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Incorporation of vitronectin into fibrin clots. Evidence for a binding interaction between vitronectin and gamma A/gamma' fibrinogen.

Vitronectin is an abundant plasma protein that regulates coagulation, fibrinolysis, complement activation, and cell adhesion. Recently, we demonstrated that plasma vitronectin inhibits fibrinolysis by mediating the interaction of type 1 plasminogen activator inhibitor with fibrin (Podor, T. J., Peterson, C. B., Lawrence, D. A., Stefansson, S., Shaughnessy, S. G., Foulon, D. M., Butcher, M., and Weitz, J. I. (2000) J. Biol. Chem. 275, 19788-19794). The current studies were undertaken to further examine the interactions between vitronectin and fibrin(ogen). Comparison of vitronectin levels in plasma with those in serum indicates that approximately 20% of plasma vitronectin is incorporated into the clot. When the time course of biotinylated-vitronectin incorporation into clots formed from (125)I-fibrinogen is monitored, vitronectin incorporation into the clot parallels that of fibrinogen in the absence or presence of activated factor XIII. Vitronectin binds specifically to fibrin matrices with an estimated K(d) of approximately 0.6 microm. Additional vitronectin subunits are assembled on fibrin-bound vitronectin multimers through self-association. Confocal microscopy of fibrin clots reveals the globular vitronectin aggregates anchored at intervals along the fibrin fibrils. This periodicity raised the possibility that vitronectin interacts with the gamma A/gamma' variant of fibrin(ogen) that represents about 10% of total fibrinogen. In support of this concept, the vitronectin which contaminates fibrinogen preparations co-purifies with the gamma A/gamma' fibrinogen fraction, and clots formed from gamma A/gamma' fibrinogen preferentially bind vitronectin. These studies reveal that vitronectin associates with fibrin during coagulation, and may thereby modulate hemostasis and inflammation.

Biotinylation↗

Fibrin regulates neutrophil migration in response to interleukin 8, leukotriene B4, tumor necrosis factor, and formyl-methionyl-leucyl-phenylalanine.

We have examined the capacity of four different chemoattractants/cytokines to promote directed migration of polymorphonuclear leukocytes (PMN) through three-dimensional gels composed of extracellular matrix proteins. About 20% of PMN migrated through fibrin gels and plasma clots in response to a gradient of interleukin 8 (IL-8) or leukotriene B4 (LTB4). In contrast, < 0.3% of PMN migrated through fibrin gels in response to a gradient of tumor necrosis factor alpha (TNF) or formyl-methionyl-leucyl-phenylalanine (FMLP). All four chemoattractants stimulated PMN to migrate through gels composed of collagen IV or of basement membrane proteins (Matrigel), or through filters to which fibronectin or fibrinogen had been adsorbed. PMN stimulated with TNF or FMLP adhered and formed zones of close apposition to fibrin, as measured by the exclusion of a 10-kD rhodamine-polyethylene glycol probe from the contact zones between PMN and the underlying fibrin gel. By this measure, IL-8- or LTB4-treated PMN adhered loosely to fibrin, since 10 kD rhodamine-polyethylene glycol permeated into the contact zones between these cells and the underlying fibrin gel. PMN stimulated with FMLP and IL-8, or FMLP and LTB4, exhibited very little migration through fibrin gels, and three times as many of these cells excluded 10 kD rhodamine-polyethylene glycol from their zones of contact with fibrin as PMN stimulated with IL-8 or LTB4 alone. These results show that PMN chemotaxis is regulated by both the nature of the chemoattractant and the composition of the extracellular matrix; they suggest that certain combinations of chemoattractants and matrix proteins may limit leukocyte movements and promote their localization in specific tissues in vivo.

Adult↗

Behavior of human dermal fibroblasts in three-dimensional fibrin clots: dependence on fibrinogen and thrombin concentration.

Fibrin sealant products are used in hemostasis and tissue sealing, and potentially as a cell delivery vehicle. In this study, fibrin sealant was evaluated as a delivery vehicle for human dermal fibroblasts. Fibroblast proliferation and migration were assessed in various dilutions of fibrin sealant by changing the fibrinogen and thrombin concentration. Fibroblasts proliferated well within three-dimensional (3-D) fibrin clots consisting of fibrinogen (5-17 mg/mL) and thrombin (1-167 U/mL). These fibroblasts also retained good morphology and growth characteristics after migrating out of the 3-D fibrin clots. Furthermore, using Western blot and fluorescence-activated cell-sorting analysis, we found that the expression of growth factors and interleukins in the entire fibroblast-fibrin construct was dependent on the fibrin sealant formulation. For example, in a formulation in which fibroblasts showed modest proliferation and migration, interleukin 8 was secreted to a lesser extent than in a formulation that supported robust proliferation and migration. To our knowledge, this is the first time that it has been shown that modifying the concentration of fibrinogen and thrombin affects fibroblast behavior within formed 3-D fibrin clots. In addition, some of these formulations present an ideal delivery vehicle for fibroblasts that could be used for the treatment of chronic wounds.

Biocompatible Materials↗

Involvement of aspartic and glutamic residues in kringle-2 of tissue-type plasminogen activator in lysine binding, fibrin binding and stimulation of activity as revealed by chemical modification and oligonucleotide-directed mutagenesis.

Modification of glutamic and aspartic acid residues of tissue-type plasminogen activator (t-PA) with 1-ethyl-3(3-dimethyl-aminopropyl)-carbodiimide leads to a decrease in affinity for lysine and fibrin, to a decrease of plasminogen activation activity in the presence of a fibrin mimic, but leaves amidolytic activity and plasminogen activation without fibrin mimic unaffected. Experiments with kringle-2 ligands and a deletion mutant of t-PA (K2P) suggests that glutamic or aspartic acid residues in K2 of t-PA are involved in stimulation of activity, lysine binding and fibrin binding. Mutant t-PA molecules were constructed by site-directed mutagenesis in which one or two of the five aspartic or glutamic acid residues in K2 were changed to asparagine or glutamine respectively. Mutation of Asp236 and/or Asp238 leads to t-PA molecules with 3- to 4-fold lower specific activity in the presence of fibrin mimic and having no detectable affinity for lysine analogs. However, fibrin binding was not influenced. Mutation of Glu254 also leads to a 3- to 4-fold lower activity, but to a much smaller reduction of lysine or fibrin binding. Residues Asp236 and Asp238 are both essential for binding to lysine derivatives, while Glu254 might be involved but is not essential. Residues Asp236, Asp238 and Glu254 are all three involved in stimulation of activity. Remarkably, mutation of residues Asp236 and/or Asp238 appears not to influence fibrin binding of t-PA whereas that of Glu254 does.

Amino Acid Sequence↗

Temporary fibrin glue occlusion of the main pancreatic duct in the prevention of intra-abdominal complications after pancreatic resection: prospective randomized trial.

OBJECTIVE: To determine whether temporary occlusion of the main pancreatic duct with human fibrin glue decreases the incidence of intra-abdominal complications after pancreatoduodenectomy (PD) or distal pancreatectomy (DP). SUMMARY BACKGROUND DATA: To the authors' knowledge, there are no randomized studies comparing outcomes after pancreatic resection with or without main pancreatic duct occlusion by injection of fibrin glue. Of three nonrandomized studies, two reported no fistulas after intracanal injection and ductal occlusion with fibrin glue after PD with immediate pancreatodigestive anastomosis, while another study reported no protective effect of glue injection. METHODS: This prospective, randomized, single-blinded, multicenter study, conducted between January 1995 and January 1999, included 182 consecutive patients undergoing PD followed by immediate pancreatic anastomosis or DP, whether for benign or malignant tumor or for chronic pancreatitis. One hundred two underwent pancreatic resection followed by ductal occlusion with fibrin glue (made slowly resorbable by the addition of aprotinin); 80 underwent resection without ductal occlusion. The main end point was the number of patients with one or more of the following intra-abdominal complications: pancreatic or other digestive tract fistula, intra-abdominal collections (infected or not), acute pancreatitis, or intra-abdominal or digestive tract hemorrhage. Severity factors included postoperative mortality, repeat operations, and length of hospital stay. RESULTS: The two groups were similar in pre- and intraoperative characteristics except that there were significantly more patients in the ductal occlusion group who were receiving octreotide, who had reinforcement of their anastomosis by fibrin glue, and who had fibrotic pancreatic stumps. However, the rate of patients with one or more intra-abdominal complications, and notably with pancreatic fistula, did not differ significantly between the two groups. There was still no significant difference found after statistical adjustment for these patient characteristic discrepancies, confirming the inefficacy of fibrin glue. The rate of intra-abdominal complications was significantly higher in the presence of a normal, nonfibrotic pancreatic stump and main pancreatic duct diameter less than 3 mm, whereas reinforcement of the anastomosis with fibrin glue or use of octreotide did not influence outcome. In multivariate analysis, however, normal pancreatic parenchyma was the only independent risk factor for intra-abdominal complications. No significant differences were found in the severity of complications between the two groups. CONCLUSIONS: Ductal occlusion by intracanal injection of fibrin glue decreases neither the rate nor the severity of intra-abdominal complications after pancreatic resection.

Adolescent↗

Reactivity of D-dimer assays with the fibrinogen--fibrin split products generated by thrombolytic agents.

The reactivity of two D-dimer assays (a latex agglutination method, D-Di test and an ELISA procedure, Asserachrom D-Di) to the various fibrin or fibrinogen degradation products generated in plasma by three different thrombolytic agents was analysed, in the presence or absence of a fibrin clot. Other assays performed in parallel were an ELISA assay for (DD)E complexes and the conventional fibrinogen degradation products (FDP) latex test on serum. The thrombolytic agents urokinase, streptokinase or tPA were added at various concentrations and incubated for different times ranging from 10 min to 24 h. The data showed that the D-dimer latex assay was always negative provided there was no fibrin in plasma and despite the presence of high FDP levels (greater than 600 micrograms/ml) in serum. In contrast, D-dimer or (DD)E complexes were measured by ELISA, but up to a given concentration (15-20 micrograms/ml) which reached a plateau and remained stable irrespective of the thrombolytic concentrations or the degradation times. In the presence of fibrin clot, fibrinolysis was extremely fast with tPA and the FDP were generated at a much higher concentration that that expected from the size of the fibrin clot. This suggests the existence of fibrinogenolysis targeted by the presence of fibrin but negative in its absence. Urokinase and streptokinase generated FDP very quickly but a much slower degradation rate of fibrin was observed. The immunoblotting confirmed these data and showed that no late FDP were formed in plasma even at high thrombolytic concentrations except when fibrin was present.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzyme-Linked Immunosorbent Assay↗

Generation and partial characterization of five monoclonal antibodies with high affinities for fibrin.

Five fibrin-specific monoclonal antibodies have been generated using three different immunogens and a unique clot/plasma screening procedure. Two of the mAbs are directed to an epitope(s) on the A alpha-chain of fibrinogen while two others seem to react with a distinct B beta-chain epitope(s). A third antibody seems to displace all the mAbs from fibrin and may be directed to a repeating structural domain in the fibrin. The Kd values obtained (approximately 10(-9)M) using dried fibrin clots suggest high avidity for fibrin. All the mAbs cross-react with the fibrin-like X-oligomer structure in solution but in the presence of fibrin this reaction seems irrelevant due to the low Kd of the mAb/fibrin reaction. These mAbs have been examined for uptake by fibrin in a laboratory circulation circuit and while the uptake was dependent on mAb concentration an increase was noted for most concentrations over the first 2 h of circulation in the presence of plasma.

Antibodies, Monoclonal↗

Colloid determination of fibrin network permeability.

The effects of polymers, dextran and polyvinylpyrolidone (PVP) and of albumin on the permeability of thrombin-induced fibrin networks developed in plasma were examined. Both PVP and dextran increased the network permeability and turbidity and increased the fibrin fibre thickness. The effect was molecular weight dependent. Derivation of the dimensionless permeability (permeability/fibre radius2) indicated that the increase in network permeability was mainly from altered arrangement of fibres and not from increased fibre thickness. The effects of albumin on network structure were similar to those of the polymers. Scanning electron microscopy of networks developed in plasma under the influence of dextran and poloxamer 188 showed fibres with increased thickness and a coarse nodular appearance. There was an increased tendency for fibres to be aggregated into clumps. It is suggested that during polymerization fibrin fibres and fibrin polymerization intermediaries behave as colloidal particles. Attractive forces between the particles are generated by soluble macromolecules such as plasma proteins or polymers. Attractive forces increase the thickness of fibrin fibres and induce a more permeable arrangement of the fibres in the network. The most likely colloidal mechanism is depletion flocculation. This would account for (1) the molecular weight dependence and concentration dependence of the effects of macromolecules, (2) the effects of macromolecules which do not bind to fibrin, (3) the effects of the surfactant poloxamer 188. Depletion flocculation may be a significant mechanism for biological regulation of fibrin network permeability by non-specific macromolecules such as soluble proteins or fibrin intermediaries.

Albumins↗

The importance of antibody specificity in measuring cross-linked fibrin degradation products by ELISA.

We and others have previously shown that plasma concentrations of XL-FDPs are accurately characterized with an enzyme-linked immunosorbent assay (ELISA) based on the monoclonal antibody DD-3B6/22, which is specific for D-dimer, and a pan-specific tag antibody (DD-4D2/182) in patients with thrombotic disorders. However, in patients treated with fibrinolytic agents, increases in non-cross-linked fibrin(ogen) degradation products are detected by the pan-specific tag antibody due to formation of complexes between non-cross-linked derivatives and XL-FDPs. Assays based on the use of fibrin degradation product-specific tag antibodies appear to be more specific, but whether they would be clinically more informative is unclear. Accordingly, in the current study we measured concentrations of XL-FDPs with two ELISAs; one based on the pan-specific tag antibody (DD-4D2/182) and another based on a fibrin degradation product-specific tag antibody (DD-1D2/48) in patients treated with three well-characterized thrombolytic regimens: one associated with minimal fibrinogenolysis (100 mg tissue-type plasminogen activator [t-PA]) over 3 h), moderate fibrinogenolysis (100 mg t-PA over 90 min), and one with marked fibrinogenolysis (1.5 MU streptokinase [SK]). In patients treated with t-PA, increases in XL-FDPs were closely correlated with fibrinogenolysis, as characterized by increases in the concentration of the Bbeta1-42 peptide, when measured with the pan-specific tag ELISA (r = 0.7), but not when measured with the fibrin degradation product-specific tag assay (r = 0.2). In patients treated with SK, concentrations of XL-FDPs were significantly higher (> 2000 ng/ml) with the pan-specific tag ELISA compared with the fibrin degradation product-specific tag ELISA (< 1000 ng/ml) 1, 2 and 8 h after start of the infusion (P < 0.01). Concentrations of XL-FDPs were also higher in patients treated with SK compared with t-PA when measured with the pan-specific tag ELISA, but lower with SK with the fibrin-specific ELISA (P < 0.01). The value of measurement of XL-FDPs in patients treated with fibrinolytic agents will need to be reappraised with the use of fibrin degradation product-specific assays, which appear to provide more accurate information on the kinetics of cross-linked fibrin lysis in patients treated with t-PA or SK.

Antibody Specificity↗

Disintegration and reorganization of fibrin networks during tissue-type plasminogen activator-induced clot lysis.

In this study, we investigated tissue-type plasminogen activator (tPA)-induced lysis of glutamic acid (glu)-plasminogen-containing or lysine (lys)-plasminogen-containing thrombin-induced fibrin clots. We measured clot development and plasmin-mediated clot disintegration by thromboelastography, and used scanning electron microscopy (SEM) to document the structural changes taking place during clot formation and lysis. These events occurred in three overlapping stages, which were initiated by the addition of thrombin, resulting first in fibrin polymerization and clot network organization (Stage I). Autolytic plasmin cleavage of glu-plasminogen at lys-77 generates lys-plasminogen, exposing lysine binding sites in its kringle domains. The presence of lys-plasminogen within the thrombin-induced fibrin clot enhanced network reorganization to form thicker fibers as well as globular complexes containing fibrin and lys-plasminogen having a greater level of turbidity and a higher elastic modulus (G) than occurred with thrombin alone. Lys-plasminogen or glu-plasminogen that had been incorporated into the fibrin clot was activated to plasmin by tPA admixed with the thrombin, and led directly to clot disintegration (Stage II) concomitant with fibrin network reorganization. The onset of Stage III (clot dissolution) was signaled by a sustained secondary rise in turbidity that was due to the combined effects of lys-plasminogen presence or its conversion from glu-plasminogen, plus clot network reorganization. SEM images documented dynamic structural changes in the lysing fibrin network and showed that the secondary turbidity rise was due to extensive reorganization of severed fibrils and fibers to form wide, occasionally branched fibers. These degraded structures contributed little, if anything, to the structural integrity of the residual clot, and eventually collapsed completely during the course of progressive clot dissolution. These results provide new perspectives on the major structural events that occur in the fibrin clot matrix during fibrinolysis.

Fibrin↗

Injectable tissue-engineered cartilage using a fibrin glue polymer.

The purpose of this study was to demonstrate the feasibility of using a fibrin glue polymer to produce injectable tissue-engineered cartilage and to determine the optimal fibrinogen and chondrocyte concentrations required to produce solid, homogeneous cartilage. The most favorable fibrinogen concentration was determined by measuring the rate of degradation of fibrin glue using varying concentrations of purified porcine fibrinogen. The fibrinogen was mixed with thrombin (50 U/cc in 40 mM calcium chloride) to produce fibrin glue. Swine chondrocytes were then suspended in the fibrinogen before the addition of thrombin. The chondrocyte/polymer constructs were injected into the subcutaneous tissue of nude mice using chondrocyte concentrations of 10, 25, and 40 million chondrocytes/cc of polymer (0.4-cc injections). At 6 and 12 weeks, the neocartilage was harvested and analyzed by histology, mass, glycosaminoglycan content, DNA content, and collagen type II content. Control groups consisted of nude mice injected with fibrin glue alone (without chondrocytes) and a separate group injected with chondrocytes suspended in saline only (40 million cells/cc in saline; 0.4-cc injections). The fibrinogen concentration with the most favorable rate of degradation was 80 mg/cc. Histologic analysis of the neocartilage showed solid, homogeneous cartilage when using 40 million chondrocytes/cc, both at 6 and 12 weeks. The 10 and 25 million chondrocytes/cc samples showed areas of cartilage separated by areas of remnant fibrin glue. The mass of the samples ranged from 0.07 to 0.12 g at 6 weeks and decreased only slightly by week 12. The glycosaminoglycan content ranged from 2.3 to 9.4 percent for all samples; normal cartilage controls had a content of 7.0 percent. DNA content ranged from 0.63 to 1.4 percent for all samples, with normal pig cartilage having a mean DNA content of 0.285 percent. The samples of fibrin glue alone produced no cartilage, and the chondrocytes alone produced neocartilage samples with a significantly smaller mass (0.47 g at 6 weeks and 0.46 g at 12 weeks) when compared with all samples produced from chondrocytes suspended in fibrin glue (p < 0.03). Gel electrophoreses demonstrated the presence of type II collagen in all sample groups. This study demonstrates that fibrin glue is a suitable polymer for the formation of injectable tissue-engineered cartilage in the nude mouse model. Forty million chondrocytes per cc yielded the best quality cartilage at 6 and 12 weeks when analyzed by histology and content of DNA, glycosaminoglycan, and type II collagen.

Animals↗

Long-term regeneration of human epidermis on third degree burns transplanted with autologous cultured epithelium grown on a fibrin matrix.

BACKGROUND: Extensive third degree burn wounds can be permanently covered by the transplantation of autologous cultured keratinocytes. Many modifications to Green and colleagues' original technique have been suggested, including the use of a fibrin matrix. However, the properties of the cultured cells must be assessed using suitable criteria before a modified method of culture for therapeutic purposes is transferred to clinical use, because changes in culture conditions may reduce keratinocyte lifespan and result in the loss of the transplanted epithelium. METHODS: To evaluate the performances of human keratinocytes grown on a fibrin matrix, we assay for their colony-forming ability, their growth potential and their ability to generate an epidermis when grafted onto athymic mice. The results of these experiments allowed us to compare side by side the performance for third degree burn treatment of autologous cultured epithelium grafts grown according to Rheinwald and Green on fibrin matrices with that of grafts grown directly on plastic surfaces. RESULTS: We found that human keratinocytes cultured on a fibrin matrix had the same growth capacity and transplantability as those cultured on plastic surfaces and that the presence of a fibrin matrix greatly facilitated the preparation, handling, and surgical transplantation of the grafts, which did not need to be detached enzymatically. The rate of take of grafts grown on fibrin matrices was high, and was similar to that of conventionally cultured grafts. The grafted autologous cells are capable of generating a normal epidermis for many years and favor the regeneration of a superficial dermis. CONCLUSION: We have demonstrated that: 1) fibrin matrices have considerable advantages over plastic for the culture of skin cells for grafting and that it is now possible to generate and transplant enough cultured epithelium from a small skin biopsy to restore completely the epidermis of an adult human in 16 days; and 2) the generated epidermis self-renews itself for years. The use of fibrin matrices thus significantly improves the transplantation of cultured epithelium grafts for extensive burns as recently demonstrated in a follow-up work.

Adolescent↗

Partial nephrectomy with fibrin glue repair: measurement of vascular and pelvicaliceal hydrodynamic bond integrity in a live and abbatoir porcine model.

PURPOSE: Some of the challenges during partial nephrectomy include control of bleeding and repair of the pelvicaliceal system. Fibrin tissue sealants have recently been used to achieve hemostasis and collecting system closure in open and laparoscopic partial nephrectomy. However, there exist little data regarding the intrinsic strength of the bond, especially when applied to the vasculature and the urinary collecting system of the transected kidney. We examined the hydrodynamic bond integrity of a commercially available fibrin tissue sealant in a live porcine animal model undergoing partial nephrectomy. MATERIALS AND METHODS: Open partial nephrectomy was performed in 19 porcine renal units. Collecting system entry was confirmed by methylene blue instillation into the proximal ureter. Fibrin tissue sealant was used to repair 16 renal units, that is 8 kidneys hardened in vivo for 10 minutes and 8 hardened in vivo for 60 minutes. In an additional 3 renal units monopolar electrocautery was used to achieve hemostasis (no fibrin glue used). The strength of vasculature repair was performed by infusing saline into the renal artery (renal vein ligated) and measuring pressure at bond rupture. Similarly the integrity of pelvicaliceal repair was evaluated by retrograde infusion of saline into the collecting system via the proximal ureter and measurement of pressure at bond rupture. RESULTS: Fibrin tissue sealant was successful in achieving prompt hemostasis and it was subjectively superior to cautery alone with regard to bleeding control. Mean renal vascular and pelvicaliceal burst pressure for fibrin sealant treated kidneys was 378 (median 420) and 166 mm Hg (median 170), respectively. There was no significant difference in 10 vs 60-minute hardening times in treated kidneys. In comparison, vascular and pelvicaliceal burst pressure for nontreated (cautery alone) kidneys was 230 (median 220) and 87 mm Hg (median 90), respectively. CONCLUSIONS: Commercially available fibrin tissue sealants can provide supraphysiological renal parenchyma and collecting system sealing pressures after partial nephrectomy. This information supports the potential use of fibrin sealants during open and laparoscopic partial nephrectomy.

Abattoirs↗

Elevated first trimester maternal levels of soluble fibrin polymer are associated with lower birthweight in twin gestation.

We assessed soluble fibrin polymer longitudinally in normal pregnancy, thrombophilic pregnancy and twin gestation Thirty-three thrombophilic pregnancies, 34 uncomplicated multiple gestations and 23 singleton normal pregnancies were studied. Maternal plasma samples were collected in the first (6-12 weeks), 2nd (13-25 weeks) and 3rd trimesters of pregnancy (26-40 weeks) and were stored at -70 degrees C until assay. Soluble fibrin polymer was assayed by enzyme-linked immunosorbent assay (ABS, Copiague, New York, USA). Statistical analysis were made by Spearman test and Levine's test for equality of variance (P < 0.05). First soluble fibrin polymer maternal levels in twin gestation were significantly higher than in normal pregnancy and thrombophilic pregnancy, (23.8 +/- 4.5 mug/ml versus 9.2 +/- 3.1 and 10.0 +/- 2.0 mug/ml respectively, P < 0.005). Second and third trimester maternal levels of SFP in twins were also significantly higher than in normal pregnancy. First trimester soluble fibrin polymer was highly correlated with birthweight in twin gestation (r = -1, P < 0.01). In the third trimester, maternal soluble fibrin polymer correlated with placental weight in twin gestation (r = 0.639, P < 0.01). Overall, soluble fibrin polymer was correlated with placental weight and birthweight in the three groups but this did not reach statistical significance. Elevated maternal plasma levels of soluble fibrin polymer in twin gestation may derive from an accelerated coagulation process due to extensive vascular remodelling. Current studies are underway to determine the utility of soluble fibrin polymer in assessing fetal growth abnormalities.

Adult↗

Fibrin sealants in surgical or traumatic hemorrhage.

PURPOSE OF REVIEW: Fibrin sealants have been used to control surgical hemorrhage for three decades, and numerous articles have reported their use in a variety of surgical procedures in both animal models and humans. This article reviews the recent literature on fibrin sealants with the specific aim of highlighting the use of fibrin sealants in planned and simulated trauma to provide background for clinicians who may consider using fibrin sealants in specific cases. An overview of the mechanisms of action of fibrin sealants, their indications, and current commercial formulations is also provided. RECENT FINDINGS: Recent studies have evaluated the use of fibrin sealants in vascular surgery, including aortic anastomosis in an animal model, gastrointestinal anastomoses, plastic surgery, urologic procedures including heminephrectomy, and other procedures. SUMMARY: Fibrin sealants continue to be used and evaluated in animal models and surgery. Their use in military settings and in civilian trauma centers, explored for several years, is not reported extensively in the literature. Recent events and the current tempo of military operations dictate that many potential scenarios exist for using fibrin sealants to control traumatic hemorrhage.

Animals↗

Treatment of refractory donor-site seromas with percutaneous instillation of fibrin sealant.

BACKGROUND: Seromas at the flap donor site can occur following reconstructive surgery, and chronic seromas are particularly difficult to treat. Intraoperative use of fibrin sealant has been shown to enhance adherence of tissue surfaces and reduce postoperative fluid drainage. It was hypothesized that percutaneous instillation of fibrin sealant is effective for the postoperative treatment of refractory donor-site seromas. METHODS: Four patients over a 3-year period developed refractory donor-site seromas that were treated with instillation of fibrin sealant. The thrombin concentration was diluted to 5 IU/ml to increase polymerization time. The seromas were completely aspirated, and 20 ml of fibrin sealant was instilled through a dual-lumen catheter. Seroma recurrence was evaluated by serial physical examinations. Results were compared with those of control patients (n = 26) with seromas that persisted at least 6 weeks postoperatively despite conservative therapy including serial aspirations and/or drain reinsertion. RESULTS: All study patients failed conservative therapy before fibrin sealant instillation, which was performed a mean of 6.1 weeks postoperatively. All four patients had immediate and complete resolution of their refractory seromas following a single fibrin sealant instillation. There were no complications or recurrences during the mean follow-up time of 73.8 weeks. The success rate for seroma resolution (100 percent) was significantly greater with fibrin sealant injection in study patients than with serial aspiration alone (23 percent) in control patients (p = 0.0077). CONCLUSIONS: Percutaneous instillation of fibrin sealant may be an effective treatment for refractory donor-site seromas. Ongoing clinical experience and prospective controlled trials will be needed to define its role in seroma treatment.

Adult↗

Role of fibronectin in staphylococcal colonisation of fibrin thrombi and plastic surfaces.

The adhesive glycoprotein fibronectin has been proposed as a mediator of adherence of certain gram-positive cocci to host cells and fibrin thrombi. This study compared the role of soluble and immobilised fibronectin in the adherence of coagulase-negative staphylococci (CNS) and Staphylococcus aureus to fibrin thrombi and plastic surfaces. Adherence of S. epidermidis to fibrin thrombi was significantly reduced when fibronectin was removed from the plasma used for thrombus preparation. Adherence was restored through restitution of fibronectin. S. epidermidis also adhered substantially more to plastic surface coated with fibronectin than to non-coated plastic. Increased adherence of CNS to plastic was also observed after coating with the 29-kDa N-terminal fragment of fibronectin. Soluble fibronectin did not affect the adherence of CNS to fibrin thrombi or plastic surfaces. The adherence of S. aureus to fibrin thrombi was significantly increased by the addition of soluble fibronectin, but not by incorporation of fibronectin into the clot. These results indicate that the binding of fibronectin is an important factor in the adherence of staphylococci to fibrin clots and plastic surfaces and, thus, colonisation of these surfaces. However, the two species of staphylococci seem to employ different mechanisms of fibronectin-mediated adherence: S. epidermidis interacts mainly with fibronectin incorporated in fibrin clots or immobilised on implanted synthetic materials, whereas S. aureus adheres to the fibrin matrix through binding of soluble fibronectin present in wound exudates.

Albumins↗

Anti-fibrin antibody binding in valvular vegetations and kidney lesions during experimental endocarditis.

In Streptococcus sanguinis (sanguis) induced experimental endocarditis, we sought evidence that the development of aortic valvular vegetation depends on the availability of fibrin. Endocarditis was induced in New Zealand white rabbits by catheter placement into the left ventricle and inoculation of the bacteria. Fibrin was localized in the developing vegetation with 99mTechnetium (Tc)-labeled anti-fibrin antibody one or three days later. When rabbit anti-fibrin antibody was given intravenously on day 1, the mass of aortic valvular vegetation was significantly reduced at day 3; infusion of non-specific rabbit IgG showed no effect. The 99mTc-labeled anti-fibrin antibody also labeled kidneys that showed macroscopic subcapsular hemorrhage. To learn if the deposition of fibrin in the kidneys was a consequence of endocarditis required a comparison of farm-bred and specific pathogen-free rabbits before and after the induction of endocarditis. Before induction, the kidneys of farm-bred rabbits were labeled, but specific pathogen-free rabbits were free of labeling and signs of macroscopic hemorrhage. After 3 days of endocarditis, kidneys of 10 of 14 specific pathogen-free rabbits labeled with 99mTc-labeled anti-fibrin antibody and showed hemorrhage. Kidney lesions were suggested to be a frequent sequellae of S. sanguinis infective endocarditis. For the first time, fibrin was shown to be required for the continued development of aortic valvular vegetations.

Animals↗