Up-regulation of protease-activated receptor-1 in diabetic glomerulosclerosis

Patients with diabetes are under a hypercoagulable state leading to generation of thrombin. It is not known whether thrombin plays a role in the progression of diabetic nephropathy. We analyzed gene expression of two thrombin receptors, protease-activated receptor-1 (PAR-1) and PAR-4 in the kidney of diabetic db/db mice. Mice developed hyperglycemia from 7 to 10 weeks of age and showed renal abnormalities such as mesangial expansion and urinary albumin excretion at 10 weeks of age. PAR-1 mRNA was up-regulated in isolated glomeruli in db/db mice compared with age-matched db/m littermates, but PAR-4 mRNA was not. In situ hybridization studies showed that PAR-1 mRNA was detected mainly at the glomerulus, and that intensive signals were observed in mesangial cells and podocytes. The up-regulation of PAR-1 in glomeruli in diabetic mice may play a role in the progression of glomerulosclerosis and abnormal urinary albumin excretion in diabetic nephropathy.

Retinoic acid enhances nephron endowment in rats exposed to maternal protein restriction

A reduced nephron complement at birth renders the kidney susceptible to renal disease in adulthood. Retinoic acid (RA; the active metabolite of vitamin A) is linked to nephrogenesis in vitro and in vivo. The aim of this study was to determine the effect of administration of retinoic acid in midgestation in rats on nephron endowment in offspring exposed to maternal protein restriction. Rats were fed either a normal-protein diet (NPD) or a low-protein diet (LPD) during pregnancy and lactation. Half of the dams in the LPD group were injected intraperitoneally with retinoic acid (20 mg/kg) during gestation at embryonic day 11.5. At 4 weeks of age, the offspring were anesthetized and perfusion-fixed, and nephron number estimated using unbiased stereological techniques. Body weight and kidney volume was significantly reduced in all LPD offspring. There was a significant 29% reduction in nephron number in the LPD group compared with the NPD offspring, whereas the number of nephrons in kidneys from the LPD + RA offspring was not significantly different compared with controls. In conclusion, administration of a single bolus dose of retinoic acid during midgestation restored nephron endowment to normal in offspring exposed to maternal protein restriction.

Normal Lactational Environment Restores Nephron Endowment and Prevents Hypertension after Placental Restriction in the Rat

Uteroplacental insufficiency in the rat restricts fetal growth, impairs mammary development, compromising postnatal growth; and increases adult BP. The roles of prenatal and postnatal nutritional restraint on later BP and nephron endowment in offspring from mothers that underwent bilateral uterine vessel ligation (restricted) on day 18 of pregnancy were examined. Sham surgery (control) and a group of rats with reduced litter size (reduced; litter size reduced at birth to five, equivalent to restricted group) were used as controls. Offspring (control, reduced, and restricted) were cross-fostered on postnatal day 1 onto a control (normal lactation) or restricted (impaired lactation) mother. BP in male offspring was determined by tail cuff at 8, 12, and 20 wk of age, with glomerular number and volume (Cavalieri/Physical Dissector method) and renal angiotensin II type 1 receptor (AT(1)R) mRNA expression (real-time PCR) determined at 6 mo. Restricted-on-restricted male offspring developed hypertension (+16 mmHg) by 20 wk together with a nephron deficit (-26%) and glomerular hypertrophy (P < 0.05). In contrast, providing a normal lactational environment to restricted offspring improved postnatal growth and prevented the nephron deficit and hypertension. Reduced-on-restricted pups that were born of normal weight but with impaired growth during lactation subsequently grew faster, developed hypertension (+16 mmHg), had increased AT(1A)R and AT(1B)R mRNA expression (P < 0.05), but had no nephron deficit. Our study identifies the prenatal and postnatal nutritional environments in the programming of adult hypertension, associated with distinct renal changes. It is shown for the first time that a prenatally induced nephron deficit can be restored by correcting growth restriction during lactation.

Glomerulotubular junction abnormalities are associated with proteinuria in type 1 diabetes

Glomerulotubular junction abnormalities, frequent in proteinuric patients with type 1 diabetes, may contribute to the progressive GFR loss in overt diabetic nephropathy. Glomerulotubular junction abnormalities were examined in patients who have type 1 diabetes with a wide range of albumin excretion rates (AER). Renal biopsies from five normoalbuminuric patients, five microalbuminuric patients, six proteinuric patients, and five control subjects were studied by light and electron microscopy. Light microscopy specimens were serially sectioned to find and classify glomerulotubular junctions. Glomerular structural parameters were estimated using stereologic methods. Glomerulotubular junction abnormalities were found in 2% of glomeruli from control and normoalbuminuric patients and in 4% of glomeruli from microalbuminuric patients. In contrast, 71% of glomeruli from proteinuric patients had glomerulotubular junction abnormalities, including five (8%) atubular glomeruli. Electron microscopy findings were typical of diabetic nephropathy. Piece-wise linear regression models with glomerular, glomerulotubular junction, and interstitial parameters as independent variables provided greater GFR (92%; P < 0.005) and AER (95%; P < 0.01) prediction than multiple regression models (81% for GFR and 72% for AER). Thus, glomerular adhesions and glomerulotubular junction abnormalities help to explain the progressive GFR loss that is associated with onset of proteinuria in type 1 diabetes. Moreover, nonlinear models provide better fit for structural-functional relationships in patients with type 1 diabetes.

A hypomorphic mutation in the mouse laminin alpha5 gene causes polycystic kidney disease

Extracellular matrix abnormalities have been found in both human and animal models of polycystic kidney disease (PKD). A new mouse PKD model has been produced through insertion of a PGKneo cassette in an intron of the gene that encodes laminin alpha5 (Lama5), a major tubular and glomerular basement membrane component that is important for glomerulogenesis and ureteric bud branching. Lama5neo represents a hypomorphic allele as a result of aberrant splicing. Lama5neo/neo mice exhibit PKD, proteinuria, and death from renal failure by 4 wk of age. This contrasts with mice that totally lack Lama5, which die in utero with multiple developmental defects. At 2 d of age, Lama5neo/neo mice exhibited mild proteinuria and microscopic cystic transformation. By 2 wk, cysts were grossly apparent in cortex and medulla, involving both nephron and collecting duct segments. Tubular basement membranes seemed to form normally, and early cyst basement membranes showed normal ultrastructure but developed marked thickening as cysts enlarged. Overall, Lama5 protein levels were severely reduced as a result of mRNA frameshift caused by exon skipping. This was accompanied by aberrant accumulation of laminin-332 (alpha3beta3gamma2; formerly called laminin-5) in some cysts, as also observed in human PKD. This constitutes the first evidence that a primary defect in an extracellular matrix component can cause PKD.

Reduced nephron number and glomerulomegaly in Australian Aborigines: A group at high risk for renal disease and hypertension

Aborigines in remote areas of Australia have much higher rates of renal disease, as well as hypertension and cardiovascular disease, than non-Aboriginal Australians. We compared kidney findings in Aboriginal and non-Aboriginal people in one remote region. Glomerular number and mean glomerular volume were estimated with the disector/fractionator combination in the right kidney of 19 Aborigines and 24 non-Aboriginal people undergoing forensic autopsy for sudden or unexpected death in the Top End of the Northern Territory. Aborigines had 30% fewer glomeruli than non-Aborigines--202,000 fewer glomeruli per kidney, or an estimated 404,000 fewer per person (P=0.036). Their mean glomerular volume was 27% larger (P=0.016). Glomerular number was significantly correlated with adult height, inferring a relationship with birthweight, which, on average, is much lower in Aboriginal than non-Aboriginal people. Aboriginal people with a history of hypertension had 30% fewer glomeruli than those without--250,000 fewer per kidney (P=0.03), or 500,000 fewer per person, and their mean glomerular volume was about 25% larger. The lower nephron number in Aboriginal people is compatible with their susceptibility to renal failure. The additional nephron deficit associated with hypertension is compatible with other reports. Lower nephron numbers are probably due in part to reduced nephron endowment, which is related to a suboptimal intrauterine environment. Compensatory glomerular hypertrophy in people with fewer nephrons, while minimizing loss of total filtering surface area, might be exacerbating nephron loss. Optimization of fetal growth should ultimately reduce the florid epidemic of renal disease, hypertension, and cardiovascular disease.

Endothelium-specific ablation of PDGFB leads to pericyte loss and glomerular, cardiac and placental abnormalities

Platelet-derived growth factor-B (PDGFB) is necessary for normal cardiovascular development, but the relative importance of different cellular sources of PDGFB has not been established. Using Cre-lox techniques, we show here that genetic ablation of Pdgfb in endothelial cells leads to impaired recruitment of pericytes to blood vessels. The endothelium-restricted Pdgfb knockout mutants also developed organ defects including cardiac, placental and renal abnormalities. These defects were similar to those observed in Pdgfb null mice. However, in marked contrast to the embryonic lethality of Pdgfb null mutants, the endothelium-specific mutants survived into adulthood with persistent pathological changes, including brain microhemorrhages, focal astrogliosis, and kidney glomerulus abnormalities. This spectrum of pathological changes is reminiscent of diabetic microangiopathy, suggesting that the endothelium-restricted Pdgfb knockouts may serve as models for some of the pathogenic events of vascular complications to diabetes.

Uteroplacental insufficiency increases apoptosis and alters p53 gene methylation in the full-term IUGR rat kidney

Uteroplacental insufficiency causes intrauterine growth retardation (IUGR), which is associated with adult onset diseases such as hypertension. Previous studies demonstrate that growth retardation in humans and rats decreases glomeruli number; however, the molecular mechanisms responsible for this reduction are unknown. Apoptosis plays a key role in renal organogenesis. We therefore hypothesized that the in utero deprivation associated with uteroplacental insufficiency decreases glomeruli, increases apoptosis, and alters the mRNA levels of key apoptosis-related proteins in full-term IUGR kidneys. To prove this hypothesis, we induced asymmetric IUGR through bilateral uterine artery ligation of the pregnant rat. We found that uteroplacental insufficiency significantly reduced glomeruli number while increasing TUNEL staining and caspase-3 activity in the IUGR kidney. A significant decrease in Bcl-2 mRNA and a significant increase in Bax and p53 mRNA further characterized the IUGR kidney. Because altered p53 CpG methylation affects p53 expression, we analyzed p53 promoter CpG methylation using methylation-sensitive restriction enzymes and real-time PCR. Uteroplacental insufficiency specifically decreased CpG methylation of the renal p53 BstU I site promoter without affecting the Hha I or the Aci I sites. Uteroplacental insufficiency also induced a relative hypomethylation from exon 5 to exon 8, which was associated with deceased mRNA levels of DNMT1. We conclude that uteroplacental insufficiency alters p53 DNA CpG methylation, affects mRNA levels of key apoptosis-related proteins, increases renal apoptosis, and reduces glomeruli number in the IUGR kidney. We speculate that these changes represent mechanisms that contribute to the fetal origins of adult disease.

Mesangial cells organize the glomerular capillaries by adhering to the G domain of laminin alpha5 in the glomerular basement membrane

In developing glomeruli, laminin alpha5 replaces laminin alpha1 in the glomerular basement membrane (GBM) at the capillary loop stage, a transition required for glomerulogenesis. To investigate domain-specific functions of laminin alpha5 during glomerulogenesis, we produced transgenic mice that express a chimeric laminin composed of laminin alpha5 domains VI through I fused to the human laminin alpha1 globular (G) domain, designated Mr51. Transgene-derived protein accumulated in many basement membranes, including the developing GBM. When bred onto the Lama5 -/- background, Mr51 supported GBM formation, preventing the breakdown that normally occurs in Lama5 -/- glomeruli. In addition, podocytes exhibited their typical arrangement in a single cell layer epithelium adjacent to the GBM, but convolution of glomerular capillaries did not occur. Instead, capillaries were distended and exhibited a ballooned appearance, a phenotype similar to that observed in the total absence of mesangial cells. However, here the phenotype could be attributed to the lack of mesangial cell adhesion to the GBM, suggesting that the G domain of laminin alpha5 is essential for this adhesion. Analysis of an additional chimeric transgene allowed us to narrow the region of the alpha5 G domain essential for mesangial cell adhesion to alpha5LG3-5. Finally, in vitro studies showed that integrin alpha3beta1 and the Lutheran glycoprotein mediate adhesion of mesangial cells to laminin alpha5. Our results elucidate a mechanism whereby mesangial cells organize the glomerular capillaries by adhering to the G domain of laminin alpha5 in the GBM.

Congenital nephropathy and ventriculomegaly: a report of four cases

Congenital nephrotic syndrome with ventriculomegaly and a normal karyotype is a rare association. We report four cases, three of which were conceived consecutively by one couple. All the cases were associated with elevated maternal serum alpha-fetoprotein. Renal histology in one fetus demonstrated colloid filled cysts distributed in the corticomedullary area. Transmission electron microscopy of the glomeruli showed normally developed foot processes and confirmatory genetic studies excluded Finnish congenital nephrotic syndrome. It is probable that congenital nephropathy in conjunction with ventriculomegaly is the result of an autosomal recessive syndrome.

Deregulated expression of the homeobox gene Cux-1 in transgenic mice results in downregulation of p27(kip1) expression during nephrogenesis, glomerular abnormalities, and multiorgan hyperplasia

Cux-1 is a murine homeobox gene that is highly expressed in the developing kidney with expression restricted to the nephrogenic zone. Cux-1 is highly expressed in cyst epithelium of polycystic kidneys from C57BL/6J-cpk/cpk mice, but not in kidneys isolated from age-matched phenotypically normal littermates. To further elucidate the role of Cux-1 in renal development, we generated transgenic mice expressing Cux-1 under the control of the CMV immediate early gene promoter. Mice constitutively expressing Cux-1 developed multiorgan hyperplasia and organomegaly, but not an overall increase in body size. Transgenic kidneys were enlarged 50% by 6 weeks of age, with the increased growth primarily restricted to the cortex. Proliferating cells were found in proximal and distal tubule epithelium throughout the cortex, and the squamous epithelium that normally lines Bowman's capsule was replaced with proximal tubule epithelium. However, the total number of nephrons was not increased. In the developing kidneys of transgenic mice, Cux-1 was ectopically expressed in more highly differentiated tubules and glomeruli, and this was associated with reduced expression of the cyclin kinase inhibitor, p27. Transient transfection experiments revealed that Cux-1 is an inhibitor of p27 promoter activity. These results suggest that Cux-1 regulates cell proliferation during early nephrogenesis by inhibiting expression of p27.

Transcriptional induction of slit diaphragm genes by Lmx1b is required in podocyte differentiation

LMX1B encodes a LIM-homeodomain transcription factor. Mutations in LMX1B cause nail-patella syndrome (NPS), an autosomal dominant disease with skeletal abnormalities, nail hypoplasia, and nephropathy. Expression of glomerular basement membrane (GBM) collagens is reduced in Lmx1b(-/-) mice, suggesting one basis for NPS nephropathy. Here, we show that Lmx1b(-/-) podocytes have reduced numbers of foot processes, are dysplastic, and lack typical slit diaphragms, indicating an arrest in development. Using antibodies to podocyte proteins important for podocyte function, we found that Lmx1b(-/-) podocytes express near-normal levels of nephrin, synaptopodin, ZO-1, alpha3 integrin, and GBM laminins. However, mRNA and protein levels for CD2AP and podocin were greatly reduced, suggesting a cooperative role for these molecules in foot process and slit diaphragm formation. We identified several LMX1B binding sites in the putative regulatory regions of both CD2AP and NPHS2 (podocin) and demonstrated that LMX1B binds to these sequences in vitro and can activate transcription through them in cotransfection assays. Thus, LMX1B regulates the expression of multiple podocyte genes critical for podocyte differentiation and function. Our results indicate that reduced levels of proteins associated with foot processes and the glomerular slit diaphragm likely contribute, along with reduced levels of GBM collagens, to the nephropathy associated with NPS.

Defects in development of the kidney, heart and eye vasculature in mice homozygous for a hypomorphic Notch2 mutation

The Notch gene family encodes large transmembrane receptors that are components of an evolutionarily conserved intercellular signaling mechanism. To assess the in vivo role of the Notch2 gene, we constructed a targeted mutation, Notch2(del1). Unexpectedly, we found that alternative splicing of the Notch2(del1) mutant allele leads to the production of two different in-frame transcripts that delete either one or two EGF repeats of the Notch2 protein, suggesting that this allele is a hypomorphic Notch2 mutation. Mice homozygous for the Notch2(del1) mutation died perinatally from defects in glomerular development in the kidney. Notch2(del1)/Notch2(del1)mutant kidneys were hypoplastic and mutant glomeruli lacked a normal capillary tuft. The Notch ligand encoded by the Jag1 gene was expressed in developing glomeruli in cells adjacent to Notch2-expressing cells. We show that mice heterozygous for both the Notch2(del1) and Jag1(dDSL) mutations exhibit a glomerular defect similar to, but less severe than, that of Notch2(del1)/Notch2(del1)homozygotes. The co-localization and genetic interaction of Jag1 and Notch2 imply that this ligand and receptor physically interact, forming part of the signal transduction pathway required for glomerular differentiation and patterning. Notch2(del1)/Notch2(del1)homozygotes also display myocardial hypoplasia, edema and hyperplasia of cells associated with the hyaloid vasculature of the eye. These data identify novel developmental roles for Notch2 in kidney, heart and eye development.

The malformed kidney: disruption of glomerular and tubular development

Renal malformations are the major cause of renal failure during early childhood. They are found in approximately 100 genetic syndromes. We review the embryologic development of the kidney and its molecular control. Important new information has been derived from mutational analysis in humans and mice. We describe how mutations in nine transcription factors, 12 signaling molecules and nine gene products involved in a variety of other cellular functions disrupt renal morphogenesis. The information presented provides a template for integrating new discoveries on the molecular basis of renal development, for classifying renal malformations observed in the clinical setting, and for identifying defective genes in affected patients.

Determination of the genomic structure of the COL4A4 gene and of novel mutations causing autosomal recessive Alport syndrome

Autosomal recessive Alport syndrome is a progressive hematuric glomerulonephritis characterized by glomerular basement membrane abnormalities and associated with mutations in either the COL4A3 or the COL4A4 gene, which encode the alpha3 and alpha4 type IV collagen chains, respectively. To date, mutation screening in the two genes has been hampered by the lack of genomic structure information. We report here the complete characterization of the 48 exons of the COL4A4 gene, a comprehensive gene screen, and the subsequent detection of 10 novel mutations in eight patients diagnosed with autosomal recessive Alport syndrome. Furthermore, we identified a glycine to alanine substitution in the collagenous domain that is apparently silent in the heterozygous carriers, in 11.5% of all control individuals, and in one control individual homozygous for this glycine substitution. There has been no previous finding of a glycine substitution that is not associated with any obvious phenotype in homozygous individuals.

[Glomerulopathy and hypomelanosis of Ito]

Hypomelanosis of Ito is a rare neuroectodermal syndrome characterized by specific cutaneous lesions and frequent musculoskeletal or visceral involvement. We report on a child with an original nephritis with major segmental abnormalities of the glomerular basement membrane. Such an association might not be fortuitous and glomerular involvement might be underestimated in hypomelanosis of Ito.

Regulation of renal EGF receptor expression is normal in Denys-Drash syndrome

In patients with Denys-Drash syndrome, mutations of the Wilms' tumor suppressor gene are associated with nephroblastomas and developmental abnormalities of the genital tract and renal glomerulus. Normally, the Wilms' tumor gene product (WT1) is expressed at high levels in visceral glomerular epithelial cells (VGEC) of the emerging fetal glomerulus. We demonstrate that WT1 could normally serve to suppress EGF receptor expression in VGEC, since immunoreactive EGF receptor is strikingly absent compared to epithelial cells of the emerging proximal and distal tubule, which lack WT1. When HEK293 cells were co-transfected with plasmids containing EGFR enhancer/promoter elements linked to a CAT reporter and plasmids containing WT1 cDNA, EGFR enhancer/promoter activity was suppressed by all wild-type WT1 isoforms, but not by deletion mutants of WT1 lacking normal zinc-finger or N-terminal domains. Surprisingly, plasmids expressing a Denys-Drash WT1 mutant (R394W) retained the ability to suppress EGFR promoter activity in this system. Furthermore, we found that immunoreactive EGFR was appropriately undetectable in glomeruli from a three-year-old girl with Denys-Drash syndrome and in sections of her Wilm's tumor. These data suggest that faulty suppression of EGFR cannot account for the abnormalities of glomerulogenesis seen in Denys-Drash patients.

Atubular glomeruli and glomerular cysts--a possible pathway for nephron loss in the human kidney?

Glomerular tufts were removed and scanning electron microscopy was used to study the interior of Bowman's capsule, in order to identify atubular glomeruli. Normal renal cortex was studied from six kidneys removed for tumour and six renal transplants removed for end-stage rejection. Atubular glomeruli occurred in normal renal cortex in less than 1 percent of glomeruli, but were more common in transplant nephropathy, representing up to 61 percent of glomeruli. Glomerular cysts were identified which also lacked a tubular connection. Both atubular glomeruli and glomerular cysts contained a contracted glomerular capillary tuft and in both, Bowman's capsule was lined mostly by parietal podocytes. It is suggested that atubular glomeruli may be precursors of the glomerular cysts. The glomerular tuft may produce filtrate which exits the glomerulus via the parietal podocytes on Bowman's capsule. In normal human kidney, the formation of atubular glomeruli by disconnection from the tubule may represent an alternative pathway for the gradual nephron loss that is associated with ageing. This process may be amplified in disease: disconnection from the tubule may be an important part of irreversible nephron damage in chronic allograft nephropathy.

Diaphragmatic hernia in Denys-Drash syndrome

We report on a newborn infant with male pseudohermaphroditism and glomerular lesions (Denys-Drash syndrome) but without Wilms tumor. A constitutional heterozygous mutation in the WT1 gene (366Arg to His) was identified. In addition the child had a large diaphragmatic hernia, so far not described in Denys-Drash syndrome. The expression of the WT1 gene in pleural and abdominal mesothelium and the occurrence of diaphragmatic hernia in transgenic mice with a homozygous WT1 deletion strongly suggests that the diaphragmatic hernia in this patient is part of the malformation pattern caused by WT1 mutations.

Congenital renal glomerular fibrosis in a case of swine chondrodysplasia

A dwarf male Large White neonate showing various external abnormalities was diagnosed to be chondrodysplasia. Microscopy revealed massive accumulation of eosinophilic homogeneous substance in the renal glomeruli, mainly along the capillary walls. The homogeneous substance, mainly consisted of type-III collagen, was not found in the primitive glomeruli in the superficial cortex, and was most frequently and intensely deposited in the mature glomeruli in the deep cortex. Electron microscopically, the deposits consisted of the collagen fibrils with various structural abnormalities. Glomerular fibrosis might be attributed to in situ production of type-III collagen by glomerular cells with differentiation and maturation, most likely by the mesangial cells.

Glomerular basement membrane abnormalities in infants with heavy proteinuria

Two Indian male children with infantile-onset heavy proteinuria (with nephrotic syndrome in 1) had thickening of the glomerular basement membrane with splitting and basket-weave appearance of lamina densa on electron microscopic evaluation of kidney tissue (like Alport's syndrome), with normal light microscopic findings and negative immunofluorescence. The proteinuria was non-familial and was not associated with microhaematuria in patient 1; transient microhaematuria, perhaps associated with urinary tract infection, was noted in patient 2. There was no neurosensory deafness in the patients or their parents. The nephrotic syndrome remitted totally in one patient over a 7-month period. The proteinuria, as well as the renal disease, was non-progressive in the second patient over a 27-month period. The significance of these basement membrane abnormalities (classically described in Alport's syndrome) in early-onset nephrotic syndrome/heavy proteinuria that is non-familial and non-progressive needs to be evaluated.

Tobramycin-induced changes in renal histology of fetal and newborn Sprague-Dawley rats

Effects on renal development were studied using tobramycin (TBM) as a model compound. Pregnant Sprague-Dawley rats were injected i.p. with TBM at 30 or 60 mg/kg body weight/day on gestational days (GD) 10-19. Kidneys from dams and conceptuses were examined on GD 20 and on postnatal day (PD) 9. The dosing regimen caused in dams moderate proximal tubular alterations and increased concentrations in serum creatinine. Fetal kidneys showed granularity and swelling of proximal tubule cells at the 30 mg/kg dose, poor glomerular differentiation at the 60 mg/kg dose, increased glomerular density at both doses, and no changes on macroscopic examination at either dose. In newborns were observed a moderate developmental delay and tubular lesions at the higher dose, and dose-related increases of glomerular density and relative medullary area at both doses. All findings were more pronounced in males. A maturational disruption of the tubular structures possibly leading to increased glomerular density was attributed to TBM exposure during renal organogenesis in the rat.

Glomerular abnormalities in children undergoing orthotopic liver transplantation

A prospective study of renal function was undertaken on an unselected group of 8 children with chronic progressive liver disease on whom a renal biopsy was performed subsequently at the time of orthotopic liver transplantation. Two patients had abnormal urinalyses and 2 elevated urinary albumin/creatinine ratios. The remainder had no clinical evidence of renal dysfunction. All had normal serum creatinine concentrations. Glomerular abnormalities were present in all renal biopsies and were of two types: hepatic glomerulosclerosis (n = 5) and minor glomerular abnormalities (n = 3). IgM immunofluorescence was present in all biopsies and IgA in 6. Elevated serum immunoglobulin levels were observed in all patients, with IgM elevation in 6, IgA in 4 and IgG in 6. C3 and/or C4 were reduced in 5 patients and increased circulating immune complexes containing IgM were noted in 4. The clinical significance of these cirrhosis-associated glomerular abnormalities can only be established by long-term follow-up studies after orthotopic liver transplantation.

[Congenital glomerular nephropathies]

Congenital glomerulopathies are rare but very severe diseases from the clinical point of view. Their origin is either located in the kidney itself or outside the kidneys. The exact differential diagnosis is only possible taking into consideration other organ systems. A histological certification is mostly inevitable. The prognosis of congenital glomerulopathies is usually bad due to the development of chronic renal failure in most cases. Therapeutic aspects are limited to a small number of specific forms. Recurrences in a renal graft, however, are usually not to be expected.

The interrelationships among filtration surface area, blood pressure, and chronic renal disease

A primary role for the kidney in hypertension has long been recognized, but the pathogenetic interactions among renal hemodynamics, hormonal and hereditary factors, and dietary sodium intake remain ill defined. Reduction in the filtration surface area, whether acquired in the course of intrinsic renal disease or after surgical renal ablation, leads to systemic hypertension as well as to progressive renal insufficiency, sequellae made even more severe by dietary sodium excess. Moreover, hypertension and progressive renal disease occur in some individuals born with a solitary kidney, and occur almost invariably with more severe degrees of dysgenesis. Hypertension is also commonly observed in certain inbred rat strains in which the filtration surface area is congenitally deficient. Based on these and other lines of evidence reviewed herein, we postulate that a renal abnormality that contributes to essential hypertension in the general population is a reduced number of glomeruli and tubules, the consequences of which are limitations in the ability to excrete sodium and thus salt-sensitive hypertension. Furthermore, congenitally decreased filtration surface area may explain why only some, but not all, patients exposed to potentially injurious renal stimuli eventually manifest chronic nephropathy, and may also account for the susceptibility of subsets of type I and type II diabetics to develop overt glomerulopathy. Clinically, tests of renal reserve capacity may serve as a useful guide to identification of those patients at risk for the development of hypertension and progressive renal disease.

Glomerular ultrafiltration in rabbits with superficial glomeruli

The determinants of glomerular ultrafiltration in superficial glomeruli of a strain of English cross-breed rabbits have been studied using micropuncture techniques. Mean arterial blood pressure in the anaesthetised rabbits was 70 +/- 2 mmHg. The glomerular filtration rate in the kidney prepared for micropuncture was 4.4 +/- 0.4 ml/min, the filtration fraction was 22 +/- 1% and renal blood flow was 33 +/- 3 ml/min, and these values were comparable to values in conscious rabbits. Glomerular capillary pressure (Pgc) averaged 31 +/- 1 mmHg, the single-nephron glomerular filtration rate (SNGFR) averaged 25 +/- 2 nl/min, and the mean ultrafiltration pressure (calculated using the whole-kidney filtration fraction) averaged 7 +/- 1 mmHg. A net positive pressure at the efferent end of the glomerular capillaries (4.4 +/- 0.9 mmHg) indicated that a state of filtration pressure disequilibrium existed, under the experimental conditions of this study, in rabbit glomeruli. The calculated glomerular ultrafiltration coefficient (Kf) was 0.08 +/- 0.01 nl s-1 mmHg-1. Thus, compared to the Munich-Wistar rat, SNGFR is lower in the rabbit. This reflects the substantially lower glomerular ultrafiltration pressure in the rabbit, although this was offset partially by a higher Kf.

Glomerular alterations in rat neonates after transplacental exposure to gentamicin

Alterations of tubules and glomerules have been reported previously in kidneys of rat neonates after aminoglycosides were given to the mother during gestation. Here, we have studied the effects of gentamicin on the development of the glomerular basement membrane (GBM). Pregnant Wistar female rates were treated with gentamicin. Deliveries occurred normally. Using electron microscopy, we looked at the deepest glomerules of the kidneys of 1-day-old neonates: myeloid bodies were found in podocytes, and the GBM appeared thicker and denser than in controls. Anionic ferritin, injected intravenously crossed the GBM in prenatally gentamicin-exposed animals, but not in controls. Furthermore, urine electrophoresis showed the presence of proteins normally found only in the urine of fetuses 2 days before birth. We suggest then, that in utero exposure to gentamicin leads to a delay of renal maturation and that the GBM is altered in juxtamedullary nephrons while it is normally differentiated and functioning in controls. Thus exposure to drugs before birth could be harmful to the GBM.

Hypoplasia of one kidney in a Sprague-Dawley rat

Pathological examination of a 4-week-old male Sprague-Dawley rat revealed hypoplasia of the left kidney. Grossly, the left kidney exhibited hypoplasia associated with absence of the ureter on the same side. Histologically, components of the cortex and medulla were mingled in the tissue, and the glomeruli and convoluted tubules were scattered in disorder, and connective tissue proliferation was also observed. The papilla and pelvis could not be identified.

Oligohydramnios sequence and renal tubular malformation associated with maternal enalapril use

We present the case of a child who died of pulmonary hypoplasia as a result of the oligohydramnios sequence. The mother was taking enalapril, as well as propranolol and hydrochlorothiazide, for treatment of hypertension associated with systemic lupus erythematosus. Autopsy examination revealed severe renal tubular malformation. Correlation of animal data with previous case reports of neonatal anuria in association with maternal angiotensin converting enzyme inhibitors suggests that these agents may have a deleterious effect on fetal renal development and general well-being.

Familial hypoplastic glomerulocystic kidney disease: a definite entity with dominant inheritance

Autosomal dominant (or possibly X-linked) inheritance of familial hypoplastic glomerulocystic kidneys is described in a mother and son who both had stable, chronic renal failure, cystic kidneys by ultrasound examination, glomerular cysts as demonstrated histologically, and malformed renal calyces. There was no evidence of other congenital abnormalities apart from prognathism, small stature and pyloric stenosis. Hepatic fibrosis was not evident in a liver biopsy specimen. These findings add further confirmation to the existence of the syndrome of familial hypoplastic glomerulocystic kidney disease with dominant inheritance.

Aldose reductase inhibition and glomerular abnormalities in diabetic rats

We examined the effects of aldose reductase inhibition (ARI) on glomerular filtration rate (GFR), albuminuria, and kidney histology in partially insulin-treated streptozocin-induced diabetic (STZ-D) rats. After 1 mo of diabetes, GFR was elevated over control values in the STZ-D rats but was not affected by treatment with statil (an aldose reductase inhibitor). In another set of rats maintained for 7 mo, albuminuria was significantly increased in the diabetic rats from 2 mo on but was also not affected by statil treatment. Similarly, histological glomerular damage and diabetes-induced kidney hypertrophy were also greater in diabetic animals but were not altered by statil treatment. The frequency of diabetic cataracts was reduced by statil, and erythrocyte and kidney sorbitol levels were normalized, confirming the efficacy of ARI. Thus, inhibition of the aldose reductase pathway with statil does not ameliorate the hemodynamic, proteinuric, histological, or growth abnormalities in this model of diabetic nephropathy.

Twin-glomeruli and duplication of glomerular capillary tuft in human kidneys

Since the turn of this century the term twin-glomeruli (TG) designates a pair of glomerular capillary tufts supplied by a single afferent arteriole. Screening for TG has been performed in a series of kidney slides from 200 unselected consecutive autopsy cases with 21 (10.5%) positive results. Serial sectioning of 21 TG-positive and 10-TG-negative kidneys revealed the frequency of TG = 0.48% (71 among 15035 glomeruli) in the first group and 0.38% (32 TG among 8241 glomeruli) in the second. In individual cases the frequency ranged from zero up to 1.73% of all glomeruli. Three types of TG could be distinguished according to the distance between glomerular hili and the degree of Bowman's capsules coalescence. A complicated spatial relationship between the glomerular vessels and surrounding tubules was demonstrated by plastic reconstructions. TG are believed to be of a variety of renal architecture probably occurring in every human kidney. On the other hand, the glomeruli with two, mostly incomplete capillary tufts, which are occasionally found in the kidneys of newborns and children with multiple malformation syndromes and kidney dysplasias, are supposed to give evidence of a disturbed development of the kidneys.

Characterization of glomeruli by immunohistochemistry and electron microscopy in a case of Wilms' tumor

A patient with an abdominal mass was found to have a Wilms' tumor. Light microscopic examination showed that, in addition to blastema, stroma, and tubules, the tumor contained an unusually large number of glomeruli. Glomerular basement membranes stained positively by immunohistochemistry for laminin, collagen type IV, fibronectin, and Goodpasture antigen. Staining for Goodpasture antigen was seen only after acid-urea treatment, which was similar to findings in fetal and infant glomeruli. Glomerular cells stained positively for actin, myosin, and desmin, but there was no staining for factor VIII or Ulex europaeus agglutinin I, indicating an absence of endothelial cells. These findings were supported by electron microscopy, which showed basement membrane material, visceral epithelial cells, and mesenchymal cells (presumably primitive mesangial cells) in glomeruli, but no patent capillaries or capillary endothelium. Hence, the glomeruli in this case of Wilms' tumor were immature and also showed aberrant glomerulogenesis.

Congenital focal glomerular lesions in only one monozygotic twin related to a probable twin transfusion syndrome

A case of congenital focal glomerular lesions involving crescent formation in only one monozygotic twin is reported. The possible effect of chronic hypotension in the pathogenesis of the lesion is discussed, considering the fact that the affected twin was probably the donor in a feto-fetal transfusion syndrome.

Single nephron hyperfiltration and proteinuria in a newly selected rat strain with superficial glomeruli

Alterations in glomerular permeability were studied in female MWF/Ztm rats, newly selected from the Munich Wistar rats with a high number of superficial glomeruli. This strain is characterized by a diminished number of functioning nephrons, an elevated arterial blood pressure and a high proteinuria averaging 24 mg/24 h. Samples of Bowman capsular space (BCS) obtained by free-flow renal micropuncture techniques with pressure control were analyzed for albumin and high-molecular-weight (HMW) proteins by ultramicrodisc electrophoresis. The measured mean albumin and HMW protein concentration in BCS were 1.72 g/l and 0.66 g/l, respectively. The glomerular filtration rate (GFR) averaged 0.74 ml/min/g kidney weight and the single nephron GFR (SNGFR) 48 nl/min. Ultrastructural studies revealed focal bleb-like alterations of the podocytes as has been observed in hyperfiltration states. We suggest that the reduced number of functioning nephrons in the kidneys of these rats could induce glomerular hyperfiltration and permselectivity changes, which cause a high glomerular protein leakage.

Multiple efferent arterioles of the human kidney glomerulus as observed by scanning electron microscopy of vascular casts

About three thousand resin vascular casts of human renal glomeruli were examined with a scanning electron microscope, and two extremely rare glomeruli with quadruple or quintuple efferent arterioles were found. Each of these multiple efferent arterioles arose independently from the glomerular capillary tuft supplied by a single afferent arteriole. In addition, 34 glomeruli possessed double or triple efferent arterioles and two showed double afferent arterioles. In one of the former cases, one of the double efferent arterioles had a heterotopic origin near the urinary pole of the glomerulus. No glomerulus with triple or more afferent arterioles was noted.

An autosomal recessive disorder with glomerular basement membrane abnormalities similar to those seen in the nail patella syndrome: report of a kindred

We present a 9-year-old boy, the product of a consanguineous marriage, with proteinuria, edema, and microscopic hematuria with mild renal impairment since age 2 yr. Renal biopsy showed the histopathologic electron microscopic changes seen in hereditary osteo-onchyodysplasia (HOOD) [Hoyer et al, 1972; Bennet et al, 1973; DelPozo and Lapp 1970; Vernier et al, 1974; Morita et al, 1973] or "nail-patella syndrome." Neither the patient nor his relatives had bone or nail abnormalities; however, 2 other sibs had died of complications of end-stage renal disease at age 6 and 9, leading us to suspect autosomal recessive inheritance of a severe nephropathy or glomerulodysplasia.

[Pathomorphologic changes in the internal organs of intact and Mycobacterium leprae-infected 9-banded armadillos]

The internal organs of nine-banded armadillos were examined histologically before and after inoculation of the animals with M. leprae. 3--4 months after the inoculation two animals developed tuberculoid structures in the lungs, liver and skin. A conclusion is made that experimental leprosy infection in nine-banded armadillos may run its course not only in the lepromatous but also in the tuberculoid form of the disease.

Hepatoblastoma with adenomatoid renal epithelium

A case is described in which a hepatoblastoma is associated with a renal malformation where adenomatoid epithelium lines Bowman's capsule and the adjacent part of the proximal tubule. The significance of this is discussed in relation to the association of developmental malformations with neoplasia.

Glomerulocystic kidney. Report of a case

We describe a rare type of congenital renal cystic disease involving the Bowman capsule and adjacent abnormal tubules. The patient had a moderate degree of proteinuria, but otherwise normal renal function. Two subcapsular hepatic cysts manifested the only other visceral involvement. This case is morphologically similar to one previously reported. A purely descriptive morphologic term is suggested for this distinctive lesion, viz, glomerulocystic kidney.