Reduction of globotriaosylceramide in Fabry disease mice by substrate deprivation

We used a potent inhibitor of glucosylceramide synthase to test whether substrate deprivation could lower globotriaosylceramide levels in alpha-galactosidase A (alpha-gal A) knockout mice, a model of Fabry disease. C57BL/6 mice treated twice daily for 3 days with D-threo-1-ethylendioxyphenyl-2-palmitoylamino-3-pyrrolidi no-propanol (D-t-EtDO-P4) showed a concentration-dependent decrement in glucosylceramide levels in kidney, liver, and spleen. A single intraperitoneal injection of D-t-EtDO-P4 resulted in a 55% reduction in renal glucosylceramide, consistent with rapid renal glucosylceramide metabolism. A concentration-dependent decrement in renal and hepatic globotriaosylceramide levels was observed in alpha-Gal A(-) males treated for 4 weeks with D-t-EtDO-P4. When 8-week-old alpha-Gal A(-) males were treated for 8 weeks with 10 mg/kg twice daily, renal globotriaosylceramide fell to below starting levels, consistent with an alpha-galactosidase A-independent salvage pathway for globotriaosylceramide degradation. Complications observed with another glucosylceramide synthase inhibitor, N-butyldeoxynojirimycin, including weight loss and acellularity of lymphatic organs, were not observed with D-t-EtDO-P4. These data suggest that Fabry disease may be amenable to substrate deprivation therapy.

Insertional mutation of the collagen genes Col4a3 and Col4a4 in a mouse model of Alport syndrome

Mice homozygous for the transgenic insertion in line OVE250 exhibit severe progressive glomerulonephritis. Ultrastructural changes in the glomerular basement membrane (GBM) at 2 weeks of age resemble those in Alport syndrome. The transgenic insertion site was mapped by FISH to mouse chromosome 1 close to Pax3. Genetic and molecular analyses identified a deletion of genomic DNA at the transgene insertion site. Exons 1 through 12 of the collagen IV gene Col4a4, exons 1 and 2 of the adjacent Col4a3 gene, and the intergenic promoter region are deleted. Transcripts of Col4a3 and Col4a4 are undetectable in mutant kidney, and both proteins are missing from the GBM. Persistent cellular proliferation in mutant kidneys suggests that interaction with the extracellular matrix may be important for cell maturation. Evolutionarily conserved sequence elements in the promoter regions of human and mouse Col4a3 and Col4a4 include a 19-bp element that was tandemly duplicated in the human lineage and a CTC box element common to several genes encoding extracellular matrix proteins. This new animal model of Alport syndrome, Col4Delta3-4, lacks both alpha3 and alpha4 chains of collagen IV and exhibits an earlier disease onset than mice lacking alpha3 only.

Differential expression of collagen type IV alpha-chains in the tubulointerstitial compartment in experimental chronic serum sickness nephritis

The expression of collagen type IV chains in the renal tubulointerstitium was investigated during the development of chronic serum sickness (CSS) in rats, a model for immune complex-mediated renal disease. Immunohistochemical studies showed increased expression of alpha4(IV) collagen early during disease development, followed by an increase in alpha1(IV) through alpha3(IV) collagen subchain expression, especially in the tubular basement membrane. Dot-blot and in situ hybridization analysis showed a transient increase in steady-state mRNA levels for all collagen IV subchains during the development of CSS, which was most abundant for alpha1(IV), alpha2(IV), and alpha4(IV). Statistical correlations were found between the mRNA levels of alpha1(IV) and alpha2(IV) collagen and between alpha3(IV) and alpha4(IV), in line with the results of others which showed that these chains are co-distributed as heterotrimer collagen type IV molecules. However, additional correlations were found between the mRNA levels coding for alpha1(IV) and alpha3(IV) collagen, and between alpha1(IV) and alpha4(IV) mRNAs in the course of CSS. These abnormal correlations support the hypothesis that changes occur in the co-expression of the collagen IV subchains during the development of CSS. In addition, a strong correlation was found between the presence in the tubulointerstitium of alpha1(IV) and alpha2(IV) collagen chains, on the one hand, and the tubulointerstitial influx of R73+ and ED1+ cells, on the other, suggesting the involvement of inflammatory cells in the observed alterations in matrix production. Changes in the relative abundance of collagen IV chains in disease states may perturb the collagen IV network in the tubulointerstitial compartment and thereby play a role in the development of renal failure.

Alternate splicing in human Na+-MI cotransporter gene yields differentially regulated transport isoforms

myo-Inositol is a ubiquitous intracellular organic osmolyte and phosphoinositide precursor maintained at millimolar intracellular concentrations through the action of membrane-associated Na+-myo-inositol cotransporters (SMIT). Functional cloning and expression of a canine SMIT cDNA, which conferred SMIT activity in Xenopus oocytes, predicted a 718-amino acid peptide homologous to the Na+-glucose cotransporter with a potential protein kinase A phosphorylation site and multiple protein kinase C phosphorylation sites. A consistent approximately 1.0- to 13.5-kb array of transcripts hybridizing with this cDNA are osmotically induced in a variety of mammalian cells and species, yet SMIT activity appears to vary among different tissues and species. An open reading frame on human chromosome 21 (SLC5A3) homologous to that of the canine cDNA (96.5%) is thought to comprise an intronless human SMIT gene. Recently, this laboratory ascribed multiply sized, osmotically induced SMIT transcripts in human retinal pigment epithelial cells to the alternate utilization of several 3'-untranslated SMIT exons. This article describes an alternate splice donor site within the coding region that extends the open reading frame into the otherwise untranslated 3' exons, potentially generating novel SMIT isoforms. In these isoforms, the last putative transmembrane domain is replaced with intracellular carboxy termini containing a novel potential protein kinase A phosphorylation site and multiple protein kinase C phosphorylation sites, and this could explain the heterogeneity in the regulation and structure of the SMIT.

Glomerular endothelial cells synthesize collagens but little gelatinase A and B

Mesangial sclerosis is a major feature of progressive renal disease. The mesangium contains mesangial cells and is bounded by the peripheral glomerular basement membrane and endothelial cells. Mesangial cells synthesize and degrade extracellular matrix. Whereas both mesangial and endothelial cells synthesize extracellular matrix components, the degradative pathway, well studied in the former, has not been investigated in endothelial cells. This study examines lines of all three glomerular cell types derived from female B6SJLF1/J mice, as well as mRNA levels for collagens alpha1(I), alpha1(IV), alpha3 (IV), alpha5 (IV), and alpha1 (VI), laminin, tenascin, matrix metalloproteinase-2 (MMP-2), and MMP-9. Type I and IV collagen synthesis was confirmed by enzyme-linked immunosorbent assay. MMP-2 and MMP-9 enzyme activity was measured by zymography. It was found that glomerular endothelial cells are a significant source of collagens, laminin, and tenascin. However, they express only low levels of MMP-2 and no detectable MMP-9. Stimulation with exogenous transforming growth factor-beta1 leads to a significant increase in collagen I, tissue inhibitors of metalloproteinase-1, and MMP-9 in conditioned media. These data suggest that glomerular endothelial cells may play an active role in extracellular matrix remodeling in glomerular disease.

Augmented expression of glomerular basement membrane specific type IV collagen isoforms (alpha3-alpha5) in experimental membranous nephropathy

In human and experimental membranous nephropathy, new extracellular matrix accumulates between, and eventually surrounds, immune deposits on the subepithelial aspect of the glomerular basement membrane (GBM). To define the nature and source of this newly deposited matrix, we studied by in situ hybridization and immunohistology the production and tissue deposition of the recently defined basement membrane type IV collagen chain isoforms alpha3, alpha4, and alpha5, the mesangium-specific alpha1 and alpha2 isoforms of type IV collagen, and the fibrillar interstitial type I collagen during the development of immunological injury in passive Heymann nephritis (PHN), a rodent model of membranous nephropathy. Our results show that steady-state mRNA levels of alpha3-alpha5 (IV) but not alpha1 (IV) are significantly increased in the glomeruli of rats with PHN at the peak of immunological injury after 14 days. Increased signal for alpha4 (IV) and the new appearance of alpha1 (I) could be clearly localized to glomerular podocytes, the target of injury in this model. In addition, increased levels of immunoreactive alpha3-alpha5 were visible in the peripheral and paramesangial GBM together with de novo deposits of type I collagen. A modest increase in mesangial staining for alpha1/alpha2 (IV) was present in PHN glomeruli. In rats depleted of complement for 5 days after PHN induction, the peak of alpha4 (IV) mRNA expression on day 14 was blunted. In conclusion, we have shown increased production of the intrinsic GBM type IV collagen isoforms alpha3-alpha5 and ectopic production of type I collagen by injured podocytes in PHN. These changes may contribute to the formation of an expanded and disorganized GBM, as seen in experimental and human membranous nephropathy.

Human Na(+)-myo-inositol cotransporter gene: alternate splicing generates diverse transcripts

Na(+)-myo-inositol cotransport activity generally maintains millimolar intracellular concentrations of myo-inositol and specifically promotes transepithelial myo-inositol transport in kidney, intestine, retina, and choroid plexus. Glucose-induced, tissue-specific myo-inositol depletion and impaired Na(+)-myo-inositol cotransport activity are implicated in the pathogenesis of diabetic complications, a process modeled in vitro in cultured human retinal pigment epithelium (RPE) cells. To explore this process at the molecular level, a human RPE cDNA library was screened with a canine Na(+)-dependent myo-inositol cotransporter (SMIT) cDNA. Overlapping cDNAs spanning 3569 nt were cloned. The resulting cDNA sequence contained a 2154-nt open reading frame, 97% identical to the canine SMIT amino acid sequence. Genomic clones containing SMIT exons suggested that the cDNA is derived from at least five exons. Hypertonic stress induced a time-dependent increase, initially in a 16-kb transcript and subsequently in 11.5-, 9.8-, 8.5-, 3.8-, and approximately 1.2-kb SMIT transcripts, that was ascribed to alternate exon splicing using exon-specific probes and direct cDNA sequencing. The human SMIT gene is a complex multiexon transcriptional unit that by alternate exon splicing generates multiple SMIT transcripts that accumulate differentially in response to hypertonic stress.

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, alpha 1-5(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 alpha 1 and alpha 2 early in the disease, but only late in the GBM. In contrast, alpha 3 and alpha 4 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 alpha 3, alpha 4 and alpha 5 than for alpha 1 and alpha 2. Expression of alpha 3(IV) was greatest in GvHD, whereas expression of alpha 4 was greatest in CSS. As determined by in situ hybridization (ISH), alpha 1 mRNA was observed dispersed in the glomerulus, but alpha 3, alpha 4, and alpha 5 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.

Renal biopsy collagen I mRNA predicts scarring in rabbit anti-GBM disease: comparison with conventional measures

Progressive loss of normal structure associated with scarring is the hallmark of chronic diseases of most organs. To test the hypothesis that measurement of interstitial collagen mRNA levels would be a useful index to predict future scarring, we developed an assay to quantitate alpha 1(I) procollagen mRNA factored for GAPDH mRNA using RT-PCR (the "CI:G ratio"). We first defined conditions under which the assay could be used for analysis of renal biopsy samples. The CI:G ratio was then used to determine whether mRNA measurements performed at an early stage of inflammation (day 7) in a model of anti-GBM disease in the rabbit would predict outcome at day 30 as measured by interstitial and glomerular scarring and renal cortical hydroxyproline accumulation. The predictive value of this assay was compared to functional (serum creatinine and urine protein:creatinine ratio) and histologic (glomerular and interstitial scoring) parameters also measured at day 7. We found that the CI:G ratio alone provided a sensitive and discriminating assay over a wide range of renal injury that predicted various parameters of scarring with an average coefficient of determination (r2) of 0.69. This predictive power was higher than that found for conventional measures, which tended to have good discriminatory capacity over limited ranges of renal injury. The CI:G ratio provided significant additional predictive power over and above that available from combinations of conventional functional or histologic parameters. We conclude that measurement of the CI:G ratio in biopsy samples deserves further assessment as a potentially useful quantitative predictor of outcome that could lead to improved clinical decision-making.

Synthesis and secretion of endothelin in a cortical collecting duct cell line

Previous experiments have shown that epithelial cells in the renal medulla produce endothelin-1 (ET-1) and possess ETB receptors. It has been suggested that medullary ET-1 may affect water and sodium absorption along the collecting ducts in an autocrine fashion. To study possible mechanisms responsible for the regulation of medullary ET-1 production, experiments were performed in M-1 cells and mIMCD-K2 cells, cell lines derived from cortical and inner medullary collecting ducts of SV40 transgenic mice, grown to confluence on collagen-coated filter inserts. Both cell lines were found to express ET-1 mRNA and to secrete ET almost exclusively into the basolateral medium as long as the transepithelial resistance was high. Inhibition of transcription with actinomycin D was followed by a decline in both ET mRNA [halftime (t1/2) = 30 min] and ET secretion (t1/2 = approximately 90 min). The addition of arginine vasopressin (AVP, 10(-8) M; 2- or 4-h exposure) or incubation of M-1 cells in hypertonic media (+50 mM NaCl, 4- or 6-h exposure) did not significantly alter ET secretion or ET-1 mRNA expression. In contrast, simultaneously increasing AVP(10(-8) M in the basolateral medium) and tonicity (+50 mM NaCl) for 4 h increased ET secretion (from 28.9 +/- 3.9 to 41.8 +/- 3.8 pg.h-1.mg protein-1; P = 0.029, n = 10) and ET-1 mRNA (control = 2,138 cpm/microliter, log of 3.33 +/- 0.048, n = 4; AVP + NaCl = 3,548.1 cpm/microliter, log of 3.55 +/- 0.09; P = 0.045, n = 5). Exposure of M-1 cells to hypertonic media (+50 mM NaCl or 100 mM mannitol) for 24 h was associated with a marked reduction of ET secretion (-83.9% with NaCl and -78.4% with mannitol; P < 0.0001). This reduction was attenuated, but not prevented, by the presence of AVP in the basolateral medium (-40%). ET-1 mRNA, in contrast, did not change with 24-h exposure to hypertonic media and increased when AVP was present. Results are compatible with the concept that generation of ET by collecting duct cells may contribute in a complex and time-dependent fashion to the paracrine control of collecting duct cell function.

Transforming growth factor-beta modulation of the alpha 1(IV) collagen gene in murine proximal tubular cells

We have examined the expression of the alpha 1(IV) collagen gene in murine proximal tubular cells (MCT) to better understand how it is regulated in parenchymal cells. Transcriptional activity was examined using luciferase reporters driven by the alpha 1(IV) promoter and varying lengths of 5'-flanking sequences. The minimal bidirectional promoter showed low intrinsic activity in MCT cells, but addition of upstream sequences increased luciferase expression. Maximal activity resided within the first 1,200 bp upstream. A minigene construct was generated by placing a portion of the alpha 1(IV) first intron downstream from the promoter region. The intronic sequences significantly decreased activity of the promoter in MCT cells and 3T3 fibroblasts but greatly enhanced expression in murine parietal yolk sac (PYS) endodermal cells. Addition of transforming growth factor-beta (TGF-beta) to MCT cultures elevated the levels of secreted type IV collagen. Treatment of either transiently or stably transfected MCT cells with TGF-beta produced an increase in the levels of expression of all of the reporters tested. These data support the hypothesis that cell-specific regulation of alpha 1(IV) collagen is dependent upon downstream sequences, which act to decrease the expression of type IV collagen in tubular epithelium. The activity of the alpha 1(IV) collagen gene in proximal tubular cells is increased by TGF-beta, which acts on the domain(s) embedded within the intergenic bidirectional promoter.

Cloning of the mouse fibronectin V-region and variation of its splicing pattern in experimental immune complex glomerulonephritis

Increased mRNA and protein expression of extracellular matrix (ECM) components, including fibronectin, occurs during the development of glomerulonephritis and glomerulosclerosis in immunologically mediated kidney diseases. However, in addition to these quantitative changes in ECM expression, qualitative changes in these molecules may contribute to malformations in the composition of the glomerular matrix. These qualitative changes may include alterations in the splicing pattern of the V-region of fibronectin, since this region plays a role in its accumulation. The splicing patterns of this region have been studied in chronic graft-versus-host disease (GvHD) in mice, a model of lupus nephritis, and in chronic serum sickness (CSS) in rats, a model of immune complex nephritis. Cloning of the mouse fibronectin V-region from kidney tissue revealed 96.1 per cent homology with the corresponding domain in rat fibronectin. PCR (polymerase chain reaction) analysis of RNA from isolated glomeruli revealed three isoforms of this region in both mouse and rat fibronectin, namely inclusion or exclusion of the whole region, or exclusion of only the CS1 domain. In both models, increased exclusion of the V-region was observed early in the disease. However, in GvHD the splicing pattern returned to normal, whereas in CSS the shift persisted during the course of the experiment. Differentiated expression of fibronectin isoforms may exert an important effect on the structure and biological function of the glomerulus and may thus play a role in the development of glomerulonephritis and glomerulosclerosis.

Developmental changes in seminiferous tubule extracellular matrix components of the mouse testis: alpha 3(IV) collagen chain expressed at the initiation of spermatogenesis

The temporal expression of type IV collagen, laminin, and entactin in the basal laminae of the seminiferous tubule during development of the mouse testis was determined. Northern blot analysis was used to examine changes in testicular mRNA for alpha 1-alpha 5 type IV collagen (IV) chains in mice ranging in age from newborn to adult (60 days). Levels for mRNA alpha 1(IV) and alpha 2(IV) chains were highest in newborns through Day 5 and remained elevated through Day 10, but then sharply declined to adult values by Day 30. In sharp contrast, alpha 3(IV) and alpha 4(IV) chain levels were low in newborns, peaked at Day 10, and then declined to adult values by Day 30. 5(IV) mRNA was elevated in newborns and at Days 5 and 10 before dropping to adult levels by Day 30. Changes in the deposition of alpha 1, alpha 2, and alpha 3(IV) collagen chains, laminin, and entactin into the inner and outer basal laminae of the seminiferous tubule were determined from the beginning of tubule formation (embryonic Day 12.5) through adulthood by immunofluorescence microscopy using polyclonal antibodies for these constituents. The alpha 1 and alpha 2(IV) chains, laminin, and entactin were deposited into the inner basal lamina at embyronic Day 12.5 and into the newly formed outer basal lamina at Day 5 after birth. The alpha 3(IV) chains were deposited into both the inner and outer basal laminae at Day 5. Thus, testicular alpha 1-alpha 3(IV) mRNA levels coincide with the incorporation of detectable collagen chains into the seminiferous basal laminae, suggesting transcriptional control of these alpha (IV) chains. Expression of of the alpha 3(IV) chain coincides with the initiation of spermatogenesis, suggesting a functional role of this chain in spermatogonial proliferation.

Role of the extracellular matrix in the development of glomerulosclerosis in experimental chronic serum sickness

Glomerulosclerosis is a severe complication of many immunologically mediated kidney diseases and is associated with a poor prognosis with respect to renal function. The aim of this study was to elucidate the role of the extracellular matrix (ECM) in the development of glomerulosclerosis in experimental immune complex glomerulonephritis. Induction of chronic serum sickness by repetitive injections of human IgG into preimmunized Wistar rats leads to the development of immune complex nephritis and glomerulosclerosis. At an early stage of the disease fibrinogen accumulation was observed along the endothelial cells, presumably related to damage of the endothelial lining. mRNA levels for several collagen types, laminin B1 and B2, and fibronectin were increased in both whole-kidney tissue and in isolated glomeruli, but morphological changes were not observed. In situ hybridization experiments demonstrated increased ECM mRNA levels in glomerular and tubular cells. Starting at week 15, glomerular mesangial matrix expansion and thickening of the glomerular basement membrane (GBM) was observed. ECM components were abundantly present. Coagulation factors were not observed at this point. ECM mRNA levels were decreased as compared to week 0, but were still above normal. Focal and segmental end-stage sclerotic lesions developed at weeks 25-30, in which fibronectin and fibrinogen were the major constituents. Other ECM components were found peripherally from these lesions in the remnants of the mesangial matrix and GBM. Sclerotic matrices did not demonstrate an increase of cellular-fibronectin, and other constituents from the circulation were not present in the lesions. Glomerular ECM mRNA was decreased to normal levels. However, a dramatic increase of ECM mRNA expression was observed at sites of inflammatory infiltrate in the perivascular, interstitial, and periglomerular regions. In conclusion, the development of glomerulosclerosis in chronic serum sickness rats is preceded by mesangial matrix expansion in which several ECM components are increasingly expressed. Steady state mRNA levels for these components are increased before morphological changes are detectable. In the final stage there is a specific accumulation of exogenous fibronectin in the glomerular end-stage sclerotic lesions. Simultaneously, an interstitial inflammatory reaction takes place leading to increased ECM production in the tissue surrounding the damaged glomeruli.

Cholesterol emboli presenting as acute allograft dysfunction after renal transplantation

Cholesterol emboli are a common complication of atherosclerotic vascular disease. A 40-yr-old renal transplant recipient who developed acute allograft dysfunction 1 day after the initiation of cyclosporine therapy and 6 days after transplantation is described. A renal allograft biopsy revealed cholesterol emboli in interlobular arteries and in glomeruli. Four previously reported cases of cholesterol emboli in renal allografts are described, and the cause and pathogenesis of atheroembolic disease are reviewed. Atheroemboli causing injury to the renal allograft may arise from either donor or recipient vessels. Vigilance for the occurrence of these emboli needs to be maintained when donor or recipient vessels demonstrate evidence of significant atherosclerotic vascular disease.

Specific accumulation of exogenous fibronectin in experimental glomerulosclerosis

The prognosis of patients showing glomerulosclerosis as a complication of an immunologically mediated kidney disease is poor. To improve the diagnosis and treatment of these patients, it is important to understand the processes involved in the development of glomerulosclerosis. In this study, we investigated the molecular composition of experimental end-stage glomerular sclerotic lesions and their pathogenesis in chronic graft-versus-host disease (GvHD) in the mouse and chronic serum sickness in the rat. Accumulation studies were performed to determine the degree of specific trapping of constituents from the circulation. Two different models were investigated to determine whether differences in disease initiation resulted in different compositions of the glomerulosclerotic lesions. In both models, glomerulosclerosis was preceded by expansion of the mesangial matrix and thickening of the glomerular basement membrane (GBM). The end-stage sclerotic lesions consisted mainly of fibronectin, which appeared to displace the other extracellular matrix (ECM) components peripherally in the mesangial matrix and GBM. The abundance of fibronectin in the lesions was not reflected in the mRNA levels for this component. Indeed, antibodies directed against the cellular form of fibronectin did not stain positive in the end-stage lesions. These findings, together with accumulation studies, suggest that specific accumulation rather than de novo synthesis of fibronectin plays a major role in the development of experimental glomerulosclerosis, which appears to be independent of the pathway of induction.

Kidney and retinal defects (Krd), a transgene-induced mutation with a deletion of mouse chromosome 19 that includes the Pax2 locus

The semidominant mutation Krd (kidney and retinal defects) was identified in transgenic line Tg8052. Krd/+ mice have a high incidence of kidney defects including aplastic, hypoplastic, and cystic kidneys. Retinal defects in Krd/+ mice include abnormal electroretinograms and a reduction of cell numbers that is most extreme in the inner cell and ganglion layers. Viability of Krd/+ mice is strongly influenced by genetic background, and growth retardation is observed in young animals. Homozygosity results in early embryonic lethality. Fluorescence in situ hybridization of a transgene-specific probe localized the insertion site to the distal region of mouse Chromosome 19. The sequence of the insertion site revealed transgene insertion into a LINE element with deletion of a single nucleotide from the 3' terminus of the transgene. A polymorphic microsatellite, D19Umi1, was identified in a junction clone and mapped in several large crosses. D19Umi1 is located 1.7 +/- 1.0 cM distal to Pax2, which encodes a paired type transcription factor expressed in embryonic kidney and eye. Deletion of Pax2 from the transgenic chromosome was demonstrated by Southern analysis of genomic DNA from (Krd/+ x SPRET/Ei)F1 mice. Additional genetic and molecular data are consistent with an approximately 7-cM deletion that includes the loci stearoyl CoA desaturase (Scd1), pale ear (ep), D19Mit17, D19Mit24, D19Mit27, D19Mit11, and Pax2. This deletion, Del(19)TgN8052Mm, will be useful for genetic and functional studies of this region of mouse Chromosome 19.

Lipopolysaccharide induces monocyte chemoattractant protein production by rat mesangial cells

Lipopolysaccharide, a potent pro-inflammatory constituent of bacterial cell walls, is capable of promoting glomerular inflammation, by both activating circulating inflammatory cells and local interactions with renal parenchymal cells. We sought to determine whether lipopolysaccharide was capable of promoting glomerular inflammation by directly stimulating mesangial cell production of monocyte chemoattractant protein 1, a recently described cytokine capable of eliciting recruitment of mononuclear phagocytes into inflammatory foci. Northern hybridization analysis revealed dose and time-dependent induction of mRNA coding for monocyte chemoattractant protein 1 in quiescent rat mesangial cells treated with lipopolysaccharide. Lipopolysaccharide-elicited induction of monocyte chemoattractant protein mRNA was detectable after 1 hour and persisted for at least 30 hours. Media isolated from rat mesangial cell cultures stimulated by lipopolysaccharide possessed monocyte chemotactic activity that was detectable at 8 hours and peaked at 24 hours; an antimonocyte chemoattractant protein antibody blocked 87% of this chemotactic activity. We suggest that lipopolysaccharide, released from bacterial cell walls, promotes glomerular inflammation by stimulating mesangial cell production of monocyte chemoattractant protein 1.

Bilateral renal parenchymal malacoplakia presenting as fever of unknown origin: case report and review

Malacoplakia is a rare inflammatory disorder seen most often in the urinary tract, where it is highly associated with coliform infection. Although first recognized by pathologists in 1902, it has received little attention from the infectious disease community. While there remains much uncertainty regarding the specific cause of malacoplakia, it appears to be associated with a defect in intracellular killing of ingested microorganisms by macrophages. We report a case of bilateral renal parenchymal malacoplakia that presented as fever of unknown origin, and we review 33 previously identified cases. Renal malacoplakia has traditionally been associated with high morbidity and mortality. More recently, treatment with antimicrobial agents such as trimethoprim or ciprofloxacin has yielded a better outcome than had been documented with other therapy. Malacoplakia should be considered in the evaluation of fever of unknown origin or of relapsing or refractory urinary tract infection. Therapy with antimicrobial agents capable of intracellular penetration is recommended.

Expression of laminin chains during myogenic differentiation

Expression of two Ae-related chains of the extracellular matrix glycoprotein laminin was induced as multipotent C3H10T1/2 mouse embryo fibroblasts differentiated into myoblasts and myofibers. C3H10T1/2 fibroblasts expressed the B1e (M(r) = 215,000) and B2e (M(r) = 205,000) laminin chains based on metabolic radiolabeling, immunoprecipitation, peptide mapping, and mRNA analysis. In contrast, myoblasts derived from C3H10T1/2 fibroblasts treated with DNA demethylating agents or transfected with the cDNA encoding MyoD expressed the Ae (M(r) = 400,000) and a novel Ae-related laminin chain (designated Ac3h, M(r) = 350,000) in addition to the B1e and B2e chains. Expression of the Ae and Ac3h chains paralleled the capacity for myofiber formation in six additional C3H10T1/2 myoblast clones with varied potentials for terminal differentiation and coincided with a switch in laminin isoforms from those of M(r) = 850,000 synthesized by C3H10T1/2 fibroblasts to those of M(r) = 900,000-950,000 synthesized by C3H10T1/2 myoblasts and myofibers. Cultures of mouse C2C12, mouse BC3H1, rat L6, and primary mouse myoblasts also synthesized the Ae, Ac3h, B1e, and B2e laminin chains. The results demonstrate that expression of the Ae and Ac3h laminin chains is associated with expression of MyoD and the mammalian myogenic differentiation program.

Cyclic AMP selectively increases renin mRNA stability in cultured juxtaglomerular granular cells

This study was undertaken to examine the regulation of renin release and gene expression in primary cultures of juxtaglomerular granular (JGG) cells. JGG cells, isolated from mouse kidney, demonstrated high purity and showed regulated renin release in vitro. Changes in steady-state renin mRNA levels were assessed by quantitative polymerase chain reaction techniques, with polymerase chain reaction amplification efficiency monitored by co-amplification of experimental samples with a dilution series of cDNA for a mutant template. When the cells were incubated in the presence or absence of forskolin, isoproterenol, or 8-bromo-cAMP plus 3-isobutyl-1-methylxanthine for 24 h or cholera toxin for 12 h, renin mRNA levels were increased 3.9-, 4.4-, 5.1-, and 3.3-fold, respectively (all, p < 0.05). A significant increase in renin mRNA levels was observed 8 h after treatment with forskolin, but no change was detectable at 4 h. Cycloheximide did not prevent the increase in renin mRNA by isoproterenol. When RNA synthesis was inhibited by incubation with actinomycin D (5 micrograms/ml), renin mRNA levels declined with a half-life of 3.0 +/- 0.8 h. Treatment with forskolin increased renin mRNA half-life to 10.8 +/- 2.7 h (p < 0.025). The half-life of beta-actin, endothelin-1, or the facilitative glucose transporter-1 (GLUT-1) mRNA expressed in the same cells was not altered, although the steady-state levels of GLUT-1 mRNA increased 2.2-fold after treatment with forskolin. These data demonstrate that cAMP increases renin release and mRNA levels in JGG cells in vitro, that the stimulatory effect of cAMP on renin mRNA is delayed but does not require new protein synthesis, and that the increased renin mRNA levels induced by cAMP are due in part to a selective increase in renin mRNA stability.

Endothelin-1 mRNA in glomerular and epithelial cells of kidney

To examine the question of the tubular localization of renal endothelin-1 (ET-1) mRNA, cDNA generated by reverse transcription of isolated rat tubule RNA was amplified by polymerase chain reaction using rat ET-1-specific oligonucleotides. Product identity was determined by restriction enzyme digestion or direct product sequencing. ET-1 mRNA was found to increase in renal tissue in a corticomedullary direction. High levels of ET-1 mRNA were found in dissected glomeruli and in juxtaglomerular cells in short-term primary culture. Among tubule segments, ET-1 mRNA was most abundant in inner medullary collecting ducts (IMCD), but products were also found with cDNA derived from proximal convoluted and straight tubules, thick ascending limbs, and outer medullary collecting ducts. In kidneys of untreated, homozygous Brattleboro rats, the increase of ET-1 mRNA along the corticomedullary axis as well as the preponderance of tubular ET-1 mRNA in IMCD was not observed. Our data show that ET-1 mRNA is present in all nephron segments studied and that its expression may be dependent on the functional state of the kidney. Our results are consistent with the proposal that ET-1 modifies tubular function in an autocrine or paracrine fashion.

Aldose reductase gene expression and osmotic dysregulation in cultured human retinal pigment epithelial cells

A "compatible osmolyte hypothesis" proposes that intracellular nonionic organic osmolytes such as sorbitol, myo-inositol, taurine, betaine, and glycerophosphorylcholine respond coordinately to changes in external osmolality, thereby maintaining the intracellular ionic milieu. Osmoregulation may be the primary physiological function of aldose reductase, which catalyzes the conversion of glucose to sorbitol. Glucose-induced sorbitol accumulation in isosmotic hyperglycemic states is associated with compensatory depletion of myo-inositol and taurine. Because such depletion may predispose to chronic diabetic complications, the relationship between osmolyte shifts and aldose reductase gene expression was studied in two human retinal pigment epithelial cell lines, one exhibiting osmoregulated and the other high basal aldose reductase gene expression. High basal expression of the aldose reductase gene was associated with rapid sorbitol accumulation and myo-inositol depletion in response to hyperglycemic (20 mM) concentrations of glucose. Myo-inositol and sorbitol behaved as compensating intracellular osmolytes by accumulating markedly in response to hyperosmolality (300 mM mannitol). Thus the pattern of response of myo-inositol to hyperglycemic and hyperosmotic levels of glucose and mannitol was related to the degree of basal aldose reductase gene expression, which may therefore influence the development of diabetic complications.

Altered aldose reductase gene regulation in cultured human retinal pigment epithelial cells

Aldose reductase (AR2), a putative "hypertonicity stress protein" whose gene is induced by hyperosmolarity, protects renal medullary cells against the interstitial hyperosmolarity of antidiuresis by catalyzing the synthesis of millimolar concentrations of intracellular sorbitol from glucose. Although AR2 gene induction has been noted in a variety of renal and nonrenal cells subjected to hypertonic stress in vitro, the functional significance of AR2 gene expression in cells not normally exposed to a hyperosmolar milieu is not fully understood. The physiological impact of basal AR2 expression in such cells may be limited to hyperglycemic states in which AR2 promotes pathological polyol accumulation, a mechanism invoked in the pathogenesis of diabetic complications. Since AR2 overexpression in the retinal pigment epithelium has been associated with diabetic retinopathy, the regulation of AR2 gene expression and associated changes in sorbitol and myo-inositol were studied in human retinal pigment epithelial cells in culture. The relative abundance of aldehyde reductase (AR1) and AR2 mRNA was quantitated by filter hybridization of RNA from several human retinal pigment epithelial cell lines exposed to hyperglycemic and hyperosmolar conditions in vitro. AR2 but not AR1 mRNA was significantly increased some 11- to 18-fold by hyperosmolarity in several retinal pigment epithelial cell lines. A single cell line with a 15-fold higher basal level of AR2 mRNA than other cell lines tested demonstrated no significant increase in AR2 mRNA in response to hypertonic stress. This cell line demonstrated accelerated and exaggerated production of sorbitol and depletion of myo-inositol upon exposure to 20 mM glucose. Therefore, abnormal AR2 expression may enhance the sensitivity of cells to the biochemical consequences of hyperglycemia potentiating the development of diabetic complications.

Type IV collagen production by rat pulmonary alveolar epithelial cells

Maintenance and repair of the pulmonary alveolar basement membrane are critical processes for preserving normal alveolar structure and function. To elucidate the mechanisms that control type IV collagen production by pulmonary alveolar epithelial cells, type II pneumocytes from rat lungs were isolated and maintained in tissue culture as monolayers. Using Northern blot analysis and metabolic labeling, we found that the cultured epithelial cells express type IV collagen mRNA and incorporate [3H]proline into type IV collagen. To determine the effects of phenotype on control of type IV collagen synthesis, we took advantage of the well-described observation that isolated type II cells lose their distinctive type II features when cultured on plastic in serum-containing medium for 7 days and assume an appearance more like that of type I epithelial cells. We found that [3H]proline incorporation into type IV collagen increased from day 1 to day 2 and thereafter decreased gradually up to day 7. Despite this decrease in [3H]proline incorporation, type IV collagen mRNA increased over the same period. If the loss of type II cell characteristics was prevented by culturing the cells in EHS matrix, a basement membrane-like extracellular matrix, there was little increase in relative abundance of type IV collagen mRNA as compared with cells cultured on plastic. We therefore conclude that type IV collagen production by isolated pulmonary alveolar epithelial cells is controlled, at least in part, by translational or post-translational mechanisms. Furthermore, the full type II cell phenotype is not required for expression of type IV collagen genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of mineralocorticoid and glucocorticoid receptor mRNA along the nephron

In the present study, a competitive polymerase chain reaction (PCR) technique was used to quantitate the relative levels of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) mRNA in microdissected nephron segments from the rat kidney and of MR mRNA from isolated principal and intercalated collecting duct cells from rabbit. RNA was isolated from cells and isolated tubules, cDNA was synthesized, and receptor cDNA was coamplified by PCR with a competitive control template. beta-Actin PCR products were also obtained from each nephron segment studied, to assess variations in RNA extraction and cDNA synthesis. MR mRNA, as determined by this competitive PCR technique, was 10-fold more abundant in cortical collecting duct (CCD), outer medullary collecting duct, and inner medullary collecting duct segments than in the proximal tubule and thick ascending limb segments (P < 0.05). Both principal and beta-intercalated cells of the CCD contained detectable levels of MR mRNA, although the levels in the principal cells were threefold higher (P < 0.01). GR mRNA was twofold more abundant in glomeruli, proximal tubule, and thick ascending limb segments than in the collecting duct segments (P < 0.05). In general, the distribution pattern of MR and GR mRNA is consistent with the distribution of adrenal corticosteroid function along the nephron.

Vascular adventitial cell expression of collagen I messenger ribonucleic acid in anti-glomerular basement membrane antibody-induced crescentic nephritis in the rabbit. A cellular source for interstitial collagen synthesis in inflammatory renal disease

BACKGROUND

Scarring in the interstitial compartment of the renal cortex heralds a poor prognosis in many forms of renal injury, however, the mechanism through which glomerular inflammation leads to interstitial scarring is not understood. In a model of anti-GBM disease in the rabbit, development of crescentic glomerulonephritis is associated with marked interstitial fibrosis and decreased renal function. We previously demonstrated that collagen accumulation in the model was preceded by increases in collagen I and IV mRNA and that these changes were primarily extraglomerular at early time points when inflammation was predominantly intraglomerular. In order to identify the cellular origins of extraglomerular collagen synthesis in this model, in situ hybridization using an alpha 2(I) procollagen probe was performed.

EXPERIMENTAL DESIGN

A 602 bp rabbit alpha 2(I) procollagen cDNA was cloned using a PCR strategy and sequenced. The nucleotide sequence of the coding region was 94% identical with the human alpha 2(I) procollagen sequence. Northern blots were performed to define conditions of specific hybridization of the anti-sense riboprobe. Tissue sections from normal rabbit kidneys and from kidneys 4, 5, 7, 10 and 14 days after injection of anti-GBM antibody were hybridized with 35S-labeled sense and anti-sense riboprobes. Cells containing alpha 2(I) mRNA were identified by autoradiography and mRNA abundance was quantitated by grain density.

RESULTS

No specific hybridization was detected with the sense probe at any time. alpha 2(I) mRNA was undetectable with the anti-sense probe in normal kidney sections. In contrast, the anti-sense probe hybridized specifically at all time points after induction of anti-GBM disease. In agreement with previous filter hybridization studies, on day 4, when inflammation was predominantly intraglomerular, cells in the periarterial adventitial compartment of renal cortex hybridized strongly. At later time points, labeling was also present in the interstitial spaces, the periglomerular region, in Bowman's space and in the glomerular tuft itself.

CONCLUSIONS

We conclude that perivascular adventitial cells are among the first to respond to glomerular inflammation and represent a pool of cells that subsequently contribute to interstitial and glomerular scarring.

Time course of stimulation of renal renin messenger RNA by furosemide

Renin secretion responds rapidly to a variety of stimuli; however, reported changes in renal renin messenger RNA (mRNA) levels in vivo have been observed only after prolonged stimulation. Studies were designed to test whether rapid changes in renin mRNA levels can be produced in vivo. In the first series, Sprague-Dawley rats received furosemide (10 mg/kg) intraperitoneally and a low sodium diet (0.05% sodium); renin secretion was significantly stimulated at 8 or 16 hours after treatment, but renin mRNA levels did not change. In a second series, rats were pretreated with deoxycorticosterone acetate (200 mg/kg) and saline drinking water for 3 days and then killed 0, 2, 4, 8, or 48 hours after furosemide administration. The renin mRNA level was unchanged at 2 hours but was stimulated twofold at 4 and 8 hours and threefold at 48 hours. In additional animals, the response of renin mRNA 4 hours after furosemide was found not to be potentiated by the converting enzyme inhibitor quinapril (5 mg/kg). The results demonstrate that with acute stimulation, renin mRNA levels lag 2-4 hours behind the change in plasma renin levels.

Laminin expression in the mouse lung increases with development and stimulates spontaneous organotypic rearrangement of mixed lung cells

The recent establishment of a role for laminin in mouse lung organogenesis (Schuger et al. 1990a,b, 1991) prompted us to study its expression in the developing lung. Laminin A and B chains were detected in the murine lung from the first hours of development onward. In situ hybridization of mRNA as well as SDS-PAGE studies of lung cells in monoculture indicated that both epithelium and mesenchyme produce complete laminin molecules. Quantitative analysis of the in situ hybridization studies showed a gradual increase in laminin expression during development which was further supported by immunohistochemistry and ELISA. The overall pattern of expression suggested that the effects of laminin in morphogenesis were not restricted to a particular stage of development. Furthermore, the increase in expression during late development supported a role for the molecule in the fetal lung, which was not previously established. We next determined whether the increase in laminin production modulated the behavior of fetal lung cells as compared with their embryonic counterparts. We previously showed that organotypic pattern formation does not occur in cultures of mixed embryonic lung cells unless exogenous laminin is added (Schuger et al., 1990b). Organotypic pattern formation is the result of cell sorting into epithelial and mesenchymal compartments and further rearrangement in a pattern resembling the tissue of origin. In the present study, we demonstrated that organotypic pattern formation occurs spontaneously in cultures of mixed fetal lung cells, which express high laminin levels. Pattern formation was abolished by antibodies to laminin. These studies suggest a correlation between laminin expression and the ability of lung cells in culture to reproduce normal tissue patterns. We conclude that laminin is critical for epithelial-mesenchymal recognition and further morphogenic interaction during both the embryonic and fetal stages of lung development.

Application of polymerase chain reaction techniques to study of rabbit renin gene expression

Studies were performed to develop techniques to assess renin mRNA in a single microdissected juxtaglomerular apparatus (JGA) of rabbit using the polymerase chain reaction (PCR) method of amplification of cDNA sequences. In preliminary studies synthetic oligonucleotide primers corresponding to regions in the rat renin cDNA sequence, which are highly conserved between mouse, rat, and man, were found to yield good amplification efficiency with a rat renin cDNA template, but little product was observed with rabbit cDNA template. We therefore employed a nested primer PCR cloning technique to clone an 839 base pair portion of the rabbit renin cDNA to obtain species-specific sequence information for primer design. Here we report the nucleotide sequence of a partial rabbit renin cDNA clone and the use of species-specific primers that permit semiquantitative assessment of rabbit mRNA levels in the single JGA.

Intracellular signaling of transcription and secretion of type IV collagen after angiotensin II-induced cellular hypertrophy in cultured proximal tubular cells

Physiologic concentrations of angiotensin II (AII) can induce cellular hypertrophy in murine proximal tubular epithelium (MCT cells). This response is characterized by an increase in cell size, new protein synthesis, and by the secretion of new basement membrane type IV collagen in the absence of cellular proliferation. The present study was undertaken to evaluate the second messengers of these AII-induced cellular events with special reference to the increase in type IV collagen secretion. In initial experiments we observed that pretreatment of MCT cells with agents that increase concentrations of intracellular cAMP, like forskolin, dibutyryl cAMP, and isobutyl-methyl-xanthine abolish AII-induced amino acid incorporation, but have no effect on control cells or on their proliferation. In addition, 10(-8) M AII significantly decreased the concentration of intracellular cAMP. Phorbolesters were without significant effect on the hypertrophy or proliferation of AII-stimulated MCT cells or their rested controls. The transfection of MCT cells with reporter genes containing regulatory elements for type IV collagen revealed that the stimulatory effects of AII on collagen type IV depend, at least to some extent, on an increase in gene transcription. Agents increasing intracellular cAMP concentrations inhibited the AII-induced increase in transcription and secretion of collagen type IV, but had no effect on MCT cells grown in media without AII. Our findings provide evidence that AII-induced changes in tubular epithelium leading to the secretion of type IV collagen are mediated by a decrease in intracellular cAMP.

Cyclosporin A stimulates transcription and procollagen secretion in tubulointerstitial fibroblasts and proximal tubular cells

The brief study described in this report was undertaken to determine whether cyclosporin A had any direct effect on the expression of tubulointerstitial procollagens in cultured renal cells. Our findings indicate that murine tubulointerstitial fibroblasts secreted significantly more procollagen type I after the addition of cyclosporin A, whereas syngeneic proximal tubular cells expressed significantly more types I and IV procollagen after cyclosporin stimulation. These increases in procollagen gene product correlated concordantly with changes in the levels of cytoplasmic mRNA with procollagen-specific cDNA probes. Transfection of these fibroblasts and proximal tubular cells with chimeric gene constructs containing enhancer/promoter elements for alpha2(I) and alpha 1(IV) procollagen linked to a chloramphenicol acetyltransferase reporter gene indicates that the stimulatory effect of cyclosporin on procollagen expression depends, at least to some extent, on an increase in transcriptional activity.

Analysis of alpha 1 (I) procollagen alpha 1 (IV) collagen, and beta-actin mRNA in glomerulus and cortex of rabbits with experimental anti-glomerular basement membrane disease. Evidence for early extraglomerular collagen biosynthesis

Renal cortical and glomerular mRNA for alpha 1 (I) and alpha 1 (IV) collagen were measured by filter hybridization during experimental anti-glomerular basement membrane disease in the rabbit. The abundance of alpha 1 (IV) mRNA was 5 times greater in total RNA isolated from glomeruli as compared with whole renal cortex from normal rabbits. In contrast, there was no difference in the relative amounts of alpha 1 (I) procollagen mRNA in these two fractions. Four days after the administration of anti-glomerular basement membrane antisera, a time histologically characterized by glomerular inflammatory cell infiltration without crescent formation, beta-actin mRNA were increased 17-fold in glomeruli and 4-fold in whole renal cortex. Renal cortical mRNA for alpha 1 (I) and alpha 1 (IV) were increased 7-fold (p = 0.07) and 9-fold (p less than 0.05), respectively compared with normal rabbit kidney cortex. In contrast, there was no significant difference in the abundance of these mRNA in glomeruli at day 4. By day 7, cortical alpha 1 (I) and alpha 1 (IVP mRNA had increased 17- and 10-fold, respectively, and these transcripts had increased 13- and 7-fold in glomeruli. Cortical alpha 1 (I) mRNA remained elevated for 35 days. These data show that large changes in collagen mRNA levels occur early in this model of crescentic nephritis in the rabbit, and that extraglomerular collagen mRNA accumulates very rapidly when glomerular inflammation occurs. Extraglomerular collagen synthesis associated with intraglomerular inflammation may help to explain the common association of interstitial fibrosis with glomerulonephritis, particularly in the periglomerular area.

Rat intestinal basement membrane synthesis. Epithelial versus nonepithelial contributions

Mesenchymal-epithelial interactions play an important role during tissue differentiation and morphogenesis. The basement membrane, which separates these compartments, appears to be critical to these interactions by providing a substratum for cell adhesion, promoting cell polarity and the differentiated phenotype. Unlike other epithelia, gut enterocytes adhere to, and migrate along a thin basement membrane as they differentiate along the crypt-villus axis with a turnover rate of 48 to 72 hours (rat). The relative importance of the enterocytes or of the mesenchymal cells of the lamina propria to the maintenance of the basement membrane is unknown. As indirect indicators of basement membrane biosynthesis, we have measured, by filter hybridization with labeled cDNA probes, the relative abundance of mRNAs for laminin and collagen IV chains in enterocyte fractions representing the crypt-villus gradient of differentiation and in cells of the underlying lamina propria. In confirmation of a gradient, mRNA for histone H2B was present as a decreasing gradient from crypt to villus, the crypt fraction containing the mitotically active enterocytes being most enriched for this transcript and, in contrast, the mRNA for beta-actin was present as an increasing gradient from crypt to villus, paralleling the abundance of microvillus core structures. The mRNAs for alpha 1(IV) and alpha 2(IV) collagen and laminin B1 and B2 chains were most abundant in the lamina propria. Little, if any, collagen IV mRNA was detectable in the enterocyte fractions. In contrast, laminin B1 and B2 mRNAs were enriched in crypt enterocytes but the steady-state level of these transcripts decreased in the superficial villus enterocyte fractions. These data suggest that the components of the intestinal basement membrane are synthesized by both mesenchymal and entodermal-derived cells. Alterations in the intestinal basement membrane structure and in cell adhesion during enterocyte differentiation may be partly mediated by changes in laminin synthesis by the enterocyte.

In situ hybridization reveals temporal and spatial changes in cellular expression of mRNA for a laminin receptor, laminin, and basement membrane (type IV) collagen in the developing kidney

The appearance of extracellular matrix molecules and their receptors represent key events in the differentiation of cells of the kidney. Steady-state mRNA levels for a laminin receptor, the laminin B1, B2, and A chains, and the alpha 1-chain of collagen IV (alpha 1[IV]), were examined in mouse kidneys at 16 d gestation and birth, when cell differentiation is active, and 1-3 wk after birth when this activity has subsided. Northern analysis revealed that mRNA expression of laminin receptor precedes the alpha 1(IV) and laminin B chains whereas laminin A chain mRNA expression was very low. In situ hybridization reflected this pattern and revealed the cells responsible for expression. At 16 d gestation, laminin receptor mRNA was elevated in cells of newly forming glomeruli and proximal and distal tubules of the nephrogenic zone located in the kidney cortex. These cells also expressed mRNA for alpha 1(IV) and laminin chains. At birth, mRNA expression of receptor and all chains remained high in glomeruli but was reduced in proximal and distal tubules. At 1 wk after birth, expression was located in the medulla over collecting ducts and loops of Henle. Little expression was detectable by 3 wk. These results suggest that cellular expression of steady-state mRNA for laminin receptor, laminin, and collagen IV is temporally linked, with laminin receptor expression proceeding first and thereafter subsiding.

Increased deposition of basement membrane macromolecules in specific vessels of the spontaneously hypertensive rat

The genetically determined chronic hypertension manifested in the Spontaneously Hypertensive Rat (SHR) serves as a useful animal model for the study of human essential hypertension. One of the earliest morphologic changes observed in the vasculature of the SHR is the development of a thickened subendothelial space (SES). Neither the biochemical composition nor the anatomic distribution of this early subendothelial deposit has been definitively determined. By combining morphologic, immunologic, and molecular biological approaches, it was demonstrated that by 15 weeks the acellular subendothelial thickening in the vasculature of the SHR results at least in part from the increased synthesis and deposition of basement membrane macromolecules. Moreover, rather than being manifest systemically, this early connective tissue lesion appears to be localized primarily to the aorta and major branches off the aortic arch.

Macrorestriction mapping of COL4A1 and COL4A2 collagen genes on human chromosome 13q34

The genes for the alpha-1 and alpha-2 chains of type IV collagen (COL4A1 and COL4A2) map to the same chromosomal band (13q34) and have a high degree of nucleotide homology. We have used pulsed field gel electrophoresis and cloned COL4A1 and COL4A2 DNA fragments as molecular probes to construct a 1200-kb macrorestriction map which encompasses both genes. The two genes are located within a 340-kb region with the 3' end of COL4A2 and the 5' region of COL4A1 separated by at least 100 kb but not more than 160 kb. These genes, therefore, are two members of a gene cluster on chromosome 13q34.

Characterization of the promoter for the alpha 1 (IV) collagen gene. DNA sequences within the first intron enhance transcription

Two overlapping clones spanning 19 kilobase pairs (kb) of the 5' end of the alpha 1 (IV) collagen gene were isolated and found to contain a single exon which encoded the 5'-untranslated sequence and 84 base pairs of the signal peptide. The 5' end of this exon was determined to be the 5' end of the transcript by S1 nuclease protection and primer extension. The nucleotide sequence of 1 kb of the 5'-flanking DNA was extremely G + C-rich (greater than 70%) and contained two GC boxes and a putative cAMP regulatory sequence. The transcriptional regulation of the alpha 1 (IV) gene was studied with chimeric gene constructs utilizing 2.5 kb of the 5'-flanking sequence coupled to the gene for chloramphenicol acetyltransferase. Transfection of this construct into differentiating F9 cells resulted in low chloramphenicol acetyltransferase activity compared to beta-actin or Rous sarcoma virus long terminal repeat promoters, although these cells produce large amounts of collagen IV. Inclusion of a 2.7-kb sequence 2.3 kb downstream from the first exon in either orientation increased the transcription of the chloramphenicol acetyltransferase construct approximately 10-fold in F9 cells, but was not active in NIH 3T3 cells, which synthesize little collagen IV. These results indicate the presence of an enhancer within the first intron, which increases the expression of this gene.

Structure of the amino-terminal portion of the murine alpha 1(IV) collagen chain and the corresponding region of the gene

Collagen IV, the major structural component of basement membranes, is composed of two genetically distinct polypeptide chains, alpha 1(IV) and alpha 2(IV). We have isolated a 522-base-pair (bp) cDNA to the 5' portion of the murine alpha 1(IV) chain mRNA from a library constructed by specific primer extension of poly(A)+ RNA from differentiated F9 cells. This cDNA includes 141 bp of 5' untranslated sequence and encodes a signal peptide plus a portion of the amino-terminal cross-linking (7 S) domain. This cDNA clone was used to obtain the 5' portion of the murine alpha 1(IV) gene from which the nucleotide sequence of exons 1-6 was determined. Exon 1 (234 bp) codes for the 5' untranslated sequence, and the first 28 residues of the protein. The 5' untranslated sequence is highly conserved between the mouse and human species and has the potential to form three mutually exclusive stem-loop structures which may play a role in post-transcriptional regulation. Exons 2-6, which code for the 7 S domain, were found to be 60, 90, 45, and 63 bp in size. The exon structure for the helical portion of the 7 S domain is different from that of the major helical domain, suggesting that they evolved differently.

Altered mRNA expression of basement membrane components in a murine model of polycystic kidney disease

Basement membranes surround the renal tubules and have been shown to limit their distension in vitro. Therefore, it has been postulated that a defect in a basement membrane component(s) underlies the pathogenesis of polycystic kidney disease. Here we have studied a murine model of congenital polycystic kidney disease and found by immunohistology, that the components of the peri-cyst basement membrane appeared to diminish with time. We also measured mRNA levels for collagen IV and laminin, and found a different pattern than in the normal mouse kidney. In normal kidneys, mRNA levels for the B1 and B2 chains of laminin were maximal at birth, and at 1 week for the alpha 1(IV) chain of collagen IV. With all three chains, the levels then rapidly declined. In contrast, mRNA for the alpha 1(IV) chain in congenital polycystic kidneys was half normal 1 week after birth and then increased. Laminin B1 and B2 chain mRNA's were 80% of normal at 1 week but were maintained at that level. As a control, beta-actin mRNA was examined and found to remain constant in both normal and diseased kidneys. In situ hybridization of cRNA probes for the alpha 1(IV) chain confirmed that cells associated with cysts were the principal source of expression of these basement membrane mRNAs. Thus, there exists an abnormal regulation of basement membrane gene expression in congenital polycystic kidney disease. The first stage is characterized by reduced levels of expression. In the second stage, the levels are abnormally high, perhaps representing a compensatory synthesis of basement membrane as cysts enlarge.

The glomerular distribution of type IV collagen and laminin in human membranous glomerulonephritis

The glomerular distribution of type IV collagen and laminin, the major collagenous and noncollagenous components of the glomerular basement membrane, was studied by immunofluorescence microscopy in idiopathic and lupus membranous glomerulonephritis. Affinity-purified antibodies against type IV collagen reacted preferentially with the inner aspect and irregularly with the adjacent outer area of the thickened basement membrane. In contrast, laminin was detected along the inner aspect of the glomerular basement membrane, in subepithelial basement membrane protrusions ("spikes"), and in the newly formed basement membrane layer above the immune deposits. We conclude that type IV collagen and laminin do not codistribute in the newly formed matrix. This aberrant antigenic distribution may reflect a loss of coordinate biosynthesis or degradation of these matrix components by visceral epithelial cells.

Partial structure of the human alpha 2(IV) collagen chain and chromosomal localization of the gene (COL4A2)

We have isolated a 2.1-kb cDNA clone from a human placental library encoding part of the alpha 2 chain of collagen IV, a major structural protein of basement membranes. The DNA sequence encodes 446 amino acids in the triple-helical domain plus the 227 amino acids of the carboxy-terminal globular domain. The latter structure is composed of two homologous subdomains and is highly conserved between the alpha 1 and alpha 2 chains. The triple-helical domain contained seven interruptions of the Gly-X-Y repeat and these interruptions were in general larger than their counterparts in the alpha 1 chain. DNA from human rodent hybrid cell lines was analyzed under conditions in which there was no cross-hybridization of the alpha 2(IV) cDNA probe with the gene for the alpha 1(IV) collagen chain. An EcoRI fragment characteristic of the alpha 2 chain had a concordance of 0.97 with chromosome 13. This result was confirmed and extended with in situ localization of the gene at 13q34. Since the alpha 1(IV) gene has previously been localized to 13q34, the two type IV collagen genes reside in the same chromosome region (13q34), possibly in a gene cluster. The presence of the genes for type IV collagen chains on chromosome 13 excludes a primary role for these genes in adult polycystic kidney disease and X-linked forms of hereditary nephritis.

Studies on the formation of glomerular immune deposits in brown Norway rats injected with mercuric chloride

Brown Norway rats injected with mercuric chloride (HgCl2) develop autoantibodies which immunolocalize along the glomerular basement membrane at first in a linear pattern and then in a granular pattern. The aim of this study was to characterize the specificity of these antibodies and to investigate the mechanisms responsible for the formation of granular immune deposits in the subepithelial zone of the glomerular basement membrane. The rats were found to develop circulating anti-laminin, anti-type IV collagen, anti-heparan sulfate proteoglycan, and anti-entactin antibodies. Antibodies against laminin and type IV collagen were found in relatively high titers in the sera and were specifically concentrated in the nephritic kidneys. Antibodies eluted from the nephritic kidneys with either linear or granular deposits reacted with basement membrane antigens synthesized and secreted by cultured rat glomerular visceral epithelial cells. Thus, in this model, the interaction of anti-laminin and type IV collagen antibodies with antigens secreted by glomerular visceral epithelial cells might, together with other mechanisms, contribute to the formation of granular immune deposits in the subepithelial part of the glomerular basement membrane.

Genes for basement membrane proteins are coordinately expressed in differentiating F9 cells but not in normal adult murine tissues

We have obtained cDNA clones coding for the A, B1, and B2 chains of laminin by screening a cDNA library prepared from mouse EHS tumor poly(A)RNA in the lambda gt11 expression vector with polyclonal antibody against denatured laminin. These cDNA clones were used in combination with a cDNA clone coding for the alpha 1 type IV collagen chain to study the regulation of genes for these basement membrane proteins in retinoic acid-induced differentiating mouse F9 teratocarcinoma cells and in various adult murine tissues. The levels of mRNA for the laminin A, B1, and B2 chains and for the alpha 1 type IV collagen chain were increased simultaneously and reached a maximum at almost the same time during the differentiation of F9 cells, suggesting coordinate expression in these cells. The tissue levels of mRNA encoding for the basement membrane components, however, varied considerably. The highest level of the B1 chain mRNA was observed in kidney, whereas, the levels of mRNA for A and B2 chains were highest in heart. Almost the same levels of expression of the alpha 1(IV) collagen mRNA were found in kidney, lung, and heart. The results indicate that the expression of genes for the basement membrane proteins is not coordinately regulated in these tissues. It is thus possible that different subunit structures of the laminin molecule may exist in tissues.

The role of neutrophil membrane glycoprotein GP-150 in neutrophil adherence to endothelium in vitro

We have previously described two patients with a congenital defect in neutrophil function characterized by an inability to form pus. The patients' neutrophils lack a membrane glycoprotein of mol wt 150,000 daltons (GP-150) on analysis by SDS-PAGE. This glycoprotein is part of a membrane antigen complex recognized by the murine monoclonal antibody (MoAb) 60.3. Addition of MoAb 60.3 to normal neutrophils produces defects in chemotaxis and phagocytosis in vitro similar to those observed in the patients. Since neutrophil adherence to vascular endothelium is prerequisite to neutrophil emigration in vivo, we examined the interaction of the patients' neutrophils and normal neutrophils treated with MoAb 60.3 with cultured endothelium. Adherence was determined as the percentage of 51Cr-labeled purified peripheral blood neutrophils which remained adherent to plastic wells or endothelial monolayers after a 45-minute incubation at 37 degrees C. The percentage of neutrophils from patient 1 remaining adherent to uncoated, fibronectin-coated, or laminin-coated plastic was similar to that observed in normal neutrophils (55% to 84% adherence with normal neutrophils v 73% to 78% adherence with the patient's neutrophils and 63% to 82% adherence with MoAb 60.3-treated normal neutrophils). The adherence of the neutrophils from patient 1 and MoAb 60.3-treated normal neutrophils to human or bovine endothelium in serum-free medium was also not significantly different from that observed in normal neutrophils (less than 10% adherence with normal, MoAb 60.3-treated, and patient neutrophils). In medium containing 10% autologous or heterologous human plasma, however, the adherence of neutrophils from patient 1 or MoAb 60.3-treated normal neutrophils to endothelial monolayers was significantly reduced (35% +/- 7% of normal neutrophils in seven experiments). Although phorbol myristate acetate (PMA) (10 ng/mL) and calcium ionophore A23187 (10(-5) mol/L) markedly increased the adherence of normal neutrophils to endothelial monolayers in serum-free medium (40% to 85% adherence), neither agent increased the adherence of the neutrophils from patient 1 or normal neutrophils treated with MoAb 60.3 (less than 5% adherence). The adherence of PMA-activated neutrophils from patient 2 to endothelial monolayers was also markedly decreased when compared with that of normal neutrophils. Postsecretory cell-free supernatants from PMA-activated normal neutrophils failed to augment adherence of neutrophils from patient 1 (less than 5% adherence).(ABSTRACT TRUNCATED AT 400 WORDS)

The composition of glomerulosclerosis. I. Studies in focal sclerosis, crescentic glomerulonephritis, and membranoproliferative glomerulonephritis

The composition of glomerulosclerosis was examined in focal sclerosis, membranoproliferative glomerulonephritis, and crescentic glomerulonephritis, using antisera specific for laminin and collagen types III and IV. Mesangial sclerosis consisted exclusively of extracellular matrix found in normal glomeruli, as did small synechiae in focal sclerosis and all synechiae in membranoproliferative glomerulonephritis. The large synechiae in focal sclerosis and all stages of the developing crescents associated with vasculitis contained mainly interstitial collagen, type III, a component not found in normal glomeruli. In the latter there were also disruptions of Bowman's capsule and an increase in the number of periglomerular interstitial cells. These observations suggested that glomerulosclerosis varied in composition and distribution, and some types of crescentic glomerulonephritis may have arisen from either cells resident in the glomerulus or cells coming from the interstitial space.

Evidence for a stem cell common to hematopoiesis and its in vitro microenvironment: studies of patients with clonal hematopoietic neoplasia

The origin and nature of cells forming the in vitro microenvironment in long-term cultures of human marrow were studied in five patients with clonal myeloproliferative disorders who were heterozygous for glucose-6-phosphatase dehydrogenase (G6PD). The results showed that cells in the adherent stromal layer forming the in vitro microenvironment were derived from the same clonal progenitors involved by the neoplasm in the four patients whose diseases originated in multipotent stem cells. In contrast, stromal cells were derived from normal progenitors in a patient with acute non-lymphocytic leukemia whose clone showed differentiative expression confined to cells in the granulocytic lineage. Mixing experiments demonstrated that the G6PD type displayed by the adherent marrow stromal cells was not obscured by contaminating non-adherent hematopoietic cells or marrow fibroblasts. The data suggest the existence of a pluripotent cell in normal hematopoiesis that gives rise to hematopoietic cells and to their micro-environment.