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PubMed1989

Effect of platelet-derived transforming growth factor (TGF) type beta 1 on murine inflammatory mononuclear phagocytes: increased fibronectin production.

The effect of transforming growth factor type beta 1 (TGF-beta 1) on mononuclear phagocytes (macrophages), cells which play an important role in the inflammatory response resulting from tissue wounding, was investigated. We found that fibronectin production by murine inflammatory macrophages is significantly enhanced by highly purified human TGF-beta 1 in a time- and dose-dependent manner. Specifically, 2 pM TGF-beta 1 was sufficient to cause significant elevation of fibronectin levels, which peaked between 24 and 48 hr of incubation. Both TGF-beta 1-induced and basal levels of fibronectin were completely abolished by cycloheximide, suggesting that protein synthesis was required. Furthermore, fibronectin mRNA levels were significantly enhanced in TGF-beta 1-treated macrophages. The inductive capacity of TGF-beta 1 appeared specific since other agents such as phorbol myristate acetate and endotoxin failed to induce fibronectin production. Since macrophages have been recently shown to secrete an inactive form of TGF-beta 1, the ability of this precursor molecule to induce fibronectin production was tested. It was found that partially purified human platelet latent TGF-beta 1 could not induce fibronectin synthesis, whereas acid treatment of the same preparation which releases mature TGF-beta 1 enhanced fibronectin production. Taken together, results presented here suggest that inflammatory macrophages can directly contribute to the formation of extracellular matrix upon interaction with TGF-beta 1 and that these cells lack the ability to augment fibronectin production in response to a platelet-derived latent form of TGF-beta 1.

Animals↗
PubMed1983

An immunofluorescent study of the distribution of fibronectin and laminin during limb regeneration in the adult newt.

Fibronectin and laminin are two extracellular glycoproteins which are involved in various processes of cellular development and differentiation. The present investigation describes changes in their distribution during regeneration of the newt forelimb, as determined by indirect immunofluorescence. The distribution of fibronectin and laminin was similar in normal limb tissue components. These glycoproteins were localized in the pericellular region of the myofibers corresponding to its basement membrane; the perineurium and endoneurium of the nerves; and the basement membranes of blood vessels, skin epithelium, and dermal glands. The cytoplasm of myofibers, axons, skin epithelium, and bone matrix lacked fluorescence for both glycoproteins. After limb amputation in the regenerating blastema, extensive presence of fibronectin, but not laminin, was seen in and around the undifferentiated blastemal cells. Increased fluorescence for fibronectin was also seen during blastema growth, blastemal cell aggregation, and early stages of redifferentiation. As redifferentiation continued, staining for fibronectin slowly disappeared from the cartilage matrix and the myoblast fusion zone. Laminin was first observed around the regenerated myotubes; this was followed by the appearance of fibronectin suggesting a sequential formation of these two components of the new myotube basement membrane. In the regenerated limb, the distribution of laminin and fibronectin was similar to that seen in normal limb. Based on the distribution pattern of these glycoproteins, it is concluded that fibronectin may play an important role in blastemal cell aggregation, cell alignment, and initiation of redifferentiation. After redifferentiation, both laminin and fibronectin may be important in the determination of the architecture of the regenerated limb.

Animals↗
PubMed1984

Expression of different regional patterns of fibronectin immunoreactivity during mesoblast formation in the chick blastoderm.

The appearance and distribution of the extracellular material glycoprotein, fibronectin, was investigated in gastrulating chick embryos using affinity-purified anti-human plasma fibronectin antibodies. Preservation of tissue structure and immunoreactivity was carried out by ethanol/acetic acid fixation or by formaldehyde/glutaraldehyde fixation. Using the former fixation method, fibronectin immunoreactivity was detected (1) at the ventral surface of the upper layer or epiblast, mainly anterior and lateral to Hensen's node, in regions where middle-layer or mesoblast cells are not yet present, and (2) sparsely in extracellular spaces of the deep layer. Using the latter fixation method, fibronectin immunoreactivity was, moreover, found at the entire ventral surface of the upper layer, i.e., also at the epithelial-mesenchymal interface, where a basement membrane was previously described. At the light microscope level, we could not detect significant immunoreactivity in the middle layer. Treatment of sections of ethanol-fixed blastoderms with testicular hyaluronidase before immunostaining for fibronectin partially demasked the antigenic sites of this glycoprotein at the epithelial-mesenchymal interface. The present report indicates that the different regional patterns of fibronectin immunoreactivity in the basement membrane of the upper layer are spatially and temporally correlated with migration and positioning of mesoblast cells. These regional patterns are probably due to differences in the composition of fibronectin-associated material such as chondroitin sulfate A and/or C proteoglycans, and/or hyaluronate, before and after mesoblast expansion, rather than to differences in the distribution of fibronectin itself. In this respect. In this respect, it is noteworthy that the chemical composition of the basement membrane of an epithelium changes as mesenchyme cells migrate over it. The results also favor the idea that fibronectin is a structural component of the whole basement membrane which is used as a substrate for migration of mesenchymal cells.

Animals↗
PubMed1986

Fibronectin is expressed by astrocytes cultured from embryonic and early postnatal rat brain.

In early primary cultures from newborn rat brain, few glial fibrillary acidic protein (GFAP)-positive glial cells expressed intracytoplasmic immunoreactivity for fibronectin. After the second week in culture, however, fibronectin was expressed by a distinct population of GFAP-positive flat astrocytes, irrespective of which brain region was studied. In cerebellar cultures, these cells were more abundant than in cortical or neostriatal cultures and often formed a major population of the GFAP-positive cells. The difference in fibronectin expression between cerebellum and the other areas studied was statistically significant. When cultures were started from 9-day-old postnatal rat brain, fibronectin-positive astrocytes appeared earlier than in those from newborn animals, in all areas studied. Further, especially in the case of cerebellum, the number of fibronectin-positive astrocytes increased as a function of time in culture. In cultures started from whole brains of 12-day-old rat embryos, fibronectin was expressed within 24 h in culture by all the cells with morphology of flat astrocytes, positive for vimentin but negative for GFAP. These results indicate that astrocytes cultured from newborn and early postnatal rat brain are a heterogeneous population of cells: depending on the brain region studied and also depending on the age of brain tissue or the time in culture, less than 1-60% of the GFAP-positive flat astrocytes expressed fibronectin. This, together with the fact that fibronectin was present in early embryonic brain cells in culture, suggests that fibronectin may be a prerequisite for the development or interactions of brain cells.

Animals↗
PubMed1984

Oral triiodothyronine administration lowers plasma fibronectin levels in humans.

It has been shown that both serum triiodothyronine (T3) and plasma fibronectin values decline with fasting and increase with treatment of diabetic ketoacidosis in a paralles manner. To evaluate the mechanism responsible for these changes, we examined the effects of both oral T3 administration and fasting in six healthy, adult subjects. Initial plasma fibronectin values were normal in four subjects (group 1) and decreased in two subjects (group 2). Initial serum T3 and thyroxine (T4) values were normal in both groups. Despite a substantial rise in serum T3 values with oral T3 administration, plasma fibronectin fell in group 1 subjects. Fasting caused a significant decline in serum T3 levels, but only a small further decline of plasma fibronectin concentrations. Serum T3 levels rose after 1 week of refeeding, whereas plasma fibronectin levels in group 1 did not return toward normal. Plasma fibronectin values did not change in group 2 subjects with oral T3, fasting, or refeeding. In conclusion, there is no simple cause-and-effect relationship between previously observed changes in plasma fibronectin and serum T3 concentrations. High doses of oral T3 will lower plasma fibronectin levels in subjects with initially normal plasma fibronectin values and a normal caloric intake.

Administration, Oral↗
PubMed1981

Primordial germ cells of Xenopus embryos: the role of fibronectin in their adhesion during migration.

Primordial germ cells (PGCs) of Xenopus laevis are highly migratory. The last section of their migratory pathway is through the dorsal mesentery of the tadpole gut. This in vivo pathway is rich in fibronectin, a glycoprotein that promotes cell adhesion and migration in vitro. Isolated PGCs are associated with cells from the mesentery and with fibronectin. Treatment with trypsin removes both the mesentery cells and the fibronectin. The PGCs do not appear to resynthesize detectable fibronectin in vitro. In contrast, cultured adult mesentery epithelial cells synthesize large amounts of fibronectin and lay it down in subcellular fibrils that align with intracellular microfilament bundles. PGCs plated on cultured mesentery cell layers adhere to them, elongate and align with the microfilament bundles of the mesentery cells. PGCs adherent to mesentery cell layers are closely associated with fibronectin; moreover, F(ab)2 fragments of anti-Xenopus fibronectin IgG inhibit the adhesion and spreading of PGCs on the mesentery. These results indicate that PGCs can adhere to mesentery cells via fibronectin produced by the latter cells and suggest that fibronectin may be involved in the migration of PGCs in vivo.

Animals↗
PubMed1990

Changes in fibronectin distribution in the developing peripheral nervous system of the chick.

The relationship of peripheral nerves with fibronectin was examined at different stages of the chick embryo using double immunofluorescent staining. Neurons were stained with a monoclonal antibody (E/C8) against intermediate filaments in neuronal processes, and fibronectin was stained with polyclonal antibodies. Prior to axonal outgrowth, fibronectin was distributed in a meshwork throughout the mesenchyme. However, soon after the initiation of axonal outgrowth, fibronectin began to disappear along neuronal pathways. Thus, during the period of active axonal growth, all neural tissues were marked by the striking absence of fibronectin. Interestingly, fibronectin reappeared along peripheral pathways soon after projection patterns were established. The presence of fibronectin in the substrate on which axons grow suggests that fibronectin may provide a permissive substrate for axon extension. The disappearance of fibronectin upon axon arrival suggests that neurons may modify the substrate of their pathway during outgrowth.

Animals↗
PubMed1984

Virus-binding activity of fibronectin: masking of hepatitis A virus.

Human plasma fibronectin interacts with viruses. When fibronectin-containing human sera negative for antibodies to hepatitis A virus (HAV) were added to suspensions of HAV, radioimmunological detection of HAV was reduced. This masking effect seemed to depend on the fibronectin concentration of the sera: plasma fibronectin purified by cryoprecipitation and affinity chromatography showed a masking effect on purified HAV which was dependent on the concentrations of fibronectin and HAV. Fibronectin peptides were obtained by subtilisin digestion: the non-collagen-binding regions of the fibronectin molecule were involved in the binding of HAV. We conclude that fibronectin has a virus-binding activity which interferes with radioimmunological methods for virus detection, and may contribute to the frequent transmission of hepatitis viruses by blood products enriched in fibronectin.

Adult↗
PubMed1982

Immunochemical analysis of fibronectin using monoclonal antibodies.

Cloned hybrid cell lines secreting antibodies directed against human plasma fibronectin were prepared according to the methods of Kohler and Milstein (Kohler, G. and Milstein, C. (1975) Nature (London) 256, 495-497 and (1976) Eur. J. Immunol. 6, 511-519). The specificity of each monoclonal antibody for fibronectin was established from autoradiograms of radioimmunoprecipitates following SDS-polyacrylamide gel electrophoresis. The monoclonal antibodies were reactive with both native and SDS-denatured fibronectin. Ascites fluids obtained from infected isogenic mice precipitated 85-95% of the 125I-labelled fibronectin radioactivity in indirect radioimmunoprecipitation tests. Localization of specific epitopes to restricted regions of the fibronectin molecule was carried out by monitoring monoclonal antibody binding to proteolytic fragments. Of the five monoclonal antibodies analyzed in this study, three recognized determinants which resided in the terminal 35 kDa region of the fibronectin monomer. Furthermore, these epitopes were localized to fragments as small as 20 kDa. Competition studies carried out using plasma fibronectins isolated from different species revealed that three monoclonal antibodies recognized sites which were relatively conserved, while two monoclonal antibodies recognized epitopic sequences which were unique to the human protein. The corresponding anti-fibronectin serum also demonstrated discriminatory capabilities. Immunofluorescent analysis of human fibroblasts grown in vitro demonstrated that all the monoclonal antibodies tested were reactive with pericellular fibronectin.

Animals↗
PubMed1984

Fibronectin-induced protein carboxy-O-methylation in aortic endothelial cells.

In a previous report (Bowersox, J.C. and Sorgente, N. (1982) Cancer Res. 42, 2547-2551) we demonstrated that the glycoprotein fibronectin is a chemoattractant for vascular endothelial cells. In probing the mechanisms by which fibronectin induces endothelial cell chemotaxis, we have discovered that the carboxy-O-methylation of cellular proteins is stimulated by fibronectin. By measuring the incorporation of L-[methyl-3H]methionine into alkali-labile, [3H]methyl ester linkages, we determined that fibronectin stimulated protein carboxy-O-methylation in aortic endothelial cells in a time- and concentration-dependent manner; the greatest stimulation occurred at 100 micrograms/ml fibronectin (approx. 35% above controls). When inhibitors of carboxymethylation were added, fibronectin-induced stimulation of protein methylation did not occur. Furthermore, inhibitors of methylation prevented the chemotaxis of endothelial cells in response to fibronectin. These data support our hypothesis that fibronectin mediates endothelial cell chemotaxis, such as that occurring during neovascularization. As carboxy-O-methylation of cell proteins is also effected by fibronectin, transmethylation reactions may be an important component of endothelial cell chemotaxis.

Adenosine↗
PubMed2006

Selective use of fetal fibronectin detection after cervical length measurement to predict spontaneous preterm delivery in women with preterm labor.

OBJECTIVE: The purpose of this study was to determine whether selective use of fetal fibronectin detection after ultrasound measurement of cervical length predicts preterm delivery in symptomatic patients better than either indicator alone. STUDY DESIGN: This prospective blinded study performed both tests on 359 women hospitalized for preterm labor between 18 and 34 completed weeks' gestation. The primary outcome was preterm delivery before 35 weeks'gestation. RESULTS: Among the 359 women included, 48 (13.4%) delivered before 35 weeks' gestation. The sensitivity, specificity, and positive and negative predictive values of cervical length < or = 25 mm were 75%, 63%, 24%, and 94%, respectively, and of fetal fibronectin > or = 50 ng/mL, 63%, 81%, 33%, and 93%. Fetal fibronectin detection was significantly (P < .001) more specific than cervical length measurement. For selective use of fetal fibronectin detection after cervical length measurement, the test was considered positive if cervical length was < or = 15 mm or if cervical length was between 16 and 30 mm with fetal fibronectin > or = 50 ng/mL. The predictive values of this test were not significantly different from those of fetal fibronectin detection (67%, 81%, 36%, and 94%). This strategy could have avoided 200 fibronectin tests. CONCLUSION: Selective use of fetal fibronectin detection after cervical length measurement is more specific than cervical length and as effective as fetal fibronectin assays in the entire population of women in preterm labor for predicting preterm birth.

Adult↗
PubMed1994

Fetal fibronectin in patients at increased risk for premature birth.

OBJECTIVE: The objective of this study was to evaluate fetal fibronectin as a screening test for subsequent preterm birth in asymptomatic pregnant women. STUDY DESIGN: Eighty-seven pregnant women at increased risk for preterm birth underwent weekly sampling of cervicovaginal secretions beginning in the middle of the second trimester and continuing until delivery or until 34 weeks of gestation, with quantitative measurement for fetal fibronectin. In addition, assessment of cervical dilatation, uterine activity, and tocolytic therapy was performed with each sampling. Preterm birth was the specific outcome measured, and the correlation of fetal fibronectin with this outcome was determined. RESULTS: Overall, 31% of the patients experienced a spontaneous preterm birth. As a predictor for delivery before 37 completed weeks of gestation, the presence of fetal fibronectin had a sensitivity of 92.6%, a specificity of 51.7%, a positive predictive value of 46.3%, and a negative predictive value of 93.9%. For delivery before 34 weeks, fetal fibronectin had a sensitivity of 92.3% and a negative predictive value of 97.8%. By means of logistic regression analysis a positive fetal fibronectin result was highly significantly correlated with preterm birth (odds ratio 3.8, p < 0.001) and more so than the presence of four or more uterine contractions per hour, tocolytic therapy, or cervical dilatation of > or = 2 cm. The addition of contractions, tocolytic therapy, or cervical dilatation to a positive fetal fibronectin result did not increase the predictive capacity of a positive fetal fibronectin alone. CONCLUSION: Fetal fibronectin in the cervicovaginal secretions of asymptomatic patients has potential value as a screening test in the identification of patients at risk for preterm birth. This test had equally high sensitivity and negative predictive value for birth before 37 weeks.

Adult↗
PubMed1997

The preterm prediction study: patterns of cervicovaginal fetal fibronectin as predictors of spontaneous preterm delivery. National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network.

OBJECTIVE: Our purpose was to determine how various temporal patterns of fetal fibronectin positivity from 24 to 30 weeks predict subsequent fetal fibronectin test results and spontaneous preterm delivery. STUDY DESIGN: A total of 2929 women had vaginal and cervical fetal fibronectin tests obtained at least once at 24, 26, 28, or 30 weeks, and 1870 women had tests performed at all four gestational ages. Fetal fibronectin values > or = 50 ng/ml were considered positive. Various patterns of positive and negative tests were evaluated for prediction of (1) whether the next fetal fibronectin test would be positive or negative and (2) the percent of women with a spontaneous preterm delivery > or = 4 weeks after the last fetal fibronectin test at < 30, < 32, < 35, and < 37 weeks' gestational age. RESULTS: Women with previous negative test results had only a 3% chance of a subsequent positive test result; however, if the last test result was positive, 29% of the next tests were positive. Of the 1870 women with tests at 24, 26, 28, and 30 weeks, 89% had all negative results, 8.4% had one positive result, 1.8% had two positive results, and 0.8% had three or four positive results. The higher the percent of positive tests at 24 to 26 weeks, at 28 to 30 weeks, or at 24 to 30 weeks, the greater the risk of subsequent spontaneous preterm birth. As an example, the risk of spontaneous preterm birth at < 30 weeks for women with two negative fetal fibronectin test results at 24 and 26 weeks was 0.3% versus 16% for women with two positive results. CONCLUSION: The presence of a positive cervical or vaginal fetal fibronectin test result predicts subsequent positive fetal fibronectin positivity and subsequent spontaneous preterm birth. The greater the percent of positive results, the higher is the risk of spontaneous preterm birth. After a positive test result, two negative results are required before the risk of spontaneous preterm birth returns to baseline.

Cervix Uteri↗
PubMed1997

Fetal fibronectin as a predictor of preterm birth in patients with symptoms: a multicenter trial.

OBJECTIVE: Our aim was to determine whether the presence of fetal fibronectin in vaginal secretions of patients with symptoms suggestive of preterm labor predicts preterm delivery. STUDY DESIGN: Patients who were examined at the hospital between 24 weeks' and 34 weeks 6 days' gestation with intact membranes, no prior tocolysis, symptoms suggestive of preterm labor, and cervical dilation < 3 cm were recruited at 10 sites. Swabs of the posterior fornix were assayed for the presence of fetal fibronectin by monoclonal antibody assay, with a positive result defined as > or = 50 ng/ml. Results were not available to the managing physicians. Tocolysis was used when clinically indicated after specimen collection. RESULTS: A total of 763 patients had fetal fibronectin results and pregnancy outcome data available for analysis. Fetal fibronectin was detected in specimens from 150 (20%) patients. Compared with patients who had negative results, patients who had positive results for fetal fibronectin were more likely to be delivered within 7 days (relative risk 25.9 [95% confidence interval 7.8 to 86]), within 14 days (relative risk 20.4 [95% confidence interval 8.0 to 53]), and before 37 completed weeks (relative risk 2.9 [95% confidence interval 2.2 to 3.7]). The negative predictive values for delivery within 7 days, within 14 days, and at < 37 weeks were 99.5%, 99.2%, and 84.5%, respectively. When we used multiple logistic regression analysis to control for potential confounding variables among singleton pregnancies, only the presence of fetal fibronectin (odds ratio 48.8, 95% confidence interval 7.4 to 320), prior preterm birth (odds ratio 8.3, 95% confidence interval 1.5 to 46.6), and tocolysis (odds ratio 4.1, 95% confidence interval 1.0 to 16.0) were associated with birth within 7 days; fetal fibronectin (odds ratio 3.6, 95% confidence interval 2.2 to 5.9), prior preterm birth (odds ratio 2.5, 95% confidence interval 1.4 to 4.4), cervical dilatation > 1 cm (odds ratio 2.9, 95% confidence interval 1.6 to 5.2), and tocolysis (odds ratio 4.5, 95% confidence interval 2.8 to 7.2) were all independently associated with delivery before 37 weeks. CONCLUSION: In a population of patients with symptoms, the presence of fetal fibronectin in vaginal secretions best defines a subgroup at increased risk for delivery within 7 days; the high negative predictive value of fetal fibronectin sampling supports less intervention for patients with this result.

Adult↗
PubMed1986

Characterization of human fibronectin glycopeptides from cystic fibrosis and control skin fibroblasts.

Fibronectins isolated from different species and tissue sources are glycosylated differently. We report here a characterization of the glycopeptides of fibronectin isolated from the culture medium of skin fibroblasts from patients with cystic fibrosis together with age-, race-, and sex-matched control subjects. The characterization of this fibronectin is of special interest because it is derived from: a non-fetal, cellular source; eight different individuals; and cystic fibrosis and control individuals. The fibronectin glycopeptides were purified by gel-permeation chromatography and Con A-Sepharose and were analyzed by anion-exchange chromatography and affinity columns of immobilized 5-hydroxytryptamine and lectins. One half of the glycopeptides of skin fibroblast fibronectin were shown to contain biantennary oligosaccharides which were core-fucosylated and partially sialylated. Although the remaining half was a complex mixture of glycopeptides, there was remarkably little inter-individual variation. No difference between cystic fibrosis and control subjects was discernible by the techniques employed here. Unlike the biantennary glycopeptides of human plasma fibronectin, those from skin fibroblast fibronectin were core-fucosylated and less highly sialylated. However, compared to human cellular fibronectin glycopeptides from fetal sources, those from skin fibroblast fibronectin were both more highly fucosylated and sialylated.

Adolescent↗
PubMed1996

Angiotensin II induction of fibronectin biosynthesis in cultured human mesangial cells: association with CREB transcription factor activation.

We assessed the effect of angiotensin II on fibronectin biosynthesis a nd transcription factor activation in adult human mesangial cells in culture. We found that 10(-5) mol/L angiotensin II tended to increase fibronectin mRNA expression within 1 hour (1.2-fold +/- 0.3-fold of that in controls), with a significant increase after 4 hours (0.3-fold +/- 0.1-fold of that in controls, p < 0.05) and 24 hours (1.9-fold +/- 0.3-fold of that in controls, p < 0.02). In conjunction with increased fibronectin mRNA levels, angiotensin II exposure resulted in a significant elevation in immunoreactive fibronectin concentrations and the incorporation of (35S)-labeled methionine into fibronectin after 2 hours (224% +/- 23% of controls, p < 0.05). Angiotensin II also induced mesangial cell activation of the cyclic adenosine monophosphate response element binding protein (CREB) transcription factor, a DNA binding protein known to recognize specific regulatory elements present on the fibronectin gene promoter. Using the electrophoretic mobility shift assay, we showed that angiotensin II increased mesangial cell expression of the activated form of CREB after 4 hours (1.2-fold +/- 0.04-fold of that in controls, p < 0.05). To determine the importance of the CREB regulatory elements in mediating angiotensin II induction of fibronectin gene transcription, JEG-3 cells were transfected with plasmids containing fibronectin promoter-chloramphenicol acetyltransferase (CAT) reporter gene constructs with (FN510) or without (FN122) the CREB regulatory motifs. Angiotensin II resulted in a significant increase in CAT activity in FN510 transfectants (1.6-fold +/- 0.2-fold of that in controls, p < 0.05), but there was no effect of angiotensin II on FN122 transfected cells. These data demonstrate that angiotensin II stimulates fibronectin biosynthesis in adult human mesangial cells and suggest that the process may be regulated at the transcriptional level.

Angiotensin II↗
PubMed1996

Short- or long-term effects of a low-protein diet on fibronectin and transforming growth factor-beta synthesis in Adriamycin-induced nephropathy.

Increased synthesis and gene expression of fibronectin or transforming growth factor-beta (TGF-beta) have been reported to be involved in the progressive process of doxorubicin hydrochloride (Adriamycin)-induced nephropathy. In the present study, the effects of dietary protein restriction on the synthesis and gene expression of fibronectin or TGF-beta were investigated by immunoprecipitation, Northern blotting, and TGF-beta bioassay in this model after subjects were given either short- or long-term low-protein diets. In the long-term diet experiment, either a normal protein diet (NPD, 20%) or low-protein diet (LPD, 5%) was fed to the Adriamycin rats for 8 weeks after the injection of Adriamycin. An 8-week LPD significantly ameliorated kidney destruction and remarkably reduced the fibronectin synthesis. Furthermore, the significant decreases of the latent TGF-beta secretion and the expression of TGF-beta 1 mRNA were observed in the Adriamycin rats fed an 8-week LPD. In the short-term diet experiment, an NPD or LPD was fed to the Adriamycin rats for 2 weeks at weeks 4, 8, or 16 after the injection of Adriamycin. A 2-week LPD did not ameliorate kidney damage. Although fibronectin synthesis by the renal cortex in the Adriamycin rats was remarkably reduced by a 2-week LPD, there was no significant decrease in the latent TGF-beta secretion in the Adriamycin rats. The mRNA expressions of fibronectin or TGF-beta 1 were not affected by a 2-week LPD in the Adriamycin rats at any stage. In conclusion, decreased fibronectin and TGF-beta synthesis may be one of the mechanisms by which the long-term dietary protein restriction ameliorates kidney damage. On the other hand, a 2-week LPD affected the only fibronectin synthesis, which thus suggested that an LPD might exert a quicker influence on the protein synthesis of fibronectin than on the transcriptional events of fibronectin.

Animals↗
PubMed1992

In vitro particulate adherence to fibronectin: correlation with in vivo particulate adherence to sites of bladder injury.

This study examined the role of fibronectin in promoting particulate attachment to sites of urothelial injury. Variables influencing adherence of the rat transitional carcinoma cell line 4909 and "non-cellular" styrene-divinylbenzene microspheres to fibronectin were studied in an in vitro system. A soluble synthetic peptide fragment (Gly-Arg-Gly-Asp-Ser [GRGDS]) duplicating the receptor binding domain of fibronectin (RGD) was used to determine whether cell adherence could be inhibited by fibronectin receptor blockade. In vitro findings were correlated with an in vivo assay of both cellular and non-cellular particulate adherence to injured urothelium. Time, plated cell density, substrate concentration, GRGDS concentration, and cell viability, were all found to be significant independent variables influencing in vitro cellular adherence (p less than 0.0001). Receptor blockade with GRGDS significantly decreased in vitro tumor cell adherence to fibronectin. In vitro microsphere binding increased as a direct function of fibronectin concentration but was not time dependent (p less than 0.0001 and p = 0.14 for fibronectin concentration and time respectively). The in vivo adherence of both tumor cells and microspheres was significantly increased in injured bladders compared to controls (p less than 0.01). Receptor blockade with GRGDS failed to inhibit in vivo cell adherence to sites of urothelial injury. Microspheres proved to be competitive inhibitors of cellular adherence in competitive binding assays. In vitro microsphere binding demonstrated a pH dependence with maximal binding at pH 7.2. These data suggest that in vitro tumor cell adherence to fibronectin differs from in vivo tumor cell adherence to sites of urothelial injury. Manipulations which inhibit in vitro adherence, specifically fibronectin receptor blockade and cell death, fail to effect in vivo binding to the extreme that non-cellular particulate appears to bind to the same site, and with similar affinity, as cellular particles.

Animals↗