Biomedical subjects

J L Barnes

Publications and source records attributed to J L Barnes.

At least 19 recordsLinked to original sources

PubMed2004

Adaptive immunity in melioidosis: a possible role for T cells in determining outcome of infection with Burkholderia pseudomallei.

Melioidosis is a potentially fatal disease caused by the bacterium Burkholderia pseudomallei. Individuals with subclinical melioidosis have no apparent clinical signs or symptoms, and are identified only by positive serology. The present study is the first to investigate cell-mediated immune (CMI) responses following in vitro stimulation with B. pseudomallei antigens in peripheral blood mononuclear cells (PBMC), collected under field conditions in Papua New Guinea (PNG) from individuals with exposure to B. pseudomallei (n = 13). While five had a clinical history of melioidosis (C(+)), the remaining individuals (n = 8) were seropositive, yet healthy with no clinical history of melioidosis (S(+)/C(-)). Proliferation and IFN-gamma production were significantly greater in lymphocyte cultures from S(+)/C(-) individuals compared to C(+) individuals (P < 0.001 and P < 0.05, respectively). These findings demonstrate that compared to C(+) patients, individuals with subclinical melioidosis have a stronger CMI response to B. pseudomallei antigens in vitro. Such a response may be essential for protection against disease progression.

Adolescent↗

PubMed2004

Age associated alterations in costimulatory and adhesion molecule expression in lupus-prone mice are attenuated by food restriction with n-6 and n-3 fatty acids.

Costimulatory and adhesion molecules are known to play a major role in the pathogenesis of systemic lupus erythematosus. Since fish oil and calorie restriction have been reported to attenuate the development of disease in lupus prone (NZBxNZW)F1 mice, the objective of this study was to assess the expression of these key inflammatory molecules in these mice fed diets differing in n-6 and n-3 fatty acid content and fed either food restricted or ad libitum. Age-associated increases in the expression of CD28, ICAM-1, and PGP-1 molecules that are involved in the recruitment of inflamed lymphocytes into the kidney were attenuated in mice restricted in food intake. The increase in costimulatory (CD80 and CD86) and adhesion (ICAM-1, PGP-1, LFA-1, and Mac-1) in peripheral blood mononuclear cells was also attenuated by food restriction and to a lesser extent by fish oil alone. Interestingly, amelioration of lupus (laminin expression and proteinuria) correlated with the above beneficial effects and could be seen even in 24-month-old mice. In summary, food restriction and fish oil delay the onset of lupus disease and increase life span in B/W mice by prolonging the maintenance of a youthful immune phenotype.

Age Factors↗

PubMed2001

Induction of multiple chemokine and colony-stimulating factor genes in experimental Burkholderia pseudomallei infection.

Melioidosis is a disease of the tropics caused by the facultative intracellular bacterium Burkholderia pseudomallei. In human infection, increased levels of IFN-gamma in addition to the chemokines interferon-gamma-inducible protein 10 (IP-10) and monocyte interferon-gamma-inducible protein (Mig) have been demonstrated. However, the role of these and other chemokines in the pathogenesis of melioidosis remains unknown. Using BALB/c and C57BL/6 mice as models of the acute and chronic forms of human melioidosis, the induction of mRNA was assessed for various chemokines and CSF (G-CSF, M-CSF, GM-CSF, IP-10, Mig, RANTES, MCP-1, KC and MIP-2) in spleen and liver following B. pseudomallei infection. Patterns of chemokine and CSF induction were similar in liver and spleen; however, responses were typically greater in spleen, which reflected higher tissue bacterial loads. In BALB/c mice, high-level expression of mRNA for all chemokines and CSF investigated was demonstrated at day 3 postinfection, correlating with peak bacterial load and extensive infiltration of leucocytes. In contrast, increased mRNA expression and bacterial numbers in C57BL/6 mice were greatest between 4 and 14 days following infection. This paralleled increases in the size and number of abscesses in liver and spleen of C57BL/6 mice at days 3 and 14 postinfection. Earlier induction of cytokine-induced neutrophil chemoattractant (KC), macrophage inflammatory protein-2 (MIP-2), monocyte chemoattractant protein-1 (MCP-1), granulocyte-macrophage CSF (GM-CSF) and macrophage CSF (M-CSF) mRNA was demonstrated in spleen, while MIP-2, MCP-1, IP-10 and Mig were demonstrated in liver of BALB/c mice when compared to spleen and liver of C57BL/6. The magnitude of cellular responses observed in the tissue correlated with increased levels of the chemokines and CSF investigated, as well as bacterial load. Compared with C57BL/6 mice, greater infiltration of neutrophils was observed in liver and spleen of BALB/c mice at day 3. In contrast, early lesions in C57BL/6 mice predominantly comprised macrophages. These results suggest that the inability of BALB/c mice to contain the infection at sites of inflammation may underlie the susceptible phenotype of this mouse strain towards B. pseudomallei infection.

Animals↗

PubMed2000

Platelet-derived growth factor receptor beta regulates migration and DNA synthesis in metanephric mesenchymal cells.

Platelet-derived growth factor (PDGF) B-chain and PDGF receptor beta (PDGFR beta) are essential for glomerulogenesis. Mice deficient in PDGF B-chain or PDGFR beta exhibit an abnormal glomerular phenotype characterized by total lack of mesangial cells. In this study, we localized PDGFR beta in the developing rat kidney and explored the biological effects of PDGF in metanephric mesenchymal cells in an attempt to determine the mechanism by which PDGF regulates mesangial cell development. Immunohistochemical and in situ hybridization studies of rat embryonic kidneys reveal that PDGFR beta localizes to undifferentiated metanephric mesenchyme and is later expressed in the cleft of the comma-shaped and S-shaped bodies and in more mature glomeruli in a mesangial distribution. We also isolated and characterized cells from rat metanephric mesenchyme. Metanephric mesenchymal cells express vimentin and alpha-smooth muscle actin but not cytokeratin. These cells also express functional PDGFR beta, as demonstrated by autophosphorylation of the receptor as well as activation of phosphatidylinositol 3 kinase in response to PDGF B-chain homodimer. PDGF B-chain also induces migration and proliferation of metanephric mesenchymal cells. Taken together with the fact that PDGF B-chain is expressed in the glomerular epithelium and mesangial area, as demonstrated in the human embryonic kidney, we suggest that PDGF B-chain acts in a paracrine fashion to stimulate the migration and proliferation of mesangial cell precursors from undifferentiated metanephric mesenchyme to the mesangial area. PDGF B-chain also likely stimulates proliferation of mesangial cell precursors in an autocrine fashion once these cells migrate to the glomerular tuft.

Animals↗

PubMed1999

Differential expression of thrombospondin and cellular fibronectin during remodeling in proliferative glomerulonephritis.

Thrombospondin-1 (TSP-1) and an alternatively spliced fibronectin (Fn)-EIIIA isoform are adhesive proteins associated with embryogenesis and tissue remodeling. We compared, by immunohistochemistry and in situ hybridization, the course of TSP-1 and Fn-EIIIA expression in a model of glomerulonephritis induced by Habu snake venom (HV) and characterized by mesangial cell migration, proliferation, and extracellular matrix (ECM) synthesis. At 24 hr after HV, TSP-1 and Fn-EIIIA proteins localized in the central aspects of lesions associated with platelets and macrophages and at the margins of lesions coinciding with mesangial cell migration (determined by Thy-1 staining). Mesangial cells at this time expressed TSP-1 but not Fn-EIIIA mRNA. TSP-1 protein and mRNA peaked in lesions at 48 hr and were associated with cell proliferation (determined by PCNA, alpha-smooth muscle actin phenotype, and expression of beta-PDGF receptor mRNA). TSP-1 expression declined at 72 hr when expression of ECM synthesis peaked, as determined by increased expression of collagen Type IV, laminin, and TGF-beta1 protein and mRNA. Mesangial cell expression of Fn-EIIIA was first observed at 48 hr and was most abundant at 72 hr after HV. Therefore, platelet- and macrophage-derived Fn-EIIIA and TSP-1 in early lesions are associated with mesangial cell migration. Mesangial cell upregulation of TSP-1 is associated with migration and proliferation but not maximal ECM accumulation, whereas mesangial cell expression of Fn-EIIIA is associated with proliferation and ECM accumulation. These results suggest distinctive temporal and spatial roles for TSP-1 and Fn-EIIIA in remodeling during glomerular disease. (J Histochem Cytochem 47:533-543, 1999)

Animals↗

PubMed1999

Expression of embryonic fibronectin isoform EIIIA parallels alpha-smooth muscle actin in maturing and diseased kidney.

In this study we examined if an association exists between expression of an alternatively spliced "embryonic" fibronectin isoform EIIIA (Fn-EIIIA) and alpha-smooth muscle actin (alpha-SMA) in the maturing and adult rat kidney and in two unrelated models of glomerular disease, passive accelerated anti-glomerular basement membrane (GBM) nephritis and Habu venom (HV)-induced proliferative glomerulonephritis, using immunohistochemistry and in situ hybridization. Fn-EIIIA and alpha-SMA proteins were abundantly expressed in mesangium and in periglomerular and peritubular interstitium of 20-day embryonic and 7-day (D-7) postnatal kidneys in regions of tubule and glomerular development. Staining was markedly reduced in these structures in maturing juvenile (D-14) kidney and was largely lost in adult kidney. Expression of Fn-EIIIA and alpha-SMA was reinitiated in the mesangium and the periglomerular and peritubular interstitium in both models and was also observed in glomerular crescents in anti-GBM nephritis. Increased expression of Fn-EIIIA mRNA by in situ hybridization corresponded to the localization of protein staining. Dual labeling experiments verified co-localization of Fn-EIIIA and alpha-SMA, showing a strong correlation of staining between location and staining intensity during kidney development, maturation, and disease. Expression of EIIIA mRNA corresponded to protein expression in developing and diseased kidneys and was lost in adult kidney. These studies show a recapitulation of the co-expression of Fn-EIIIA and alpha-SMA in anti-GBM disease and suggest a functional link for these two proteins.

Actins↗

PubMed1999

Regulation of renal laminin in mice with type II diabetes.

This study examines the regulation of renal laminin in the db/db mouse, a model of type II diabetes characterized by extensive remodeling of extracellular matrix. Immunohistochemistry demonstrated an increase in the contents of laminin chains including beta1 chain in the mesangium and tubular basement membranes at 1, 2, 3, and 4 mo of diabetes. Immunofluorescence with an antibody against the recently discovered laminin alpha5 chain showed that in the normal mouse, the protein had a restricted distribution to the glomerular and tubular basement membranes with scant expression in the mesangium of older mice. In the diabetic mouse, the laminin alpha5 chain content of the glomerular and tubular basement membranes was increased, with marked expression in the mesangium. Northern analysis revealed a significant decrease in the renal cortical contents of alpha5, beta1, and gamma1 chain mRNA in the diabetic mice compared to control, at each of the time points. In situ hybridization showed decreased abundance of alpha5 transcripts in the glomeruli of diabetic mice compared to nondiabetic controls. Analysis of mRNA changes by Northern and in situ hybridization studies demonstrated that the reduction in laminin transcripts involved both glomerular and tubular elements. These observations demonstrate that laminin accumulation in the db/db mice with type II diabetes is due to nontranscriptional mechanisms. Because previous investigations in rodents with type I diabetes have shown that the increase in renal laminin content was associated with a corresponding increment in laminin chain transcript levels, it appears that the mechanisms underlying augmentation in renal matrix laminin content may be distinct in the two types of diabetes.

Animals↗

PubMed1998

Thrombin regulates PDGF expression in bovine glomerular endothelial cells.

The proteolytic enzyme thrombin is produced during activation of the coagulation pathway. Intraglomerular fibrin deposition and thrombosis are common pathologic features of several glomerular diseases, including transplant rejection. The effect of thrombin on platelet-derived growth factor (PDGF) production and DNA synthesis in well characterized bovine glomerular endothelial cells (G/endo) was studied. DNA synthesis was measured as the amount of [3H]thymidine incorporated into acid-insoluble material. PDGF released in the supernatant was measured by Western blotting and by a radioreceptor assay. PDGF mRNA expression was analyzed by solution hybridization, using human genomic PDGF B-chain (c-sis) and A-chain cDNA probes. G/endo constitutively secrete PDGF activity in serum-free medium. Thrombin stimulates PDGF production and increases the expression of mRNA that hybridizes with labeled B-chain but not A-chain probe, whereas epidermal growth factor and transforming growth factor-alpha stimulate the expression of PDGF A-chain mRNA. In addition, thrombin stimulates DNA synthesis with a peak effect at 24 h. Unlike endothelial cells from other microvascular beds, G/endo did not respond to any of the three PDGF isoforms BB, AB, or AA. These data demonstrate that bovine G/endo produce PDGF and that thrombin stimulates de novo synthesis of PDGF from these cells. Because mesangial, but not bovine, G/endo express PDGF receptors, PDGF released by G/endo is likely to modulate mesangial cell functions such as proliferation and matrix production by means of a paracrine mechanism.

Animals↗

PubMed1997

Calorie restriction decreases platelet-derived growth factor (PDGF)-A and thrombin receptor mRNA expression in autoimmune murine lupus nephritis.

Calorie restriction (CR) and supplementation with fish oil (FO) are known to increase the life span and diminish histological evidence of glomerulonephritis in lupus prone (NZB x NZW)F1 (B/W) mice. Cellular proliferation is an important pathological element in the development of lupus nephritis, and we have examined the expression of thrombin receptor (TR) and the mitogenic agents PDGF-A and -B. Weanling B/W mice were fed either ad libitum or a calorie restricted (CR; 40% less calories than ad libitum) diet supplemented with either 5% (w/w) corn oil (CO) or FO. CR animals consumed 2.7-3.0 g of wet food per day versus 4.5-5.0 g for the ad libitum animals. Renal RNA was extracted from young (3.5-4.0 months of age) and old (8-10 months of age) mice. Densitometric analysis (reference gene GAPDH) of blots from Northern (PDGF-A and -B) and ribonuclease protection assays (TR) produced the following data: (i) in young mice no signal was detected for PDGF-A, -B and TR in all four groups, while the signals were readily detectable in old mice; (ii) in old mice low and similar levels of PDGF-B were detected, and neither CR nor the source of lipid altered its expression; (iii) CR significantly inhibited PDGF-A and TR expression in both CO (ad libitum versus CR; PDGF-A, 3.25-fold, P < 0.025; TR, 3.7-fold, P < 0.01) and FO (ad libitum versus CR; PDGF-A, 4.56-fold, P < 0.01; TR, 3.6-fold, P < 0.025) groups; (iv) although FO (versus CO) produced a trend towards decreased expression, results were not statistically significant. We conclude that suppression of renal disease in lupus-prone mice by CR is accompanied by decreased expression of PDGF-A and the thrombin receptor.

Animals↗

PubMed1997

Platelets in glomerular disease.

Platelets are viewed as inflammatory cells and play an important role in hemostasis and wound repair. During activation, platelets secrete a wide variety of products that have multiple effects on target cell behavior during tissue remodeling. Among these secretory products are chemotactins, growth factors and fibrogenic substances. This review examines evidence for a role of platelets in glomerular disease and discusses mechanisms of how platelet secretory products may alter permselectivity of the glomerular basement membrane, resulting in enhanced immune complex localization. Also, platelet secretory products may stimulate glomerular remodeling after injury through mechanisms involving cell migration, proliferation and extracellular matrix synthesis, ultimately distorting the normal glomerular architecture and function.

Blood Platelets↗

PubMed1996

Inhibition of mesangial cell proliferation by platelet factor 4.

Platelet factor 4(PF4), an abundant platelet secretory product, is a strong candidate for modulating glomerular pathology. Because PF4 might be released from platelets and influence intrinsic cell growth during glomerular injury, the effect of PF4 on fetal calf serum- and platelet-derived growth factor (PDGF)-induced mesangial cell mitogenesis was examined. Mitogenesis was measured as the amount of 3H-thymidine incorporated into acid-precipitable material as well as by autoradiography. The effect of PF4 on mesangial cell expression of mRNA for PDGF A chain and transforming growth factor-beta (TGF-beta 1) was also examined. Fetal calf serum (10%)- and PDGF (10 ng/mL)-stimulated increases in mesangial cell 3H-thymidine incorporation were inhibited by incremental concentrations of PF4 (1 to 25 micrograms/mL) showing a maximum reduction of approximately 80% at 25 micrograms/mL of PF4. PF4 was effective when added 24 h before and 1, 4, and 8 h, but not 16 h after the addition of PDGF, indicating that inhibition occurred at delayed events in cell-cycle regulation. PF4 inhibited PDGF-induced increments in mRNA encoding PDGF A chain and TGF-beta 1. Also, PF4 did not interfere with PDGF receptor binding. The results of this study show that PF4 is a negative regulator of mesangial cell proliferation and suggest an interference in cell growth by pathways associated with modulation of the autocrine growth factors PDGF and TGF-beta 1.

Animals↗

PubMed1995

Expression of plasminogen activator-inhibitor-1 (PAI-1) during cellular remodeling in proliferative glomerulonephritis in the rat.

Pericellular proteolysis involves the plasminogen activator/plasmin system and plays an important role in cell remodeling involving cell migration and extracellular matrix turnover. Studies in this laboratory have previously characterized a model of proliferative glomerulonephritis induced by Habu snake venom (HSV) in the rat that involves cell migration, proliferation, and extracellular matrix accumulation. Because plasminogen activator-inhibitor-1 (PAI-1) has been used as a marker for cell migration as well as matrix accumulation, we were interested in examining the temporal and spatial expression and cellular sources of PAI-1 mRNA and translated protein over the course of HSV-induced proliferative glomerulonephritis. The results showed a highly localized and progressive expression of PAI-1 mRNA and translated protein by in situ hybridization and immunohistochemistry at the margins and periphery of glomerular lesions 8 and 24 hr after HSV. The expression of PAI-1 in glomerular lesions localized to the same sites as mesangial cell marker proteins, desmin and Thy-1.1, indicating that mesangial cells synthesize this important regulator proteolysis. Few cells expressed PAI-1 in the central aspects of glomerular lesions at later time intervals (48 and 72 hr) when cell proliferation and expression of extracellular matrix (fibronectin protein and mRNA) were maximal. Therefore, the expression of PAI-1 in this model was associated more with early events related to cell migration than with proliferation or extracellular matrix synthesis. These observations support the hypothesis that the plasminogen activator/plasmin system is involved in cell migration in early remodeling during glomerular disease.

Animals↗

PubMed1995

Expression of alternatively spliced fibronectin variants during remodeling in proliferative glomerulonephritis.

Fibronectin (Fn) plays an important role in tissue remodeling during embryogenesis, wound repair, and vascular disease, and is thought to regulate cellular processes such as cell adhesion, migration, proliferation, and differentiation through specialized domains within the molecule. In addition, Fn can be alternatively spliced at three regions: extradomains EIIIA, EIIIB, and a variable segment V, potentially giving rise to functionally distinct variants of the molecule. We have previously shown a sequential expression of cellular Fn first by platelets, followed by macrophages, then mesangial cells in habu snake venom-induced proliferative glomerulonephritis (Am J Pathol 145: 585-597, 1994). These studies examined the cellular sources and glomerular localization of Fn in general but did not distinguish between the various alternatively spliced isoforms. In this study, we examine by in situ hybridization and immunohistochemistry the temporal expression and cellular sources of EIIIA, EIIIB, and V in a model of proliferation glomerulonephritis that has cell migration, proliferation, and extracellular matrix synthesis as features of tissue remodeling. Macrophages were the first cells to express Fn mRNA showing an EIIIA+, EIIIB-, and V95+ pattern beginning at 8 hours after habu snake venom injection. Migrating mesangial cells at the margins of early lesions (8 and 24 hours) did not overexpress mRNA encoding these Fn variants, but immunofluorescence microscopy revealed V95 and EIIIA protein at the margins of lesions. EIIIB was absent in lesions at this time. At 48 hours and peaking at 72 hours after habu snake venom injection, mesangial cells in central aspects of glomerular lesions expressed abundant mRNA and protein for V95 and EIIIA. EIIIB mRNA and protein was slight in the mesangium at these times. Parietal epithelial cells, particularly adjacent to glomerular lesions, also expressed abundant mRNA and protein for all three variants throughout the course of the disease, beginning at 24 hours after habu snake venom injection. Expression of mRNA and protein for all three isoforms declined by 2 weeks after habu snake venom injection. These studies show that migrating mesangial cells do not require their own synthesis of Fn and suggest that they might rely on exogenous sources of Fn, particularly V95+ and EIIIA+ forms. Commencement of enhanced expression of EIIIA and EIIIB mRNA and protein by resident glomerular cells coincided with the temporal course of cell proliferation, acquisition of alpha-smooth muscle cell actin phenotype, and matrix synthesis, suggesting that Fn isoforms have specific functions during the course of glomerular remodeling.

Alternative Splicing↗

PubMed1995

In situ hybridization in the study of the kidney and renal diseases.

In situ hybridization (ISH), combined with immunohistochemistry, has become a powerful tool in the investigation of temporal and spatial relationships between specific cellular sources of mRNA and ultimate localization of translated protein. This review provides a discussion on basic ISH methods and a comprehensive examination of the literature on applications of ISH to the study of nephrogenesis, normal kidney, and renal disease. The review covers literature examining expression of mRNA encoding growth factors, proteins involved in signal transduction and transcription, proteolysis, extracellular matrix and a variety of other products involved in regulating cell remodeling during nephrogenesis. Expression of mRNA encoding many of these products diminishes in normal adult renal tissue, only to be reactivated during renal disease. Such a recapitulation of the expression of mRNAs involved in nephrogenesis might indicate that similar cellular events are required for remodeling during renal disease. In addition, ISH has allowed for the investigation of interactions between cells intrinsic to the kidney and inflammatory cells (and their biologically active products) recruited from exogenous sources. Although diagnostic use of ISH is currently limited, the implications for the use of this methodology in future clinical applications is promising.

Adult↗

PubMed1994

Developmental changes in rat renal 11 beta-hydroxysteroid dehydrogenase.

11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) transforms endogenous glucocorticoids to their respective "biologically inert" 11-dehydro derivatives. A decrease in enzyme activity allows glucocorticoids to induce mineralocorticoid-like renal sodium retention. Since positive sodium balance is required for optimum growth in the newborn, we hypothesized that renal 11 beta-OHSD activity would be low in the postnatal period, a time of active growth. To test this, incubations with corticosterone were carried out using minces or homogenates prepared from kidneys of newborn, 8-day-old, and mature Sprague-Dawley rats. 11 beta-OHSD activity in renal minces, assessed by the percent of corticosterone (10(-8) M) transformed to 11-dehydrocorticosterone (compound A), was significantly lower in the newborn kidney (newborn 45.7 +/- 3.8%, 8 day 70.2 +/- 3.8%, and adult 73.4 +/- 3.1%, P < 0.001 1 vs. 8 day). Parallel studies were conducted using an antibody directed against liver 11 beta-OHSD counter stained with immunofluorescent labeled IgG. Kidneys from mature rats were brightly stained at S2 and S3 segments of proximal tubules. In contrast, staining was barely detectable in kidneys from the newborn and 8-day-old rats. When enzyme kinetics were examined in kidney homogenates (average protein concentration 2.5 mg/ml) in the presence of 200 microM NADP+, the apparent Km for corticosterone in the adult was 4.42 x 10(-6) M with a corresponding Vmax of 1.33 x 10(-9) mol/min/mg protein, while the apparent Km for corticosterone in the newborn was calculated to be 12.8 x 10(-8) M with a Vmax of 2.08 x 10(-11) mol/min/mg protein.(ABSTRACT TRUNCATED AT 250 WORDS)

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1994

Sequential expression of cellular fibronectin by platelets, macrophages, and mesangial cells in proliferative glomerulonephritis.

Fibronectin (Fn) regulates cell migration, proliferation, and extracellular matrix formation during embryogenesis, angiogenesis, and wound healing. Fn also promotes mesangial cell migration and proliferation in vitro and contributes to extracellular matrix formation and tissue remodeling during glomerular disease. In this study, we examined, by immunohistochemistry and in situ hybridization, the temporal glomerular localization and cellular sources of Fn in Habu snake venom (HSV)-induced proliferative glomerulonephritis. Early HSV-induced glomerular lesions consisted of microaneurysms devoid of resident glomerular cells and filled with platelets, leukocytes, and erythrocytes. Over the course of the disease, mesangial cells migrated into the lesions, proliferated, and formed a confluent cellular mass. Fn was present in lesions beginning at 8 hours, with highest intensity at 72 hours and diminishing at 2 weeks after HSV. Staining for Fn at 8 and 24 hours after HSV was attributed to platelets and macrophages. In situ hybridization and phenotypic identification of cell types within lesions revealed macrophages as the predominant source of cellular Fn mRNA at these times. At 48 hours after HSV, Fn mRNA was expressed in proliferating mesangial cells in addition to macrophages. Most cells in lesions at 72 hours after HSV were mesangial, at a time when expression of Fn mRNA peaked. Cellular expression for Fn mRNA and translated protein declined at 2 weeks after HSV. These studies support the hypothesis that Fn, derived from platelets and macrophages, provides a provisional matrix involved with mesangial cell migration into glomerular lesions. Fn produced by mesangial cells might contribute to the formation of a stable extracellular matrix.

Animals↗

PubMed1994

Mesangial cell migration precedes proliferation in Habu snake venom-induced glomerular injury.

BACKGROUND: Mesangial cells migrate in response to platelet released products in vitro (Am J Pathol 1991;138:859). Cell migration, in addition to proliferation might play a role in cell remodeling during the course of proliferative glomerular disease. EXPERIMENTAL DESIGN: In this study, we examined mesangial cell migration in vivo in a platelet-dependent model of proliferative glomerulonephritis induced by Habu snake venom. Mesangial cell migration was assessed by phenotypic identification and temporal location of mesangial cells within glomerular lesions in serial time studies from 8 to 48 hours after Habu snake venom. Autoradiography of [3H]thymidine incorporation into cells was employed to identify and temporally separate cell division and proliferation from cell motility and other related events. RESULTS: Early (8-hour) lesions consisted of microaneurysms devoid of mesangial cells. By 24 hours, glomeruli showed mesangial cells at the margins of lesions adjacent to intact glomerular tufts, followed by the presence of clusters of cells at 30 and 36 hours. By 48 hours, most lesions were filled with proliferating mesangial cells. Cells containing [3H]thymidine were rarely observed until 30 hours, at which point they were found in advanced lesions. Marginating cells did not contain [3H]thymidine, suggesting that the location of these cells was not related to cell division but rather to migration. Platelet depletion eliminated platelets from lesions and substantially retarded mesangial cell migration into glomerular lesions indicating mesangial cell migration is, in part, dependent on platelets or their secretory products. CONCLUSIONS: These studies show that mesangial cells can migrate in vivo and suggest that cell migration is an important early step in cell redistribution and remodeling during glomerular injury in this model of proliferative glomerulonephritis.

Animals↗

PubMed1993

Human rheumatoid factor cross-idiotypes. IV. Studies on WA XId-positive IgM without rheumatoid factor activity provide evidence that the WA XId is not unique to rheumatoid factors and is distinct from the 17.109 and G6 XIds.

The WA cross-idiotype (XId) is the major XId among human monoclonal rheumatoid factors (mRF) and is almost always associated with the light (L) chain XId, 17.109, and the heavy (H) chain XId, G6. A cell line, 35G6, was cloned that bears the WA XId, but shows no reactivity with immunoglobulin G (IgG) and is negative for the 17.109 and G6 XIds. The 35G6 L chain appears to be derived from the same VKIII-JKI genes as most WA mRFs L chains. In contrast to the WA mRFs H chains in which VH1 genes are used, the 35G6 IgM expresses a VH3 gene. Sequence comparisons with other WA XId-positive mRF suggested several common structural features that may be related to the WA XId and differences that may relate to lack of IgG reactivity. Cells similar to 35G6 have previously been described in pokeweed mitogen-stimulated cell lines of peripheral blood lymphocytes from normal individuals and patients with rheumatoid arthritis and type II mixed cryoglobulinemia. These observations were confirmed, and in addition, it was shown that the majority of WA XId-positive cells in these cultures were negative for the 17.109 and G6 XIds. The presence of the WA XId in the absence of IgG reactivity suggests that the WA XId is more directly associated with an antigen specificity other than IgG, and its association with RF activity may be incidental. It is postulated that these WA XId-positive RF-negative antibodies may serve a physiologic role as natural antibodies to a pervasive pathogen, and that IgG reactivity is a consequence of somatic diversification accompanying proliferation of the WA XId-positive RF-negative cell.

Amino Acid Sequence↗