Fibrinogen as a factor of thrombosis: experimental study

The β-fibrinogen gene 455G/A polymorphism associated with cardioembolic stroke in atrial fibrillation with low CHA2DS2-VaSc score

Previous work has suggested that ischemic stroke (IS) may be more likely to occur in individuals with a genetic predisposition. In this study, we investigated the potential association of IS-relevant genetic risk factors with cardioembolic stroke (CES) in atrial fibrillation (AF) patients with low CHA2DS2-VaSc score. Genotyping was performed using the GenomeLab SNPstream genotyping platform for five IS-relevant SNPs (MMP-9 C1562T, ALOX5AP SG13S114A/T, MTHFR 677 C/T, FGB 455 G/A, and eNOS G298A) in 479 AF patients with CES and 580 age and sex-matched AF patients without CES. The multivariate analysis adjusted for potential confounders and demonstrated that FGB 455 G/A was independently associated with increased risk of CES in AF patients and the significance remained after Bonferroni correction in the additive, dominant, and recessive models with ORs of 1.548 (95% CI: 1.251–1.915, P = 0.001), 1.588 (95% CI: (1.226–2.057, P = 0.003), and 2.394 (95% CI: 1.357–4.223, P = 0.015), respectively. Plasma fibrinogen levels were significantly higher in patients with the A allele compared with patients with genotype of GG (3.29 ± 0.38 mg/dl vs. 2.87 ± 0.18 mg/dl, P < 0.001). We found for the first time that the A allele of FGB 455 G/A was a risk factor for CES in AF patients, probably by elevating the level of plasma fibrinogen.

Quartz Crystal Microbalance Study of Protein Adsorption on Chitosan, Chitosan/Poly(vinyl pyrrolidone) Blends and Chitosan-graft-Poly(vinyl pyrrolidone) Surfaces

Adsorption behaviour of bovine serum albumin (BSA) onto chitosan (CS), chitosan/poly(vinyl pyrrolidone) blends (CS/PVP blends), and chitosan- graft-poly(vinyl pyrrolidone) (CS- graft-PVP) surfaces were investigated using quartz crystal microbalance (QCM). The adsorbed quantities of protein on the three surfaces were examined and were found to decrease in the following order: CS > CS/PVP blends > CS- graft-PVP. The kinetics of BSA adsorption in the early stage was analysed. The Langmuir isotherm model was used to describe the BSA adsorption behaviour on CS and its derivates. The attachment, detachment rate constants, and the association constants ( Ka ) were of the same order of magnitude, whereas the Ka for BSA on CS- graft-PVP surface was the lowest of the three surfaces. The adsorbed protein layer structure was also estimated. For CS- graft -PVP, most of the proteins adsorbed on the surface were of side-on structure, whereas for CS only about 40% of the proteins were of side-on structure.

Venous thrombosis and oral contraceptives: current status

The use of oral contraceptives is associated with an increased risk of venous thrombosis. It is now generally accepted that women who use oral contraceptives that contain so-called third-generation progestins (desogestrel or gestodene) are exposed to a twofold higher risk of venous thrombosis than women who use oral contraceptives that contain the second-generation progestin levonorgestrel. Coagulation studies demonstrated that oral contraceptives increase the plasma level of prothrombin, decrease the level of protein S and induce acquired activated protein C resistance. The changes in hemostatic parameters can explain why women who use oral contraceptives are exposed to an increased risk of venous thrombosis and why the risk is further increased in third-generation oral contraceptive users.

Clinical significance of microembolus detection by transcranial Doppler sonography in cardiovascular clinical conditions

Transcranial Doppler can detect microembolic signals, which are characterized by unidirectional high intensity increase, short duration, and random occurrence, producing a "whistling" sound. Microembolic signals have been proven to represent solid or gaseous particles within the blood flow. Microemboli have been detected in a number of clinical cardiovascular settings: carotid artery stenosis, aortic arch plaques, atrial fibrillation, myocardial infarction, prosthetic heart valves, patent foramen ovale, valvular stenosis, during invasive procedures (angiography, percutaneous transluminal angioplasty) and surgery (carotid, cardiopulmonary bypass). Despite numerous studies performed so far, clinical significance of microembolic signals is still unclear. This article provides an overview of the development and current state of technical and clinical aspects of microembolus detection.

Hyperfibrinogenemia Alone Does Not Affect the Patency of Microvascular Anastomosis

Preventing vascular thrombosis in microsurgery is a prerequisite for a successful outcome. High plasma fibrinogen levels have been associated with thromboembolic risk in patients with cancer or cardiovascular disease. Patients with these comorbidities and associated hyperfibrinogenemia oftentimes require microsurgical reconstruction. This situation causes us to hesitate. Previously in our experience, 8 of 10 patients with hyperfibrinogenemia (> 500 mg/dL) underwent successful free-tissue transfer after oral cancer ablation. Based on this clinical observation, we investigated whether hyperfibrinogenemia contributes to the patency of a microvascular anastomosis. Optimal dosage of fibrinogen (300 mg/kg, intravenously) significantly increased the fibrinogen level in the plasma of the rodent hyperfibrinogenemia model. Forty male Lewis rats (weight = 300-350 g) were injected intravenously by normal saline and fibrinogen (300 mg/kg), respectively (n = 20 in each subgroup). Femoral artery and femoral vein division and reanastomosis were performed after 2 hours in rats with or without fibrinogen injection. The platelet count, prothrombin time (PT), activated partial thromboplastin time (APTT), and the platelet aggregation test induced with adenosine diphosphate (ADP) were also measured preoperatively. The ratios of circulating activated platelets as demonstrated by p-selectin (CD62P) was analyzed by flow cytometry preoperatively and 2 hours postoperatively. Laser Doppler flowmetry was used to assess the patency of the anastomosis preoperatively and 2 hours postoperatively. Vascular patency was assessed 7 days postoperatively. The results showed that the platelet count, PT and APTT levels had no significant difference among the control and the experimental group. There were no significant differences found in the ratios of CD62P expression (P = 0.65) and ADP aggregation test (P = 0.17) in comparing both groups. There were no statistical differences in the patency rates (P > 0.05) or perfusion units of femoral arteries (P = 0.84) and femoral veins (P = 0.51) after vessels division and reanastomosis, respectively. In summary, there was no correlation between experimentally induced hyperfibrinogenemia and the enhancement of thrombosis risk after microvascular surgery. This experimental data can lend support to the idea that microvascular anastomosis could be safely performed in patients with hyperfibrinogenemia alone without untoward thrombotic complications.

Competitive interfacial adsorption of blood proteins

The competitive adsorption of blood proteins is of great importance for the treatment of thrombosis using a colloidal drug delivery system. The aim of this study is to investigate competitive adsorption of albumin (BSA) and human immunoglobulin G (HIgG) against fibrinogen (Fb). The competitive adsorption of blood proteins was investigated using interfacial rheology at physiological pH. The influence of bulk concentration, temperature and pH on the interfacial adsorption of protein molecules was determined at the air/aqueous interface. As expected, the results indicated that increase in bulk concentration enhanced the interfacial adsorption. Structure and molecular weight of the protein molecules under investigation had influence on interfacial adsorption leading to a competition at the interface. HIgG is more flexible and surface active molecule than BSA. Thus, HIgG replaced BSA and Fb at the air/aqueous interface. In the presence of Fb, BSA adsorbed rapidly initially and then, was replaced by Fb at the interface. The kinetics of displacement of albumin at the interface was rather slow. In conclusion, the investigation of competitive adsorption of blood proteins may be useful biotechnologically, as it will provide useful information for the production of an antithrombogenic material, which will adsorb albumin rather than Fb.

Microvascular consequences of thrombosis in small venules: an in vivo microscopic study using a novel model in the ear of the hairless mouse

Little is known of the development of chronic microvascular alterations following small vessel thrombosis, which is probably due to the lack of appropriate experimental models. Herein we report the first results on thrombosis-associated long-term changes of microvascular permeability and vessel tortuosity and diameter and blood perfusion using the ear of the hairless mouse, and intravital fluorescence microscopy. Thrombosis was induced photochemically in small venules (diameter: 75 to 100 microm) using light/dye exposure (fluorescein isothiocyanate-dextran 150,000), and the microcirculation compromised by the blockade of blood drainage was analyzed before and 30 minutes after induction of thrombosis as well as repeatedly over a 28-day observation period. Thrombus formation resulted in a marked increase (p<0.05) of microvascular permeability (0.85+/-0.11) when compared with baseline values (0.46+/-0.04). Permeability remained elevated (p<0.05) at days 1 (0.67+/-0.07), 3 (0.58+/-0.02), and 7 (0.60+/-0.06), but returned to normal after 28 days (0.43+/-0.03). Tortuosity, diameter, and red blood cell velocity of venular segments, located upstream of thrombus formation, were found unchanged during the entire 28-day observation period. This was probably due to the fact that blood flow from the thrombosis-affected tissue was frequently drained into nonaffected tissue via preexisting "through-fare" channels, serving as venulo-venular collaterals. In accordance, in 10 to 20% of these venular segments the direction of blood perfusion was found changed, while those changes were only rarely observed in venular vessel segments of the nonthrombotic contralateral ears. We conclude that thrombosis in small cutaneous venules is primarily characterized by an increased vascular permeability, reflecting an inflammatory response, similar to what is known from thrombophlebitis in patients. The model presented herein may be a versatile tool to study pathogenesis of chronic microcirculatory derangements in microthrombosis and their prevention by novel therapeutic strategies.