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C K Abrass

Publications and source records attributed to C K Abrass.

At least 19 recordsLinked to original sources
PubMed2006

Abnormal development of glomerular endothelial and mesangial cells in mice with targeted disruption of the lama3 gene.

Mice with targeted disruption of the lama3 gene, which encodes the alpha3 chain of laminin-5 (alpha3beta3gamma2, 332), develop a blistering skin disease similar to junctional epidermolysis bullosa in humans. These animals also develop abnormalities in glomerulogenesis. In both wild-type and mutant animals (lama3(-/-)), podocytes secrete glomerular basement membrane and develop foot processes. Endothelial cells migrate into this scaffolding and secrete a layer of basement membrane that fuses with the one formed by the podocyte. In lama3(-/-) animals, glomerular maturation arrests at this stage. Endothelial cells do not attenuate, develop fenestrae, or form typical lumens, and mesangial cells (MCs) were not identified. LN alpha3 subunit (LAMA3) protein was identified in the basement membrane adjacent to glomerular endothelial cells (GEnCs) in normal rats and mice. In developing rat glomeruli, the LAMA3 subunit was first detectable in the early capillary loop stage, which corresponds to the stage at which maturation arrest was observed in the mutant mice. Lama3 mRNA and protein were identified in isolated rat and mouse glomeruli and cultured rat GEnCs, but not MC. These data document expression of LAMA3 in glomeruli and support a critical role for it in GEnC differentiation. Furthermore, LAMA3 chain expression and/or another product of endothelial cells are required for MC migration into the developing glomerulus.

Animals↗
PubMed2001

Insulin alters heterogeneous nuclear ribonucleoprotein K protein binding to DNA and RNA.

The interaction of the multimodular heterogeneous nuclear ribonucleoprotein (hnRNP) K protein with many of its protein and nucleic acid partners is regulated by extracellular signals. Acting as a docking platform, K protein could link signal-transduction pathways to DNA- and RNA-directed processes such as transcription, mRNA processing, transport, and translation. Treatment of hepatocyte culture with insulin increased K protein tyrosine phosphorylation. Insulin altered K protein interaction with RNA and DNA in vitro. Administration of insulin into mice had similar effects on K protein in liver. Coimmunoprecipitations of RNA with K protein revealed preferential in vivo K protein binding of a subset of transcripts, including the insulin-inducible c-fos mRNA. These results suggest a class of insulin pathways that signal nucleic acid-directed processes that involve K protein.

Animals↗
PubMed2001

Lupus nephritis: lessons from experimental animal models.

Lupus nephritis is a frequent and severe complication of SLE. In the last decades, animal models for SLE have been studied widely to investigate the immunopathology of this autoimmune disease because abnormalities can be studied and manipulated before clinical signs of the disease become apparent. In this review an overview is given of our current knowledge on the development of lupus nephritis, as derived from animal models, and a hypothetical pathway for the development of lupus nephritis is postulated. The relevance of the studies in experimental models in relationship with our knowledge of human SLE is discussed.

Animals↗
PubMed2001

A process for reducing workload and enhancing residents' education at an academic medical center.

Academic medical centers are under increasing pressure to find alternatives to residents for the provision of patient care and to expand and improve the educational opportunities for residents. To address these concerns, the authors performed a study of the medical wards at Harborview Medical Center, a county-owned medical center managed by the University of Washington School of Medicine. Admitting diagnoses, provider names, and billings were obtained from professional practice plan billing records. Based on the distribution of admitting diagnoses, a subset of patients was identified that could be removed from routine care by residents and could instead be cared for by non-physician providers (i.e., physician assistants and nurse practitioners) using clinical pathways. The cohort was large enough to reduce the number of patients per resident to within national accreditation guidelines, and to provide faculty with more time available for teaching. The authors summarize the approach used to identify the new model for care delivery indicated above and the plans made to implement that model and to analyze its impact on the quality of patient care, hospital costs, residents' education, and the process of implementing change. The authors conclude that solutions to the problems of workload and education that they confronted will vary by department and hospital setting. Yet a systematic approach to discovering solutions, such as they present, can be adapted to any setting.

Academic Medical Centers↗
PubMed2000

Differential expression of laminin chains and anti-laminin autoantibodies in experimental lupus nephritis.

Mice with chronic graft-versus-host disease (GvHD) develop a lupus-like disease with severe immune complex glomerulonephritis. Previous studies with this model have shown that anti-laminin autoantibodies are involved in immune complex formation and that glomerular laminin expression alters qualitatively. The present study investigated glomerular laminin chain expression and autoantibody reactivity with matrix antigens during disease development in mice with chronic GvHD, killed before and 6, 8, 10, and 11 weeks after disease induction, using antibodies raised against laminin chain peptides, in immunofluorescence and western blotting studies. Decreased glomerular expression of the laminin beta1 chain, unaltered expression of the laminin beta2 and gamma1 chains, and increased expression of the laminin alpha1 chain and filamin/actin-binding protein 280 (ABP 280) were found during disease progression. Furthermore, 4 weeks after disease induction, autoantibodies appeared which were reactive with laminin alpha1, beta1, beta2, and gamma1 chains, and filamin in rat mesangial cell matrix. Ten weeks after disease induction, autoantibodies reacted with filamin, and beta2 and gamma1 laminin chains. Autoantibodies reacted with laminin chains only and not with other proteins in matrices extracted from glomeruli of normal and diseased mice. Staining with H50, an anti-laminin alpha1 chain/anti-filamin monoclonal autoantibody derived from an MRL/lpr mouse with spontaneous lupus nephritis, confirmed these observations and showed identical anti-laminin/anti-filamin autoantibody reactivity in two different models for lupus nephritis. In summary, differential glomerular expression of laminin chains was found during the development of chronic GvHD. Concomitantly with expression of the laminin alpha1 chain and/or filamin in the glomerulus, anti-laminin alpha1 and/or anti-filamin reactivity was present, pointing towards a role for (neo) antigen expression in the epitope spreading of the immune response. Furthermore, glomerular expression of laminin beta1 decreased in conjunction with decreased presence of anti-laminin beta1 reactivity, presumably due to antigen masking or shedding of immune complexes into the urine. These changes in anti-laminin chain autoantibodies, with concomitant alterations in the glomerular expression of laminin chains, may aggravate progressive immune injury in this model for lupus nephritis.

Animals↗
PubMed2000

The nature of chronic progressive nephropathy in aging rats.

Increases in glomerular size and thickening of the glomerular basement membrane are constant features that accompany growth and maturation in animals. Yet, some animals have chronic progressive nephropathy characterized by glomerulosclerosis and tubulointerstitial fibrosis. In these animals, clinically significant reductions in glomerular filtration rate may compromise health, particularly when other renal diseases occur concomitantly. Progressive thickening of the glomerular basement membrane is accompanied by changes in its composition, which may be responsible for changes in podocyte morphology and proteinuria. Within the tubulointerstitium, generalized accumulation of fibronectin and thrombospondin are accompanied by blood vessel proliferation. Fragility of these blood vessels with intermittent bleeding may initiate an inflammatory process that leads to focal areas of tubular atrophy and scarring. The pathogenesis of these lesions is unknown. Genetic background, sex, and environmental factors influence the tempo of progressive sclerosis, although these factors are not primary determinants of this lesion. This review highlights the structural changes that occur in the kidney with aging. Because the lesions are structurally similar, information gleaned from studies of aging animals should be relevant to understanding the loss of renal function that occurs in aging humans.

Aging↗
PubMed2000

IGFBP-5(201-218) stimulates Cdc42GAP aggregation and filopodia formationin migrating mesangial cells.

BACKGROUND: We have previously shown that insulin-like growth factor-I (IGF-I) and IGF binding protein-5 (IGFBP-5) induce mesangial cell migration using separate stimulatory and effector pathways. The IGFBP-5 stimulatory pathway is mediated by the serine/threonine kinase IGFBP-5 receptor, which is activated by the carboxy-terminal peptide IGFBP-5201-218. In this study, we examined the direct effects of IGFBP-5201-218 on stimulatory and effector pathways that lead to a change in mesangial cell (MC) phenotype. METHODS: Rapid actin reorganization, formation of filopodia, and characterization of novel substratum attachment structures that develop during IGFBP-5-mediating migration were examined by light, immunofluorescence, and electron microscopy. Using a wounding assay, migration was measured after the addition of stimulants and inhibitors. RESULTS: Stimulation of MCs with IGFBP-5201-218 induces rapid actin reorganization and loss of peripheral focal adhesions. The MCs develop long cellular extensions where f-actin and beta-actin terminate in unique substratum attachments. Fluorescence microscopy of stimulated cells shows that Cdc42GAP aggregates within minutes following treatment with IGFBP-5201-218. In contrast, IGF-I increases staining for Rac-1, but not Cdc42GAP, in association with the formation of prominent leading lamellae without filopodia. Staurosporin inhibits cell migration and Cdc42GAP aggregation only when added within the first hour, suggesting that it inhibits the stimulatory effect of IGFBP-5201-218 by blocking the IGFBP-5 receptor serine/threonine kinase activity. CONCLUSIONS: These data demonstrate that IGFBP-5201-218 preferentially activates Cdc42 and induces the formation of long filopodia with unique substratum attachments that produce a novel mode of locomotion.

Actins↗
PubMed1999

Unique changes in interstitial extracellular matrix composition are associated with rejection and cyclosporine toxicity in human renal allograft biopsies.

Renal allograft loss from chronic rejection or cyclosporine toxicity (CsAT) is characterized by progressive interstitial fibrosis, yet the protein composition of these lesions is unknown. The normal tubular basement membrane (TBM) contains laminin (LM), collagen IV (containing collagen IV alpha chain 1 [COL4A1] and COL4A2), thrombospondin (TSP), and fibronectin (FN). Only TSP and FN extend beyond the TBM into the interstitial space. Very scanty amounts of interstitial collagens (I and III) are detected in the interstitium. In a pilot study of human renal allograft biopsy specimens, three patterns of extracellular matrix (ECM) composition were identified. Pattern 1 showed no change in ECM composition; pattern 2 showed generalized accumulation of collagens I and III in the interstitium; and pattern 3 showed new expression of COL4A3 and LM-beta2 in the proximal TBM. Criteria were established for the clinicopathological diagnosis of CsAT and rejection. These diagnoses were correlated with the ECM composition in 22 renal allograft biopsy specimens. Control groups were examined in a similar manner and included native kidney biopsy specimens from patients with other allografts (n = 7), renal biopsy specimens from patients with glomerular disease (n = 9), and renal allograft biopsy specimens from patients without clinicopathological evidence of renal disease. These data show that rejection is associated with pattern 3 and CsAT is associated with pattern 2. Thus, detection of ECM composition may be a useful adjunct to standard microscopy in distinguishing rejection from CsAT in renal allograft biopsy specimens. These data suggest that interstitial fibrosis associated with rejection and CsAT result from different pathogenic mechanisms.

Biopsy↗
PubMed1998

Rat mesangial cells express two unique isoforms of laminin which modulate mesangial cell phenotype.

Rat mesangial cells express two unique isoforms of laminin which can be modulated by culture medium composition. To define further the nature of laminin expressed by cultured rat mesangial cells, synthesis of individual laminin chains, as well as their trimeric association, was examined. Based on data from Northern analysis of mRNA expression, immunoblots, immunofluorescence staining and radioimmunoprecipitation of biosynthetically labeled proteins, mesangial cells express laminin beta1, beta2, and gamma1 chains. Mesangial cells do not express laminin alpha1 or alpha2. MC produce a unique alpha chain, designated alpha'm. These laminin chains assemble into two major isoforms. One contains alpha'mbeta1gamma1, co-precipitates with entactin and is assembled into the fibrillar extracellular matrix. The second isoform contains alpha'mbeta2 and a presumed gamma chain that migrates in gel slightly ahead of gamma1. The beta2-containing isoform is concentrated in punctate sites on the cell surface. In addition, mesangial cells display different phenotypes when plated on laminin-1 (alpha1beta1gamma1), as compared to purified beta2. An LRE-containing peptide of laminin beta2 serves as an attachment site for mesangial cells and is sufficient to induce the phenotype observed with intact beta2. These data suggest that laminin isoform expression plays an important role in mesangial cell phenotype and function.

Animals↗
PubMed1997

Heparin binding domain of insulin-like growth factor binding protein-5 stimulates mesangial cell migration.

Insulin-like growth factor I (IGF-I) binding protein-5 (IGFBP-5) is produced by mesangial cells (MCs) and likely functions to modulate glomerular IGF-I activity. Although IGFBP-5 may be inhibitory for IGF-stimulated MC activity, preliminary studies suggested that IGFBP-5 acts directly on MCs. To investigate this further, we evaluated the effects of IGFBP-5 on rat MC migration. We found that the carboxytruncated fragment, IGFBP-5-(1-169), inhibited IGF-I-stimulated migration, but intact IGFBP-5 simulated migration when IGF-I was not present. Demonstration that 125I-labeled IGFBP-5 directly binds to MCs further supports an independent role for IGFBP-5. Because heparin inhibited MC binding of 125I-IGFBP-5, we tested the heparin binding peptide, IGFBP-5-(201-218), for stimulatory activity. IGFBP-5-(201-218) stimulated MC migration, and this effect was inhibited by heparin. Because the disintegrin, kistrin, blocked IGF-I-induced migration but not migration induced by IGFBP-5-(201-218), the migratory induction mechanism for the two peptides is different. These data indicate that separate, specific regions of IGFBP-5 are responsible for interactive effects with IGF-I as well as direct effects on MC activity.

Amino Acid Sequence↗
PubMed1997

Insulin-like growth factor I (IGF-I) induces unique effects in the cytoskeleton of cultured rat glomerular mesangial cells.

Resident glomerular mesangial cells (MCs) have complex cytoskeletal organizations that maintain functional and structural integrity. The ability of cells to replicate, coordinate movement, change shape, and interact with contiguous cells or extracellular matrix depends on cytoskeletal organization. MCs synthesize insulin-like growth factor (IGF-I), express IGF-I receptors, and respond to IGF-I with increased proliferation. We noted that IGF-I treatment of mesangial cells was associated with a change in morphology. Therefore, these studies were undertaken to define specific IGF-I-mediated changes in cytoskeletal protein organization. Rat MCs were propagated from birth in culture without supplemental insulin. Quiescent, subconfluent cultures were treated with IGF-I (100 nM) for 1 hr. Rearrangements in f-actin, alpha-smooth muscle actin, beta-actin, vimentin, and vinculin were seen by fluorescence microscopy. As the cytoskeleton rearranged, alpha-smooth muscle actin dissociated from the f-actin bundles and beta-actin became polymerized under the leading lamellar edge. Ultrastructural changes were consistent with increased membrane turnover and metabolic activity. The normally sessile mesangial cell was induced by IGF-I to express a wound-healing phenotype characterized by movement and increased pinocytosis. These changes are different from those induced by insulin and have important implications for mesangial cell function.

Animals↗
PubMed1997

Diabetes induces changes in glomerular development and laminin-beta 2 (s-laminin) expression.

Offspring of diabetic mothers have developmental renal abnormalities; thus, we investigated the effects of the diabetic milieu on kidney development. Four groups of host rats, including insulin-deficient and insulin-treated streptozotocin-induced diabetic rats, normal controls, and insulin-treated nondiabetic rats, were prepared. After 38 days, rats received ocular implants of E14 fetal rat kidneys. Nine days later the fetal kidney grafts were harvested for analysis of glomerular development and expression of fibronectin, laminin, laminin-beta 2, and alpha-smooth muscle actin and m170, two additional markers of mesangial maturation. The rate of glomerular maturation was delayed in grafts placed in hyperglycemic, insulin-deficient diabetic rats. These glomeruli contained few mesangial cells or matrix, and laminin-beta 2 expression was reduced as compared with controls. Mesangial expression of alpha-smooth muscle actin and m170 was not detected. In contrast, grafts placed in insulin-treated diabetic animals had increased numbers of mesangial cells and expanded mesangial matrix. The content of laminin-beta 2 and expression of m170 and alpha-smooth muscle actin were also increased in these grafts. These data show that hyperglycemia and insulin status influence laminin isoform expression and play important roles in mesangial development.

Actins↗
PubMed1996

Endogenous origin of glomerular endothelial and mesangial cells in grafts of embryonic kidneys.

To address origins of glomerular endothelial and mesangial cells in embryonic mammalian kidneys, we established interspecies grafts between rats and mice, in which fetal kidneys were implanted into the anterior eye chamber of adult hosts. After 5-7 days, hosts bearing grafts received intravenous injections with species-specific monoclonal antibodies (MAbs) to matrix components. In all cases, glomerular basement membranes and mesangial matrices labeled solely for donor-derived matrix. Additionally, microvessel extracellular matrices within grafts were usually of donor origin. To examine directly the origin of glomerular endothelial and mesangial cells, we grafted embryonic gestational days 11-12 (E11-12) kidneys from normal mice into anterior eye chambers of host reverse-orientation splice acceptor 26 mice, which are transgenic animals that express beta-galactosidase in every cell. When grafts were developed for beta-galactosidase activity, host cells were seen in peripheral vessels, but the majority of glomerular endothelial cells were of donor, not host, origin. Where host-derived-endothelial cells were found in glomeruli, donor endothelial cells were present as well. Mesangial cells were always of donor origin. When E11 mouse kidneys were labeled with the endothelial cell-specific Bandeiraea simplicifolia isolectin B4, we determined that endothelial cells are present from the inception of metanephrogenesis. Together, the evidence shows that cells of endogenous kidney origin were almost entirely responsible for development of the glomerular microvasculature in oculo. External vessels from the host, although important for graft maintenance, were not major contributors to the glomerulus.

Animals↗
PubMed1996

Insulin induces rapid and specific rearrangement of the cytoskeleton of rat mesangial cells in vitro.

Mesangial cells (MCs) grown without supplemental insulin (SI-MCs) express a quiescent phenotype and extracellular matrix (ECM) composition similar to MCs in vivo. In contrast, MCs routinely propagated in insulin (SI+MCs) are stimulated to proliferate, change their phenotype, and produce large amounts of collagens I and III. These effects of insulin may in part be mediated through cytoskeletal rearrangement. Differences in cytoskeletal arrangement were compared between SI-MCs and SI+MCs and 1 hr after addition of insulin (1 nM) or IGF-1 (100 nM) to SI-MCs. Cells were examined by light microscopy, electron microscopy, and immunostaining for specific cytoskeletal proteins and fibronectin. Insulin induced rapid rearrangement of stress fibers. Surface ruffling, actin aggregation, vimentin retraction, rearrangement of vinculin in focal adhesions, and fibronectin extraction were apparent. These direct effects of insulin on the SI-MC cytoskeleton occurred before insulin-induced changes in ECM composition. IGF-I induced cytoskeletal reorganization distinct from insulin. These observations demonstrate that insulin and IGF-I have unique effects on the MC cytoskeleton, which is turn may mediate secondary ligand effects on MCs.

Animals↗
PubMed1995

Induction of nodular sclerosis by insulin in rat mesangial cells in vitro: studies of collagen.

These studies evaluated the contribution of insulin to the development of the abnormal mesangial matrix that characterizes diabetic nephropathy and is common to mesangial cells in culture. Glomeruli were isolated from a single rat and divided into two aliquots. In one set (SI-MC), the insulin contained in the medium was only that contributed by the fetal calf serum (20%). For the other set, the tissue culture medium was supplemented with 1 microM insulin (SI+MC). Mesangial cell outgrowths from each condition were isolated, cloned, and propagated. At passage 4, mesangial cells were characterized by morphology and cell markers, and compared in terms of composition and appearance of the secreted extracellular matrix. SI-MC grew in nests of cells surrounded by a thin layer of matrix that was rich in collagen IV. In contrast, mesangial cells supplemented with insulin aggregated into macroscopic "hillocks" rich in collagens I and III as described previously. Insulin (1 microM) or IGF-I (0.1 microM) was subsequently added to the medium of SI-MC. Insulin, but not IGF-I, induced a change in culture morphology and collagen accumulation characteristic of SI+MC. In contrast to SI+MC, SI-MC express insulin receptors and at physiologic concentrations insulin is a more potent stimulator of MC proliferation than is IGF-I. Insulin-induced changes in the collagenous composition of the accumulated ECM were directionally correlated with the rate of collagen I synthesis measured by biosynthetic labeling experiments and collagens III and IV as determined by ELISA. These data demonstrate that insulin alters the phenotype of mesangial cells in culture and their expression of interstitial and basement membrane collagens. These observations implicate insulin as a factor in the pathogenesis of mesangial matrix accumulation in diabetic nephropathy. Furthermore, a method for culturing mesangial cells that accumulate an extracellular matrix that is similar in composition to normal mesangial matrix provides a new model system for future studies of mesangial cell biology.

Animals↗
PubMed1995

Phenotypic modulation of rat glomerular visceral epithelial cells by culture substratum.

The interaction of cells with their supporting extracellular matrix influences cellular phenotype, cellular proliferation, protein synthetic profile, and specific gene activation. To examine the ability of culture substratum to modulate the phenotype expressed by glomerular epithelial cells (GEC) in culture, GEC were grown on plastic culture plates coated with collagen gels (Type I collagen, Vitrogen) or a complex matrix from the Englebreth-Holm-Swarm tumor (Matrigel). Cultures were examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). On untreated plastic, GEC grew in a random pattern. Cells were flat and thin with many filamentous processes. When grown on collagen I gels, GEC grew to confluence as a tight monolayer with typical cobblestone appearance. These cells demonstrated surface microvilli and a central cilium. TEM showed an epithelial appearance with tight junctions. When plated on the surface of Matrigel, GEC formed nests of cells that gradually burrowed into the gel. Proliferation on this matrix was extremely slow. TEM demonstrated that there are surface projections that abut the matrix and that the nests of cells are hollow with a central lumen. SEM demonstrated nests of cells that formed a sphere. Surface microvilli were not as abundant as cells grown on Vitrogen, and cilia were not seen. Cells could be removed from one surface, plated onto another, and would shift phenotype to that observed for subcultures primarily plated onto that surface. Cells on each complex substrate, as well as GEC plated on tissue culture plates coated with individual matrix proteins were biosynthetically labeled with (35S)methionine. The profile and rate of protein synthesis were modified by the plating substrate. These observations demonstrate that rat GEC can be induced to display variable phenotypes in culture that are determined by the plating substrate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗