glomerular basement membrane thickness, glomerular area, major and minor axes, perimeter, diameter, roundness and mean optical density were analyzed. Biochemical analyses were used to determine concentrations of blood urea, serum creatinine, sodium and potassium. In GM-group rats, glomeruli were larger and glomerular basement membrane was diffusely and irregularly thickened with neutrophil cell infiltration. Glomerular area, major axis, minor axis, diameter and perimeter were significantly higher in GM-group compared to C-group rats. Opposite to this, glomerular optical density and average roundness were larger in C-group than in gentamicin-treated animals. Our results clearly showed morphological and structural alterations of glomeruli and glomerular basement membrane as well as alterations of proximal tubules in adult rats exposed to high doses of gentamicin.     

Oligomeganephronic renal hypoplasia with tapetoretinal degeneration

Summary Bilateral renal hypoplasia with oligomeganephronia, associated with bilateral tapetoretinal degeneration was observed in a child; this association has been reported only once before. Light, ultrastructural and immunofluorescent microscopic studies of the renal tissue were performed. The glomeruli were few and hypertrophic, with numerous mesangial cells, mesangial deposits, focal glomerular sclerosis and prominent thickened basement membrane. Two types of tubular changes were observed: focal necrosis of proximal tubules and focal atrophy of tubules surrounded by a thickened basement membrane. Mild fibrosis with few lymphocytes could be observed in the interstitium. A congenital reduction in the number of nephrons, related to a yet unknown pathological process may explain these morphological changes in part.     

Production of monoclonal antibodies to fibronectin, type IV collagen and other antigens of the human glomerulus

A series of monoclonal antibodies to human glomerular antigens was prepared by immunisation of a mouse with isolated whole glomeruli, followed by boosting with particulate glomerular basement membrane and fusion of murine spleen cells with the NSI-myeloma line. Hybridoma supernatants were screened jointly by a radioimmunoassay involving binding to isolated glomeruli, and by a 4-layer immunoperoxidase technique applied to polyester wax-embedded sections. Seven monoclonal antibodies with different specificities (PHM7-PHM13) were established and repeatedly cloned. Each antibody displayed a distinctive distribution within the glomerulus, including different patterns of staining of mesangial cells, mesangial matrix and glomerular basement membrane, in addition to extra-glomerular basement membranes and extracellular matrix. All antibodies also stained cellular outgrowths of isolated glomeruli cultured in vitro, and showed additive binding to cultured cells by radioimmunoassay. Physical characterization using absorptions with purified substrates, plus specific chemical and enzymatic digestions, indicated that PHM12 is directed against type IV collagen. PHM13 is directed against fibronectin as shown by absorption with purified fibronectin and immunoprecipitation of a 220 000 MW glycoprotein. The remaining 5 monoclonal antibodies, which react with carbohydrate (PHM7) or protein (PHM8-PHM11) determinants, were shown to be nonreactive with type IV collagen, fibronectin or other known glomerular components including sialic acid, laminin, amyloid P-component or various glycosaminoglycans. These monoclonal antibodies therefore appear to define a new series of human glomerular antigens, or possibly closely related antigenic determinants, which are synthesized by glomerular cells and incorporated into the mesangium and glomerular basement membrane. These antibodies, by providing markers for at least 2 antigens known to be important in glomerular cell-matrix interactions, should prove useful in research into the mechanisms involved in renal pathology.     

Enzymatic dissection of the glomerulus

White rat kidneys were fixed in perfusion, postfixed with 10% glutaraldehyde, and cut into 1-mm slices. The slices were treated with a sequential digestion over 4 days with trypsin, pepsin, and pronase E. This treatment dissolved the glomerular basement membrane and the mesangial matrix. Teasing the slides in buffer released many glomeruli and tubules which were prepared for scanning electron microscopy while attached to gelatine glass cover slips. Four human renal biopsies were similarly treated. The enzymatic removal of the basement membrane permitted viewing of the basilar or capillary slide of loosened podocytes and their processes. The cell body of the podocytes often exhibited a considerable area of contact with the basement membrane. The primary and secondary podocyte processes and foot processes maintained a continuous contact with the basement membrane. Human podocytes, although larger, were similar to the rat. Podocytes from minimal change disease showed severe retraction and flattening of primary and secondary processes and foot processes. Extensive visualization of the basilar surface of the exposed endothelial tubes was possible with this technique. The fenestrated and nonfenestrated portions were revealed including the axial area where the endothelial cells contact the mesangial cells and matrix, which formed an impression on the surface of the endothelium. The mesangial cells and their connecting processes (the mesangial network) were revealed extending from the peripheral lobule to the glomerular hilus where they merged with lacis cells. The mesangial cells exhibited a variety of processes which anchored into the mesangial matrix. At the hilus, these cells assumed a flat, villous, lacy appearance, and these cells encircled the large hilar capillaries. Glomeruli with afferent and efferent arterioles and associated Goormaghtigh (lacis) cells were identified. The transition between mesangial, Goormaghtigh, and smooth muscle cells was observed. These observations provide a unique view of the organization of the rat and human glomerulus and suggest the potential for the use of the present technique in the study of diseased glomeruli.     

Participation of endothelial cells in the development of glomerulosclerosis: a study on murine serum sickness nephritis with mitomycin C

To investigate the participation of endothelial cells in glomerulosclerosis, the study was performed in serum sickness nephritis (SSN) with administration of mitomycin C (MMC). SSN was induced in 8 week male Fisher rats by sensitizing them with albumin, chicken egg (EA). Then MMC (0.5 mg/kg bodyweight) was injected daily for 3 days and they were killed at 1, 2, 4 and 6 week intervals. Significant mesangial expansion and sclerosis were observed in the experimental mixed SSN-MMC group in comparison to the SSN or MMC control group from 1 week to 6 weeks (P < 0.05). Moreover at 1 week, double contour appearance of the glomerular capillary wall, basement membrane splitting and disruption were observed light microscopically in the mixed SSN-MMC group. Electron microscopy revealed peripheral capillary basement membrane disruption with huge subepithelial, mesangial osmiophilic deposits and epithelial foot process effacement. At 6 weeks, disappearance of the endothelial cell fenestration and subepithelial basement membrane-like material formation were observed in the MMC group. Based on these results, it is suggested that MMC induced assault on the glomerular endothelial cell produces prominent glomerular capillary basement membrane disruption at the early phase of SSN, resulting in the accumulation of huge subepithelial and mesangial deposits, mesangial cell proliferation, production of the extracelluar matrix component and initiation of glomerulosclerosis.     

On glomerular structural alterations in type-1 diabetes

Glomerular structural modifications were measured in kidney biopsies from two follow-up studies in type-1 diabetic patients with microalbuminuria and in kidney donors. Stereologic methods were used to obtain data on glomerular composition and absolute quantities per glomerulus to supplement data on diabetic glomerulopathy previously published. Diabetic patients at baseline (n=37) showed significant changes compared with controls (n=11). The volume fraction of tuft/glomerulus was increased, the proportion of capillary surface facing peripheral basement membrane was decreased (0.72+/-0.04 vs 0.77+/-0.03, P=0.0008), the ratio of mesangial surfaces, urinary/capillary, was decreased (0.67+/-0.17 vs 1.11+/-0.28, P<10(-4)), and the average capillary diameter was increased (8.9+/-0.9 microm vs 7.5+/-1.0 microm, P=0.0002). The total volume of mesangial extracellular material per glomerulus was increased (P=0.01), whereas glomerular volume was not significantly different from controls. Follow-up biopsies after antihypertensive treatment with ACE-inhibitor (n=7) or beta-blocker (n=6; 36-48 months) and after intensive insulin treatment (n=7; 24-33 months) showed no change. In a conventionally treated group (n=9), the glomerular volume, the volume of extracellular material/glomerulus, and the capillary length increased. The mean capillary diameter did not correlate with the glomerular volume. In conclusion, the development of diabetic glomerulopathy entails structural modifications of the glomerular tuft. Antihypertensive and intensified insulin treatment seem to slow the progression of ultrastructural changes.     

The potential protective role of taurine against 5-fluorouracil-induced nephrotoxicity in adult male rats

Nephrotoxicity is common with the use of the chemotherapeutic agent 5-Fluorouracil (5-FU). The current study aimed to investigate the probable protective effect of taurine (TAU) against 5-FU-induced nephrotoxicity in rats using biochemical, histological and ultrastructural approaches. Twenty-four rats were equally divided into control, TAU, 5-FU and 5-FU + TAU groups.5-FU significantly elevated levels of blood urea nitrogen (BUN), creatinine, and uric acid; while it reduced activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). Also, 5-FU induced significant elevation in malondialdehyde (MDA) levels accompanied with marked decline in γ-glutamyltranspeptidase (GGT) and alkaline phosphatase (AP) levels in kidney tissues. These biochemical alterations were accompanied by histopathological changes marked by destruction of the normal renal structure, in addition to ultrastructural alterations represented by thickened and irregular glomerular basement membranes, congested glomerular capillaries, damaged lining fenestrated endothelium, mesangial cells hyperplasia with expanded mesangial matrix, and distorted podocyte’s processes. Also, the proximal (PCT) and distal (DCT) convoluted tubules showed thickened basement membranes, destructed apical microvilli and loss of basal infoldings of their epithelial cells.Administration of TAU to 5-FU-treated rats reversed most of the biochemical, histological, and ultrastructural alterations. These results indicate that TAU has a protective effect against 5-FU-induced nephrotoxicity.     

Differential expression of collagen IV isoforms in experimental glomerulosclerosis

Expansion of the glomerular mesangial matrix (MM), thickening of the glomerular basement membrane (GBM), and eventually the development of glomerulosclerosis are often seen in immunologically mediated kidney diseases. In addition to quantitative changes in the extracellular matrix (ECM), qualitative changes in ECM molecules may contribute to alterations in the composition of the glomerular matrix. The expression of collagen IV, α1–5(IV) mRNA, and polypeptides was therefore investigated during the development of chronic graft-versus-host disease (GvHD) in mice, a model for lupus nephritis, and in chronic serum sickness (CSS) in rats, a model for membranous nephropathy. Immunohistochemical studies showed increased mesangial expression of α1 and α2 early in the disease, but only late in the GBM. In contrast, α3 and α4 increased in the GBM during disease, but not in the MM. The mRNA levels for all collagen IV chains were increased in isolated glomeruli before morphological alterations were detectable. The mRNA increase was earlier and more profound for α3, α4 and α5 than for α1 and α2. Expression of α3(IV) was greatest in GvHD, whereas expression of α4 was greatest in CSS. As determined by in situ hybridization (ISH), α1 mRNA was observed dispersed in the glomerulus, but α3, α4, and α5 mRNAs were mainly located in cells at the periphery of the glomerular tuft. The changes in the relative abundance of collagen IV mRNA in disease states may perturb the collagen IV network, altering glomerular structure and function, and may thereby play a central role in the development of glomerulonephritis and glomerulosclerosis. © 1998 John Wiley & Sons, Ltd.     

Mitochondrial Enlargement and Basement Membrane Thickening of Renal Proximal Tubules, Possible Initiators of Microalbuminuria in Non-Insulin-Dependent Diabetics (NIDDM)

To clarify the morphological changes in renal proximal tubules at the onset of diabetic nephropathy, we observed 177 biopsy samples from patients with Non-Insulin-Dependent Diabetics (NIDDM) using light and electron microscopy. Group I had no proteinuria (P.u.), group II had p.u. >0.5 g /day, group III had p.u. > 0.5 g day, group IV had serum creatine level (Cr) >1.5mg/dl. Twenty age-matched normal patients and 80 patients with IgA nephropathy were used as controls. In groups I and II, the following features were significantly different from those in the controls: spherical enlargement of mitochondria (MT) in proximal tubule cells, hypertrophy of proximal tubule cells and their nuclei, and thickening of both the proximal tubule basement membrane (TBM) and the glomerular basement membrane (GBM). Among the his-tological changes observed in group I, the thickness of the GBM and TBM indicated that the disease would lead to diabetic nephropathy. MT enlargement was positively correlated with nuclear and cytoplasmic enlargement of the proximal tubule cells in diabetic patients (p<0.05), but was not correlated with other morphological changes or disease prognosis. Glomerular nodular lesions, glomerular sclerotic change, and cortical tubulointerstitial fibrosis became evident in groups III and IV. From the above, we concluded that MT enlargement and thickening of the TBM are possible causes of reduced active transport in the proximal tubules, causing microalbuminuria in diabetics, and initial impairment of post-tubule transport. Acta Pathol Jpn 42: 793–799, 1992.     

Mitochondrial enlargement and basement membrane thickening of renal proximal tubules, possible initiators of microalbuminuria in non-insulin-dependent diabetics (NIDDM).

To clarify the morphological changes in renal proximal tubules at the onset of diabetic nephropathy, we observed 177 biopsy samples from patients with Non-Insulin-Dependent Diabetics (NIDDM) using light and electron microscopy. Group I had no proteinuria (p.u.), group II had p.u. < or = 0.5 g/day, group III had p.u. > 0.5 g/day, group IV had serum creatine level (Cr) > 1.5 mg/dl. Twenty age-matched normal patients and 80 patients with IgA nephropathy were used as controls. In groups I and II, the following features were significantly different from those in the controls: spherical enlargement of mitochondria (MT) in proximal tubule cells, hypertrophy of proximal tubule cells and their nuclei, and thickening of both the proximal tubule basement membrane (TBM) and the glomerular basement membrane (GBM). Among the histological changes observed in group I, the thickness of the GBM and TBM indicated that the disease would lead to diabetic nephropathy. MT enlargement was positively correlated with nuclear and cytoplasmic enlargement of the proximal tubule cells in diabetic patients (p < 0.05), but was not correlated with other morphological changes or disease prognosis. Glomerular nodular lesions, glomerular sclerotic change, and cortical tubulointerstitial fibrosis became evident in groups III and IV. From the above, we concluded that MT enlargement and thickening of the TBM are possible causes of reduced active transport in the proximal tubules, causing microalbuminuria in diabetics, and initial impairment of post-tubule transport.     

Effect of beta-D-xyloside on the renal glomerular cells. II. Morphological studies

The effect of p-nitrophenyl-beta-D-xylopyranoside on the renal glomerulus was studied. Rat kidneys were labeled with [35S]sulfate in the presence or absence of beta-xyloside by using an isolated organ perfusion system and were processed subsequently for morphological studies. By using electron microscopy, preferential intracytoplasmic vesiculation of the visceral epithelium was observed in the beta-xyloside-treated kidneys. The vesicles were distributed throughout the cytoplasm, particularly in the vicinity of Golgi apparatus. They were acid-phosphatase negative, devoid of clathrin-coat, and contained osmium-impregnated reaction products. The visceral epithelial foot processes remained firmly attached to the glomerular basement membrane. No loss of cell-surface associated sialoglycoproteins, as evidenced by colloidal iron staining, was observed. No significant change in the morphological features of glomerular endothelial or mesangial cells was noted. By using electron microscopy autoradiography, a significant increase in the number of silver grains over the epithelium, and a decrease in the number over the extracellular matrices was observed. The majority of the grains were either associated with intracytoplasmic vesicles or Golgi apparatus. The mean grain densities (concentration of radiation) increased by 3.6-fold for the epithelium, and decreased by 2.4- and 1.6-fold for the basement membrane and mesangial matrix, respectively. The grain densities over the endothelial and mesangial cells were similar in control and experimental groups. These data indicate that xyloside induces selective alterations in Golgi apparatus of the visceral epithelium and a dramatic imbalance in the de novo synthesized sulfated macromolecules of cellular and extracellular compartments.     

Migration of simian virus 40 from the vascular system into the glomerular mesangial region

The behavior of simian virus 40 (SV40) injected into the vascular system was investigated in the rat glomerulus. The kidney was perfused via the abdominal aorta with a serum-free culture medium for 5 min, with PBS solution containing SV40 and then with the same medium for 15 min at 37 degrees C. In the glomeruli, SV40 particles were detected in the lumen of the capillaries, fenestrations of endothelial cells and lamina rara interna of the glomerular basement membrane. They were also found in the mesangial matrix and mesangial cells. Invaginations of their membrane were observed on several surface areas where SV40 particles were localized close to the surface. Similarly, when the particles were injected into the tail vein, they were detected in the lamina rara interna, the mesangial matrix, and in vacuoles of mesangial cells at 2 h after the injection. These results indicate that SV40 particles migrate from the vascular system into the mesangial matrix, and are then endocytosed in vivo by mesangial cells.     

A stereological study of the renal glomerular vasculature in the db/db mouse model of diabetic nephropathy

In diabetic nephropathy, glomerular hypertrophy is evident early in response to hyperglycaemia. Alterations of capillary length and vascular remodelling that may contribute to glomerular hypertrophy and the subsequent development of glomerulosclerosis remain unclear. The present study used the db/db mouse model of Type 2 diabetes to examine the glomerular microvascular changes apparent with long-term diabetic complications. Unbiased stereological methods and high-resolution light microscopy were used to estimate glomerular volume, and glomerular capillary dimensions including length and surface area in 7-month-old db/db diabetic mice and age-matched db/m control mice. The db/db diabetic mice showed significant glomerular hypertrophy, corresponding with elevated blood glucose levels, and increased body weight and kidney weight, compared with db/m control mice. Glomerular enlargement in db/db mice was associated with increases in the surface area (5.387 +/- 0.466 x 10(4) microm2 vs. 2.610 +/- 0.287 x 10(4) microm2; P < 0.0005) and length (0.3343 +/- 0.022 x 10(4) microm vs. 0.1549 +/- 0.017 x 10(4) microm; P < 0.0001) of capillaries per glomerulus, compared with non-diabetic mice. Stereological assessment at the electron microscopic level revealed increased glomerular volume density of mesangial cells and mesangial matrix, and thickening of the glomerular basement membrane in db/db mice. These results demonstrate that glomerular hypertrophy evident in advanced diabetic nephropathy in this model is associated with increased length and surface area of glomerular capillaries. The contribution of angiogenesis and vasculogenesis to the glomerular microvascular alterations in response to hyperglycaemia remain to be determined.     

Rapid development of renal lesions in diabetic DBA mice infected with the D-variant of encephalomyocarditis virus (EMC-D).

Marked hyperglycaemia and renal lesions developed rapidly in DBA mice infected with 10 plaque-forming units of the D-variant of encephalomyocarditis virus (EMC-D). Renal alterations were demonstrated in the glomeruli, tubular epithelium and small vessels 2 months after infection. Glomerular changes were characterized by mesangial thickening due to an increase of basement membrane-like material in the mesangial matrix. Nodular glomerular lesions were commonly observed 3 months after infection, whereas distinct thickening of the glomerular basement membrane was rarely seen. Besides these glomerular changes, glycogen inclusions in the distal tubular epithelium and medial degeneration in the arterioles were also noticed. The EMC-D-infected DBA mouse appears to be a useful experimental model for the study of human diabetic nephropathy.     

Rapid development of renal lesions in diabetic DBA mice infected with the D-variant of encephalomyocarditis virus (EMC-D)

Marked hyperglycaemia and renal lesions developed rapidly in DBA mice infected with 10 plaque-forming units of the D-variant of encephalomyocarditis virus (EMC-D). Renal alterations were demonstrated in the glomeruli, tubular epithelium and small vessels 2 months after infection. Glomerular changes were characterized by mesangial thickening due to an increase of basement membrane-like material in the mesangial matrix. Nodular glomerular lesions were commonly observed 3 months after infection, whereas distinct thickening of the glomerular basement membrane was rarely seen. Besides these glomerular changes, glycogen inclusions in the distal tubular epithelium and medial degeneration in the arterioles were also noticed. The EMC-D-infected DBA mouse appears to be a useful experimental model for the study of human diabetic nephropathy.     

Qualitative alterations in laminin expression in experimental lupus nephritis.

Previous studies have revealed quantitative alterations in laminin-1 expression at the mRNA and protein levels during the development of glomerulonephritis and glomerulosclerosis in chronic graft-versus-host disease in mice, a model for lupus nephritis. We have now studied the qualitative alterations in laminin expression with two monoclonal antibodies that recognize epitopes on either the E8 or the P1 fragment of laminin-1. Both of these fragments are involved in cell-matrix and matrix-matrix interactions. In normal glomeruli these laminin epitopes are present only in the mesangial matrix; during embryogenesis, however, they are also present in the glomerular basement membrane. The distribution of laminin epitopes was first studied by using immunofluorescence in kidneys of mice with graft-versus-host disease at different points in time after disease induction. Reflection contrast and immunoelectron microscopy were performed after in vivo injection of the horseradish peroxidase-coupled monoclonal antibodies. In glomeruli of mice 8 weeks after disease induction, both injected antibodies bound specifically in electron-dense immune deposits in the mesangium and subepithelially along the glomerular basement membrane as well as in the expanded mesangial matrix. At 11 and 12 weeks after disease induction, when focal and segmental glomerulosclerosis had developed, the antibodies additionally bound in the matrix subendothelially along the glomerular basement membrane and at the periphery of end-stage sclerotic lesions. To study changes in the distribution of laminin epitopes over time, mice were injected with either monoclonal antibody before induction of graft-versus-host disease. The antibodies were detected 8 and 12 weeks later in the mesangial matrix of mice with lupus nephritis. Once segmental glomerulosclerosis had developed, the antibodies were additionally detected within the thickened glomerular capillary wall. The specific binding of anti-laminin monoclonal antibodies in electron-dense immune deposits further substantiates the hypothesis that anti-laminin autoantibodies participate in glomerular immune complex formation in this model, as suggested by earlier studies. Furthermore, our results show that the distribution of glomerular laminin epitopes in the matrix is altered during the development of glomerular disease. These changes in the structure of the glomerular basement membrane may contribute to the abnormal cell-matrix and matrix-matrix interactions during the development of glomerular disease in this model for lupus nephritis.