A stable, sensitive assay for human fibronectin

Inhibition of fibroblast cell adhesion on substrate by coating with 2-methacryloyloxyethyl phosphorylcholine polymers

Fibroblast adhesion and growth behavior were examined on various polymers coated on a poly(ethylene telephthalate) (PET) substrate. The polymers are poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylatel copolymer (PMB)s with different MPC unit compositions, and poly(2-hydroxyethyl methacrylate). Surface analysis by dynamic contact angle measurement revealed that the mobility of the polymer chain on the PET substrate depended on the MPC unit composition, but there was no significant difference between the PMBs with 3-10 mol% MPC units and poly(HEMA). Fibronectin adsorption on the polymer surface from a cell culture medium was determined by immunoassay. The adsorbed fibronection was evenly distrubuted in every polymer, however, the amount was reduced with an increase in the MPC unit composition in the PMB. This result suggested that the MPC unit could weaken the interaction between the polymer surface and proteins. When fibroblast L-929 cells, were cultured on the polymers, the cells adhered and the number of cells increased on not only the hydrophobic poly(BMA) but also on the hydrophilic poly(HEMA). However, the number of cells that adhered on the PMB surface decreased with an increase in the MPC unit composition. This was a result of the fibronectin adsorption behavior. Thus, it could be concluded that since the PMB could suppress cell adhesion proteins e.g. fibronectin, the PMB showed excellent cell adhesive resistance properties.

Current status of fibronectin in transfusion medicine: focus on clinical studies

It has long been hypothesized that fibronectin (Fn) is essential to the function of the reticuloendothelial system (RES) and that the reversal of Fn deficiency in critically ill patients would result in a clinical benefit to these patients. Fn administration to deficient patients was postulated to improve the function of the RES, decrease the incidence of organ failure, sepsis and ultimately mortality. Over the past 15 years, several clinical studies have been performed to test these hypotheses. The initial anecdotal studies using cryoprecipitate (a plasma fraction enriched in Fn) revealed promising results but were neither controlled nor blinded. Further controlled studies were published utilizing both cryoprecipitate and purified Fn. Unfortunately, the great majority of authors found no beneficial effects of Fn administration in critically ill patients, in relation to incidence of organ failure, sepsis, or mortality. These results do not support the use of Fn in this setting. Fn utilization in wound healing has shown promising results in case reports. Although its role in wound healing is not yet fully delineated, initial reports with corneal wounds show a beneficial influence of Fn administration. Further studies are needed to determine the exact function(s) of Fn in a healing wound. Efficacy must still be shown in controlled clinical trials; dosing and administration regimens need to be elucidated.

Effect of auranofin on plasma fibronectin, C reactive protein, and albumin levels in arthritic rats

Auranofin, a member of a class of compounds with disease modifying activity, was given to arthritic rats to determine if it could reverse the abnormal plasma concentrations of fibronectin (Fn), C reactive protein (CRP), and albumin, which were unaffected by treatment with non-steroidal anti-inflammatory drugs (NSAIDs). When auranofin was orally administered for two weeks to adjuvant induced arthritic rats it significantly inhibited swelling of the injected and non-injected paws at doses of 3 and 10 mg/kg. Rocket electroimmunoassay measurement of plasma proteins in normal, arthritic, and auranofin treated arthritic rats indicated that auranofin at 10 mg/kg significantly decreased (by 77%) the abnormally high concentration of arthritic rat plasma Fn, though it had no effect on Fn concentrations when administered to normal rats. CRP, which was raised approximately twofold above normal in arthritic rats, was reduced by 56% after treatment of arthritic rats with auranofin at 10 mg/kg, though CRP concentrations in normal rats were unaffected by auranofin treatment. Depressed albumin concentrations in arthritic rats were significantly enhanced (by 30%) by dosing with 10 mg/kg of auranofin. At the 3 mg/kg dose, auranofin did not significantly change plasma concentrations of Fn, CRP, and albumin in arthritic rats. At a dose of 10 mg/kg, however, auranofin, in addition to inhibiting chronic systemic paw inflammation, also altered abnormal concentrations of plasma Fn, CRP, and albumin in the adjuvant arthritic rat, thus distinguishing auranofin from standard NSAIDs we have previously tested.

Single-step purification of rat C-reactive protein and generation of monospecific C-reactive protein antibody

Although Sepharose-phosphorylcholine affinity chromatography has been used extensively to purify some acute phase proteins, the operation has usually been a laborious multi-step procedure. By modifying previously described multi-step protein purification assays, centigram quantities of pure rat C-reactive protein (CRP) could be obtained in a single chromatographic step using affinity chromatography. Rat serum was passed over a column of p-aminophenylphosphorylcholine and extraneous proteins eluted with Tris-saline-Ca2+ buffer. Similar to other purification procedures, CRP was eluted with phosphorylcholine in a Tris-saline-Ca2+ buffer. The technical detail which distinguished this procedure from others, was the use of a phosphorylcholine gradient shallow enough (0.95 mM-2.5 mM) to resolve the eluent into two peaks; the first peak was composed largely of the contaminant, serum amyloid protein (SAP), and the second was composed of CRP. Although there was some overlap between the first and second peak, pure CRP could be obtained by pooling fractions from the trailing shoulder of the second peak. Using this single step procedure, a greater than 25% yield of SAP-free, purified CRP could be obtained. The purified CRP was free of SAP contamination as measured by sodium dodecyl sulfate gradient polyacrylamide gel electrophoresis. Purified CRP was determined to be free of rat albumin, IgG and the C3 component of complement using immunoelectrophoresis. This one-step affinity column chromatography procedure provides a simple, efficient method for collecting large quantities of rat CRP pure enough to be used to obtain a monospecific goat, anti-rat CRP antibody.

Fibronectin in acute and chronic inflammation

Recent evidence suggests that fibronectin (Fn), a high molecular weight glycoprotein, may be used as an indicator protein in rats with adjuvant-induced arthritis. Rocket immunoelectrophoresis, using purified goat anti-rat Fn, provided a specific and sensitive means of measuring plasma Fn in rats during the development of various inflammatory disease states. It was shown that normal rat plasma Fn levels of approximately 400 micrograms/ml double within 24 hours after injection of adjuvant. Plasma Fn levels in this model of chronic systemic inflammatory joint disease were tracked for more than 4 months and remained significantly higher than normal. On the other hand, a carrageenan-induced inflammatory response in the pleural cavity of rats resulted in a large local accumulation of leukocytes, but no change in plasma Fn levels. A carrageenan-induced model of acute inflammation resulted in increased paw swelling within 6 hours and enhanced plasma Fn levels within 24 hours; plasma Fn levels returned to normal within 1 week. Quantitation of plasma Fn levels in the rat may provide a useful biochemical parameter for the study of chronic systemic inflammatory diseases.

Fibronectin: applications to clinical medicine

In summary, the role of fibronectin in clinical medicine is not yet certain. Correlation of sepsis and organ failure with decreased fibronectin levels is still to some degree questionable; controlled clinical trials are urgently needed. The risk of hepatitis, AIDS, and other transfusion-transmitted diseases must be balanced by data substantiating the clinical efficacy of fibronectin therapy. To date, no results from controlled trials using purified fibronectin have been reported. Final judgement must be reserved pending results of appropriate human studies. It is likely, however, that even if fibronectin is proven to be clinically useful, the patient population which will achieve some benefit from its use will be restricted to septic and/or critically ill patients. As noted by Mosher and Grossman however, physicians treating such patients would likely welcome any new and effective therapeutic intervention.

Hemagglutination assay for human serum fibronectin

A hemagglutination assay for human serum fibronectin (Fn) is described. The assay is based on the capacity of Fn to bind to gelatin. Purified and human serum Fn agglutinate chromic chloride treated sheep red cells coated with gelatin in a quantitative and reproducible manner. The lowest Fn concentration giving positive hemagglutination was found to be 7 micrograms/ml, a sensitivity making it suitable for measurement of Fn in both normal and pathologic sera. The assay is simple and rapid and does not require specialized equipment.

Fibronectin assays and their clinical application: a review

Cold insoluble globulin (fibronectin) was discovered 30 years ago but recently there has been a remarkable growth of knowledge concerning its interaction with the cell cytoskeleton and its role in cell-cell and cell-matrix adhesion. The protein is also a major plasma opsonin with a role in regulating fixed macrophage activity and it is this area in which clinical applications are now beginning to develop. Methods are discussed for measuring the concentration of the protein and its opsonic function in vitro, and for the evaluation of fixed macrophage function in vivo. Also discussed are the metabolism of the protein, the implications of opsonin depletion in patients with serious injury or infection and the attempts to reverse this with plasma protein replacement therapy.

Plasma fibronectin as a marker for cancer and other diseases

The blood concentration of the high-molecular-weight glycoprotein fibronectin showed great promise as a marker for cancer and certain other disease states. However, it now appears that plasma fibronectin levels are influenced by many factors (e.g., age, sex, nutritional state, trauma, shock, inflammation, certain drugs), sometimes giving conflicting responses. Furthermore, unrecognized pitfalls exist in fibronectin determinations with respect to blood sampling methods, plasma preparation, plasma storage, and re-use and assay methods. It is concluded that the plasma fibronectin level, as frequently reported, has little value as a marker for cancer and other disease states.

A rapid and highly sensitive solid-phase enzyme immunoassay specific for human fibronectin using a characterized monoclonal antibody

A solid-phase enzyme immunoassay (EIA) was developed for the quantitation of human fibronectin in body fluids and cell culture media. In the assay a human fibronectin-specific murine monoclonal IgG1 (f-33) was used as capture antibody and polyclonal rabbit anti-fibronectin as detector antibody. The antibody showed no reactivity to purified monkey, dog, rabbit, horse, sheep, mouse, bovine or chicken fibronectins. The determinant of the monoclonal antibody was mapped to the cell-binding region of the fibronectin molecule. This localization was based on the use of purified fragments of fibronectin, immunoblotting, EIA and inhibition of fibroblast adhesion and spreading by the antibody. The detection limit of the fibronectin assay was 2 ng/ml. The assay was used for the quantitation of fibronectin in human plasma, urine and cerebrospinal fluid specimens and culture media of human cells.

Native and degraded fibronectin: new immunological methods for distinction

Two methods for quantitative determination of the high molecular weight glycoprotein, fibronectin, have been developed. Both methods are based on enzyme-linked immunoadsorbent (ELISA) techniques. In the first of the methods an antibody against fibronectin is used to trap the antigen. This double antibody technique can detect a slight decrease in the concentration of fibronectin stored for 5 days compared to the amount of fibronectin in the freshly purified preparation. In the second method, gelatin which is known to bind specifically to fibronectin, is used to catch fibronectin. By this method less than 1% of the fibronectin present in a freshly prepared preparation is measured after storage for 5 days. The results obtained with the two methods applied on a freshly prepared and a stored fibronectin are in agreement with sodium dodecylsulphate polyacrylamide gel electrophoresis followed by immunoblotting before and after gelatin-Sepharose adsorption. These techniques demonstrate that all the freshly prepared fibronectin adsorbs to gelatin-Sepharose, while stored fibronectin, which is broken down to numerous peptides, still reacts with the fibronectin antibody, but does not adsorb to gelatin-Sepharose. The two ELISA techniques were applied on amniotic fluid, cerebrospinal fluid and urine. The results indicated significant degradation of fibronectin in urine, and less degradation of fibronectin in amniotic and spinal fluid.

Ultrastructural localization of fibronectin in duct cells of human minor salivary glands and its immunochemical detection in minor salivary gland secretion

Fibronectin (Fn) was localized in duct cells by means of a light and electron microscopic immunohistochemical technique. The subcellular localization demonstrated that Fn is synthesized in these cells and thus not exclusively produced by cells with a mesodermal background. Fn concentration, as measured by radioimmunoassay, was higher in saliva from the minor salivary glands than in unstimulated whole saliva, whereas Fn was undetectable in stimulated parotid saliva. Fn is thus a conspicuous component in unstimulated resting saliva. Fn may be an important factor, negative or positive, for the integrity of the oral hard and soft tissues because it has the capability to bind and agglutinate microorganisms.

A competitive inhibition assay for gelatin binding fibronectin

A competitive inhibition assay for functional fibronectin (Fn), based on ELISA technology, is described. The assay measures Fn's physiologic ability to bind to denatured collagen (gelatin). Affinity-purified Fn inhibits the binding of alkaline phosphatase coupled Fn to gelatin-coated wells of a microtiter plate in a concentration-dependent manner. The assay range is 50-500 micrograms Fn/ml, which is suitable for the measurement of plasma Fn in both normal and opsonin deficient individuals. It is reproducible over an eightfold dilution of plasma and is resistant to interference by normal plasma proteins. The assay described is quick, quantitative, and reproducible, and satisfies the need for a measure of functional Fn activity in the clinical laboratory.