Observation of arterial and venous thrombus formation by scanning and transmission electron microscopy

Propranolol Reduces the Development of Lesions and Rescues Barrier Function in Cerebral Cavernous Malformations: A Preclinical Study

[Figure: see text].

Photothrombosis combined with thrombin injection establishes a rat model of cerebral venous sinus thrombosis

OBJECTIVE

Cerebral venous sinus thrombosis (CVST) is a rare but life-threatening disease and an animal model for in-depth study of CVST is needed. This study aimed to develop a rat model suitable for studying clinically relevant aspects of CVST and investigating its dynamic pathophysiological changes during a 7-day period.

METHOD

A photothrombosis method was used to create a rat sinus-vein thrombosis model. A spot size-adjustable Diode Pumped Solid State laser (DPSS) combined with thrombin injection occluded the rostral and caudal superior sagittal sinus (SSS). The model was used to evaluate pathophysiological changes at different time points over 7 days. Evans Blue dye injection was used to detect alterations in blood-brain barrier (BBB) permeability. Brain water content was also measured. Moreover, we examined changes in brain infarct volume, neurological function, as well as histology after induction of CVST.

RESULT

CVST in rats significantly altered BBB permeability, consistent with the development of brain edema. It was accompanied by an increase in brain infarct volume and deficits in neurological function that began on day 1, peaked on day 2, and typically improved by day 7 due to the neuroprotective effects of angiogenesis and gliocyte proliferation.

CONCLUSION

In this study, we describe a rat model that produces clinically relevant pathophysiology and pathology that will facilitate evaluation of therapeutic regimens for CVST. Furthermore, our results indicate a period of optimal clinical intervention for patients with CVST, which may reduce the probability of dependency and death.

Dicarbonyl proteome and genome damage in metabolic and vascular disease

Methylglyoxal is a potent protein-glycating agent. It is an arginine-directed glycating agent and often modifies functionally important sites in proteins. Glycation forms mainly MG-H1 [Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)ornithine] residues. MG-H1 content of proteins is quantified by stable isotopic dilution analysis-MS/MS and also by immunoblotting with specific monoclonal antibodies. Methylglyoxal-modified proteins undergo cellular proteolysis and release MG-H1 free adduct for excretion. MG-H1 residues have been found in proteins of animals, plants, bacteria, fungi and protoctista. MG-H1 is often the major advanced glycation end-product in proteins of tissues and body fluids, increasing in diabetes and associated vascular complications, renal failure, cirrhosis, Alzheimer's disease, arthritis, Parkinson's disease and aging. Proteins susceptible to methylglyoxal modification with related functional impairment are called the DCP (dicarbonyl proteome). The DCP includes albumin, haemoglobin, transcription factors, mitochondrial proteins, extracellular matrix proteins, lens crystallins and others. DCP component proteins are linked to mitochondrial dysfunction in diabetes and aging, oxidative stress, dyslipidaemia, cell detachment and anoikis and apoptosis. Methylglyoxal also modifies DNA where deoxyguanosine residues are modified to imidazopurinone MGdG {3-(2'-deoxyribosyl)-6,7-dihydro-6,7-dihydroxy-6/7-methylimidazo-[2,3-b]purine-9(8)one} isomers. MGdG was the major quantitative adduct detected in vivo. It was linked to frequency of DNA strand breaks and increased markedly during apoptosis induced by a cell-permeant glyoxalase I inhibitor. Glyoxalase I metabolizes >99% methylglyoxal and thereby protects the proteome and genome. Gene deletion of GLO1 is embryonically lethal and GLO1 silencing increases methylglyoxal concentration, MG-H1 and MGdG, premature aging and disease. Studies of methylglyoxal glycation have importance for human health, longevity and treatment of disease.

Comparison of anticoagulation and thrombolysis treatments in a rat model of superior sagittal sinus thrombosis

Superior sagittal sinus thrombosis (SSST) is a form of cerebral venous sinus thrombosis (CVST) routinely treated with anticoagulation therapy. Anticoagulation and thrombolysis treatment effects on neurological function, venous recanalization and brain edema were compared after SSST in rats. Male Sprague-Dawley rats underwent non-fatal SSST induction and were divided into no treatment (control), anticoagulation (heparin), carotid artery thrombolysis and local thrombolysis groups (each n = 50). Within each group, an equal number of rats (n = 10) were treated with anticoagulation and thrombolysis at day 3 or weeks 1, 2, 3 or 4 following SSST. Magnetic resonance venography (MRV) was conducted within 24 h of anticoagulation and thrombolysis treatments to determine recanalization, structural abnormalities and cerebral edema quantitated by wet-dry methods. Neurological function (Rotarod test) and histological abnormalities were compared. Severe brain edema, flattened gyri and coronal swelling were observed following SSST. Recanalization rates in carotid artery and local thrombolysis were higher than in anticoagulation (both p < 0.001). Carotid artery and local thrombolysis brain water contents were 79.6±0.1% and 79.2±0.1%, respectively, significantly lower than 83.9±0.1% and 84±0.1% in anticoagulation and controls, respectively (all p < 0.05), after treatments at day 3 following SSST. Increasing SSST onset to treatment time worsened neurological function ( p < 0.05). Maximum treatment benefits were observed <2 weeks post-SSST using local thrombolysis and, to a lesser extent, carotid artery thrombolysis. Thrombolysis may produce better functional outcomes if employed early rather than as a second-line treatment following anticoagulant failure.

Coagulation abnormalities in the trauma patient: the role of point-of-care thromboelastography

Current recommendations for resuscitation of the critically injured patient are limited by a lack of point-of-care (POC) assessment of coagulation status. Accordingly, the potential exists for indiscriminant blood component administration. Furthermore, although thromboembolic events have been described shortly after injury, the time sequence of post-injury coagulation changes is unknown. Our current understanding of hemostasis has shifted from a classic view, in which coagulation was considered a chain of catalytic enzyme reactions, to the cell-based model (CBM), representing the interplay between the cellular and plasma components of clot formation. Thromboelastography (TEG), a time-sensitive dynamic assay of the viscoelastic properties of blood, closely parallels the CBM, permitting timely, goal-directed restoration of hemostasis via POC monitoring of coagulation status. TEG-based therapy allows for goal-directed blood product administration in trauma, with potential avoidance of the complications resulting from overzealous component administration, as well as the ability to monitor post-injury coagulation status and thromboprophylaxis. This overview addresses coagulation status and thromboprophylaxis management in the trauma patient and the emerging role of POC TEG.

Progressive postinjury thrombocytosis is associated with thromboembolic complications

BACKGROUND

Our previous investigation demonstrated that despite routine chemoprophylaxis, thrombelastography, which is a comprehensive test measuring the viscoelastic properties of blood, identified a hypercoagulable state in a cohort of critically ill surgical patients that was associated with thromboemobolic events. Furthermore, because thrombelastography allows for the comprehensive assessment of coagulation status, this work suggested that platelet hyperactivity is a component of the hypercoagulable state. We hypothesized that progressive postinjury thrombocytosis contributes to a hypercoagulable state that is associated with thrombelastography.

METHODS

One thousand four hundred and forty severely injured patients surviving >48 h were entered into a database prospectively over 12 years. The variables that were evaluated in associated with thrombocytosis (platelet count >450,000) included age, Injury Severity Score, packed red blood cell transfusions in 12 h, and thromboemobolic complications (TE) (deep venous thrombosis, pulmonary embolus, mesenteric thrombosis, stroke, and arterial thrombosis). The time frame for the development of thrombocytosis was assessed at greater or less than 7 days postinjury. Logistic regression was used to identify the independent variables predictive of thrombocytosis and to adjust the association of thrombocytosis with TE for other risk factors. C-statistic was used to assess the discriminative power of thrombocytosis for prediction of TE.

RESULTS

The mean age was 37.4 ± 0.4 years. The Injury Severity Score was 29.3 ± 0.3, and mean red blood cell transfusions in 12 h was 4.4 ± 0.2 units. Injury via blunt force occurred in 76% of patients, and 72% of patients were male. Thrombocytosis was identified in 447 (31%) patients and was noted almost exclusively >7 days postinjury (98%). TE developed in 35 (8%) of the 447 patients with thrombocytosis, compared with 45 (4.5%) of the remaining 993 patients who did not develop thrombocytosis. Persistent thrombocytosis >7 days was associated with TE (P > .0001). Logistic regression analysis indicated that when adjusted for intensive care unit duration of stay, transfusions, age, and Injury Severity Score, patients with sustained thrombocytosis more than 3 days were noted to have a 1.4 × increased risk of TE (odds ratio, 1.12; 95% confidence interval, 1.04-1.2; P = .002; C-statistic = 0.82).

CONCLUSION

Persistent thrombocytosis in critically injured patients receiving routine chemoprophylaxis is associated with thrombotic complications. Subsequent investigation is warranted to differentiate enzymatic from platelet hypercoagulability to ascertain the role of antiplatelet therapy for prevention of TE.

Differentiation of enzymatic from platelet hypercoagulability using the novel thrombelastography parameter delta (delta)

BACKGROUND

Thrombelastography (TEG) allows for rapid global assessment of coagulation function. Our previous work demonstrated that a hypercoagulable state identified by TEG's G value was associated with thromboembolic events in a cohort of critically ill surgical patients despite routine chemoprophylaxis. We hypothesized that a hypercoagulable state could be differentiated into enzymatic or platelet etiology through the use of thrombus velocity curves; specifically the time to maximum rate of thrombus generation (TMRTG) and the novel TEG parameter, delta. (Delta)

METHODS

We retrospectively studied 10 critically ill surgical patients receiving thromboprophylaxis for at least 72 h by TEG, using kaolin activated citrated samples. Thrombus velocity curves were plotted for each patient, and delta was calculated as the difference between the TEG parameters R and SP, corresponding to the time to maximum rate of thrombus generation (TMRTG), which reflects the enzymatic contribution to clot formation. The TEG parameter G, (G = 5000 x A/100-A) also was determined for each patient. As G is derived from amplitude (A), it reflects overall net clot strength. A hypercoagulable state was defined as delta < 0.6 min and/or G > 11 dynes/cm(2).

RESULTS

A hypercoagulable state was identified via delta in 6 patients (60%); all of whom remained hypercoagulable following heparinase addition, suggesting chemoprophylaxis was ineffective. Of six patients with a hypercoagulable G value, 50% had a normal delta suggesting the presence of platelet hypercoagulability. Delta closely correlated with TMRTG (r = 0.94). However, the varying contribution of platelets to hypercoagulability, was shown by a nonlinear, weak correlation of delta and TMRTG with G (r = 0.11 and r = 0.14, respectively).

CONCLUSION

Delta reflects changes in thrombin generation as measured by TMRTG, allowing for differentiation of enzymatic from platelet hypercoagulability. Future studies will be required to validate these findings.

Tissue inhibitor of metalloproteinase-1 is an early marker of acute endothelial dysfunction in a rodent model of venous oxidative injury

Although there are extensive research data regarding arterial endothelial dysfunction, the effects of venous endothelial dysfunction are not well characterized. Matrix metalloproteinases (MMPs) have a defined role in vascular remodeling. MMPs are endopeptidases that are capable of degrading extracellular matrix proteins. We hypothesize that tissue inhibitor of metalloproteinase-1 (TIMP-1) can serve as an indicator of acute venous endothelial dysfunction in a rat model of oxidative injury. The experimental groups evaluated were as follows: rats not undergoing oxidative injury (controls), rats that received rose bengal but no laser (shams), and rats that received both rose bengal and laser illumination, resulting in an oxidative injury. Animals were evaluated at baseline (control, shams) and at 1 hr and 1 day post-oxidative injury. mRNA expression was determined by gene array technology and real-time polymerase chain reaction, plasma and vein wall TIMP-1 protein concentrations were determined by enzyme-linked immunosorbent assay, and vein wall morphometrics (cells/five high-power fields) were performed. B-cell lymphoma 2-like gene expression was upregulated at both 1 hr and 1 day post-injury. TIMP-1 protein and mRNA expression were significantly increased post-oxidative injury. One hour postinjury, vein wall polymorphonuclear leukocytes were present in significant numbers. Our results support the hypothesis that increased expression of TIMP-1 in venous endothelium and plasma may serve as an early indicator of endothelial dysfunction.

The Effect of Negative Pressure Therapy on the Femoral Vein Blood Flow and Wall Structure

Negative pressure therapy has been recently used for managing lymphatic or infective groin complications. The aim of this study was to investigate any possible association between application of negative pressure therapy in the groin area and deep-vein thrombosis. Acute surgical wounds were created at the inguinal areas in 7 pigs. Different negative pressures ranging from −50 to −200 mmHg were applied directly over the femoral vessels, and blood flow alterations were studied using a Doppler ultrasound. Femoral vein specimens were also removed for histological examination after 12 hours of therapy. It has been demonstrated that negative pressure therapy does not significantly alter the baseline lower limb venous return. Histology demonstrated several changes, which are associated with vein thrombogenesis. The hemodynamic and pathological findings still leave a potential for thrombogenic effects of negative pressure therapy and warrant care to protect the femoral veins, with the use of thrombosis prophylaxis measures.

MAC mode atomic force microscopy studies of living samples, ranging from cells to fresh tissue

Magnetic AC mode (MAC mode) atomic force microscopy (AFM), a novel type of tapping mode AFM in which the cantilever is driven directly by a magnetic field, is a powerful tool for imaging with high spatial resolution and better signal-to-noise in liquid environment. It may largely extend the application of AFM to living samples, especially those are sensitive to cantilever forces, even to multilayer tissue samples. However, there are few reports on the imaging of living cells by MAC mode AFM previously. In our present study, we explore the optimal imaging conditions of MAC mode AFM on living astrocytes and fresh arterial intima surface. We also used nude tips for PicoTREC panel (i.e., Aux in BNC, a new data collecting channel) to image living samples and discussed its difference with phase imaging. We show that living biological samples can be imaged by MAC mode AFM at details of comparable resolution as those by high resolution scanning electron microscopy. Furthermore, the combination of height, amplitude, phase and TREC panel signals provide abundant informations for the characteristics of living samples, such as topography, profile, stiffness and adhesion.

Aspirin in the prevention and treatment of venous thromboembolism

This review summarizes available evidence on effects of aspirin on incidence and outcomes of venous thromboembolism (VTE). From a pathophysiological point of view, inhibition of platelet aggregation is associated with an impaired thrombus formation both in an experimental model of venous thrombosis and in vivo. Epidemiological evidence in support of a beneficial effect of acetylsalicylic acid on VTE incidence is provided by the Antiplatelet Trialists' Collaboration meta-analysis of studies on the use of antiplatelet agents in cardiovascular risk reduction, showing a significant 25% risk reduction of pulmonary embolism. Moreover, a meta-analysis on older trials of antiplatelet agents in postsurgical VTE prevention and the large Pulmonary Embolism Prevention trial demonstrate a protective effect of the same magnitude: 25-30%. However, as low-molecular-weight heparins (LMWH) and vitamin K antagonists (VKA) have shown a superior efficacy and safety profile, and no direct comparisons have been made between aspirin, LMWH and VKA in prolonged use, the most recent guidelines advise against aspirin monotherapy for thromboprophylaxis in the surgical patient. Currently, there is no evidence to support a role for aspirin in air travel-related VTE. Regarding prevention of recurrent VTE, studies are ongoing to determine the potential role of aspirin after a first unprovoked VTE.