Altered renal morphology in transgenic mice with cholecystokinin overexpression

Although cholecystokinin is a regulatory peptide with a predominant role in the brain and the gastrointestinal tract, there is an increasing evidence for its role in the kidney. The aim of this study was to reveal morphological changes in the structure of kidney of mice with cholecystokinin overexpression by means of light, transmission and scanning electron microscope, and atomic force microscopy. Using immunohistochemistry the expression of important basement membrane proteins collagen IV, laminin and fibronectin, as well the distribution of cholecystokinin-8 in the renal structures was evaluated. The altered morphology of kidneys of mice with cholecystokinin overexpression was seen by all microscopic techniques used. The renal corpuscles were relatively small with narrow capsular lumen. The basement membranes of renal tubules were thickened and the epithelial cells were damaged, which was more pronounced for distal tubules. Characteristic feature was the increased number of vesicles seen throughout the epithelial cells of proximal and especially in distal tubules reflecting to the enhanced cellular degeneration. The relative expression of laminin but not collagen IV in the glomerular basement membrane was higher than in the tubular basement membranes. The content of fibronectin, in opposite, was higher in tubular membranes. Cholecystokinin-8 was clearly expressed in the glomeruli, in Bowman’s capsule, in proximal and distal tubules, and in collecting ducts. Ultrastructural studies showed irregularly thickened glomerular basement membranes to which elongated cytopodia of differently shaped podocytes were attached. As foot processes were often fused the number of filtration pores was decreased. In conclusion, cholecystokinin plays important role in renal structural formation and in functioning as different aspects of urine production in mice with cholecystokinin overexpression are affected-the uneven glomerular basement membrane thickening, structural changes in podocytes and in filtration slits affect glomerular filtration, while damaged tubular epithelial cells and changed composition of thickened tubular basement membranes affect reabsorption.     

In vitro growth and differentiation of human kidney tubular cells on a basement membrane substrate

Summary Kidney cortical tubular cells, mainly proximal tubular cells, isolated from human kidney and grown either on a basement membrane substrate in chemically defined medium or on plastic in serum-supplemented medium, had substantial proliferative potential and could be propagated for more than 10 generations or 8 passages before senescence. Basement membrane produced on a plastic substrate by the HR-9 endodermal cell line could replace serum supplementation in promoting tubular cell growth. Tubular cells grown on an HR-9 basement membrane substrate exhibited stable epithelial morphology over an extended period of time; in the presence of 5% serum they differentiated into organized structures such as hemicysts and cell cords. Cells grown on plastic failed to differentiate and gradually degenerated. Tubular cells on HR-9 basement membrane were characterized by densely packed microvilli, abundant rough endoplasmic reticulum and free polysomes, basal cell membrane interdigitations, a well-developed endocytotic apparatus, and conspicuous junctional complexes—all features of the proximal tubular cell. Compared with cells on plastic substrate, there were higher levels of the brush border enzymes γ-glutamyl transpeptidase,l-leucine aminopeptidase, and alkaline phosphatase in cells maintained on an HR-9 basement membrane substrate, further supporting the conclusion that a basement membrane substrate promoted differentiation of tubular cells. These data and morphological observations indicate that a basement membrane substrate can promote growth and both functional and morphologic differentiation of human kidney tubular cells. This work was supported by the Veterans Administration.     

Light and Electron Microscopical Studies of the Renal Lesion in Dogs With Pyometra

Kidney biopsies from 23 bitches with pyometra and an entire kidney from four pyometra bitches were examined by light microscopy. Kidney tissue was also taken from three bitches at different intervals after ovariohysterectomy for pyometra. All the pyometra bitches had membranous glomerulonephritis or mixed proliferative and membranous glomerulonephritis. Two of the bitches had intraglomerular hyaline nodules resembling those seen in conjunction with diabetes in human beings. The degree of glomerular damage could be correlated with the reduction in glomerular filtration rate determined by function tests. The proximal tubules generally contained numerous hyaline droplets but the degree of this change could not be correlated to the degree of glomerular damage. A yellow pigment, a lipofuscin, was regularly present in the proximal tubules as well as epithelial proliferation and mitoses. Focal atrophy of tubules also occurred, presumably because of obliteration of glomeruli. The cortical interstitium contained collections of mature and immature plasma cells, often surrounding the glomeruli. When the kidneys from three bitches were examined after ovariohysterectomy for pyometra, the glomerular damage in two had regressed to leave only slight thickening of the capillary walls. In the third bitch, examined only 14 days after ovariohysterectomy, healing was partial. Kidney tissue from five bitches was also examined by electron microscopy. The glomerular endothelial cells were swollen and the basement membrane was grealy thickened. With more severe degrees of glomerular damage, an electron-dense material was deposited along the inner surface of the basement membrane and the swollen mesangial cells contained numerous inclusions. There was focal fusion of the foot processes of the glomerular epithelial cells; in one bitch with heavy proteinuria, the fusion was widespread. The proximal tubules contained numerous protein absorption droplets representing resorbed protein. The tubular basement membrane at all levels was thickened. Because of similarities with some other types of renal damage (nephrotoxic nephritis in dogs and acute proliferative glomerulonephritis in human beings), the possibility is broached that the renal lesion in pyometra is the result of an immunobiological process.     

Abnormal extracellular matrix and excessive growth of human adult polycystic kidney disease epithelia.

Human autosomal dominant polycystic kidney disease (ADPKD) epithelia were grown in primary monolayer cultures and their properties compared with intact kidney epithelial cultures derived from individually microdissected normal human kidney proximal convoluted tubules (PCT), proximal straight tubules (PST), and cortical collecting tubules (CCT). In vivo, ADPKD cyst epithelia exhibited a thickened basement membrane, and immunofluorescence demonstrated the presence of laminin, fibronectin, type IV collagen, and heparan sulfate proteoglycan in basement membranes and type I collagen in the interstitium. ADPKD epithelia grown in culture synthesized and secreted basally a unique, extracellular matrix that took the form of proteinaceous spheroids when the cells were grown on dried, type I collagen. Incorporation of H2[S35O4] into basement membrane extracts was increased more than ten-fold in ADPKD epithelia by comparison to normal PST and CCT. In addition to incorporation into the normal tubular basement membrane 220 kD band, radioactivity was also seen at 175 kD and 150 kD in ADPKD extracts. Growth in culture of cyst-lining ADPKD epithelia was more rapid than normal tubules, and was abnormal since there was no absolute requirement for added extracellular matrix. However, when ADPKD epithelia were grown on different, exogenous matrix protein components, a profound influence on both structure and epithelial cell proliferation was seen. Growth on a complete basement membrane three-dimensional gel derived from the Engelbreth-Holm-Swarm (EHS) sarcoma led to a reduction in the numbers of spheroids and increase in amorphous filaments. Incorporation of [3H]-thymidine into ADPKD epithelia was greater than into normal PCT, PST, and CCT and was also greatly modified by the type of extracellular matrix components provided. In studies using single matrix components, the strongest proliferative response was seen when ADPKD epithelia were plated on type I collagen greater than type IV collagen greater than fibronectin greater than laminin. These findings suggest that the excessive growth of cyst-lining epithelia may be, at least in part, a result of abnormal basement membrane and extracellular matrix production by ADPKD cells.     

Passive Heymann nephritis induced by rabbit antiserum to membrane antigens isolated from rat visceral yolk-sac microvilli

Passive Heymann nephritis (PHN) is an animal model of immune-complex-induced renal disease resembling human membranous glomerulonephritis. It was induced in rats by injecting rabbit antiserum directed against glycoprotein antigens isolated from rat embryonic visceral yolk-sac microvilli (VYS-MV). The glycoprotein antigens were isolated by extracting the VYS-MV with detergent Nonidet P-40 followed by gel filtration in Sephacryl S-300 and finally by lectin affinity chromatography with Ricinus communis agglutinin I. In vitro immunofluorescent localization studies demonstrated that the nephritogenic antibodies were localized along the apical region of the visceral yolk-sac endodermal cells and the brush border of the proximal tubular cells of the kidney. Rats injected with a single dose of the antiserum manifested proteinuria. Indirect immunofluorescent studies showed that the injected rabbit IgG was localized in vivo along the capillary walls of the glomerulus in a granular fashion. Electron microscopic examination of the same kidney glomeruli revealed numerous electron-dense deposits along the lamina rara externa of the glomerular basement membrane. Fusion of the epithelial foot processes was also present. These findings represent the typical immunopathological characteristics of Heymann nephritis. Furthermore, with the aid of Ouchterlony analysis, the antiserum against the isolated VYS antigens exhibited an immunoprecipitin band which was in common with that formed by the antiserum against the homogeneous nephritogenic antigen (gp330) of renal brush border origin. Thus, the nephritogenic antigens which have been found to be associated with the brush border of the renal proximal tubules may also be present or cross-reacted in the microvilli of the rat embryonic visceral yolk-sac.     

Ultrastructural localization of lectin-binding sites in different basement membranes

Summary In the present work we localized binding sites for the lectins WGA, RCA I, con A and SBA at the ultrastructural levels in morphologically different basement membranes. These different basement membranes included (a) thin ones, for example, tubular basement membrane of the mouse kidney which separates epithelial cell layers from mesenchymal cells and glomerular basement membrane which separates epithelial cells from other epithelial cells, (b) thick multilayered ones, for example, Reichert's membrane which is built up during the embryonic development of rodents and as an example of a pathologically thickened basement membrane, the basement membrane of the Engelbreth-Holm-Swarm (EHS) sarcoma. We were able to show that, in contrast to the thick multilayered basement membranes, the thin ones showed a strong positive SBA-binding pattern. Thick basement membranes otherwise revealed very strong labelling with the lectins WGA and RCA I. Our findings lead us to conclude that thin and thick basement membranes differ markedly in the quality and quantity of the carbohydrates which they contain.     

The anionic barrier system in the mesonephric renal glomerulus of the arctic lamprey,Entosphenus japonicus (Martens) (Cyclostomata)

Summary To examine the selective permeability of the nephrons of lower vertebrates, the permeability of the glomerulus in the kidney of an arctic lamprey, Entosphenus japonicus (Martens), to native anionic ferritin or cationized ferritin was studied by observing the distribution of ionized anionic groups in renal tissues. The cationized ferritin molecules injected into the dorsal aorta penetrated rapidly into the glomerular basement membrane layer through fenestrae present in the capillary endothelium and were subsequently excreted into the urinary spaces via the interstices between foot processes of the visceral epithelial cells. Native anionic ferritin, on the other hand, passed only minimally through the capillary wall. Cytochemical staining of fixed tissue or perfusion of the kidney in situ with cationic cacodylate-iron colloid revealed that the ionized anionic groups of acid mucopolysaccharides were distributed on both the luminal and abluminal surfaces of endothelial cells, and in the thick fibrous lamina rara interna of the glomerular basement membrane; they were especially dense on the surfaces of visceral epithelial cells and their foot processes. These results suggest that the mesonephric glomerulus of the arctic lamprey possesses a functionally well developed anionic barrier system comparable to that of the mammalian metanephric glomerulus.     

Mesangioproliferative Glomerulonephritis in Mink with Encephalitozoonosis

Renal specimens from 6 mink with encephalitozoonosis were studied by light and electron microscopy and immunohistochemistry. The glomeruli of affected kidneys had a mesangioproliferative glomerulonephritis which was characterized by an increase in mesangial cells and matrix in most glomeruli. Some glomeruli were partially or completely sclerosed. There were protein or granular casts in the cortical and medullary tubules. Interstitial nephritis, vasculitis and tubular cysts were found. Electron microscopy demonstrated extensive matrix and increased cellularity in the mesangial areas. Glomeruli showed segmentally thickened or wrinkled capillary basement membranes. Electron dense deposits were found in the glomerular basement membranes and mesangium. Peroxidase-anti-peroxidase immunohistochemistry demonstrated that IgG and IgM positive material was present as granular deposits in the glomerular basement membrane and occasionally in the mesangium.     

The fine structure of the mesonephros of the lamprey,Entosphenus japonicus Martens

Summary The fine structure of the mesonephric kidney of the lamprey, Entosphenus japonicus Martens, has been investigated with the electron microscope and discussed from the viewpoint of comparative morphology of the mesonephros.The structure of the capillary wall of the glomerulus essentially coincides with that of higher vertebrates, though its basement membrane is remarkably thick (300–400 m) because of a dense accumulation of fibrillar material between the endothelium and the basal lamina of epithelial cell. No obvious fenestration of the endothelial cell has been observed in the glomerulus or capillaries in any part of this organ.The kidney tubule is divided into three segments: 1. neck segment composed of ciliated cells with numerous mitochondria and glycogen particles, 2. proximal tubule composed of brush bordered cells provided with extensive pinocytotic vesicles and lysosomal granules in the apical cytoplasm and with lamellar membranes in the basal, and 3. distal tubule characterized by cells which, with their abundant mitochondria and branched tubular endoplasmic reticulum (about 500 Å diameter) with a central core, closely resemble the chloride cells in the gill filament of some teleosts. The possibility that the lamellar membranes in the proximal tubule cells correspond to basal infoldings is discussed.The extensive development of the tubular reticulum and of the mitochondria in the distal tubule cells is believed to reflect the active absorption of urine chloride in the urinary tubule of lamprey mesonephric kidney evidenced by physiologists. The proximal tubule is suggested to take a part also in the urinary transport of water and ions, as the lamellar membranes found in the cells of this portion likely correspond to the basal infoldings in more advanced forms of the kidney.The epithelial cells of the ureteric duct are characterized by granules suggesting a mucous secretion. No fine structure implying an absorptive activity in this duct has been observed.     

Transmembrane collagen XVII is a novel component of the glomerular filtration barrier

The kidney filtration barrier consists of the capillary endothelium, the glomerular basement membrane and the slit diaphragm localized between foot processes of neighbouring podocytes. We report that collagen XVII, a transmembrane molecule known to be required for epithelial adhesion, is expressed in podocytes of normal human and mouse kidneys and in endothelial cells of the glomerular filtration barrier. Immunoelectron microscopy has revealed that collagen XVII is localized in foot processes of podocytes and in the glomerular basement membrane. Its role in kidney has been analysed in knockout mice, which survive to birth but have high neonatal mortality and skin blistering and structural abnormalities in their glomeruli. Morphometric analysis has shown increases in glomerular volume fraction and surface densities of knockout kidneys, indicating an increased glomerular amount in the cortex. Collagen XVII deficiency causes effacement of podocyte foot processes; however, major slit diaphragm disruptions have not been detected. The glomerular basement membrane is split in areas in which glomerular and endothelial basement membranes meet. Differences in the expression of collagen IV, integrins α3 or β1, laminin α5 and nephrin have not been observed in mutant mice compared with controls. We propose that collagen XVII has a function in the attachment of podocyte foot processes to the glomerular basement membrane. It probably contributes to podocyte maturation and might have a role in glomerular filtration.     

Chemical characterization of glomerular and tubular basement membranes of cattle of different ages

Glomerular and tubular basement membranes were isolated from fetal, neonatal, young and adult bovine kidneys.An isolation method with sieves for both glomeruli and tubules from the same kidney was developed. A detergent procedure appeared to give purer glomerular and tubular basement membrane preparations than the generally used sonication method. No large differences were found in the composition of glomerular and tubular basement membrane of adult animals.Glomerular and tubular basement membrane preparations of the four age groups showed an increase with age of hydroxylysine and both 3- and 4-hydroxyproline. The most marked increases appeared at different stages of development, that of tubular basement membrane being between fetal and neonatal stages and glomerular basement membrane between 18 weeks old and adult animals. The ratio of 3- to 4-hydroxyproline increased considerably during development. Total imino acid content was higher for both types of basement membrane from adult than from young animals, while total content of hydroxylysine plus lysine remained fairly constant.The increase in hydroxylation of lysine was accompanied by a corresponding change in glucose and galactose content so that the ratio of galactose to hydroxylysine or glucose to galactose remained constant. Fucose content of both types of basement membranes was the same for all age groups but content of aminosugars and mannose gradually increased with age.     

Mixed Organic Solvents Induce Renal Injury in Rats

To investigate the injury effects of organic solvents on kidney, an animal model of Sprague-Dawley (SD) rats treated with mixed organic solvents via inhalation was generated and characterized. The mixed organic solvents consisted of gasoline, dimethylbenzene and formaldehyde (GDF) in the ratio of 2∶2:1, and were used at 12,000 PPM to treat the rats twice a day, each for 3 hours. Proteinuria appeared in the rats after exposure for 5–6 weeks. The incidences of proteinuria in male and female rats after exposure for 12 weeks were 43.8% (7/16) and 25% (4/16), respectively. Urinary N-Acetyl-β-(D)-Glucosaminidase (NAG) activity was increased significantly after exposure for 4 weeks. Histological examination revealed remarkable injuries in the proximal renal tubules, including tubular epithelial cell detachment, cloud swelling and vacuole formation in the proximal tubular cells, as well as proliferation of parietal epithelium and tubular reflux in glomeruli. Ultrastructural examination found that brush border and cytoplasm of tubular epithelial cell were dropped, that tubular epithelial cells were partially disintegrated, and that the mitochondria of tubular epithelial cells were degenerated and lost. In addition to tubular lesions, glomerular damages were also observed, including segmental foot process fusion and loss of foot process covering on glomerular basement membrane (GBM). Immunofluorescence staining indicated that the expression of nephrin and podocin were both decreased after exposure of GDF. In contrast, increased expression of desmin, a marker of podocyte injury, was found in some areas of a glomerulus. TUNEL staining showed that GDF induced apoptosis in tubular cells and glomerular cells. These studies demonstrate that GDF can induce both severe proximal tubular damage and podocyte injury in rats, and the tubular lesions appear earlier than that of glomeruli.     

Extralysosomal localisation of acid phosphatase in the rat kidney

 There is strong evidence that acid phosphatase (AcPase) plays an important role in the catabolism of the glomerular basement membrane (GBM) and the removal of macromolecular debris resulting from ultrafiltration. Recent enzyme histochemical investigations provide new evidence of the antithrombotic and anti-inflammatory function of ADPase and on the distribution of AcPase in mouse kidney tubule cells. By means of 3 mM cerium as the trapping agent and 1 mM p-nitrophenyl phosphate as the substrate, extralysosomal AcPase could be demonstrated at the ultrastructural level. Following a mild perfusion fixation (2% formaldehyde + 0.07% glutaraldehyde), an effective postfixation and short enzyme incubations (20 min) with microwave irradiation, highly specific enzyme histochemical reaction product and reasonable structural preservation were obtained. Extralysosomal, membrane-bound AcPase was observed along the endoplasmic reticulum, the trans-Golgi cisternae, the nuclear envelope, basal infoldings of the proximal and distal tubular cells and on glomerular profiles, e.g. cell membranes of podocytes, endothelium and basement membrane. Large amounts of extralysosomal AcPase were observed in the basement membrane of glomeruli, in contrast to no AcPase activity in the tubular and mesangial basement membrane. The observed difference in AcPase activity in the tubular epithelial basement membrane and the GBM supports the idea that AcPase in GBM specifically serves in the clearance of macromolecular debris to facilitate ultrafiltration. In the GBM a laminar distribution is observed, suggesting that both epithelial and endothelial cells are involved in the production of AcPase. Accepted: 16 September 1997     

The ultrastructural localization of two basement membrane components: entactin and laminin in rat tissues

The localization of two noncollagenous components of basement membranes, laminin and entactin, was determined in rat kidney, muscle, and small intestine using electron immunohistochemistry. In the renal glomerulus anti-laminin antibodies reacted with the basement membrane of peripheral capillary loops and with mesangial matrix. In the peripheral capillary loop laminin was preferentially distributed in both laminae rarae. This was in contrast to anti-entactin that localized in peripheral capillary loops but not in mesangial matrix. Even in the peripheral capillary loops it had a different distribution than laminin. Entactin was found predominantly in the lamina rara interna. In renal tubular basement membranes both antibodies localized throughout the full thickness of the basement membranes, with laminin having a preferential distribution in the lamina rara, whereas entactin was more evenly distributed. In the basement membrane of the duodenal mucosa entactin localized in the lamina densa, whereas laminin was present in both laminae. In skeletal muscle both antibodies had similar localization in all basement membranes. These results demonstrate that entactin is an intrinsic component of basement membranes. They also demonstrate that basement membranes from different tissues have subtle variations in content and/or assembly of the different components. It is likely that these variations may be reflected in different functional properties.     

Ultrastructure of the kidney of a South American caecilian,Typhlonectes compressicaudus (Amphibia,Gymnophiona)

The ultrastructure of the renal corpuscle, the neck segment, the proximal tubule and the intermediate segment of the kidney of a South American caecilian, Typhlonectes compressicaudus (Amphibia, Gymnophiona) was examined by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and freeze-fracture technique. The glomerular filter apparatus consists of the podocyte epithelium, a distinct basement membrane, a subendothelial space and the capillary endothelium. Emanating from the podocyte cell body, several long primary processes encircle neighboring capillaries. The short slender foot processes originating from the primary processes interdigitate with those from other primary processes, thereby forming the meandering filtration slit. Thick bundles of microfilaments are found in the primary processes, but absent in the foot processes. The basement membrane consists of a lamina rara externa and a rather thin lamina densa (50 nm thickness). The wide subendothelial space contains abundant microfibrils, a few collagen fibrils and many thin processes of mesangial cells. The endothelium is flat and fenestrated (compared to mammals displaying relatively few fenestrations); some of the fenestrations are bridged by a diaphragm. The glomerular mesangium is made up of the mesangial cells and a prominent mesangial matrix containing microfibrils and collagen fibrils. The cells of the neck and intermediate segments display numerous cilia with their microtubules arranged in the typical 9 + 2 pattern. The basal bodies of the cilia are attached to thick filaments with a clear crossbanding pattern of 65 nm periodicity. The proximal tubule is composed of cells typical for this segment (PT cells) and light cells lacking a brush border (bald-headed cells). The PT cells measure 10-25 micron in height and 15-30 micron in width and do not interdigitate at their lateral borders with each other. Their basolateral cell membrane is amplified by many folds projecting into lateral intercellular spaces and into basal recesses. The brush border is scarce and composed of loosely arranged short microvilli.     

Ultrastructural colocalization of nidogen-1 and nidogen-2 with laminin-1 in murine kidney basement membranes

Nidogen-1, a key component of basement membranes, is considered to function as a link between laminin and collagen type IV networks. Recently a new member of the nidogen family, nidogen-2, has been characterized. Preliminary immunohistochemical data indicated that nidogen-1 and nidogen-2 show a similar tissue distribution at the light microscopic level. We have now localized nidogen-1 and nidogen-2, as well as their corresponding mRNAs, at the light and electron microscopic levels in adult mouse kidney, by in situ hybridization and immunogold histochemistry, as well as carrying out double labeling with laminin-1. Both nidogen-1 and nidogen-2 mRNAs are found not only in mesenchymal cells of embryonic tissues, but also in all epithelial and endothelial cells in adult mouse kidney. Both nidogens are ubiquitous basement membrane components in the mouse kidney, being found in glomerular, tubular, and capillary compartments and Bowman’s capsule. Furthermore, a substantial fraction of nidogen-1 and nidogen-2 colocalizes with laminin-1. The results indicate that nidogen-1 and nidogen-2 could well substitute for one another in some of their biological activities in kidney, for example, stabilizing basement membrane networks in vivo. Accepted: 8 December 1999     

Osteoprotegerin in Exosome-Like Vesicles from Human Cultured Tubular Cells and Urine

Urinary exosomes have been proposed as potential diagnostic tools. TNF superfamily cytokines and receptors may be present in exosomes and are expressed by proximal tubular cells. We have now studied the expression of selected TNF superfamily proteins in exosome-like vesicles from cultured human proximal tubular cells and human urine and have identified additional proteins in these vesicles by LC-MS/MS proteomics. Human proximal tubular cells constitutively released exosome-like vesicles that did not contain the TNF superfamily cytokines TRAIL or TWEAK. However, exosome-like vesicles contained osteoprotegerin (OPG), a TNF receptor superfamily protein, as assessed by Western blot, ELISA or selected reaction monitoring by nLC-(QQQ)MS/MS. Twenty-one additional proteins were identified in tubular cell exosome-like vesicles, including one (vitamin D binding protein) that had not been previously reported in exosome-like vesicles. Twelve were extracellular matrix proteins, including the basement membrane proteins type IV collagen, nidogen-1, agrin and fibulin-1. Urine from chronic kidney disease patients contained a higher amount of exosomal protein and exosomal OPG than urine from healthy volunteers. Specifically OPG was increased in autosomal dominant polycystic kidney disease urinary exosome-like vesicles and expressed by cystic epithelium in vivo. In conclusion, OPG is present in exosome-like vesicles secreted by proximal tubular epithelial cells and isolated from Chronic Kidney Disease urine.     

The absence of one or both nidogens does not alter basement membrane composition in adult murine kidney

Nidogen-1 and nidogen-2 are major components of all basement membranes and are considered to function as link molecules between laminin and collagen type IV networks. Surprisingly, the knockout of one or both nidogens does not cause defects in all tissues or in all basement membranes. In this study, we have elucidated the appearance of the major basement membrane components in adult murine kidney lacking nidogen-1, nidogen-2, or both nidogens. To this end, we localized laminin-111, perlecan, and collagen type IV in knockout mice, heterozygous (+/-) or homozygous (-/-) for the nidogen-1 gene, the nidogen-2 gene, or both nidogen genes with the help of light microscopic immunostaining. We also performed immunogold histochemistry to determine the occurrence of these molecules in the murine kidney at the ultrastructural level. The renal basement membranes of single knockout mice contained a similar distribution of laminin-111, perlecan, and collagen type IV compared to heterozygous mice. In nidogen double-knockout animals, the basement membrane underlying the tubular epithelium was sometimes altered, giving a diffuse and thickened pattern, or was totally absent. The normal or thickened basement membrane of double-knockout mice also showed a similar distribution of laminin-111, perlecan, and collagen type IV. The results indicate that the lack of nidogen-1, nidogen-2, or both nidogens, plays no crucial role in the occurrence and localization of laminin-111, collagen type IV, and perlecan in murine tubular renal basement membranes.     

Über den granulofilamentären Umbau von Sekretgranula im schleimbildenden Epithel der Endocervix der Frau

Summary Glio-vascular relationships were studied in the developing rat cervical spinal cord with electron microscopy. Capillaries were first evident on the eleventh prenatal day and were surrounded by undifferentiated cells and neuroblasts separated from the capillary wall by a perivascular space. This space persisted until day thirteen, when basement membranes began to appear. Small cellular processes containing glycogen were visible adjacent to the capillary basement membrane beginning at day fifteen and became more prominent as development proceeded. The origin of these cellular processes was not apparent, but they were most likely collaterals of epithelial elements. In prenatal animals neuroblasts or neurons were in direct contact with the capillary basement membrane. Cells resembling adult astrocytes were first observed during the nineteenth day. Astrocytic processes completely invested the capillaries, separating them from neurons in the spinal cord of all postnatal animals.The author wishes to acknowledge the helpful guidance of Dr. Edith A. Maynard during the course of this study.     

De Novo Expression of Sodium-Glucose Cotransporter SGLT2 in Bowman’s Capsule Coincides with Replacement of Parietal Epithelial Cell Layer with Proximal Tubule-like Epithelium

In kidney nephron, parietal epithelial cells line the Bowman’s capsule and function as a permeability barrier for the glomerular filtrate. Bowman’s capsule cells with proximal tubule epithelial morphology have been found. However, the effects of tubular metaplasia in Bowman’s capsule on kidney function remain poorly understood. Sodium-glucose cotransporter 2 (SGLT2) plays a major role in reabsorption of glucose in the kidney and is expressed on brush border membrane (BBM) of epithelial cells in the early segment of the proximal tubule. We hypothesized that SGLT2 is expressed in tubularized Bowman’s capsule and used our novel antibody to test this hypothesis. Immunohistochemical analysis was performed with our SGLT2 antibody on C57BL/6 mouse kidney prone to have tubularized Bowman’s capsules. Cell membrane was examined with periodic acid-Schiff (PAS) stain. The results showed that SGLT2 was localized on BBM of the proximal tubules in young and adult mice. Bowman’s capsules were lined mostly with normal brush border-less parietal epithelial cells in young mice, while they were almost completely covered with proximal tubule-like cells in adult mice. Regardless of age, SGLT2 was expressed on BBM of the tubularized Bowman’s capsule but did not co-localize with nephrin in the glomerulus. SGLT2-expressing tubular cells expanded from the urinary pole toward the vascular pole of the Bowman’s capsule. This study identified the localization of SGLT2 in the Bowman’s capsule. Bowman’s capsules with tubular metaplasia may acquire roles in reabsorption of filtered glucose and sodium.