Purified fibronectin administration to patients with severe abdominal infections. A controlled clinical trial

Fibronectin extra domain a limits liver dysfunction and protects mice during acute inflammation

Background and aim

The primary transcript of fibronectin (FN) undergoes alternative splicing to generate different isoforms, including FN containing the Extra Domain A (FN_EDA+), whose expression is regulated spatially and temporarily during developmental and disease conditions including acute inflammation. The role of FN_EDA+ during sepsis, however, remains elusive.

Methods

Mice constitutively express the EDA domain of fibronectin (EDA^+/+); lacking the FN EDA domain (EDA^-/-) or with a conditional ablation of EDA + inclusion only in liver produced FN (alb-CRE⁺EDA floxed mice) thus expressing normal plasma FN were used. Systemic inflammation and sepsis were induced by either LPS injection (70 mg/kg) or by cecal ligation and puncture (CLP) Neutrophils isolated from septic patients were tested for neutrophil binding ability.

Results

We observed that EDA^+/+ were protected toward sepsis as compared to EDA^-/- mice. Also alb-CRE⁺EDA floxed mice presented reduced survival, thus indicating a key role for EDA in protecting toward sepsis. This phenotype was associated with improved liver and spleen inflammatory profile. Ex vivo experiments showed that neutrophils bind to a larger extent to an FN_EDA + coated surface as compared to FN, thus potentially limiting their over-reactivity.

Conclusions

Our study demonstrates that the inclusion of the EDA domain in fibronectin dampens the nflammatoryi consequences of sepsis.

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 An English language literature search using MEDLINE, EMBASE, SCISEARCH, and compu terized databases of unpublished research in addition to bibliographic review was performed, and duplicate independent review of 41 articles by two observers identified six relevant randomized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.

Plasma fibronectin as a marker of sepsis

OBJECTIVES

To evaluate the value of plasma fibronectin (pFN) as a diagnostic marker of sepsis.

SUBJECTS AND METHODS

Plasma FN was determined in patients showing sepsis-related symptoms who had blood cultures performed. These patients were assigned to one of two groups according to their clinical situation: (1) Clinical Septic Group: patients with sepsis according to American College of Chest Physicians/Society of Critical Care Medicine (ACCP/SCCM) criteria; (2) Fever Peak Group: patients who did not fulfil sufficient ACCP/SCCM criteria for sepsis. Two additional control groups were also established: (3) Non-infectious Diseases Control Group and (4) Healthy Control Group.

RESULTS

Plasma FN levels, microbiological and clinical data were compared among the different patient groups. For each group, the number of patients, median and mean pFN levels and the 95% confidence interval of the mean were: (1) n = 43, 102 mg/l, 122 mg/l (100-144); (2) n = 70, 185 mg/l, 207 mg/l (184-231); (3) n = 22, 175 mg/l, 181 mg/l (151-211); and (4) n = 22, 256 mg/l, 261 mg/l (229-292). Bonferroni's test of multiple comparisons was able to detect a significant difference between pFN concentrations corresponding to the septic group, compared to the remaining groups (pANOVA < 0.001 ).

CONCLUSION

Plasma FN appears to act as a marker of sepsis in that patients showed diminished pFN levels. Along with other clinical and laboratory variables, the use of this marker would allow a rapid diagnosis of sepsis and limit the number of blood cultures to be processed and the number of antibiotic prescriptions, particularly when symptoms are insidious and diagnosis is doubtful. We propose further and more complex studies using a higher number of patients.

Reversal of gelatin-impaired wound healing in rats by exogenous fibronectin

Animal experiments have shown that administration of gelatin results in a deprivation of plasma fibronectin (FN) and impaired wound healing. For further elucidation of these findings a therapy study with purified human FN was performed in rats. Fifty animals received a standard burn injury of 1% body surface and were divided into five experimental groups. Positive controls given no further treatment or treated with solvent only served for estimation of normal healing. For a negative control, 10 animals received three intraperitoneal injections of gelatin (58 mg/kg body wt) on Days 0, 1, and 2 after injury. They exhibited a striking lack of plasma FN (Day 1) and a significant delay of wound contraction (Days 7 and 14). In the therapy groups each administration of gelatin was followed by an intraperitoneal or intracardiac injection of FN (58 mg/kg body wt) 1 hr later. In these animals the negative effect of gelatin upon plasma FN and wound contraction was prevented. According to this study wound healing is menaced by FN deficiency and can be optimized by substitution of exogenous FN.

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.

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.

Liver dysfunction in critical illness

Abnormal liver function commonly accompanies critical illness. Ischaemic hepatitis occurs with shock and is characterised by elevated plasma aminotransferase concentrations. 'ICU jaundice' occurs later in critical illness, especially after trauma and sepsis. The major biochemical abnormality is conjugated hyperbilirubinaemia. The clinical setting suggests that hepatic ischaemia and hepatotoxic actions of inflammatory mediators are the major aetiological factors. Massive blood transfusion, effects of nutritional support and drug toxicity may contribute. Both the presence and degree of jaundice are associated with increased mortality in several nonhepatic diseases. It is proposed that Kupffer cell phagocytic depression associated with liver dysfunction permits systemic spread of endotoxin and inflammatory mediators and thus predisposes to multiple organ failure. Immunosuppression, metabolic abnormalities, impaired drug oxidation and myocardial depression may contribute to the poor prognosis. There is no specific treatment, but prompt resuscitation, definitive treatment of sepsis and meticulous supportive care will likely reduce the incidence and severity.

[Human plasma fibronectin. Comparison of methods for preparation of a concentrate for therapeutic use from different sources]

Three methods, successive precipitations, affinity chromatography on immobilized gelatin and immunoaffinity chromatography with monoclonal anti-fibronectin antibodies were optimized and compared in order to be used for large scale preparation of human plasma fibronectin (Fn). The functional properties of the various Fn preparations were investigated by means of two assays: quantitation of the gelatin-binding activity by ELISA and quantitation of the Fn-mediated attachment of fibroblasts on plastic. Functional alterations of the purified Fn were observed when it was isolated by successive precipitations. Both chromatographic methods provide a rapid and convenient way for isolation of pure and functional Fn. Mass production of monoclonal antibodies is too expensive and legislative requirements for the therapeutic use of monoclonal antibodies are limiting factors for the choice of immunopurification as large scale isolation procedure. Plasma Fn can be isolated from different sources: fresh frozen plasma, cryoprecipitate supernatant or by-products from factor VIII preparation. When gelatin-Sepharose chromatography is performed under optimized conditions, fibronectins isolated from these sources show similar properties. Large scale purifications of Fn from a by-product of factor VIII preparation were performed either by gelatin affinity chromatography or by successive precipitations. These two purification methods can be easily scaled-up since the data obtained closely correlate with analytical results. The chromatographic method supplies a higher purified (98 vs 75%) and functional (95 vs 50%) material when compared with successive precipitations. Yield is also higher (50 vs 26%). The starting material undergoes viral inactivation and the affinity purified Fn, sterile, atoxic, apyrogen, which can be freeze-dried without additives fulfils all requirements for an injectable product.

Multiple organ failure--a role for plasma exchange?

Two patients with multiple organ failure, septicaemia and a deteriorating clinical course were treated by plasma exchange in addition to standard supportive measures. Dramatic improvements were seen in cardio-respiratory (patient 1), neurological and renal parameters (patient 2) which were attributable to the exchanges. Plasma exchange might be of value as adjunctive therapy where overwhelming septicaemia occurs with multiple organ failure.

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.

Intraabdominal infection: pulmonary failure

Since its first description in 1967, the mortality of the adult respiratory distress syndrome (ARDS) has remained unchanged despite the increasing sophistication of supportive techniques. Few patients now die of refractory hypoxemia, the majority succumbing to the multiple systems organ failure syndrome, commonly due to sepsis. Sepsis is both the most common cause of ARDS, usually involving the abdomen, and the most frequent complication, usually affecting the lungs. ARDS is, thus, increasingly seen as the pulmonary component of multiple systems organ failure, triggered by the systemic response to sepsis. In critically ill patients, impairment of hepatic function and of the barrier function of the gut mucosa allows translocation of endotoxin derived from the aerobic Gram-negative bacteria within the gut. This releases mediators which are responsible for the activation of cellular and humoral cascades, resulting in the pathological changes seen in ARDS. This sequence of events underlines the importance of therapies directed at abnormal colonization of the gastrointestinal tract and elimination of the gut endotoxin pool. Selective decontamination of the digestive tract is attractive in that it attacks the problem from 2 sides: first, by eliminating colonization, it appears effective in preventing secondary infection and, second, it may also play a role in reducing the enteric endotoxin pool. Recent descriptions of pathological oxygen supply dependency in both ARDS and septic patients emphasize the similarity of pathophysiological abnormalities in the 2 conditions. Intensive supportive therapy to achieve adequate oxygen transport and aggressive investigation and surgical management of septic foci are the cornerstones of management of the established syndrome.

Plasma fibronectin concentrations in blood products

Plasma fibronectin is an important opsonic protein of the mononuclear phagocyte system (MPS). In this study, plasma fibronectin concentrations were measured in stored and fresh whole blood, fresh frozen plasma and AGH cryoprecipitate. Stored whole blood had the lowest concentrations (151 +/- 50 mg/l). The concentrations in fresh whole blood plasma (227 +/- 66 mg/l) and fresh frozen plasma (224 +/- 78 mg/l) were similar but significantly higher than in stored whole blood (p less than 0.05). In contrast, AHG cryoprecipitate had the highest fibronectin concentrations (3249 +/- 502 mg/l) (p less than 0.001). In correcting fibronectin deficiency the best results can thus be expected from an infusion of cryoprecipitate, but fresh whole blood and fresh frozen plasma may also increase depressed fibronectin levels.

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.

Reticuloendothelial failure in chronic intra-abdominal sepsis: the role of opsonic fibronectin

Severe sepsis leads to depression of the reticuloendothelial (RE) system with delayed bloodstream clearance of particulate matter and bacteria. Fibronectin may be an important opsonin of the RE system and low fibronectin levels often accompany severe sepsis in man. We have investigated the effect of prolonged intra-abdominal sepsis on plasma fibronectin concentrations and RE function. Serial plasma fibronectin concentrations were determined in rabbits for 2 weeks after either the induction of sepsis (appendix abscess) (n = 6) or laparotomy only (n = 6). RE function was measured at 2 weeks by determining the clearance kinetics and organ distribution of low dose technetium tin colloid (TTC). There was an early transient depression in plasma fibronectin values followed by elevated concentrations at 48-72 h which were more marked in the sepsis group. There was a delay in the blood clearance with reduced hepatic and increased bone uptake of TTC. We conclude that depletion of opsonic fibronectin is unlikely to be an important factor contributing to the impairment of RE function associated with intra-abdominal sepsis and that RE depression in septic animals is due to intrinsic Kupffer cell dysfunction.

Clinical use of antithrombin III concentrates

The biochemical and biological properties of antithrombin III (AT III) and the clinical consequences of a deficiency of this inhibitor are described. Therapy with concentrates of purified AT III has been carried out for about 10 years and the present experience is reviewed. In a relatively small number of patients with congenital AT III deficiency it is necessary, under certain condition to substitute AT III. A considerably more frequent use of AT III concentrates has been made in acquired AT III deficiency, especially in shock and diffuse intravascular coagulation (DIC). This therapy was shown to be promising since the duration of DIC could be considerably shortened and the frequency of fatal events could be significantly diminished. No undesirable side effects of substitution with virus-sterilized AT III concentrates have been hitherto observed.

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.

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.