Reversal of fibronectin and opsonic deficiency in patients. A controlled study

Does Fibronectin Reduce Mortality in Sepsis? A Meta-Analysis

We examine the effect of fibronectin administration on mortality in sepsis. An English language literature search using MEDLINE, EMBASE, SCISEARCH, and compu terized databases of unpublished research in addition to bibliographic review was performed, and duplicate independent review of 41 articles by two observers identified six relevant randomized clinical trials. Study quality and descriptive information concerning the pop ulation, intervention, and outcome measurements were assessed. Three of six trials demonstrated favorable mor tality trends, but none reached statistical significance. Results of the 282 patients in all six trials yield a com mon odds ratio of 0.97 and a 95% confidence interval of 0.58 to 1.61. These results do not show a statistically significant effect favoring treatment, but neither do they exclude a clinically important benefit. The benefit of fibronectin in decreasing mortality in sepsis is not sup ported by these studies. However, methodological heterogeneity and the possibility of a Type II error, as well as our understanding of the role of fibronectin in the pathophysiology of sepsis, do not allow for a firm negative conclusion regarding the therapeutic efficacy of fibronectin in sepsis. A large, rigorously designed trial should be considered once investigators can reach a consensus regarding current methodological and patho physiological controversies.

Burn Wound Sepsis

Wound sepsis remains perhaps the most feared sequela in the patient who has suffered major burn injuries and leads to overwhelming mortality among patients with extensive burn wounds. The presence of large areas of devitalized, necrotic tissue, coupled with the profound immunosuppression that usually follows major injury, sets the stage for rapid microbial proliferation in the wound; when microbes invade subjacent, previously vi able tissues, invasive burn wound sepsis is defined. Top ical antimicrobial drugs probably have only a limited effect in preventing wound sepsis, and organisms now frequently emerge that are resistant to the commonly used topical agents. Salient factors in the diagnosis and treatment of invasive wound sepsis are discussed in this review. Prevention of wound sepsis, however, is one of the primary objectives of current burn care. Early burn wound excision and immediate wound closure with autograft or a suitable biologic dressing has emerged as the best means for prevention of generalized wound sepsis.

Endotoxin, tumor necrosis factor, and dexamethasone effects on human endothelial cell fibronectin dynamics: synthesis, matrix assembly, and receptor expression

The three inflammatory modulators endotoxin, tumor necrosis factor (TNF) alpha, and dexamethasone (DEX) were studied for their effects on fibronectin (FN) dynamics in human umbilical vein endothelial cells. Cell culture supernatants were analyzed for new soluble pool FN synthesis. Endotoxin (LPS) (10 micrograms/mL) decreased the newly synthesized soluble pool of FN (p < 0.05). An increase in soluble FN was demonstrated with 1 and 10 ng/mL TNF alpha (p < 0.05). DEX decreased newly synthesized endothelial cell (EC) FN in the soluble pool at 4, 40, and 400 micrograms/mL (p < 0.05). Extracellular matrix FN content was examined using immunofluorescence. The thick FN mesh seen in control cells contrasted with a decreased FN matrix after treatment with each of the three study agents. Immunoprecipitation of the FN receptor alpha 5 beta 1 integrin from [35S]methionine-labelled cell extracts demonstrated down regulation of receptor expression by both TNF alpha and DEX as compared with control samples. These data indicate that LPS, TNF alpha, and DEX may weaken EC-substratum adhesion by differential effects on FN synthesis and secretion, FN incorporation into the extracellular matrix, and down regulation of FN receptor expression.

Decreased plasma fibronectin concentrations in preterm infants with septicaemia

Changes in plasma fibronectin concentrations were determined during bacterial septicaemia in extremely preterm infants. The study was a prospective study of fibronectin concentrations in infants of less than 30 weeks' gestation. Concentrations were determined at birth, before sepsis, and throughout the episode of sepsis. Fibronectin concentrations at birth or immediately before sepsis were not significantly different between those infants who developed septicaemia and those who did not (98 (15) v 97 (10) micrograms/ml). In the infants with septicaemia, fibronectin concentrations decreased significantly on day 1 (106 (13) v 173 (18) micrograms/ml for the controls) and remained significantly lower on day 2 (123 (26) v 201 (17) micrograms/ml). By day 5 fibronectin concentrations had increased and were no longer statistically different from controls. Fibronectin is a key modulator of the immune response, with important functions in neutrophil adhesion, bacterial opsonisation, T cell activation, and vascular integrity. Acute depletion of plasma fibronectin during sepsis in preterm neonates may further abrogate their ability to control sepsis.

Incorporation of circulating fibronectin into various tissues during sepsis: colocalization with endogenous tissue fibronectin

We studied the plasma clearance and tissue incorporation of intravenously infused purified human plasma fibronectin into various tissues during a period of acute lung vascular injury induced by lethal postoperative bacteremia in sheep. Lung, liver, spleen, and heart tissue were examined for both endogenous sheep tissue fibronectin as well as the experimentally infused human fibronectin using dual-label immunofluorescence. Awake sheep (n = 4) received a postoperative iv infusion of 5 x 10(9) live Pseudomonas over a 60-min infusion interval. Bacterial challenge was started 2 hr after starting the iv fibronectin infusion of purified human plasma fibronectin (100 mg iv bolus; 4 hr iv at 100 mg/hr). Human fibronectin displayed a biphasic rate of clearance from the plasma with entrance into lymph. Human fibronectin readily incorporated in all tissues studied, including the lung which was the focus of vascular injury. Analysis of tissue sections by dual-label immunofluorescence indicated that the exogenous human fibronectin colocalized with the endogenous sheep fibronectin. Thus, the plasma fibronectin concentration may influence the lung vascular barrier due to its incorporation into the tissue pool of fibronectin. Moreover, the plasma may serve as a reservoir for soluble fibronectin which can enter and colocalize with the insoluble tissue pool of fibronectin in various tissues.

Plasma fibronectin levels as predictive of survival in major thermal injury

Plasma fibronectin levels, assayed by rocket immunoelectrophoresis, were measured in adult burn patients with 25-75 per cent total body surface area burns. Significant differences in the level of plasma fibronectin were detected in the one fatally injured patient prior to death (at 48 and 24 h) as a precipitous and persistent drop to 0.07 and 0.09 g/l, respectively. This deficiency coincided with early clinical signs of sepsis, the severity of which was not clinically apparent prior to overwhelming sepsis and incipient shock. This report supports previous suggestions that secondary deficiencies in plasma fibronectin may be predictive of mortality occurring after day 6 postburn. The need for routine assay of plasma fibronectin using rocket immunoelectrophoresis is demonstrated.

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.

Pre-, intra-, and postoperative antibiotics

Endogenous contamination from perforation or rupture of the gastrointestinal tract; exogenous contamination from missiles, knives, or invasive lines and tubes; and immunodepression related to the severity of injury are responsible for the increased infectious complications noted in patients who have undergone laparotomy for abdominal trauma. Perioperative use of clindamycin and an aminoglycoside, a second- or third-generation cephalosporin, or an enhanced-spectrum penicillin is clearly beneficial in lowering the incidence of intra-abdominal and wound infections. A 12- to 48-hour length of administration of antibiotics after operation is as effective as regimens of longer duration, although presently used dosages may be inadequate in severely injured patients. Adjunctive surgical maneuvers such as peritoneal irrigation with saline-containing antibiotic(s) remain controversial. Perioperative use of antibiotic prophylaxis, coupled with early operation and appropriate surgical technique, results in a 4.4% rate of intra-abdominal abscesses and a 5.1% rate of wound infections after laparotomy for abdominal trauma in modern trauma centers.

Modern approaches to the therapy of septic shock

Bacteremia from gram-negative rods is a great cause of concern for hospital physicians today. Shock-complicating gram-negative sepsis has a mortality rate of 60% and above, despite early diagnosis and treatment. Intensive research efforts have shown new pathophysiological mechanisms and mediators involved in septic shock, with changes in recommended treatment protocols. In this report, the authors review the use of corticosteroids, fibronectin, naloxone hydrochloride, and immunotherapy, with emphasis on theoretical considerations and relevant clinical experience. Although these treatment methods may have been promising initially, data from large double-blind human trials are either lacking or unencouraging. While continued research and modern therapeutic approaches should improve future survival rates from septic shock, use of the therapies reviewed should be considered experimental at this time.

Influence of preoperative intravenous nutrition upon hepatic protein synthesis and plasma proteins and amino acids

The influence of 3 and 7 days of preoperative intravenous nutrition (IVN) on the capacity for protein synthesis in liver and on concentrations of plasma proteins and amino acids were investigated in patients with gastrointestinal malignancy. Thirty patients with gastrointestinal neoplasms who had lost more than 5 kg of weight over 3 months were randomized into three groups to receive preoperatively: (a) no IVN, (b) IVN for 3 days (0.18 gN/kg/day as amino acid; 30 kcal/kg/day as glucose), or (c) IVN for 7 days. Free access to a hospital diet was available to all patients including 10 patients who had not lost weight who served as controls. In the three groups of patients who had lost weight, median transferrin and fibronectin were lower than for controls, whereas other proteins and amino acids were comparable. After feeding, samples of liver were obtained peroperatively and the potential rates of protein synthesis were calculated from the in vitro incorporation of (14C)-leucine, into protein. Preoperative IVN significantly increased the potential rate of protein synthesis in liver after 3 days. Plasma amino acids were comparable with controls whereas in the unfed-group concentrations suggested utilization of alanine and breakdown of muscle. Three days of IVN also increased plasma fibronectin and IgA but increases of prealbumin, IgM, and complement C3 were only significant in the group fed for 7 days. On the 7th postoperative day plasma proteins were decreased similarly in each group. This study shows that concentrations of several plasma proteins, in preoperative patients reflect net rates of hepatic protein synthesis and are susceptible to depletion during starvation and repletion by 3 or 7 days of IVN.

Plasma fibronectin synthesis in normal and injured humans as determined by stable isotope incorporation

In humans, plasma fibronectin decreases early after operative injury, burn, or trauma, followed by a rapid restoration with a secondary decline typically observed if such patients become septic. We determined the rate of plasma fibronectin and plasma fibrinogen synthesis in normal subjects and injured patients using a stable isotope incorporation technique with [15N]glycine. During a constant 14-h infusion of [15N]glycine, the enrichment of [15N]glycine in both the free plasma glycine precursor pool as well as the urinary hippurate pool was determined; the latter used as an estimate of intracellular hepatic precursor enrichment. [15N]Glycine enrichment in both plasma fibronectin and fibrinogen was also quantified. The synthesis rate (Js/V) expressed in micrograms per milliliter of plasma per hour and the fractional synthesis rate (FSR) expressed as percentage of the plasma pool produced per day were determined. In normal subjects, the FSR for plasma fibronectin using 15N enrichment into urinary hippurate was 35.35 +/- 1.46%/d, whereas the Js/V was 4.45 +/- 0.19 micrograms/ml plasma per h. In normal subjects, the FSR for plasma fibronectin using 15N enrichment into free plasma glycine was 14.73 +/- 0.63%/d, whereas the Js/V was 1.98 +/- 0.09 micrograms/ml plasma per h. Early (2-3 d) after burn injury, fibronectin synthesis was increased (Js/V = 5.74 +/- 0.36; P less than 0.05), whereas later after injury, fibronectin synthesis began to decline (Js/V = 3.52 +/- 0.24; P less than 0.05) based on 15N enrichment of urinary hippurate. In contrast, the Js/V and FSR of plasma fibrinogen, a well-documented acute-phase plasma protein, revealed a sustained elevation (P less than 0.05) after injury in both the trauma and burn patients. Thus, plasma fibronectin synthesis is elevated early postinjury, which may contribute to the rapid restoration of its blood level. However, once fibronectin levels have normalized, the synthesis of plasma fibronectin appears to decline.

Progressive loss of fibronectin-mediated opsonic activity in plasma cryoprecipitate with storage. Role of fibronectin fragmentation

Septic injured patients often manifest a deficiency of plasma fibronectin. Several studies have shown improvements in organ function in such patients following infusion of fibronectin-rich plasma cryoprecipitate, while other studies found no improvement. One explanation for these differences may be the use of plasma cryoprecipitate which has been stored for various time intervals prior to its use as a source of fibronectin. This investigation tested the hypothesis that the opsonic activity of fibronectin in cryoprecipitate may decline with increased storage duration. Using a bioassay of opsonic activity, we evaluated human plasma cryoprecipitate that was stored at either -20 or -80 degrees C for various intervals (2 weeks to 12 months) after its preparation from fresh donor plasma. Our findings demonstrated that the opsonic activity of fibronectin in cryoprecipitate declined with increasing time of storage. Significant loss (p less than 0.05) of opsonic activity was first evident after 2 months of storage. Storage at -80 degrees C did not prevent this decline in opsonic activity as compared to storage at -20 degrees C. Immunoblot analysis revealed extensive fragmentation of the dimeric fibronectin (440 kdaltons) and the presence of lower molecular weight fragments in 4- to 12-month-old plasma cryoprecipitate. Therefore, plasma cryoprecipitate of varying ages (storage time) when used as a source of fibronectin for replacement therapy to support phagocytic function in septic injured patients may result in different fibronectin-mediated responses. The decline in activity may be due, in part, to fragmentation of the fibronectin molecule.

Interaction of soluble fibronectin with group B streptococci

Fibronectin binds to a variety of bacterial species, and we hypothesized that differential fibronectin binding might influence the invasive potential of group B streptococci (GBS). Human plasma fibronectin purified by a standard two-step chromatographic procedure was radiolabeled with 3H. Fifty GBS strains (invasive, colonizing, or bovine) representing serotypes Ia (10 strains), Ib (6 strains), Ia/c (6 strains), II (10 strains), III (11 strains), IV (1 strain), and nontypable (6 strains) were tested. No source or serotype variability was detected among GBS strains, and binding was uniformly less than 1.5% of available fibronectin. Lack of detectable binding occurred at both the log and stationary growth phases and persisted despite treatment with trypsin or neuraminidase or opsonization with immunoglobulin G containing high levels (greater than 40 micrograms/ml) of antibody specific for the Ia, II, or III GBS capsular polysaccharides. Incubation with GBS did not inhibit fibronectin binding to the Cowan 1 strain of Staphylococcus aureus. Strain COH 31-15, an isogenic, type III, capsule-deficient mutant of COH 31r/s, also failed to bind fibronectin. In contrast to other streptococci, GBS do not have readily detectable receptors for soluble fibronectin as part of their surface structures. If present, binding sites for soluble fibronectin are deep to surface structures, obscured from host defense systems, or require the presence of other factors to facilitate their recognition of fibronectin. The uniform ability of GBS to resist binding to soluble fibronectin could be a significant virulence factor in the pathogenesis of invasive infections of infants.

Enhanced endotoxin effects in plasma fibronectin-deficient rats

Immunoreactive plasma fibronectin depletion has been associated with the presence of collagen-fibronectin complexes in patients after trauma and in animal models of traumatic and burn injuries. However, the role of plasma fibronectin in the development of sepsis after traumatic and burn injuries in patients is unknown. Treatment of patients and animals with purified human plasma fibronectin ameliorates some of the clinical and metabolic effects of systemic endotoxemia. We report that the induction of immunoreactive plasma fibronectin deficiency by gelatin infusion is associated with enhanced effects of intraperitoneal Escherichia coli endotoxin injection. We have observed a significant increase in the concentrations of ammonia in plasma of treated rats compared with those in control rats administered the same dose of endotoxin.

Pharmacologic management of the critically ill patient in the perioperative period--emphasis on the sepsis syndrome

The critically ill perioperative patient requires complex pharmacologic management. The ability to measure circulating drug concentrations has helped the clinician to properly modulate therapy, especially with potentially toxic agents. Postoperative sepsis remains a difficult therapeutic problem. Controversial therapies, such as the use of corticosteroids and the utility of newer pharmacologic approaches, are beginning to be properly tested in multicenter trials. Improvements in technology (e.g., development of monoclonal antibodies), biochemistry, and pharmacology have resulted in the development of exciting, new pharmacologic avenues for the management of the critically ill perioperative patient.

The effect of fibronectin therapy and fibronectin deficiency on healing of rat burns and excision wounds

Rats with standardized burns and skin excision wounds were treated i.p. with human fibronectin or swine skin gelatin. Controls received bovine albumin, solvent, or no treatment. Wound healing was assessed by planimetry, additionally plasma fibronectin was determined. Solvent or albumin did not influence the healing process, neither did fibronectin. However, when opsonizing fibronectin was additionally consumed by application of gelatin, a significant retardation of wound healing was observed. The results support the opinion that fibronectin is of essential importance for posttraumatic opsonization of gelatin-like material originating from the damaged tissue.

Immunomodulation following burn injury

Severe burn injury is accompanied by suppression of almost all the components of immunity; such suppression undoubedly contributes to infectious complications in the burned patient. There has now been substantial experimental progress made in devising approaches to prevent or minimize these immune defects; however, clinical application is still limited.

Fibronectin replacement in patients with fulminant hepatic failure

Patients with fulminant hepatic failure have low levels of the plasma opsonizing protein fibronectin together with cardiovascular disturbances similar to those in septic shock where microembolization of capillary beds by particulate debris has been proposed to lead to multi-organ failure. Six patients with fulminant hepatic failure received a bolus injection of a concentrated fibronectin-rich preparation. The mean plasma immunoreactive fibronectin level increased from 53 +/- SE 12 micrograms ml-1 initially to 295 +/- 30 micrograms ml-1 (P less than 0.001) at 1 h after fibronectin administration. The in vitro plasma opsonic activity was also increased from 5.6 +/- 3.6% of control to 102 +/- 13% (P less than 0.005) at 1 h. No similar effect was observed with the clearance of microaggregated albumin, but as its clearance is probably not dependent on fibronectin it may reflect a different aspect of reticuloendothelial cell function. No significant changes were observed in cardiopulmonary function or oxygen utilization and it is possible this is because clearance of opsonized particles is limited by damage to Kupffer cells.

Plasma fibronectin and complement activation in coronary bypass surgery

In patients with severe sepsis, plasma fibronectin concentrations are reduced and complement is activated. It is not known whether complement activation interferes with plasma fibronectin. Cardiopulmonary bypass is known to activate complement. We have therefore used this operation to study the effect of complement activation on plasma fibronectin in the absence of sepsis. After 15 min of bypass the percentage changes of plasma fibronectin and haematocrit were similar (65.9 +/- s.e.m. 4.8 and 67.0 per cent +/- s.e.m. 2.3, respectively), but the changes in C3 and C5 (58.4 +/- s.e.m. 4.8 per cent and 52.5 per cent +/- s.e.m. 2.1) were significantly greater than those of the haematocrit, indicating complement consumption. During the first 60 min of bypass there was a significant increase in the neutrophil count which is compatible with complement activation. It is unlikely that complement activation alone, in the absence of sepsis, contributes to the reduction of plasma fibronectin concentrations.

Plasma fibronectin: relevance for anesthesiology and intensive care

Plasma fibronectin has been postulated to be an essential mediator of normal reticuloendothelial system (RES) function. The acute depletion of fibronectin is thought to impair RES function, whereas its repletion in states of deficiency has been reported to improve RES function. In vitro studies have documented fibronectin's ability to bind to some nonbacterial microaggregates and to promote the phagocytosis of bound targets by the RES. These properties may, however, be influenced by the in vivo milieu. There is substantial evidence for a parallelism between RES function and plasma fibronectin levels following blunt trauma in animal models; however, this association is not seen in experimentally induced intravascular coagulation, acute inflammation, and sepsis. Clinically, subnormal fibronectin levels are clearly associated with the triad of intravascular coagulation, organ failure and sepsis. Fibronectin is, however, not the only plasma protein reduced in these patients, nor is it an outstanding predictor of such complications. The therapeutic efficacy of fibronectin administration remains controversial. Whereas initial reports suggested therapeutic benefits of fibronectin-enriched cryoprecipitates, subsequent studies have produced negative results. Prospective, randomized, controlled clinical trials with purified fibronectin are needed before fibronectin should be recommended as an adjunct to the established principles of intensive care.

Fibronectin and the critically ill patient: current status

In summary, deficiency of plasma fibronectin has now been documented in a variety of clinical entities. Persistently low fibronectin may have prognostic value, and in certain patients may provide a clue to occult sepsis and potential organ failure. The clinical benefit of infusion of fibronectin-rich cryoprecipitate or purified human plasma fibronectin has yet to be determined in well-controlled randomized clinical trials. However, if such results become available then infusion of plasma fibronectin may provide a valuable therapeutic modality in the care of the critically-ill patient.

Fibronectin levels in stressed and septic patients fed with total parenteral nutrition

Plasma fibronectin concentrations were measured in healthy persons as well as in septic and stressed patients. A decrease in plasma fibronectin concentration was shown in volunteers receiving a low energy (600 kcal), amino acids- and lipid-deficient diet. Increased fibronectin levels were measured in stressed and septic patients, not receiving enteral nutrition, after adequate total parenteral nutrition (TPN during 1 week). It is concluded that total parenteral nutrition facilitates improved fibronectin synthesis in stressed and septic patients. Total parenteral nutrition containing an amino acid mixture rich in branched amino acids (50.2% BCAA) is not superior to TPN containing a standard amino acid mixture (15.6% BCAA) in this respect.

Immunotherapy of neonatal septicemia

This chapter has reviewed the deficiencies in immune defense that place the neonate, particularly the premature infant, at increased risk of invasive bacterial disease. We also have reviewed the literature on the rationale for exchange transfusion, granulocyte transfusion, intravenous immunoglobulin, and fibronectin administration as immunotherapeutic agents in infected infants. There have been no randomized controlled trials of exchange transfusion, immunoglobulin, or fibronectin administration in human infants with infection. Granulocyte transfusion in the infected newborn infant has been studied in a controlled fashion, but the results of clinical trials are conflicting. Thus, all of these interventions appear to need further evaluation. We therefore recommend that in the septic newborn infant with neutropenia and an I/T ratio greater than or equal to 0.8, who fails to demonstrate a favorable response to conventional antibacterial chemotherapy and cardiopulmonary support, the administration of approximately 1 X 10(9) irradiated granulocytes per kg may be beneficial. In the absence of equipment to isolate the granulocytes, a double-volume exchange transfusion with fresh heparinized whole blood will provide a similar quantity of functional phagocytes.

Reversal of opsonic deficiency in surgical, trauma, and burn patients by infusion of purified human plasma fibronectin. Correlation with experimental observations

Plasma fibronectin deficiency has been documented in critically ill surgical, trauma, and burn patients. Human plasma fibronectin was isolated by gelatin-Sepharose affinity chromatography and evaluated with respect to its opsonic activity following pasteurization, its in vivo clearance kinetics, and its short-term influence on cardiovascular hemodynamics in postoperative septic sheep. Six patients with low plasma fibronectin levels were also evaluated with respect to temporal changes of immunoreactive fibronectin and opsonic activity following infusion of fibronectin at a dose calculated to elevate the plasma fibronectin level to 400 micrograms/ml. With utilization of three different in vitro radioisotopic phagocytic assays, i.e., liver slice assay, peritoneal macrophage monolayer assay, and Kupffer cell monolayer assay, retention of opsonic activity by fibronectin following pasteurization was documented. The normal biphasic kinetics associated with plasma clearance of fibronectin were also not altered by pasteurization. In postoperative septic sheep with hemodynamic instability, intravenous infusion of 500 mg of purified human fibronectin initiated no abnormal hemodynamic response. Indeed, as compared with placebo, the infusion of fibronectin into the postoperative septic sheep resulted in a more stable systemic vascular resistance and pulmonary vascular resistance with a higher arterial pressure. It also elevated immunoreactive fibronectin levels (p less than 0.05) and increased opsonic activity (p less than 0.05). Surgical, trauma, and burn patients (ages 18 to 80 years) with low plasma fibronectin levels (160 to 236 micrograms/ml) manifested no disturbance in cardiovascular, respiratory, or hematologic parameters following fibronectin infusion (590 to 988 mg per patient), but did display an early increase of opsonic activity. This standardized, pasteurized, and opsonically active preparation of purified human plasma fibronectin (5.0 mg/ml after reconstitution) has utility for future randomized clinical trials in injured patients with sepsis.

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.

The effect of proteolytic degradation of plasma fibronectin on the responses of functional and immunometric assays for intact fibronectin

Numerous studies have been made into the nature and importance of altered levels of plasma fibronectin seen in a range of clinical disorders. However, fibronectin is highly sensitive to the proteolytic degradation which may accompany some of these conditions. The influence of such degradation on the assays used is frequently unknown. We have investigated the effects of controlled protease degradation on the responses of an electroimmuno and a functional assay, using purified fibronectin. Tryptic digestion influenced the assays more than thrombin, in relation to the degree of breakdown. Both enzymes reduced the functional (gelatin-binding) activity whilst tryptic cleavage increased the apparent concentration by electroimmunoassay. The findings demonstrate that certain assays may be inappropriate for those clinical conditions where levels of intact fibronectin are of most interest. It is also necessary, then, to determine the degree of fibronectin breakdown when measuring pathological levels.

The clinical evaluation of plasma fibronectin as a marker for nutritional depletion and repletion and as a measure of nitrogen balance

Plasma fibronectin has been suggested as a possible marker for nutritional repletion or depletion. This study was undertaken to evaluate the usefulness of plasma fibronectin in patients who received intense nutritional support. Twenty-seven patients referred to our Nutritional Support Services were followed for 3 to 5 wk; 22 received parenteral hyperalimentation alone, two received enteral alone, and three received a combination of both. Plasma fibronectin, serum albumin, serum transferrin, total lymphocyte counts, and 24-hr urine nitrogen balance studies were performed weekly; anthropometric measurements were performed every other week. Plasma fibronectin concentration, measured by laser nephelometry, showed a significant rise (p less than 0.005) in all patients after 1 wk of nutritional therapy; however, there was no significant difference among the subsequent weeks. Plasma fibronectin did not correlate with nitrogen balance studies, serum albumin, or total lymphocyte counts. A correlation between serum transferrin and plasma fibronectin was found not to be clinically useful. Thus, plasma fibronectin is sensitive to nutritional repletion after 1 wk of therapy, but is not useful thereafter. The relationship among nutritional status, immunologic function, plasma fibronectin, and other serum proteins are discussed.

Lung vascular injury with protease infusion. Relationship to plasma fibronectin

Fibronectin exists in a soluble form in plasma and in an insoluble form in tissues. Plasma fibronectin can modulate phagocytic function as well as incorporate into the tissue matrix where it is believed to influence microvascular integrity and tissue repair. The temporal alterations in plasma and lung lymph fibronectin were studied in relation to increased pulmonary vascular permeability induced by protease infusion. The acute sheep lung lymph fistula model was used. A 39% decrease in plasma fibronectin (control = 421 +/- 67 micrograms/ml) was observed 2.5 hours (255 +/- 43 micrograms/ml) after protease infusion. There was an elevation of lymph fibronectin early after protease infusion, followed by a progressive decline. Concomitant with the decrease in plasma fibronectin, an increase in lymph flow (QL) of greater than 200% (from a control of 6.7 +/- 1.0 ml/hr to 13.9 +/- 1.4 ml/hr) was observed within 2.5 hours. Also, there was a sustained elevation in the total protein lymph/plasma concentration (L/P) ratio, which was maximal at 2.5 hours. The transvascular protein clearance (TVPC = QL X L/P) was 4.5 +/- 0.7 ml/hr at the control period and 13.1 +/- 2.0 ml/hr by 2.5 hours. This was indicative of increased flux of protein-rich fluid across the pulmonary endothelial barrier. Lung vascular permeability stabilized after 2.5 hours as manifested by a slowly declining L/P ratio. Thus, plasma fibronectin deficiency may contribute to the etiology of increased lung vascular permeability with protease infusion. Since the progressive decline in plasma fibronectin was not reflected in a proportional increase in lymph fibronectin, plasma fibronectin may have sequestered in tissues such as the lung, or perhaps in reticuloendothelial cells during the injury phase. Whether the progressive decrease in plasma fibronectin reflects its incorporation into the endothelial barrier matrix where it may mediate stabilization of the pulmonary microvascular barrier remains to be determined.

The response of fibronectin to differing parenteral caloric sources in normal man

The relationship between circulating fibronectin concentration and nutritional status was examined in eight healthy male (31 +/- 1 yr old) volunteers in three nutritional states: the postabsorptive state, after 10 days of protein-caloric starvation, and during the 10th day of refeeding by total parenteral nutrition. Plasma fibronectin was significantly decreased from 330 +/- 22 to 154 +/- 11 micrograms/ml (p less than 0.001) from the postabsorptive to starved state which was accompanied by appropriate changes in body weight, anthropometric measurements, and nitrogen balance. Plasma fibronectin levels were restored to 402 +/- 39 micrograms/ml following 10 days of total parenteral nutrition. The plasma fibronectin response was greater (p less than 0.05) during total parenteral nutrition with dextrose as the nonprotein calorie source as compared to a 50% dextrose/50% lipid regimen. These results suggest that the calorie source must be considered during interpretation of plasma fibronectin levels in patients undergoing parenteral nutrition.

Plasma fibronectin in relation to surgical trauma

Plasma concentrations of fibronectin, alpha 2-macroglobulin and orosomucoid were monitored immunochemically in 20 patients before, during and after surgery. At 2 h after the induction of anaesthesia fibronectin concentrations were lowered 31 +/- 6% (SEM) compared to values obtained 1-3 d preoperatively. However, the fibronectin concentration decreased 17 +/- 5% (SEM) compared to preoperative values at the beginning of surgery. Most of the decline was thus not caused by the operative trauma. The perioperative changes in fibronectin concentrations did not differ from those found in alpha 2-macroglobulin and, up to 2 h postoperatively, orosomucoid.

[Changes in levels of plasma fibronectin after surgery for digestive cancer]

Fibronectin is a large, adhesive glycoprotein, also called opsonic alpha 2 surface-binding glycoprotein. This glycoprotein which participates in all adhesions may modulate wound healing; plasma fibronectin, because it is opsonically active, may mediate reticulo-endothelial activity. Citrated plasma samples were analysed from twenty surgical patients with digestive cancer. The samples were obtained preoperatively and on 1st, 3rd, 7th, 14th and 28th postoperative days. Fibronectin assay was made by laser immunonephelometry. Other samples were obtained from a population of 340 healthy male and female subjects whose age ranged from 10 to 70 years, so that reference could be made to the standard mean of fibronectin related to the age of each patient. In the surgical patients, there was a significant decrease in fibronectin from the first to the third postoperative day. On the 7th day, there was a secondary increase of fibronectin levels which exceeded the preoperative values at the 14th and 28th days. There was no plasma dilution when the samples were collected, this being shown by protidaemia, osmolarity and haematocrit which were measured at the same time. "Septic" and "non septic" patients were compared. For septic patients, fibronectin levels were lower and the secondary increase occurred later than in the non septic patients. Patients with no secondary increase did not recover and died. Fibronectin levels were compared with other classical parameters of nutritional assessment, i.e. albumin, prealbumin, transferrin and urinary creatinine indexes. These parameters were not well correlated. However, this study may indicate the usefulness of fibronectin as an indicator of nutritional status and of non specific host defence.