SEARCH · Search PubMed

Results for “Fibronectins”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources

PubMed1996

Fibronectin and fibronectin fragments modulate the expression of proteinases and proteinase inhibitors in human periodontal ligament cells.

Fragments of the matrix molecule fibronectin (FN) have been shown to modulate tissue remodeling activity by inducing matrix metalloproteinases (MMPs) in synovial fibroblasts. These molecules could contribute to the tissue degradation that occurs during periodontal disease if they also modulate the expression of proteinases in cells of the periodontal ligament (PDL). We tested the hypothesis that FN and specific FN fragments induce the expression of specific proteinases in PDL cells. Using substrate zymograms, reverse zymograms and Western immunoblots, we found that PDL cells constitutively express 72 kDa gelatinase, urokinase-type plasminogen activator (uPA) and at least three inhibitors whose molecular masses correspond to those of the tissue inhibitors of metalloproteinases (TIMPs). A fourth, previously uncharacterized, proteinase inhibitor of approximately 22 kDa was also observed in some cell isolates. PDL cells, when exposed to a 120 kDa proteolytic FN fragment containing the cell-binding domain, were induced to express collagenase and stromelysin and also demonstrated an increased secretion of the serine proteinase uPA. Expression of collagenase increased with increasing concentrations (0.001 microM-1 microM) of the 120 kDa FN fragment. This fragment also induced the expression of a 20 kDa inhibitor, but not of the higher-molecular-mass inhibitors, in PDL cells. The observed alterations in proteinases were associated specifically with the 120 kDa FN fragment, since similar responses were not seen when PDL cells were exposed to either a 60 kDa heparin-binding FN fragment or a 45 kDa collagen/gelatin-binding FN fragment. PDL cells exposed to intact FN did not express the proteinases induced by the 120 kDa fragment but did express 92 kDa gelatinase and the 20 kDa proteinase inhibitor. These data suggest that FN and specific FN fragments can differentially induce the expression of proteinases in PDL cells. Thus, functional regions of FN may modulate many of the functions of PDL cells that contribute to periodontal disease, wound healing and maintenance of extracellular matrix in periodontal tissues.

Cells, Cultured↗

PubMed2002

Fibronectin peptides derived from two distinct regions stimulate adipocyte differentiation by preventing fibronectin matrix assembly.

Here, we show that fibronectin (FN) peptides derived from two distinct regions promote the insulin-induced adipocyte differentiation of ST-13 cells by preventing FN fibrillogenesis. ST-13 cells formed numerous FN fibrils under nonadipogenic conditions, whereas this FN fibrillogenesis was suppressed by adipose induction with insulin. The insulin-induced adipocyte differentiation was promoted by an amino-terminal 24-kDa fragment of FN, accompanied by further suppression of FN fibrillogenesis. The 24 K fragment prevented FN matrix assembly by direct incorporation into the FN matrix. Like the 24 K fragment, a peptide from the 14th type III repeat, termed FNIII14, which suppressed the integrin alpha 5 beta 1-mediated adhesion of ST-13 cells to FN, accelerated the adipocyte differentiation by preventing FN fibrillogenesis without direct incorporation into the FN matrix. FNIII14 induced the conformation change of beta1 integrins of K562 cells from active to resting, as judged by FACS analysis using a monoclonal antibody AG89 directed to an active beta1 integrin-dependent epitope. Binding of a (125)I-labeled FN fragment containing the RGD cell adhesive site to ST-13 cell surface was dissociated by FNIII14, with a concomitant binding of FNIII14 itself to the cell surface. The affinity labeling of ST-13 cells using biotinylated FNIII14 showed that FNIII14 specifically bound to a nonintegrin membrane protein with M(r) of around 50 kDa. Thus, the results indicated that prevention of FN fibrillogenesis by the 24 K Fib 1 fragment and FNIII14 caused the promotion of adipocyte differentiation of ST-13 cells and that the former was due to the direct incorporation into the FN matrix and that the latter might be interpreted by negative regulation of FN receptor alpha 5 beta 1 activity.

Adipocytes↗

PubMed2001

Expression of gene for EIIIA- and EIIIB- fibronectin, fetal types of fibronectin, during gastric ulcer healing in rats.

Fibronectin (FN) is important for wound healing via cell proliferation, adhesion, differentiation, and matrix formation. Fetal types of FN mRNA, which include the region of EIIIA or EIIIB, are well expressed during embryonic development and wound healing. This study was done to investigate the mRNA expression of full-length FN, EIIIA- and EIIIB-FN, and the localization of FN in the gastric tissues during ulcer healing with northern blot analysis and immunohistochemical technique. Gastric ulcers in rats were produced by acetic acid. EIIIA- and EIIIB-FN mRNA were not detected in normal gastric tissues, but were expressed in the ulcerated tissues throughout the healing phase. However, on day 60 (in the scarred phase), the EIIIA- and EIIIB-FN mRNA had disappeared. The levels of full-length FN mRNA were increased from day 3 to 32 compared with the control levels, and decreased to the control levels on day 60. Full-length FN was predominantly localized at the mesenchyme around the infiltrating inflammatory cells in the granulation tissues and the basement membranes of the nonproliferating epithelial cells, which were regenerated at the ulcer margin. Thus, fetal gene transcripts of FN suggest the important role of fetal FN in gastric ulcer healing, mainly via the migration of mesenchymal and epithelial cells.

Animals↗

PubMed1998

Fibronectin is chemotactic for CT 26 colon carcinoma cells: sub-lines selected for increased chemotaxis to fibronectin display decreased tumorigenicity and lung colonization.

CT 26 murine colon carcinoma cells demonstrated directional migration (chemotaxis) in response to fibronectin (FN). Sub-lines were derived by positive and negative selection to FN across Transwell filters of 8 microm pore size. The FL6 sub-line (positively selected) demonstrated a significantly increased chemotactic response (P<0.01) to FN compared with parental CT 26 cells, while the FU7 sub-line (negatively selected) showed a reduced chemotactic response to FN (P<0.01). Comparable levels of alpha4, alpha5, alphav and beta1 integrins, which mediate FN attachment, were expressed on positively and negatively selected sub-lines and parental CT 26 cells. Activation of integrins with Mn2+ suggested that the integrins expressed on FL6 cells were in the fully activated state; in contrast FU7 cells displayed only partially activated integrins. Cell attachment and integrin activation status of the sub-lines correlated with their chemotactic response to FN. In vivo FL6 cells showed a significantly reduced tumour growth rate s.c. and a reduction in the number of lung colonies formed following i.v. injection compared with parental CT 26 and FU7 cells. In contrast FU7 cells displayed a significant increase in s.c. tumour growth and the number of lung colonies when compared with the parental line and FL6 sub-line. The results indicate that interaction between integrin receptors expressed on cancer cells and FN plays a central role in the chemotactic response of CT 26 colon carcinoma cells, and that in this model cells selected for chemotaxis to FN displayed a reduced malignant potential.

Adenocarcinoma↗

PubMed1990

Interaction of heparin with fibronectin and isolated fibronectin domains.

Fluorescence polarization, gel exclusion chromatography and affinity chromatography were used to characterize the interaction of heparins of different size with human plasma fibronectin (Fn) and several of its isolated domains. The fluid-phase interaction of Fn with heparin was dominated by the 30 kDa and 40 kDa Hep-2 domains located near the C-terminal ends of the A and B chains respectively. The 30 kDa Hep-2A domain from the heavy chain was indistinguishable from the 40 kDa Hep-2B domain in this respect; the presence of an additional type III homology unit in the latter had no effect on the binding. Evidence was provided that each Hep-2 domain has two binding sites for heparin. The N-terminal Hep-1 domain reacted weakly in fluid phase even though it binds strongly to immobilized heparin. Fn and Hep-2 fragments were rather undiscriminating in their reaction with fluoresceinamine-labelled heparins of different sizes. However, oligosaccharides smaller than the tetradecasaccharide (14-mer) bound Fn with a 5-10-fold lower affinity. These results suggest that the Hep-2 domains of Fn are able to recognize a broad spectrum of oligosaccharides that presumably vary significantly with respect to the amount and spatial distribution of charge.

Binding Sites↗

PubMed2003

Functional analysis of fibronectin isoforms in chondrogenesis: Full-length recombinant mesenchymal fibronectin reduces spreading and promotes condensation and chondrogenesis of limb mesenchymal cells.

Fibronectin (FN), a large dimeric glycoprotein, functions primarily as a connecting molecule in the extracellular matrices of tissues by mediating both cell-matrix and matrix-matrix interactions. All members of the FN family are products of a single FN gene; heterogeneity arises from the alternative splicing of at least three regions (IIIB, IIIA, and V) during processing of a common primary transcript. During chick embryonic limb chondrogenesis, FN structure changes from B+A+ in precartilage mesenchyme to B+A- in differentiated cartilage, and exon IIIA has been shown to be necessary for the process of mesenchymal cellular condensation, a requisite event that precedes overt expression of chondrocyte phenotype. This study aims to investigate the mechanistic action of the FN isoforms in mesenchymal chondrogenesis and, in particular, to identify the specific cellular function in mesenchymal condensation mediated by the mesenchymal (B+A+) FN isoform. Full-length cDNAs corresponding to four splice variants (B+A+, B+A-, B-A+, B-A-) of FN were constructed, and expressed the corresponding proteins using a baculovirus expression vector system. Cell adhesion assays with purified proteins showed that, although the relative levels of cell attachment were approximately the same, chick limb-bud mesenchymal cells spread up to 40 % less on mesenchymal (B+A+) FN than on cartilage (B+A-) FN, (B-A+) FN, or plasma (B-A-) FN. Cellular condensation and chondrogenic differentiation were also promoted in high-density micromass cultures of limb mesenchymal cells plated onto B+A+ FN. These observations suggest that the process of mesenchymal condensation is mediated at least in part by the enhanced ability of chondrogenic mesenchymal cells to migrate and aggregate as a consequence of residing in and interacting with mesenchymal FN. Our findings are consistent with and provide a mechanistic basis for previous observations that rounding of limb mesenchymal cells precedes the onset of chondrogenesis.

Animals↗

PubMed2000

Development and use of monoclonal antibodies to chicken fibronectin to show that the chicken hepatocellular carcinoma cell line, LMH, constitutively expresses fibronectin.

Fibronectin (Fn) is a high molecular weight glycoprotein and acute phase reactant that contributes to a variety of cellular activities including proliferation and wound healing. Production of Fn is influenced by cytokines such as IL-1alpha, IL-6 and TNF -alpha, and in serum Fn levels can function as an indicator of sepsis and reticulo-endothelial function. Here we describe the production of a panel of mAb to chicken Fn and give evidence that a chicken hepatocellular carcinoma cell line, LMH, constitutively expresses Fn. A capture ELISA to measure chicken Fn was developed using an IgG1 mAb (AV62) as the capture Ab, and biotinylated AV63 (IgG2b) as the detecting Ab. This study identified a single commercially available mAb directed against human Fn that also recognised chicken Fn. By contrast, the anti-chicken Fn mAbs did not cross-react with either human or bovine Fn.

Animals↗

PubMed1985

The oncofetal domain of fibronectin defined by monoclonal antibody FDC-6: its presence in fibronectins from fetal and tumor tissues and its absence in those from normal adult tissues and plasma.

An IgG1 monoclonal antibody, FDC-6, was established, which defines a unique fibronectin (FN) domain, located between the "Hep-2" and the "Fib-2" domains, in the COOH-terminal region of FNs isolated from hepatoma, sarcoma, and fetal fibroblasts. A systematic study with this antibody indicates the presence of two classes of human FNs. (i) FN from fetal connective tissue, placenta, amniotic fluid, hepatoma, and colon carcinoma as well as cell lines from fetal tissues (WI-38), hepatomas (HuH-6 and HuH-7), and sarcoma (VA13) was characterized by the presence of the FDC-6-defined domain and by a high molecular weight (subunit Mr, 310,000-335,000). (ii) In contrast, FN from normal adult tissues and plasma was characterized by a lower molecular weight (subunit Mr, 285,000-295,000) and lack of reactivity with FDC-6 and is therefore devoid of the FDC-6-defined domain. The FDC-6-defined domain is therefore called the "oncofetal" domain, and FN containing this domain is hereby called "oncofetal FN" (onf FN). The onf FN is similar to the previously known "cellular-form" FN. FN from normal adult tissues and plasma, lacking the oncofetal domain, is hereby called "normal FN" (nor FN). The nor FN is similar to the previously known "plasma-form" FN. Development of FN from fetal to adult form is associated with loss of the oncofetal domain defined by the FDC-6 antibody, and oncogenic transformation is associated with activation in synthesis of the oncofetal domain defined by the FDC-6 antibody.

Animals↗

PubMed1999

Dynamics and elasticity of the fibronectin matrix in living cell culture visualized by fibronectin-green fluorescent protein.

Fibronectin (FN) forms the primitive fibrillar matrix in both embryos and healing wounds. To study the matrix in living cell cultures, we have constructed a cell line that secretes FN molecules chimeric with green fluorescent protein. These FN-green fluorescent protein molecules were assembled into a typical matrix that was easily visualized by fluorescence over periods of several hours. FN fibrils remained mostly straight, and they were seen to extend and contract to accommodate movements of the cells, indicating that they are elastic. When fibrils were broken or detached from cells, they contracted to less than one-fourth of their extended length, demonstrating that they are highly stretched in the living culture. Previous work from other laboratories has suggested that cryptic sites for FN assembly may be exposed by tension on FN. Our results show directly that FN matrix fibrils are not only under tension but are also highly stretched. This stretched state of FN is an obvious candidate for exposing the cryptic assembly sites.

Amino Acid Sequence↗

PubMed1997

Covalent cross-linking of fibronectin to fibrin is required for maximal cell adhesion to a fibronectin-fibrin matrix.

In a blood clot, fibrin and plasma fibronectin (pFN) are covalently cross-linked by activated factor XIII (factor XIIIa) to form pFN-fibrin multimers. To determine the functional significance of covalent pFN-fibrin interactions, we have developed an in vitro model which allows the incorporation of recombinant FN (recFN) molecules into a covalently cross-linked recFN-fibrin matrix. Using the baculovirus expression system, we have expressed recFN monomers composed of the amino-terminal 70-kDa region and the first 11 type III repeats (WT) with mutations in the glutamines at positions 3 and 4 (Q2) or at 3, 4, and 16 (Q3). Examination of the covalent incorporation of these recFNs into fibrin clots confirms that glutamines 3 and 4 are major participants in FN-fibrin cross-linking as the mutation of these sites reduces cross-linking efficiency by 65%. Additional mutation of the glutamine at position 16, however, eliminates >99% of cross-linking suggesting that it also may be factor XIIIa reactive. When the Q3 recFN-fibrin clots were used as substrates for cell adhesion, there was a decrease in both cell attachment and spreading when compared with the WT recFN-fibrin clots. These data demonstrate that for maximal cell attachment to a FN-fibrin clot, FN must be cross-linked to fibrin by factor XIIIa.

3T3 Cells↗

PubMed2002

The low density lipoprotein receptor-related protein mediates fibronectin catabolism and inhibits fibronectin accumulation on cell surfaces.

Low density lipoprotein receptor-related protein (LRP) is a member of the low density lipoprotein receptor family, which functions as an endocytic receptor for diverse ligands. In this study, we demonstrate that murine embryonic fibroblasts (MEF-2 cells) and 13-5-1 Chinese hamster ovary cells, which are LRP-deficient, accumulate greatly increased levels of cell-surface fibronectin (Fn), compared with LRP-expressing MEF-1 and CHO-K1 cells. Increased Fn was also detected in conditioned medium from LRP-deficient MEF-2 cells; however, biosynthesis of Fn by MEF-1 and MEF-2 cells was not significantly different. When LRP-deficient cells were dissociated from monolayer culture, increased levels of Fn remained with the cells, as determined by cell-surface protein biotinylation, suggesting an intimate relationship with cell surface-binding sites. The LRP antagonist, receptor-associated protein (RAP), promoted Fn accumulation in association with MEF-1 cells, whereas expression of full-length LRP in MEF-2 cells substantially decreased Fn accumulation, confirming the role of LRP in this process. Purified LRP bound directly to immobilized Fn, and this interaction was inhibited by RAP. Furthermore, MEF-1 cells degraded (125)I-Fn at an increased rate, compared with MEF-2 cells. (125)I-Fn degradation by MEF-1 cells was inhibited by RAP. These results demonstrate that LRP functions as a catabolic receptor for Fn. The function of LRP in Fn degradation and the ability of LRP to regulate levels of other plasma membrane proteins represent possible mechanisms whereby LRP prevents Fn accumulation on cell surfaces.

Animals↗

PubMed2004

Assembly of exogenous fibronectin by fibronectin-null cells is dependent on the adhesive substrate.

The role of endogenously synthesized fibronectin (FN) in assembly was studied with cells lacking or expressing FN. Cells were cultured as homogeneous or mixed populations on surfaces coated with different matrix proteins. Compared with FN-expressing cells, FN-null cells poorly assembled exogenous plasma FN (pFN) when adhered to vitronectin or the recombinant cell-binding domain (III(7-10)) of FN. Vitronectin had a suppressive effect that was overcome by co-adsorbed pFN or laminin-1 but not by soluble FN. In co-cultures of FN-expressing cells and FN-null cells, endogenous FN was preferentially assembled around FN-expressing cells regardless of the adhesive ligand. If the adhesive ligand was vitronectin, exogenous pFN assembled preferentially around cells expressing cellular FN or recombinant EDa- or EDa+ FN. In co-cultures on vitronectin of FN-null cells and beta(1) integrin subunit-null cells, fibrils of cellular FN and pFN were preferentially deposited by FN-null (beta(1)-expressing) cells immediately adjacent to (FN-secreting) beta(1)-null cells. In co-cultures on vitronectin of FN-null cells and beta(1)-null cells expressing a chimera with the extracellular domain of beta(1) and the cytoplasmic domain of beta(3), preferential assembly was by the chimera-expressing cells. These results indicate that the adhesive ligand is a determinant of FN assembly by cells not secreting endogenous FN (suppressive if vitronectin, non-suppressive but non-supportive if III(7-10), supportive if pFN or laminin-1) and suggest that efficient interaction of freshly secreted cellular FN with a beta(1) integrin, presumably alpha(5)beta(1), substitutes for integrin-mediated adherence to a preformed matrix of laminin-1 or pFN to support assembly of FN.

Animals↗

PubMed2006

The "linker" region (amino acids 38-47) of the disintegrin elegantin is a novel inhibitory domain of integrin alpha5beta1-dependent cell adhesion on fibronectin: evidence for the negative regulation of fibronectin synergy site biological activity.

Disintegrins are a family of potent inhibitors of cell-cell and cell-matrix adhesion. In this study we have identified a region of the disintegrin elegantin, termed the "linker domain" (amino acids 38-47), with inhibitory activity toward alpha(5)beta(1)-mediated cell adhesion on fibronectin (Fn). Using a chimeric structure-function approach in which sequences of the functionally distinct disintegrin kistrin were introduced into the elegantin template at targeted sites, a loss of inhibitory function toward alpha(5)beta(1)-mediated adhesion on Fn was observed when the elegantin linker domain was substituted. Subsequent analysis comparing the inhibitory efficacies of the panel of elegantin-kistrin chimeras toward CHO alpha(5) cell adhesion on recombinant Fn III(6-10) fragments showed that the loss of inhibitory activity associated with the disruption of the elegantin linker domain was dependent upon the presence of a functional Fn III(9) synergy site within the Fn III(6-10) substrate. This suggested that the elegantin linker domain inhibits primarily the activity of the Fn synergy domain in promoting alpha(5)beta(1) integrin-mediated cell adhesion. Construction of a cyclic peptide corresponding to the entire region of the elegantin linker domain showed that this domain has intrinsic alpha(5)beta(1) inhibitory activity comparable with the activity of the RGDS peptide. These data demonstrate a novel biological function for a disintegrin domain that antagonizes integrin-mediated cell adhesion.

ADAM Proteins↗

PubMed2000

Cellular invasion by Staphylococcus aureus involves a fibronectin bridge between the bacterial fibronectin-binding MSCRAMMs and host cell beta1 integrins.

Although Staphylococcus aureus is primarily considered an extracellular pathogen, recent evidence suggests that this bacterium can invade a variety of nonprofessional phagocytic cells. Here we investigate the early stages of cellular invasion by S. aureus and determine the bacterial and host components that are required for this process. S. aureus expresses two cell surface-associated fibronectin (FN)-binding proteins (FnbpA and FnbpB) that mediate the interaction of the bacteria with both soluble and solid-phase FN in vitro. Using a mutant of S. aureus that lacks the expression of both Fnbps, we show that the expression of either protein is necessary for efficient uptake by the mouse fibroblast line GD25beta1A. Invasion could be inhibited by soluble recombinant proteins encompassing either the FN-binding D repeat region or the A region (and B repeats) of FnbpA, suggesting that the activities of both regions are important in this process. We demonstrate that FN is also required for invasion of this cell line. In the presence of FN-depleted fetal bovine serum, the invasion level was reduced by approximately 40% compared to in the presence of whole fetal bovine serum. Invasion could be further reduced by the addition of anti-mouse FN antibodies to the assay. Finally, we utilize a mutant mouse fibroblast line, which lacks beta1 integrin expression, to demonstrate that host cell beta1 integrins are necessary for efficient cellular invasion. The level of invasion of the mutant cell line GD25 was reduced by approximately 97% compared to the beta1-expressing complemented cell line GD25beta1A. In addition, invasion of the GD25beta1A cell line could be inhibited by an RGD-containing peptide, further implicating a role for integrins in this process. Based on these observations, we put forward a model of S. aureus invasion in which host FN forms a bridge between the bacterial Fnbps and host cell beta1 integrins, leading to bacterial uptake.

Adhesins, Bacterial↗

PubMed2001

A novel fibronectin binding site required for fibronectin fibril growth during matrix assembly.

Fibronectin (FN) assembly into a fibrillar extracellular matrix is a stepwise process requiring participation from multiple FN domains. Fibril formation is regulated in part by segments within the first seven type III repeats (III1-7). To define the specific function(s) of this region, recombinant FNs (recFNs) containing an overlapping set of deletions were tested for the ability to assemble into fibrils. Surprisingly, recFN lacking type III repeat III1 (FNDeltaIII1), which contains a cryptic FN binding site and has been suggested to be essential for fibril assembly, formed a matrix identical in all respects to a native FN matrix. Similarly, displacement of the cell binding domain in repeats III9-10 to a position close to the NH2-terminal assembly domain, as well as a large deletion spanning repeats III4-7, had no effect on assembly. In contrast, two deletions that included repeat III2, DeltaIII1-2 and DeltaIII2-5, caused significant reductions in fibril elongation, although binding of FN to the cell surface and initiation of assembly still proceeded. Using individual repeats in binding assays, we show that III2 but not III1 contains an FN binding site. Thus, these results pinpoint repeat III2 as an important module for FN-FN interactions during fibril growth.

Animals↗

PubMed1989

The influence of fibronectin administration on the incidence of sepsis and septic mortality in severely injured patients. The Medical College of Georgia Fibronectin Research Group.

Eighty-five trauma patients between the ages of 18 and 55, with American College of Surgeon's (ACOS) trauma scores greater than or equal to 7 were entered into a double-blind, randomized, placebo-controlled study to assess the efficacy of prophylactic fibronectin (Fn) administration on clinical course, sepsis development, and septic mortality. Patients were randomized on admission to receive purified human virus-inactivated Fn or placebo control (human serum albumin, HSA). Fn or HSA was administered on a daily basis if and when the patient was Fn deficient (less than 75% normal). When a Fn deficiency was not evident, the patient received saline. Seventy one patients developed Fn deficiencies during their initial clinical course: 36 received Fn, 35 received HSA. Fourteen patients did not develop a Fn deficiency after trauma and thus received only saline. Analysis of admission data demonstrated no significant differences between the three groups with respect to extent of injury (injury severity score, ACOS trauma score) or physiologic assessments of organ function (serum creatinine, bilirubin, lactic acid). On day 1 after trauma, Fn levels were shown to correlate with other plasma proteins and cellular components (range of r values, 0.24 to 0.75; all p less than 0.05), but not with organ function parameters. Eighteen of 85 patients became septic as judged by clinical criteria. Ten of these patients had received Fn (10 of 36), five had received HSA (5 of 35), and three had received only saline (3 of 14) before the development of sepsis (differences not significant). When septic, nine of 17 patients developed Fn deficiencies. Six patients received Fn while septic, three received albumin, and eight received saline. Seven patients died: 5 of 6 Fn patients, 1 saline, and 1 HSA recipient. Our data suggest that exogenous Fn repletion in states of deficiency does not alter clinical course, the development of sepsis, or septic mortality.

Adolescent↗

PubMed2000

Plasma concentration of biologically active fibronectin and fibronectin bound to gelatin-like material in a porcine model of hyperdynamic endotoxic shock.

Due to its opsonizing role, plasma fibronectin (pFN) binds to circulating degradation products deriving from collagenous structures and mediates their elimination by the reticuloendothelial system (RES). In septic shock, an overflow of this material may lead to a lack of pFN and an impaired RES activity. In fact, low pFN levels have been reported to correlate with unfavorable clinical outcome. However, dysfunction of the RES is also caused by other shock related factors, and death from septic shock also has been observed in the presence of normal FN levels. To investigate the involvement of opsonic FN in the progression of sepsis, we discriminated between biologically active FN and FN bound to gelatin-like material in pigs developing a hyperdynamic endotoxic shock. All FN determinations were performed with the immunochemical assay. Discrimination between free FN and complexed FN was achieved by separation on gelatin sepharose. A continuous decrease of total FN and free FN was observed in the septic group reaching 57% and 50% of the initial level at the end of the 5-h observation period, respectively. However, a significant difference was not detected before both the microcirculatory and macrocirculatory alterations indicative of hyperdynamic endotoxic shock were completely established. Complexed FN was increased slightly in both groups without any group specific differences. We conclude that the FN-mediated opsonization of circulating gelatine-like material does not play a critical role in early circulatory shock.

Animals↗

PubMed1995

Human eosinophils preferentially survive on tissue fibronectin compared with plasma fibronectin.

BACKGROUND: Eosinophil-derived inflammatory mediators including cytokines are considered to be important in the pathogenesis of allergic inflammation. Fibronectin (Fn) has been shown to be a physiological trigger of autocrine cytokine production by human eosinophils. Fn is encoded by a single gene, but alternate splicing of the primary RNA transcript results in polypeptide diversity in a cell type-specific fashion. Thus, tissue Fn contains approximately 50% more of the CS-1 cell binding region recognized by the integrin alpha 4 beta 1 compared with plasma Fn. OBJECTIVE: Since eosinophils are predominantly tissue-dwelling cells we compared the effect of tissue and plasma Fn on eosinophil survival in culture. METHODS: The viability and cytokine generation of eosinophils (> 99.9% pure) cultured for up to 4 days in 96 well plates coated with tissue Fn, plasma Fn or BSA was compared. RESULTS: There was a significant difference in the ability of tissue Fn to support eosinophil survival compared with plasma Fn (P < 0.01). Optimal survival with tissue Fn was seen at 25 micrograms/well (70% +/- 2.0% viability at 3 days vs 7% +/- 2.2% viability on BSA). Significant (P < 0.001) cell viability on tissue Fn was observed for up to 4 days in culture (54% +/- 6.0%) compared with BSA coated wells. Addition of autologous mononuclear cells (final concentration 0.5%, 1% or 2%) resulted in plasma Fn-dependent eosinophil survival comparable to that of 99.9% pure eosinophils adherent to tissue Fn. Tissue Fn-dependent survival was significantly inhibited by anti-interleukin-3, anti-granulocyte macrophage colony stimulating factor (GM-CSF) and anti-IL-5 monoclonal antibodies. Picogram quantities of these three cytokines were detected in supernatants from eosinophils cultured for 3 days on tissue Fn using specific enzyme-linked immunosorbent assays (ELISAs). Eosinophil survival on tissue Fn was significantly inhibited by anti-beta 1 and alpha 4 beta 1 monoclonal antibody (MoAb) and also by a MoAb specific for the CS-1 motif in the IIICS region of Fn. CONCLUSION: These observations show preferential survival of eosinophils cultured on tissue Fn as a result of alpha 4 beta 1-dependent interaction with the CS-1 region of tissue Fn triggering autocrine cytokine synthesis and release, thereby promoting their survival and persistence within the tissues.

Cell Survival↗