Suppression of fibrin(ogen)-driven pathologies in disease models through controlled knockdown by lipid nanoparticle delivery of siRNA

Fibrinogen plays a pathologic role in multiple diseases. It contributes to thrombosis and modifies inflammatory and immune responses, supported by studies in mice expressing fibrinogen variants with altered function or with a germline fibrinogen deficiency. However, therapeutic strategies to safely and effectively tailor plasma fibrinogen concentration are lacking. Here, we developed a strategy to tune fibrinogen expression by administering lipid nanoparticle (LNP)-encapsulated small interfering RNA (siRNA) targeting the fibrinogen α chain (siFga). Three distinct LNP-siFga reagents reduced both hepatic Fga messenger RNA and fibrinogen levels in platelets and plasma, with plasma levels decreased to 42%, 16%, and 4% of normal within 1 week of administration. Using the most potent siFga, circulating fibrinogen was controllably decreased to 32%, 14%, and 5% of baseline with 0.5, 1.0, and 2.0 mg/kg doses, respectively. Whole blood from mice treated with siFga formed clots with significantly decreased clot strength ex vivo, but siFga treatment did not compromise hemostasis following saphenous vein puncture or tail transection. In an endotoxemia model, siFga suppressed the acute phase response and decreased plasma fibrinogen, D-dimer, and proinflammatory cytokine levels. In a sterile peritonitis model, siFga restored normal macrophage migration in plasminogen-deficient mice. Finally, treatment of mice with siFga decreased the metastatic potential of tumor cells in a manner comparable to that observed in fibrinogen-deficient mice. The results indicate that siFga causes robust and controllable depletion of fibrinogen and provides the proof-of-concept that this strategy can modulate the pleiotropic effects of fibrinogen in relevant disease models.

Activation of the Catalytic Activity of Thrombin for Fibrin Formation by Ultrasound

The regulation of enzyme activity is a method to control biological function. We report two systems enabling the ultrasound-induced activation of thrombin, which is vital for secondary hemostasis. First, we designed polyaptamers, which can specifically bind to thrombin, inhibiting its catalytic activity. With ultrasound generating inertial cavitation and therapeutic medical focused ultrasound, the interactions between polyaptamer and enzyme are cleaved, restoring the activity to catalyze the conversion of fibrinogen into fibrin. Second, we used split aptamers conjugated to the surface of gold nanoparticles (AuNPs). In the presence of thrombin, these assemble into an aptamer tertiary structure, induce AuNP aggregation, and deactivate the enzyme. By ultrasonication, the AuNP aggregates reversibly disassemble releasing and activating the enzyme. We envision that this approach will be a blueprint to control the function of other proteins by mechanical stimuli in the sonogenetics field.

Early morphological changes in tissues when replacing abdominal wall defects by bacterial nanocellulose in experimental trials

Experimental trials were done on five dogs to explore if an anterior abdominal wall defect could be repaired using wet (99.9%), compact BNC membranes produced by the Мedusomyces gisevii Sa-12 symbiotic culture. The abdominal wall defect was simulated by middle-midline laparotomy, and a BNC membrane was then fixed to open aponeurotic edges with blanket suture (Prolene 4-0, Ethicon). A comparative study was also done to reinforce the aponeurotic defect with both the BNC membrane and polypropylene mesh (PPM) (Ultrapro, Ethicon). The materials were harvested at 14 and 60 days postoperative to visually evaluate their location in the abdominal tissues and evaluate the presence of BNC and PPM adhesions to the intestinal loops, followed by histologic examination of the tissue response to these prosthetics. The BNC exhibited good fixation to the anterior abdominal wall to form on the 14th day a capsule of loose fibrin around the BNC. Active reparative processes were observed at the BNC site at 60 days post-surgery to generate new, stable connective-tissue elements (macrophages, giant cells, fibroblasts, fibrin) and neocapillaries. Negligible intraperitoneal adhesions were detected between the BNC and the intestinal loops as compared to the case of PPM. There were no suppurative complications throughout the postsurgical period. We noticed on the 60^th day after the BNC placement that collagenous elements and new capillary vessels were actively formed in the abdominal wall tissues, generating a dense postoperative cicatrix whose intraperitoneal adhesions to the intestinal loops were insignificant compared to the PPM graft.

Circulating levels of inflammatory cytokines (IL-1β and TNF-α), resistance to activated protein C, thrombin and fibrin generation in uncomplicated pregnancies

We studied 33 women during normal uneventful pregnancies and with no history of previous adverse pregnancy events for markers of activated coagulation and thrombin activity including prothrombin fragment 1.2(PF1.2), thrombin- antithrombin (TAT), and soluble fibrin polymer (SFP). In addition, we measured potential thrombin generation through the addition of thromboplastin to patient plasma in the presence of a throm-bin-specific chromogenic substrate determined serially over a period of time - Endogenous Thrombin Potential assay (ETP). This assay was performed with plasma treated and untreated with activated protein C (APC). The fibrinolytic system was assessed by measurement of thrombin activatable fibrinolysis inhibitor (TAFI). These findings were correlated with the levels of pro-inflammatory cytokines, interleukine-1β and tumor necrosis factor-α. Our data supports previous reports that indicate that resistance to activated protein C and coagulation activation markers are commonly increased in the later 2/3rds of pregnancy. There are no differences in thrombin generation potential, as determined by the ETP assay without the addition of APC, in the three trimesters. However, the thrombin reserve (TR), the ETP result without APC divided by the ETP result with the addition of APC, is increased above the reference range in the 2nd and 3rd trimesters. Patients with increased TR and resistance to APC had increased levels of TNF-α. Increased proinflammatory cytokines are reportedly associated with changes in the APC system with a decrease in the ability to generate APC. A sub-group of pregnancies with APC resistance had increased levels of TNF-α and may be important in the risk for adverse pregnancy outcomes.

Recombinant factor VIIa addition to haemophilic blood perfused over collagen/tissue factor can sufficiently bypass the factor IXa/VIIIa defect to rescue fibrin generation

INTRODUCTION

Factor VIII (FVIII) or factor IX (FIX)-deficient haemophilic patients display deficits in platelet and fibrin deposition under flow detectable in microfluidics. Compared to fibrin generation, decreased platelet deposition in haemophilic blood flow is more easily rescued with recombinant factor VIIa (rFVIIa), whereas rFVIIa requires FXIIa participation to generate fibrin when tissue factor (TF) is absent.

AIMS

Perfusion of haemophilic whole blood (WB) over collagen/TF surfaces was used to determine whether rFVIIa/TF was sufficient to bypass poor FIXa/FVIIIa function in blood from patients with haemophilia A and B.

METHODS

Whole blood treated with high-dose corn trypsin inhibitor (40 μg mL-1 ) from seven healthy donors and 10 patients was perfused over fibrillar collagen presenting low or high TF (TFlow or TFhigh ) at wall shear rate of 100 s-1 .

RESULTS

With WB from healthy controls, platelet deposition and fibrin accumulation increased as TF increased. Factor-deficient WB (1-3% of normal) displayed striking deficits in platelet deposition and fibrin formation at either TFlow or TFhigh . In contrast, mildly factor-deficient WB (14-32%) supported fibrin formation under flow on TFhigh /collagen. With either TFlow or TFhigh , exogenously added rFVIIa (20 nm) increased platelet deposition and fibrin accumulation in WB from factor-deficient patients (1-3% of normal) to levels commensurate with untreated healthy WB.

CONCLUSION

The absence of FIXa/FVIIIa in patients with severe haemophilia results in deficits in fibrin formation that cannot be rescued by wall-derived TF ex vivo. The effects of rFVIIa on platelet adhesion and rFVIIa/TF can act together to reinforce thrombin generation, platelet deposition and fibrin formation under flow.

The possible role of NS3 protease activity of hepatitis C virus on fibrogenesis and miR-122 expression in hepatic stellate cells

The various roles of hepatitis C virus (HCV) NS3 protein in viral pathogenesis are emphasized, especially in the progression of fibrosis and tumors. The levels of miR-122 have been widely accepted as a critical factor in viral pathogenesis and disease progression. However, the possible correlation between miR-122 levels and fibrosis state has been less investigated. Therefore, in this study, plasmids expressing protease competent and protease mutated non-structural proteins 3 (NS3) were transfected into LX-2 cell line. Subsequently, the total RNA was extracted and real-time PCR was performed to measure the expression level of miR-122, collagen type 1 alpha 1 (COL1A1), alpha smooth muscle actin (α-SMA), and tissue inhibitor of metaloproteinase 1 (TIMP-1). Moreover, the transforming growth factor beta (TGF-β) levels in the supernatants of transfected cells were evaluated by ELISA. The gene expression analysis of fibrotic genes and TGF-β cytokine in LX-2 cells showed that protease competent NS3 had a significant fibrogenic impact when compared to protease defective NS3 or GFP control plasmids (P <0.001). The results also demonstrated that the expression of miR-122 was downregulated in both versions of the cells transfected with NS3 plasmids (P <0.01) irrespective of protease function. These results suggested that the protease function of NS3 protein is a crucial factor for the induction of hepatic fibrosis but it doesn't play a complete role in the expression of miR-122.

Laboratory evidence of disseminated intravascular coagulation is associated with a fatal outcome in children with cerebral malaria despite an absence of clinically evident thrombosis or bleeding

BACKGROUND

A procoagulant state is implicated in cerebral malaria (CM) pathogenesis, but whether disseminated intravascular coagulation (DIC) is present or associated with a fatal outcome is unclear.

OBJECTIVES

To determine the frequency of overt DIC, according to ISTH criteria, in children with fatal and non-fatal CM.

METHODS/PATIENTS

Malawian children were recruited into a prospective cohort study in the following diagnostic groups: retinopathy-positive CM (n = 140), retinopathy-negative CM (n = 36), non-malarial coma (n = 14), uncomplicated malaria (UM), (n = 91), mild non-malarial febrile illness (n = 85), and healthy controls (n = 36). Assays in the ISTH DIC criteria were performed, and three fibrin-related markers, i.e. protein C, antithrombin, and soluble thrombomodulin, were measured.

RESULTS AND CONCLUSIONS

Data enabling assignment of the presence or absence of 'overt DIC' were available for 98 of 140 children with retinopathy-positive CM. Overt DIC was present in 19 (19%), and was associated with a fatal outcome (odds ratio [OR] 3.068; 95% confidence interval [CI] 1.085-8.609; P = 0.035]. The levels of the three fibrin-related markers and soluble thrombomodulin were higher in CM patients than in UM patients (all P < 0.001). The mean fibrin degradation product level was higher in fatal CM patients (71.3 μg mL(-1) [95% CI 49.0-93.6]) than in non-fatal CM patients (48.0 μg mL(-1) [95% CI 37.7-58.2]; P = 0.032), but, in multivariate logistic regression, thrombomodulin was the only coagulation-related marker that was independently associated with a fatal outcome (OR 1.084 for each ng mL(-1) increase [95% CI 1.017-1.156]; P = 0.014). Despite these laboratory derangements, no child in the study had clinically evident bleeding or thrombosis. An overt DIC score and high thrombomodulin levels are associated with a fatal outcome in CM, but infrequently indicate a consumptive coagulopathy.

Role of fibrinogen in massive injury

Coagulation is a complex cascade whose intact functioning is essential in helping control hemorrhage after injury. While traditionally ascribed to the combined effects of acidosis, hypothermia, factor consumption and factor dilution, coagulopathy is also directly related to injury as well as hypofibrinogenemia and hyperfibrinolysis. Low fibrinogen concentration is readily determined with standard laboratory profiling, but direct analysis of hyperfibrinolysis relies on either thromboelastography or rotational thromboelastometry. Both conditions offer opportunities for therapeutic intervention, and inhibition or abrogation of hyperfibrinolysis in particular may significantly improve survival in patients with injury and massive hemorrhage. Herein, we explore the underpinnings of trauma associated coagulopathy, the basic science behind the role of fibrinogen in acute traumatic coagulopathy, and the rationale behind and the data derived from management of hypofibrinogenemia as well as hyperfibrinolysis.

Thrombin generation and fibrin clot formation under hypothermic conditions: an in vitro evaluation of tissue factor initiated whole blood coagulation

BACKGROUND

Despite trauma-induced hypothermic coagulopathy being familiar in the clinical setting, empirical experimentation concerning this phenomenon is lacking. In this study, we investigated the effects of hypothermia on thrombin generation, clot formation, and global hemostatic functions in an in vitro environment using a whole blood model and thromboelastography, which can recapitulate hypothermia.

METHODS

Blood was collected from healthy individuals through venipuncture and treated with corn trypsin inhibitor, to block the contact pathway. Coagulation was initiated with 5pM tissue factor at temperatures 37°C, 32°C, and 27°C. Reactions were quenched over time, with soluble and insoluble components analyzed for thrombin generation, fibrinogen consumption, factor (f)XIII activation, and fibrin deposition. Global coagulation potential was evaluated through thromboelastography.

RESULTS

Data showed that thrombin generation in samples at 37°C and 32°C had comparable rates, whereas 27°C had a much lower rate (39.2 ± 1.1 and 43 ± 2.4 nM/min vs 28.6 ± 4.4 nM/min, respectively). Fibrinogen consumption and fXIII activation were highest at 37°C, followed by 32°C and 27°C. Fibrin formation as seen through clot weights also followed this trend. Thromboelastography data showed that clot formation was fastest in samples at 37°C and lowest at 27°C. Maximum clot strength was similar for each temperature. Also, percent lysis of clots was highest at 37°C followed by 32°C and then 27°C.

CONCLUSIONS

Induced hypothermic conditions directly affect the rate of thrombin generation and clot formation, whereas global clot stability remains intact.

[Dependence of the anticoagulant activity of starch and inulin on their degree of sulfonation]

We have studied a relationship between the degree of sulfonation and anticoagulant activity of starch from Solanum tuberosum (molecular weight, 25000-30000 Da; sulfonation degree, 0.4-2.5) and inulin from Helianthus tuberosus (molecular weight, 7000-8000 Da; sulfonation degree, 0.6-1.6). Starch and inulin sulfates (i) increased the time of appearance of fibrin clots in plasma in coagulometric tests and (ii) reduced (via antithrombin) the rate of thrombin-induced hydrolysis of a chromogen substrate. The antithrombin (aIIa) activity of starch sulfates reached 16.8-70.0 IU/mg and the activity against factor Xa (aXa activity) was 2.3-16.6 IU/mg. The antithrombin activity of inulin sulfates was within 5.5-11.4 IU/mg and the activity against factor Xa (aXa activity) was within 0-1.4 IU/mg. An increase in the degree of sulfonation led to a growth in the anticoagulant activity of starch sulfates. The anticoagulant activity of starch sulfates and inulin sulfate with sulfonation degree 1.0 is mediated by antithrombin, which is the plasma inhibitor of serine proteases.

Differential contributions of monocyte- and platelet-derived microparticles towards thrombin generation and fibrin formation and stability

BACKGROUND

Microparticles (MPs) are sub-micron vesicles shed by activated or apoptotic cells, including platelets and monocytes. Increased circulating MPs are associated with thrombosis; however, their role in thrombogenesis is poorly understood.

OBJECTIVE

To determine how MPs promote thrombin generation and modulate fibrin density and stability.

METHODS

Platelets and monocytes were isolated from healthy donors. Platelets were stimulated with calcium ionophore, thrombin receptor agonist peptide (TRAP) or TRAP/convulxin. Monocytes and human monocytic THP-1 cells were stimulated with lipopolysaccharide (LPS). MPs were isolated, washed by high-speed centrifugation and assessed using the following: transmission electron microscopy (TEM), Nanoparticle Tracking Analysis (NTA), flow cytometry, tissue factor (TF) activity, prothrombinase activity, thrombin generation, and clot formation, density and stability.

RESULTS

MPs from monocytes (M-MPs) and platelets (PMPs) had similar shapes and diameters (100-300 nm). M-MPs had TF activity (16.7 ± 2.4 pm TF per 10(6) MP), supported prothrombinase activity and triggered shorter thrombin generation lag times than buffer controls (5.4 ± 0.5 vs. 84.2 ± 4.8 min, respectively). Compared with controls, M-MPs supported faster fibrin formation (0.24 ± 0.24 vs. 76.7 ± 15.1 mOD min(-1) , respectively), 38% higher fibrin network density and higher clot stability (3.8-fold higher turbidity in the presence of tissue plasminogen activator). In contrast, PMPs did not have TF activity and supported 2.8-fold lower prothrombinase activity than M-MPs. PMPs supported contact-dependent thrombin generation, but did not independently increase fibrin network density or stability. Interestingly, PMPs increased rates of thrombin generation and fibrin formation (1.7- and 1.3-fold, respectively) when mixed with THP-1-derived MPs.

CONCLUSION

MPs from platelets and monocytes differentially modulate clot formation, structure and stability, suggesting unique contributions to thrombosis.

The cardioprotective effects of marrubiin, a diterpenoid found in Leonotis leonurus extracts

ETHNOPHARMACOLOGICAL RELEVANCE

Leonotis leonurus L. (Lamiaceae) is used as a traditional medicine for a variety of ailments in South Africa. The diterpene marrubiin is the major product constituent in specimens of this plant occurring in South Africa.

MATERIALS AND METHODS

Marrubiin isolated from South African specimens of L. leonurus in addition to an organic extract of L. leonurus were tested in vivo, ex vivo and in vitro for their anticoagulant, antiplatelet and anti-inflammatory activities.

RESULTS

Marrubiin and the organic extract suppressed coagulation, platelet aggregation and inflammatory markers. For the coagulation markers it was found that the organic extract and marrubiin significantly prolonged activated partial thromboplastin time (APTT). Fibrin and D-dimer formation were drastically decreased. These findings were observed in an ex vivo model and an obese rat model. Chemokines enhance leukocyte recruitment to inflammatory sites. TNF-α and RANTES secretion were significantly reduced by the extract and marrubiin when determined in the obese rat model relative to the controls. Calcium mobilization and TXB(2) synthesis were suppressed by the extract and marrubiin. An in vitro model was used to elucidate the antiplatelet mechanism and it was found that the extract and marrubiin inhibited platelet aggregation by inhibiting the binding of fibrinogen to glycoprotein (GP) IIb/IIIa receptor in a concentration dependent manner.

CONCLUSION

The findings reflect that marrubiin largely contributes to the extract's anticoagulant, antiplatelet and anti-inflammatory effects observed.

Activation of hemostasis in brain dead organ donors: an observational study

BACKGROUND

Brain death is associated with a systemic inflammatory response resulting in diminished organ function in individuals transplanted with organs from brain dead donors. As inflammation is accompanied by activation of coagulation, we hypothesized that activation of hemostasis occurs in brain dead organ donors.

OBJECTIVES

To assess the hemostatic status in brain dead organ donors.

PATIENTS AND METHODS

In this study, we systematically assessed the hemostatic system in samples taken from 30 brain dead donors. As controls, blood samples from 30 living kidney donors were included.

RESULTS AND CONCLUSIONS

Compared with the living donors, brain dead donors showed significant platelet activation (assessed by glycocalicin plasma levels), and a profound dysbalance in the von Willebrand factor/ADAMTS13 axis, which is key in platelet attachment to damaged vasculature. Furthermore, compared with the living donors, brain dead donors showed a significantly increased activation of secondary hemostasis with formation of fibrin (assessed by plasma levels of prothrombin fragment 1 + 2, fibrinopeptide A and D-dimer). Finally, brain dead donors showed profound hypofibrinolysis as assessed by a global clot lysis assay, which was attributed to substantially elevated plasma levels of plasminogen activator inhibitor type 1. Collectively, our results show activation of hemostasis and dysregulated fibrinolysis in brain dead organ donors. This prothrombotic state may contribute to formation of microthrombi in transplantable organs, which potentially contributes to deterioration of organ function.

Improvement of spatial fibrin formation by the anti-TFPI aptamer BAX499: changing clot size by targeting extrinsic pathway initiation

BACKGROUND

Tissue factor pathway inhibitor (TFPI) is a major regulator of clotting initiation and a promising target for pro- and anticoagulation therapy. The aptamer BAX499 (formerly ARC19499) is a high-affinity specific TFPI antagonist designed to improve hemostasis. However, it is not clear how stimulation of coagulation onset by inactivating TFPI will affect spatial and temporal clot propagation.

OBJECTIVE

To examine the BAX499 effect on clotting in a spatial, reaction-diffusion experimental system in comparison with that of recombinant activated factor VII (rVIIa).

METHODS

Clotting in plasma activated by immobilized tissue factor (TF) was monitored by videomicroscopy.

RESULTS

BAX499 dose-dependently improved coagulation in normal and hemophilia A plasma activated with TF at 2 pmole m(-2) by shortening lag time and increasing clot size by up to ~2-fold. The effect was TFPI specific as confirmed by experiments in TFPI-depleted plasma with or without TFPI supplementation. Clotting improvement was half-maximal at 0.7 nm of BAX499 and reached a plateau at 10 nm, remaining there at concentrations up to 1000 nm. The BAX499 effect decreased with TF surface density increase. RVIIa improved clotting in hemophilia A plasma activated with TF at 2 or 20 pmole m(-2) , both by shortening lag time and increasing spatial velocity of clot propagation; its effects were strongly concentration dependent.

CONCLUSIONS

BAX499 significantly improves spatial coagulation by inhibiting TFPI in a spatially localized manner that is different to that observed with rVIIa.

Influence of antibiotic therapy on the level of selected angiogenic factors in patients with benign gynecologic tumors--preliminary report

An increased fibrin level enhances the activity of proangiogenic factors and may contribute to tumor formation. Formation of new blood vessels during angiogenesis leads to neoplasm development through interaction with factors such as basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and interleukins. The aim of this study was to investigate the influence of perioperative antibiotic therapy in women with benign gynecological tumors with regard to basic fibroblast growth factor level, fibrinogen concentration and fibrin viscosity. The influence of clindamycin plus metronidazole therapy (group I) and cephazolin therapy (group II) on fibrinogen concentration, level of bFGF and fibrin viscosity was studied in women diagnosed with nonmalignant myomas and cysts. In patients with benign gynecologic tumors, higher bFGF levels (51.40 +/- 13.72 pg/ml), fibrinogen concentration (348.26 +/- 164.74 mg/dl) and fibrin viscosity (2.63 +/- 0.36 mPa) were observed, as compared with healthy women. There were strong indications that antiangiogenic activity occurred with both clindamycin plus metronidazole and cephazolin, although the response to these particular antibiotic therapies was different. The use of various drug therapies in groups I and II resulted in faster and delayed antiangiogenic effects, respectively. Further research is essential to provide more detailed information about the mechanisms of the induction of antiangiogenic activity by perioperative adjuvant antibiotic treatment.

Discordant fibrin formation in hemophilia

BACKGROUND

The conversion of fibrinogen to fibrin and its crosslinking to form a stable clot are key events in providing effective hemostasis.

OBJECTIVES

To evaluate the relationship of fibrinopeptide (FP) release and factor (F) XIII activation in whole blood from hemophiliacs.

PATIENTS/METHODS

We investigated FPA and FPB release, FXIII activation and fibrin mass in tissue factor-initiated coagulation in whole blood from individuals with hemophilia and healthy subjects.

RESULTS

In hemophiliacs, the rates of fibrin formation were delayed as compared to healthy individuals. FPA/FPB release and FXIII activation were decreased in hemophiliacs vs. healthy individuals: 5.4 +/- 0.7 microM min(-1) to 1.7 +/- 0.4 microM min(-1) (P = 0.003), 2.3 +/- 0.6 microM min(-1) to 0.5 +/- 0.1 microM min(-1) (P = 0.025), and 12.1 +/- 0.7 nM min(-1) to 3.1 +/- 0.7 nM min(-1) (P < 0.0005), respectively. More FPA was released in hemophiliacs (6.6 +/- 1.2 microM) prior to clot time (CT) than in healthy individuals (2.6 +/- 0.4 microM, P = 0.013), whereas FPB and activated FXIII levels remained comparable. FXIII activation, which normally coincides with FPA release, was delayed in hemophiliacs. At CT in normal blood, the FPA concentration was 2.6-fold higher than that of FPB (P = 0.003), whereas in hemophiliacs this ratio was increased to 6.6-fold (P = 0.001).

CONCLUSIONS

These data suggest that essential dynamic correlations exist between the presentations of fibrin I, fibrin II, and FXIIIa. The 'discordance' of fibrin formation in hemophiliacs results in clots that are more soluble than normal (43% lower mass; P = 0.02). The resulting poor physical clot strength probably plays a crucial role in the pathology of hemophilia.

Pathogenesis of thrombosis

The hemostatic process is a host defense mechanism to preserve the integrity of the closed high pressure circulatory system. This process must remain inactive but poised to minimize extravasation of blood from the vasculature following tissue injury. Given the complexity of the hemostatic mechanism, paradigms developed from biochemical and cell biological approaches have been revisited by studying thrombus formation in a live animal by intravital microscopy. Many of these paradigms have proven accurate, but others need to be reconsidered given the results of whole animal experiments.

Congenital disorder of glycosylation Ia: new differentially expressed proteins identified by 2-DE

Congenital disorders of glycosylation (CDG) comprise a family of inherited multisystemic disorders resulting from the deficiency of glycosylation pathways. N-glycosylation defects are classified as two biochemical and genetic established types, of which CDG-Ia is the most frequent. We performed 2-DE proteomic analysis on serum from two functional hemizygous CDG-Ia patients bearing T237M and D65Y missense changes. Comparative analysis of control/patient serum proteome allowed us to identify differential expression of 14 proteins. The most remarkable groups included proteins involved in immune response, coagulation mechanism and tissue protection against oxidative stress. The patient bearing D65Y mutation had less favourable clinical outcome and showed more abnormalities in the spot patterns, suggesting that the proteomic results might also be correlated with the phenotype of CDG patients. This study describes for the first time the differential expression of alpha(2)-macroglobulin, afamin, fibrin and fibrinogen in CDG disorder and shows how the proteomic approach might be useful for understanding its physiopathology.

An endogenously deposited fibrin scaffold determines construct size in the surgically created arteriovenous loop chamber model of tissue engineering

BACKGROUND

An arteriovenous loop (AVL) enclosed in a polycarbonate chamber in vivo, produces a fibrin exudate which acts as a provisional matrix for the development of a tissue engineered microcirculatory network.

OBJECTIVES

By administering enoxaparin sodium - an inhibitor of fibrin polymerization, the significance of fibrin scaffold formation on AVL construct size (including the AVL, fibrin scaffold, and new tissue growth into the fibrin), growth, and vascularization were assessed and compared to controls.

METHODS

In Sprague Dawley rats, an AVL was created on femoral vessels and inserted into a polycarbonate chamber in the groin in 3 control groups (Series I) and 3 experimental groups (Series II). Two hours before surgery and 6 hours post-surgery, saline (Series I) or enoxaparin sodium (0.6 mg/kg, Series II) was administered intra-peritoneally. Thereafter, the rats were injected daily with saline (Series I) or enoxaparin sodium (1.5 mg/kg, Series II) until construct retrieval at 3, 10, or 21 days. The retrieved constructs underwent weight and volume measurements, and morphologic/morphometric analysis of new tissue components.

RESULTS

Enoxaparin sodium treatment resulted in the development of smaller AVL constructs at 3, 10, and 21 days. Construct weight and volume were significantly reduced at 10 days (control weight 0.337 +/- 0.016 g [Mean +/- SEM] vs treated 0.228 +/- 0.048, [P < .001]: control volume 0.317 +/- 0.015 mL vs treated 0.184 +/- 0.039 mL [P < .01]) and 21 days (control weight 0.306 +/- 0.053 g vs treated 0.198 +/- 0.043 g [P < .01]: control volume 0.285 +/- 0.047 mL vs treated 0.148 +/- 0.041 mL, [P < .01]). Angiogenesis was delayed in the enoxaparin sodium-treated constructs with the absolute vascular volume significantly decreased at 10 days (control vascular volume 0.029 +/- 0.03 mL vs treated 0.012 +/- 0.002 mL [P < .05]).

CONCLUSION

In this in vivo tissue engineering model, endogenous, extra-vascularly deposited fibrin volume determines construct size and vascular growth in the first 3 weeks and is, therefore, critical to full construct development.

Recombinant tissue plasminogen activator may reduce frequency of central venous access device infection in hemophilia patients undergoing immune tolerance therapy

Many patients with hemophilia, particularly those with inhibitory antibodies, utilize central venous access devices (CVADs) to facilitate frequent infusions. Infection of these devices is a common complication of factor replacement therapy. This communication reports our center's experience with CVAD infection in three patients with severe hemophilia A undergoing immune tolerance therapy (ITT) in whom intermittent infusions of recombinant tissue plasminogen activator (rTPA, Cathflo Activase) were utilized. In this small experience, patients experienced a decreased frequency of gram-positive infections when receiving routine rTPA treatments. Larger randomized trial should be performed in this patient population at high risk of CVAD infection.

Anti-thrombin as a prognostic biomarker candidate for patients with recurrent glioblastoma multiform under treatment with perillyl alcohol

Perillyl alcohol (POH) is a naturally occurring monoterpene with antiangiogenic and anti-tumoral properties. This chemotherapeutic agent has proven effectiveness in several clinical trials, including an ongoing phase I, comprising patients with recurrent glioblastoma multiform (GBM) under treatment with POH by intranasal administration. Proteomics offers tools to distinguish states of biological systems according to protein expression differences and therefore, can be used to gain pathological insights and to search for disease follow-up biomarkers. In this work, a differential gel electrophoresis (DIGE) proteomic approach was used to search for plasma proteins that correlated with the disease progression in 10 of these patients. Our results pointed antithrombin (down) and fibrinogen (up) regulated after a four months treatment deserving to be further verified as prognostic markers for this treatment. Possible links between tumor progression and anti-thrombin expression level are also discussed.

Inhibition of tyrosine kinase activity prevents the adhesive and cohesive properties of platelets and the expression of procoagulant activity in response to collagen

INTRODUCTION

Platelet activation leads to signal transduction mechanisms, in which phosphotyrosine proteins play a relevant role.

MATERIAL AND METHODS

Platelet suspensions were independently activated by collagen and thrombin in the absence and in the presence of two tyrosine kinase inhibitors, tyrphostin 47 and genistein. Samples were processed to visualize morphological changes by electron microscopy, to evaluate changes in cytoskeletal assembly, to analyze modifications in the expression of activation dependent antigens, and the procoagulant activity at the surface level by flow cytometry. Additional experiments applying flow conditions were performed to assess the effect of inhibiting tyrosine phosphorylation on primary platelet adhesion and fibrin formation.

RESULTS

Inhibition of tyrosine phosphorylation blocked shape change and cytoskeletal assembly induced by collagen, and inhibited, though partially, those effects due to thrombin. Both activating agents induced the expression of the intraplatelet antigens CD62P and CD63 at the surface, although only collagen promoted expression of anionic phospholipids. Both tyrphostin 47 and genistein prevented those effects. The extent of platelet adhesion on both collagen-coated and subendothelial surfaces was significantly diminished by the presence of the tyrosine kinase inhibitors assayed. Fibrin formation was also significantly reduced.

CONCLUSIONS

Platelet shape change and secretion during platelet activation depends on tyrosine phosphorylation. In addition, primary adhesion of platelets induces signaling through tyrosine kinases to achieve full spreading, and results in the exposure of a procoagulant surface on platelets.

A global assay of haemostasis which uses recombinant tissue factor and tissue-type plasminogen activator to measure the rate of fibrin formation and fibrin degradation in plasma

The global assay of Overall Haemostasis Potential we previously described has been refined. The coagulation cascade in platelet-poor plasma is triggered by adding a minimal dose of recombinant tissue factor together with purified phospholipids and calcium; fibrinolysis is initiated by adding recombinant tissue type-plasminogen activator in a concentration similar to what can be obtained during thrombolysis. Numerical differentials of optical densities reflecting rates of fibrin formation and degradation are calculated by a new software, and the Coagulation Profile (Cp) and the Fibrinolysis Profile (Fp) are determined. The combined effect of these counteractive systems is expressed as a ratio of Cp to Fp, called the Overall Haemostasis Index. Commercially available coagulant-deficient patient plasma samples and plasma with various amounts of added PAI-1 are examined; changes of fibrin turbidity demonstrate that this assay can determine Cp and Fp in a physiologically relevant way. Increased Cp and decreased Fp in prothrombotic patients, as well as expected effects of heparin or a thrombin inhibitor on Cp and Fp, suggest that our method can detect hypercoagulability and assist in monitoring antithrombotic treatment. Ongoing studies will show whether this simple assay can be of value in clinical routine.

Changes in fibrinogen and fibrin induced by a peptide analog of fibrinogen gamma365-380

BACKGROUND

The effects of synthetic peptides with sequences derived from the gamma-chain of fibrinogen on the functional properties of fibrinogen and fibrin were investigated.

METHODS

Methods included thrombelastography, clot turbidity measurement, clot elasticity measurement, platelet aggregation, and scanning transmission electron microscopy (STEM).

RESULTS

Peptide gamma369-380 (NH(2)-WATWKTRWYSMK-COOH) showed the greatest impact on fibrin structure, compared with the 76 other overlapping dodecapeptides. Addition of this peptide, or peptide gamma365-380 (NH(2)-NGIIWATKTREWYSMK-COOH) to a mixture of fibrinogen and thrombin resulted a shorter clotting time, higher clot turbidity, lower clot elastic modulus, a higher degree of D-trimer and D-tetramer formation, and impaired plasmin proteolysis of the clot. In STEM, fibrin formed in the presence of peptide gamma369-380 consisted of a more extensive array of linear fibrils typically consisting of 20 or more molecules. Fibrils were better organized than those from non-peptide containing mixtures.

CONCLUSIONS

Replacement of the tryptophan residue gamma376 massively reduced the effect of the peptide on fibrin structure. Binding of the peptide to fibrinogen induces conformational changes, which result in accelerated clotting and increased lateral association of fibrin protofibrils. The results imply a relevant functional role of sites interacting with peptide gamma369-380 region in the fibrinogen molecule.

Ligneous periodontitis and gingival antioxidant status: report of two cases

Ligneous periodontitis (LP) is a rare periodontal disease in which plasminogen deficiency and fibrin deposition both play a part, resulting in characteristic gingival enlargement and periodontal breakdown. Recent data suggest that oxidant/antioxidant changes are significant in the pathology of oral diseases. This study examines the gingival histopathology in 2 cases with LP. To examine the antioxidant (AO) status, the activity of the major AOs glutathione (GSH), catalase (CAT), and glutathione S-transferase (GST) and the malondialdehyde (MDA) levels, a product of lipid peroxidation, were measured and compared with healthy control subjects. The histopathologic examination of the gingiva revealed subepithelial fibrin accumulation and irregular extensive downward proliferation of the epithelium. Biochemical analysis showed that the CAT, GST, and MDA levels were higher in LP patients than in the control subjects, and the GSH level was lower. Our preliminary findings show that in LP, the AO capacity of the gingiva changes or decreases and lipid peroxidation increases, which suggests that oxidative stress is involved in the pathology of the periodontal breakdown observed in this disease.

Anodic cell-protein deposition on inverse inkjet printed micro structured gold surfaces

The transformation of fibrinogen into fibrin is biologically activated in a complex multi-step process known as the coagulation cascade. This transformation can also be triggered by anodic surfaces. It has been suggested that this mechanism is a result of an electron transfer from the anode to the fibrinogen molecule resulting in the formation of fibrin. In this study we used this pathway to simultaneously deposit vital cells (fibroblasts and keratinocytes) and fibrin on micro structured gold electrodes. The electrodes were produced using a novel inverse inkjet-printing technology in combination with subsequent gold-sputtering, resulting in minimal structure-sizes of 35 microm (+/-6 microm). Cell deposition and fibrin-coagulation were found to occur on the anode only, following exactly the micro structured electrode surface. Successful deposition was limited by the minimal voltage (0.8 V) needed for the formation of fibrin and the maximum voltage (1.85 V) resulting in the deterioration of the Au-electrodes due to electrolysis and possible damaging of the deposited cells due to the formation of molecular chlorine. Furthermore, it was demonstrated that this technique is suitable to co-cultivate different cell types in a layered fashion. Subsequent to the electrically mediated anodic cell-protein deposition, cells were cultivated for up to 4 days and then characterized by vital fluorescence staining, methyl violet-staining and scanning electron microscopy. Cell-vitality was found to be dependent on the experimental setup; in this study non-vital cells were only observed, when sequentially depositing two different cell types. Finally, the coagulation mechanism was studied using HPLC, SDS-gel-chromatography and ATR/FTIR.

An acquired inhibitor that produced a delay of fibrinopeptide B release in an asymptomatic patient

An asymptomatic, 29-year-old woman was referred to our hospital before surgery because in the basic study of hemostasis she showed a prolonged thrombin time (TT) and a normal reptilase time (RT). She had not received any anticoagulants so, to account for these abnormal results the presence of an inhibitor or a dysfibrinogenemia was suspected. A 1:1 mixture of the patient's plasma with control plasma did not correct the TT. Dysfibrinogenemia was excluded because the defibrinated plasma retained the inhibitory activity when mixed with normal plasma. When 0.02 mg/ml of Protamine Sulphate (a concentration that neutralizes 1 U/mL of heparin in normal plasma) was added to the patient's plasma, the inhibitory activity did not disappear. IgG from the patient and from normal serum was isolated. The patient's IgG was able to prolong the TT of a normal plasma and of a purified fibrinogen. The patient IgG did not impair the catalytic activity of thrombin, because no difference was observed in the hydrolysis of S-2238 by 1 U NIH human thrombin with normal or patient IgG. The time course of the thrombin-mediated fibrinopeptide-release from normal fibrinogen with the patient's IgG, showed a delay in the fibrinopeptide B (FPB) release without affecting the fibrinopeptide A (FPA) release. This patient has an IgG antibody that delays fibrinopeptide B release of fibrinogen.

The combined effect of fibrin formation and factor XIII A subunit Val34Leu polymorphism on the activation of factor XIII in whole plasma

The first step in the activation of blood coagulation factor XIII (FXIII) is the proteolytic cleavage of the potentially active A subunit (FXIII-A) by thrombin at Arg37-Gly38. Both fibrin formation and FXIII-A Val34Leu polymorphism influence the rate of proteolytic activation of purified factor XIII, however their relative importance and interaction in determining the time of onset and the rate of FXIII activation in whole plasma have not yet been explored. In the present study it was shown that in plasma, fibrin formation preceded the truncation of FXIII-A by thrombin, the activation process took place exclusively on the surface of newly formed fibrin and activated FXIII remained associated with the fibrin clot. The time of fibrin formation closely correlated with the time of FXIII activation, while there was no significant relationship between the time of FXIII activation and FXIII-A Val34Leu genotype. However, in the case of Leu34 variant the lag phase between fibrin formation and FXIII-A truncation was significantly shorter than in the case of Val34 variant. The results suggest that in whole plasma the onset of FXIII activation is determined by fibrin formation, while the rate of activation is modulated by Val34Leu polymorphism.

Factor XI enhances fibrin generation and inhibits fibrinolysis in a coagulation model initiated by surface-coated tissue factor

In-vitro studies have shown that thrombin-mediated factor XI activation enhances thrombin and fibrin formation, rendering the clot more thrombogenic and protecting it from lysis by activation of thrombin activatable fibrinolysis inhibitor. These effects of factor XI are only observed when coagulation is initiated by a low concentration of soluble tissue factor. At high concentrations of soluble tissue factor no effects of factor XI are seen on coagulation and fibrinolysis. In vivo, tissue factor is present in large amounts in the vascular wall. This makes it difficult to extrapolate these in-vitro findings on factor XI to the in-vivo situation. To address the question of whether factor XI could play a role in coagulation initiated on a tissue factor-containing surface we devised a static in-vitro coagulation model in which clotting is initiated in recalcified citrated plasma by tissue factor coated on the bottom of microtiter plates. The effect of factor XI was studied with an antibody that blocked the activation of factor IX by activated factor XI. The tissue factor coating strategy produced clotting times similar to those obtained with cultured tissue factor-expressing vessel wall cells (smooth muscle cells, fibroblasts and activated endothelial cells) grown to confluence in the same wells. A factor XI-dependent effect on clot formation and clot lysis was observed depending on the plasma volume used. In clots formed from small amounts of plasma (100 microl) no effect of factor XI was detected. In larger clots (200-300 microl) factor XI not only increased prothrombin activation and the fibrin formation rate but also inhibited fibrinolysis. Effects of factor XI were observed at short clotting times (3-4 min) similar to the clotting times found on cultured tissue factor-expressing vessel wall cells. This is in contrast with earlier studies using soluble tissue factor, in which effects of factor XI were only observed at much longer clotting times using low soluble tissue factor concentrations. We conclude that factor XI not only enhances coagulation initiated by surface bound tissue factor but also protects the clot against lysis once it is formed. On the basis of these results, we propose a coagulation model in which initial clot formation in the proximity of the tissue factor surface is not factor XI dependent. Clot formation becomes dependent on factor XI in the propagation phase when the clot is increasing in size. These findings support a role for factor XI in the propagation of clot growth after tissue factor-dependent initiation.

Antithrombotic effect of tissue and plasma type angiotensin converting enzyme inhibitors in experimental thrombosis in rats

This study compared the antithrombotic effect of plasma angiotensin converting enzyme inhibitors (ACE-Is): captopril (CAP), enalapril (ENA) and tissue ACE-Is: perindopril (PER), quinapril (QUIN) in experimental venous and arterial thrombosis. Normotensive Wistar rats were treated p.o. with CAP (75 mg/kg), ENA (20 mg/kg), PER (2 mg/kg) and QUIN (3 mg/kg) for 10 days. The influence of ACE-Is on coagulation and fibrinolytic systems as well as platelet function was evaluated. The hypotensive effect of ACE-Is was equal in all groups. QUIN maintained the final carotid blood flow at the highest value in comparison to PER and plasma ACE-Is. The arterial thrombus weight was reduced in PER and QUIN groups while venous thrombus weight was also reduced after CAP. Tissue and plasma ACE-Is caused the inhibition of platelet adhesion and aggregation. A reduction of fibrin generation, prolongation of prothrombin time (PT), activated partial thromboplastin time (APTT) and shortening of euglobulin clot lysis time (ECLT) were observed after PER and QUIN treatment. In conclusion, given in equipotent hypotensive doses, tissue ACE-Is exerted more pronounced antithrombotic effect than plasma ACE-Is in experimental thrombosis. The differences between tissue and plasma ACE-Is in terms of their more pronounced inhibition of experimental thrombosis may be related to the intensified activation of fibrinolysis and inhibition of coagulation.

Enoxaparin inhibits fibrin sheath formation and decreases central venous catheter colonization following bacteremic challenge

OBJECTIVE

Inhibition of fibrin sheath formation by enoxaparin decreases catheter colonization. Fibrin-binding radioactive tracer and catheter weights quantify fibrin reduction.

DESIGN

Controlled experimental study of central venous line colonization.

SETTING

Animal laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

Central venous lines were introduced into right external jugular veins of 254 animals in three groups: enoxaparin, Fibrimage, and catheter weight. The enoxaparin group (n = 196) received daily enoxaparin injections (n = 97) or catheter implantation only (n = 99); 176 received tail vein injections of Staphylococcus epidermidis on postoperative day (POD) 10. Twenty rats received saline injections as a control. On POD 13, catheters were removed and incubated in broth at 37 degrees C for 48 hrs. Turbid samples were plated. In the Fibrimage group (n = 39), 20 rats receiving enoxaparin were compared with 19 controls without enoxaparin; all received S. epidermidis injections on POD 10. Fibrimage, fibrin-binding radiolabeled tracer, was given 1 hr before catheter removal. In the weight group (n = 19), six rats received enoxaparin; 13 did not. All received injections of S. epidermidis on POD 10.

MEASUREMENTS AND MAIN RESULTS

Positive plates underwent analytic profile index testing, ensuring correlation with inoculum. Results were compared using Fisher's exact or chi-square tests. Gamma counts were determined in the Fibrimage group. Catheter tip weights were recorded. Results from the Fibrimage and weight groups were compared using Student's t-test. The enoxaparin group had fewer catheters colonized (17 of 77) vs. no enoxaparin (42 of 99; p < .01). Pericatheter sheaths contained less fibrin compared with controls. Fibrimage group gamma counts were significantly decreased for the enoxaparin subgroup (x = 2244 counts per minute) vs. controls (x = 3767 counts per minute; p < .0002). The weight of catheter tips treated with enoxaparin (x = 39 mg) vs. controls (x = 90 mg) was also significantly decreased (p < .0001).

CONCLUSIONS

Enoxaparin decreases the amount of fibrin surrounding central venous catheters. The incidence of catheter colonization decreases when the amount of fibrin within the pericatheter sheath decreases.

The influence of anti-endothelial/antiphospholipid antibodies on fibrin formation and lysis on endothelial cells

The prothrombotic mechanisms associated with antiphospholipid antibodies remain incompletely defined. Antibody binding to endothelial cells in vitro is a feature of antiphospholipid antibody-positive sera. We hypothesised that impairment of endothelium-dependent fibrinolysis by antiphospholipid/anti-endothelial antibodies is a contributory factor in the pathogenesis of thrombosis. We also aimed to confirm the displacement of annexin-V from endothelial cells and enhanced fibrin formation. Binding of immunoglobulin (Ig) from antiphospholipid antibody-positive sera to endothelial cells was examined using a cell-based enzyme-linked immunosorbent assay. Effects on fibrin formation and lysis were examined on cultured endothelial cell monolayers. Plasminogen activator inhibitor-1 (PAI-1) was assayed in supernatants. We confirmed antibody binding to endothelial cells. With four of 14 antiphospholipid antibody-positive sera there was some prolongation of fibrin clot lysis time, consistent with impairment of endothelial fibrinolytic activity. Secretion of PAI-1 was significantly correlated with clot lysis time on endothelial cell monolayers incubated with antiphospholipid/anti-endothelial antibody-positive sera, but not with control sera. IgG from antiphospholipid antibody-positive sera had little effect on endothelial cell surface annexin-V expression. We conclude that impaired endothelial fibrinolysis is a potential prothrombotic mechanism in subjects with antiphospholipid antibodies. We were unable to confirm enhanced displacement of annexin-V from endothelium by antiphospholipid antibodies.

Are There Patients With Acute Ischemic Stroke and Atrial Fibrillation That Benefit From Low Molecular Weight Heparin?

Background and Purpose— Treatment doses of heparins are not recommended for acute ischemic stroke. Despite this, their use in this setting is widespread. We investigated whether subgroups of patients with acute ischemic stroke and atrial fibrillation, identified by clinical, hemostatic ( d- dimer, prothombin fragments 1+2 [F 1+2 ], soluble fibrin monomer), or inflammatory (C-reactive protein [CRP]) variables might have a differential response to low molecular weight heparin (LMWH) over aspirin. In addition, we sought to identify factors associated with a poor clinical outcome at 3 months.

Methods— We conducted a post hoc subgroup analysis of a randomized, placebo-controlled, double-blind trial (Heparin in Acute Embolic Stroke Trial) designed to test the hypothesis that treatment doses of LMWH (dalteparin; 100 IU/kg BID) would be superior to aspirin (160 mg per day) in patients with acute ischemic stroke and atrial fibrillation. For the current analysis, 431 participants were included. The primary outcome measure was a poor outcome at 3 months, defined as death or dependency in activities of daily living. Using regression analysis, we determined whether any of the chosen variables were associated with a differential response to dalteparin (treatment interaction) or with poor outcome.

Results— In the multivariable logistic regression model, none of the clinical, hemostatic, or inflammatory variables were associated with a significant treatment interaction. Stroke severity (odds ratio [OR], 1.09 [95% CI, 1.07 to 1.12]), increasing age (OR, 1.09 [CI, 1.05 to 1.14]), CRP level (OR, 1.32 [CI, 1.04 to 1.66]), and F 1+2 level (OR, 1.77 [CI, 1.07 to 2.91]) were independently associated with a poor outcome at 3 months.

Conclusions— Our study does not support the use of treatment doses of LMWH in any of the studied subgroups of patients with acute ischemic stroke and atrial fibrillation. Age, stroke severity, CRP, and F 1+2 were predictive of poor outcome at 3 months.

Validation, Calibration, and Specificity of Quantitative D-Dimer Assays

Assays for D-dimer antigen are based on monoclonal antibodies reactive with epitopes found on fibrin fragment D-dimer but not on fibrinogen fragment D, other fibrinogen degradation products, or native fibrinogen. The antibodies react with conformational epitopes generated by factor XIII-induced linkage of the C-terminal appendages of the fibrin gamma-chains of adjacent D-domains within a fibrin polymer. For some monoclonal antibodies, degradation of the cross-linked fibrin compound by plasmin is an additional requirement for the generation of the epitope. In clinical plasma samples, D-dimer antigen assays detect an array of fibrin compounds of different molecular weights, including fibrin fragment D-dimer as well as higher-molecular-weight fibrin degradation products and fibrin X-oligomers. Most D-dimer antigen represents cross-linked soluble fibrin present in circulation rather than degradation products from particulate clots. Due to differences in epitope reactivity, harmonization of D-dimer antigen assays can only be achieved with standard preparations containing a similar variety of cross-linked fibrin compounds. Assay technologies include manual latex agglutination assays, automated latex-enhanced light-scattering immunoassays, enzyme-linked immunoassays, and others.

Intracameral tissue plasminogen activator to prevent severe fibrinous effusion after congenital cataract surgery

BACKGROUND/AIMS

To evaluate the efficacy of intracameral recombinant tissue plasminogen activator (r-TPA) in prevention of fibrinous effusion after lensectomy, anterior vitrectomy, and posterior chamber intraocular lens (PCIOL) implantation in patients with congenital cataract.

METHODS

The study was done as a double masked randomised clinical trial between April 2002 and November 2003 in Farabi Eye Hospital. 34 eyes of 26 patients with congenital cataract were included in the study and randomised into two groups (18 cases and 16 controls). Mean age was 8.1 years (3--14 years). Each eye underwent lensectomy and anterior vitrectomy with PCIOL implantation. At the end of surgery 20 microg r-TPA was injected intra-camerally in the case group. The control group received only balanced salt solution. All patients received periocular, systemic, and topical steroids after surgery. Patients underwent follow up examinations for 3 months.

RESULTS

The incidence of intraocular fibrin membrane formation was significantly lower in the case group on days 1, 3, 7, 14 (p=0.02, p=0.01, p=0.01, and p=0.01, respectively, chi(2) test), but there was no significant difference on days 30 and 90. The frequency of pigmented intraocular lens precipitates was significantly lower in the case group at the end of the third month (p<0.001, chi(2) test). No gross ocular side effects were noted after r-TPA injection.

CONCLUSION

It seems that prophylactic intracameral r-TPA is effective in prevention of fibrinous effusion at least in the first 2 weeks after cataract extraction in the paediatric age group and decreases the incidence of pigmented IOL precipitates.

Humoral heart rejection (severe allograft dysfunction with no signs of cellular rejection or ischemia): incidence, management, and the value of C4d for diagnosis

Severe allograft dysfunction after heart transplant (HT), without ischemia or evidence of cellular rejection upon endomyocardial biopsy (EMB), is a rare but potentially fatal condition that suggests humoral rejection (HR). Its incidence, and the methods of choice for its diagnosis and management, remain uncertain. We retrospectively studied 445 HT patients (April 1991-December 2003) to determine incidence of HR diagnosed by clinical and conventional histopathological criteria. We used immunofluorescence (IF) techniques to test archived frozen EMB issue for IgM, IgG, C1q, C3, fibrin and C4d. Twelve patients (2.7%) fulfilled the criteria for HR after a mean time post-HT of 21.3 +/- 24.7 months (range: 2-72 months). Patients were treated with high doses of steroids and plasmapheresis, with successful recovery in 11 cases. IF studies using classical markers were mainly negative for the six patients with enough EMB tissue for testing. All six patients showed positivity for C4d during the HR episode but not before or after. Humoral rejection was observed in less than 3% of HT patients. Plasmapheresis treatment was highly effective. Classical IF tests were not useful for diagnosis, but C4d appears to be useful both for confirmation of diagnosis and for monitoring response to treatment.

Hyperproduction of fibrin and inefficacy of antithrombin III and alpha2 macroglobulin in the presence of bacterial porins

Bacterial porins enhance the thrombin activity upon chromogen substrate chromozym. Should porin-dependent enhancement of thrombin activity take place also upon fibrinogen in vivo, this might greatly increase the fibrin production which, in turn, might lead to blood vessel obstruction. In this study, we demonstrate fibrin hyperproduction in a simplified coagulative system, consisting of fibrinogen and thrombin-pure molecules, in the presence of bacterial porins. In particular, bacterial porins, in the presence of thrombin, significantly increased the fibrin production compared with thrombin alone. Also, fibrin hyperproduction took place even in the presence of the thrombin inhibitors antithrombin III (AT III) or alpha2 macroglobulin (alpha2M). However, the thrombin-fibrinogen reaction in the presence of AT III or alpha2M did not generate fibrin, unless porins were present. In conclusion, porins not only enhance thrombin activity but also inhibit the antithrombin activity exerted by AT III or alpha2M. We hypothesize that, because of porins activity, fibrin is largely generated due to thrombin hyperactivation. Moreover, further fibrin is produced by thrombin, which is not blocked by two serpins for the presence of porins. These results might be relevant as to the occurrence of disseminated intravascular coagulation in sepsis by gram-negative bacteria, which are known to produce porins.

Studies on the basis for the properties of fibrin produced from fibrinogen-containing gamma' chains

Human fibrinogen 1 is homodimeric with respect to its gamma chains (gammaA-gammaA'), whereas fibrinogen 2 molecules each contain one gammaA (gammaA1-411V) and one gamma' chain, which differ by containing a unique C-terminal sequence from gamma'408 to 427L that binds thrombin and factor XIII. We investigated the structural and functional features of these fibrins and made several observations. First, thrombin-treated fibrinogen 2 produced finer, more branched clot networks than did fibrin 1. These known differences in network structure were attributable to delayed release of fibrinopeptide (FP) A from fibrinogen 2 by thrombin, which in turn was likely caused by allosteric changes at the thrombin catalytic site induced by thrombin exosite 2 binding to the gamma' chains. Second, cross-linking of fibrin gamma chains was virtually the same for both types of fibrin. Third, the acceleratory effect of fibrin on thrombin-mediated XIII activation was more prominent with fibrin 1 than with fibrin 2, and this was also attributable to allosteric changes at the catalytic site induced by thrombin binding to gamma' chains. Fourth, fibrinolysis of fibrin 2 was delayed compared with fibrin 1. Altogether, differences between the structure and function of fibrins 1 and 2 are attributable to the effects of thrombin binding to gamma' chains.

Regulation of tissue factor-induced coagulation and platelet aggregation in flowing whole blood

Photochemically induced thrombosis (a thrombin-dependent process) was measured in rats treated with moderate doses of anticoagulants, but which appeared to be unchanged. We considered the possibility that platelet-inhibiting agents, which also indirectly inhibit coagulation, would act as more potent antithrombotic agents. Inhibitors used as such were prostaglandin E1 (PGE1), which elevates cyclic AMP levels, and the P2Y12 ADP-receptor antagonist, AR-C69931MX. Effects of these agents were investigated in an ex vivo model system, in which whole blood under coagulant conditions was perfused over fibrinogen at defined wall shear rate. Perfusion of blood (rat or human) in the presence of tissue factor resulted in deposition of activated platelets and subsequent aggregate formation, along with exposure of procoagulant phosphatidylserine (PS) on the platelet surface and formation of fibrin fibers. In the presence of PGE1 aggregation was completely inhibited, but platelet adhesion and PS exposure were only party reduced, while fibrin formation was hardly affected. Treatment with AR-C69931MX caused similar, but less complete effects. These results indicate that in tissue factor-triggered blood under conditions of flow: (i) the platelet procoagulant response is independent of aggregate formation; (ii) the platelet-inhibiting effect of PGE1 and AR-C69931MX is sufficient to suppress aggregation, but not platelet adhesion and coagulation. These platelet inhibitors thus maintain their aggregation-inhibiting effect at sites of thrombin formation.

Association between the severity of sepsis and the changes in hemostatic molecular markers and vascular endothelial damage markers

It is well known that disorders of coagulation and fibrinolysis play a major role in the development of organ dysfunction during sepsis. Furthermore, the importance of the early initiation of anticoagulation therapy for severe cases has been emphasized based on the success of recent clinical trials. The purpose of this study is to search for useful markers for predicting organ dysfunction. Plasma samples were prospectively collected from 78 patients within 48 h after the onset of sepsis. Hemostatic markers and endothelial damage markers were compared between the patients with and without organ dysfunction. The WBC and platelet counts were not different between the groups. In contrast, fibrin/fibrinogen degradation products, D-dimer, thrombin-antithrombin complex, plasmin alpha2-antiplasmin complex, soluble fibrin, and total plasminogen activator inhibitor-1 were significantly higher, and the antithrombin activity and protein C levels were lower in the patients with organ dysfunction. Thus, the changes in the hemostatic molecular markers were associated with organ dysfunction from an early stage of sepsis, and antithrombin and protein C activities were found to be the most reliable markers.

The ultrastructure of fibrinogen-420 and the fibrin-420 clot

Fibrinogen-420 is a minor subclass of human fibrinogen that is so named because of its higher molecular weight compared to fibrinogen-340, the predominant form of circulating fibrinogen. Each of the two Aalpha chains of fibrinogen-340 is replaced in fibrinogen-420 by an Aalpha isoform termed alphaE. Such chains contain a globular C-terminal extension, alphaEC, that is homologous with the C-terminal regions of Bbeta and gamma chains in the fibrin D domain. The alphaEC domain lacks a functional fibrin polymerization pocket like those found in the D domain, but it does contain a binding site for beta2 integrins. Electron microscopy of fibrinogen-340 molecules showed the major core fibrinogen domains, D-E-D, plus globular portions of the C-terminal alphaC domains. Fibrinogen-420 molecules had two additional globular domains that were attributable to alphaEC. Turbidity measurements of thrombin-cleaved fibrinogen-420 revealed a reduced rate of fibrin polymerization and a lower maximum turbidity. Thromboelastographic measurements also showed a reduced rate of fibrin-420 polymerization (amplitude development) compared with fibrin-340. Nevertheless, the final amplitude (MA) and the calculated elastic modulus (G) for fibrin-420 were greater than those for fibrin-340. These results suggested a greater degree of fibrin-420 branching and thinner matrix fibers, and such structures were found in SEM images. In addition, fibrin-420 fibers were irregular and often showed nodular structures protruding from the fiber surface. These nodularities represented alphaEC domains, and possibly alphaC domains as well. TEM images of negatively shadowed fibrin-420 networks showed irregular fiber borders, but the fibers possessed the same 22.5-nm periodicity that characterizes all fibrin fibers. From this result, we conclude that fibrin-420 fiber assembly occurs through the same D-E interactions that drive the assembly of all fibrin fibrils, and therefore that the staggered overlapping molecular packing arrangement is the same in both types of fibrin. The alphaEC domains are arrayed on fiber surfaces, and in this location, they would very likely slow lateral fibril association, causing thinner, more branched fibers to form. However, their location on the fiber surface would facilitate cellular interactions through the integrin receptor binding site.

Selective inducible nitric oxide synthase inhibition attenuates organ dysfunction and elevated endothelin levels in LPS-induced DIC model rats

We examined the role of nitric oxide (NO) produced by an inducible isoform of NO synthase (iNOS) using N[6]-(iminoethyl)-lysine (L-NIL), a selective iNOS inhibitor, in the rat model of lipopolysaccharide (LPS)-induced disseminated intravascular coagulation (DIC) and investigated changes in organ function, plasma levels of NOX (metabolites of NO) and endothelin. We induced experimental DIC by the sustained infusion of 30 mg kg(-1) LPS for 4 h via the tail vein. We then investigated the effect of L-NIL (6 mg kg(-1), from - 0.5 to 4 h) on LPS-induced DIC. Blood was withdrawn at 4 and 8 h, and all four groups (LPS with or without L-NIL at 4 and 8 h) consisted of eight rats. Three of the animals in the 8-h LPS group died, and we examined blood samples from five rats in this group. None of the other rats died. The LPS-induced elevation of creatinine, alanine aminotransferase, glomerular fibrin deposition and plasminogen activator inhibitor was significantly suppressed by L-NIL coadministration, although L-NIL did not affect the platelet count, fibrinogen concentration or the level of thrombin-antithrombin complex. Moreover, plasma levels of the D-dimer that reflect the lysis of cross-linked fibrin were significantly increased by L-NIL coadministration in the LPS-induced DIC model. Plasma levels of NOX and endothelin were obviously increased by LPS infusion. However, both levels were significantly suppressed in the LPS + L-NIL group, when compared with the LPS group. Although mean arterial pressure (MAP) was significantly decreased between 2 and 8 h compared with the control in the LPS group, this depression was significantly attenuated in the LPS + L-NIL group. Our results suggest that NO induced by iNOS contributes to hypotension (depressed MAP), the progression of hepatic and renal dysfunction, microthrombus deposition and elevated endothelin levels in the rat model of LPS-induced DIC.

Fibrinogen and fibrin

Fibrinogen is a large, complex, fibrous glycoprotein with three pairs of polypeptide chains linked together by 29 disulfide bonds. It is 45 nm in length, with globular domains at each end and in the middle connected by alpha-helical coiled-coil rods. Both strongly and weakly bound calcium ions are important for maintenance of fibrinogen's structure and functions. The fibrinopeptides, which are in the central region, are cleaved by thrombin to convert soluble fibrinogen to insoluble fibrin polymer, via intermolecular interactions of the "knobs" exposed by fibrinopeptide removal with "holes" always exposed at the ends of the molecules. Fibrin monomers polymerize via these specific and tightly controlled binding interactions to make half-staggered oligomers that lengthen into protofibrils. The protofibrils aggregate laterally to make fibers, which then branch to yield a three-dimensional network-the fibrin clot-essential for hemostasis. X-ray crystallographic structures of portions of fibrinogen have provided some details on how these interactions occur. Finally, the transglutaminase, Factor XIIIa, covalently binds specific glutamine residues in one fibrin molecule to lysine residues in another via isopeptide bonds, stabilizing the clot against mechanical, chemical, and proteolytic insults. The gene regulation of fibrinogen synthesis and its assembly into multichain complexes proceed via a series of well-defined steps. Alternate splicing of two of the chains yields common variant molecular isoforms. The mechanical properties of clots, which can be quite variable, are essential to fibrin's functions in hemostasis and wound healing. The fibrinolytic system, with the zymogen plasminogen binding to fibrin together with tissue-type plasminogen activator to promote activation to the active enzyme plasmin, results in digestion of fibrin at specific lysine residues. Fibrin(ogen) also specifically binds a variety of other proteins, including fibronectin, albumin, thrombospondin, von Willebrand factor, fibulin, fibroblast growth factor-2, vascular endothelial growth factor, and interleukin-1. Studies of naturally occurring dysfibrinogenemias and variant molecules have increased our understanding of fibrinogen's functions. Fibrinogen binds to activated alphaIIbbeta3 integrin on the platelet surface, forming bridges responsible for platelet aggregation in hemostasis, and also has important adhesive and inflammatory functions through specific interactions with other cells. Fibrinogen-like domains originated early in evolution, and it is likely that their specific and tightly controlled intermolecular interactions are involved in other aspects of cellular function and developmental biology.

The impact of cardiac ischemia and reperfusion on markers of activated haemostasis and fibrinolysis during cardiopulmonary bypass: comparison of plasma levels in arterial and coronary venous blood

INTRODUCTION

Activation of coagulation and fibrinolysis is common among patients undergoing cardiopulmonary bypass (CPB) surgery. Little is known, however, about the impact of myocardial ischemia and reperfusion on coagulation activation and fibrinolysis in this clinical setting.

STUDY DESIGN AND METHODS

We determined the levels of coagulation activation and fibrinolysis markers (CAFM) in 19 patients with severe coronary heart disease (CHD) during CPB surgery. FXIIa, tissue factor (TF), FVIIa, tissue plasminogen activator/plasminogen activator inhibitor-1 complexes (tPA/PAI-1), prothrombin fragments 1+2 (F1+2), D-dimers (DD) and plasmin-plasmin inhibitor complexes (PPI) were measured at baseline, prior to and after cardioplegic myocardial ischemia. Simultaneous blood samples were drawn from the aorta and the coronary sinus to evaluate arteriovenous CAFM plasma level gradients.

RESULTS

Myocardial ischemia induced significant increases in gradients of FXIIa and F1+2 levels across the coronary circulation without influencing systemic levels of these markers significantly. Systemic levels of FXIIa, tPA/PAI-1, F1+2, DD and PPI increased significantly during CPB operation. There was a significant linear correlation between FXIIa, FVIIa, F1+2, DD and PPI.

CONCLUSIONS

Myocardial ischemia induces contact activation and thrombin generation rather than release of tPA and might thus contribute to postoperative thromboembolic complications. Surgery itself and CPB cause activation of coagulation and fibrinolysis as already described. A significant association between FXIIa, FVIIa, F1+2, DD and PPI suggests a relationship between contact activation, thrombin generation, fibrin formation and fibrinolysis.

Some comments on John Ferry's most enduring paper

In this brief memoir, I reflect on the great insight John Ferry exhibited in his extremely influential 1952 paper on the mechanism of fibrinogen being changed into fibrin.

Fibrinopeptides and fibrin gel structure

The mechanisms involved in fibrin gel formation are reviewed. Furthermore, a new concept of the role of fibrinopeptide release in this process is presented.