| 1. |
- Arbring, Kerstin, 1961-
(author)
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Two worlds, one goal : A Clinician’s Perspective on Laboratory Analyses in Anticoagulant Treatment
- 2023
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Doctoral thesis (other academic/artistic)abstract
- Almost precisely a century ago, in the 1920s and 1930s, cattle bled to death in North America after being fed moldy hay containing sweet clover, the yellow Melilotus officinalis, and the white Melilotus albus. The toxic substance in the hay inhibiting blood coagulation was identified and named dicumarol. Further development resulted in warfarin, an oral anticoagulant that has been used for over 70 years and still is, even though newer direct-acting oral anticoagulants (DOACs) are mainly replacing it. For some patients, warfarin is still the drug of choice. A safe warfarin treatment needs repeated blood sample analysis (PT-INR), and with the new DOACs come new laboratory challenges. The aim of this thesis was to investigate ways laboratory methods can contribute to improving oral anticoagulant treatment. Paper I explores genetic variants of the enzyme targeted by warfarin, VKORC1. The result shows that the haplotype VKORC1*2 is the most important of the VKORC1 haplotypes for warfarin dosage, with a lower dose requirement. The VKORC1*2 haplotype was also related to more unstable PT-INR levels. Paper II describes a cross-section study comparing warfarin treatment control, as PT-INRs within the intended therapeutic range, in primary health care centers (PHCCs) and specialized anticoagulation clinics (ACCs). Both settings showed good therapeutic control, with at least as good therapeutic control in the PHCCs as in the ACCs. Today, almost all warfarin treatment in our region is centralized to ACCs. Paper III focuses on the modification of a point-of-care PT method. A ratio of PT from two different dilutions of each patient sample was calculated and used as an indirect measure of DOAC activity. There were close correlations between the PT ratio and drug concentrations measured at the hospital laboratory. The detection level varies between DOACs and may limit its use in some situations. Paper IV evaluated the MRX PT DOAC, an assay based on the PT ratio principle. It was found to be able to detect potentially interfering DOAC levels in plasma samples. Confirmatory testing is recommended, as is sensitivity improvement for the detection of specific interferences.
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| 2. |
- Chaireti, Roza, 1979-
(author)
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Thrombin generation in different cohorts : Evaluation of the haemostatic potential
- 2013
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Doctoral thesis (other academic/artistic)abstract
- The aim of this thesis is to evaluate thrombin generation in patients with thrombophilia (Paper I), in patients with venous thromboembolism (Paper II), in healthy women during the menstrual cycle (Paper III), in patients with liver disease (Paper IV) and in patients with mild deficiency of factor VII (Paper V).For this purpose, thrombin generation was measured in platelet poor plasma by the calibrated automated thrombogram (CAT®) assay. Thrombin generation expresses the overall haemostatic potential, in contrast to the more traditional coagulation tests, which concentrate on individual factors or coagulation pathways. The thrombin generation markers that were measured and studied were: lagtime (clotting time), endogenous thrombin potential (ETP, total thrombin concentration), peak (maximum thrombin concentration) and time to peak (ttpeak).The cohorts for Papers I and II are part of a larger cohort (The LInköping Study on Thrombosis, LIST), which included 516 consecutive patients who presented at the Emergency Department of Linköping University Hospital, Sweden with the clinical suspicion of venous thrombosis. In Paper I thrombin generation was measured in the absence of thrombomodulin in patients with thrombophilia (factor V Leiden, n=98 and prothrombin G20210A mutation, n=15) and in an equal number of age- and gendermatched controls. The results were associated with the presence of thrombosis, as well as gender and age. It was shown that thrombin generation did not differ significantly among patients and controls. Patients with and patients without thrombophilia who had suffered a thrombosis upon inclusion had longer lagtime compared with their counterparts without thrombosis. Neither age nor gender had any effect on the results.In Paper II, thrombin generation at the time of an acute thromboembolic episode was studied as a potential early marker for recurrence during a 7-year follow-up in 115 patients with venous thrombosis upon inclusion. It was shown that patients with recurrences during follow-up had longer lagtime and ttpeak at the time of the acute thrombosis, whereas those without recurrences had higher ETP and peak. Those results were particularly evident in the group of patients with an unprovoked thrombosis upon inclusion.In Paper III, thrombin generation was measured in the follicular and luteal phase of a normal menstrual cycle in 102 healthy women not taking oral contraceptives. The results were associated with haemostatic parameters (fibrinogen, antithrombin, D-dimer, plasminogen activator inhibitor-1, factors VII, VIII, X and von Willebrand) as well as the physiological concentrations of oestradiol, progesterone, antimüllerian hormone and sex hormone-binding globulin and the number of pregnancies and deliveries for these women. ETP was significantly higher during the luteal phase. However, this could not be explained by the elevation of other procoagulant factors during the same phase. Progesterone was found to exert a more significant effect on haemostasis than oestradiol during both phases (multiple regression analysis).In Paper IV, thrombin generation was measured in the presence and absence of thrombomodulin in 47 patients with portal vein thrombosis, PVT (11 with cirrhotic PVT and 36 with non-cirrhotic PVT), 15 patients with Budd-Chiari syndrome and 24 patients with cirrhosis, as well as 21 healthy controls. Since 15 patients with PVT (2 with cirrhotic PVT and 13 with non-cirrhotic PVT) and 10 patients with Budd-Chiari syndrome were treated with warfarin at the time of the blood sampling, an equal number of patients matched for age, gender and prothrombin time-international normalized ratio with atrial fibrillation and no hepatic diseases were used as controls. It was shown that hypercoagulability, expressed as total and maximum concentration of generated thrombin as well as thrombomodulin resistance [thrombin generation markers measured in the presence]/[thrombin generation markers measured in the absence of thrombomodulin] was pronounced in the groups of patients with cirrhosis, regardless of the presence of splanchnic thrombosis.In Paper V, thrombin generation in the presence of human and different concentrations of rabbit thromboplastin was measured in 10 patients with mild deficiency of factor VII and in 12 controls. In these patients, the levels of factor VII varied slightly depending on the origin of the thromboplastin used in the reagent. Nine out of 10 patients had a mutation in common (Arg353Gln), which was, however, not associated with the diversity in the factor VII measurements due to the origin of thromboplastin. ETP in patients with mild factor VII deficiency was about 86% of the ETP in the control group. The expected thrombin generation patterns with increasing concentrations of thromboplastin did not differ depending on the origin of thromboplastin in the patient group.
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| 3. |
- Heenkenda, Menikae Kanchena, 1982-
(author)
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Understanding and Managing Thrombotic Risks in Medical Conditions : One Size Does Not Fit All
- 2024
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Doctoral thesis (other academic/artistic)abstract
- Hemostasis is a critical physiological process that stops bleeding at the site of an injury while ensuring normal blood flow elsewhere, thereby preventing excessive clot formation that could lead to dangerous conditions like thrombosis. This delicate balance is influenced by genetics, medical conditions such as cancer, and various medications. When a blood vessel is damaged, platelets adhere to the exposed area, become activated, and aggregate to form an initial plug. Coagulation factors, particularly thrombin, create a strong fibrin network to stabilize the clot. Disruptions in this process can result in significant bleeding or dangerous clot formation.This thesis aims to explore and understand the factors affecting coagulation and the risks of thrombotic events in different medical contexts. This includes studying genetic variability in the protease-activated receptor 4 (PAR4) gene (specifically the Ala120Thr variant) among sub-Saharan African populations, identifying genetic and non-genetic risk factors for venous thromboembolism (VTE) in patients with the brain cancer glioblastoma multiforme (GBM), and investigating the impact of intravenous morphine on platelet activity in patients with ST-elevation myocardial infarction (STEMI) treated with ticagrelor, a P2Y12 inhibitor. The A allele of the rs773902 single-nucleotide polymorphism (SNP) in the PAR4 gene (F2RL3) substitutes threonine for alanine at the 120th protein position (Thr120). This allele is more prevalent in African populations compared to Caucasian populations, although previous studies did not specify the geographic ancestry of participants. Thr120 is associated with higher PAR4-induced human platelet aggregation and Ca2+ flux. Our study found that the frequency of the A allele in the Somali population is significantly lower than previously reported for African Americans. The A allele frequency in Somalis is 38%, compared to 63% for African Americans. The A allele frequency in Somalis is closer to that of the Maasai population in Kenya (41%), but vastly different from the Esan population in Nigeria (68%). Certain cancers, such as GBM, are associated with a higher risk of VTE, including deep vein thrombosis (DVT) and pulmonary embolism (PE). Our research identified blood group B as a significant risk factor for patients with GBM (OR=6.91; 95% CI=2.2–24.1; P =0.001). Also, GBM tumors in the frontal lobe are associated with an increased risk of VTE (OR=3.14; 95% CI=1.1–10.7; P =0.05). Our study on morphine, commonly used for pain management in STEMI patients, found that morphine is associated with increased platelet aggregation one hour after percutaneous coronary intervention (PCI), impacting the efficacy of ticagrelor. Morphine delays platelet inhibition by affecting the pharmacodynamics of antiplatelet therapy, likely by delaying gastric emptying. However, this effect is short-lived, as platelet reactivity returns to similar levels in both groups 12 hours post-PCI. Despite this immediate impact on platelet function, our research found no significant differences in biomarkers of platelet activity, coagulation, or inflammation between the morphine and non-morphine groups. Additionally, all patients in our study were administered unfractionated heparin injections or bivalirudin infusion during primary PCI, which may help control the risk of blood clot formation. These studies collectively emphasize the need for individualized strategies to manage thrombotic risks and coagulation. The significant genetic variability among sub-Saharan African populations highlights the need for precise genetic research to understand how genetics influence coagulation and develop personalized medical strategies. The increased risk of cancer-associated thrombosis, particularly in patients with GBM, calls for individualized anticoagulant therapies based on unique risk profiles, such as blood group typing and tumor location. Incorporating these insights into clinical practice can help healthcare providers better identify high-risk patients and tailor thromboprophylaxis strategies accordingly. Similarly, the impact of morphine on patients with STEMI treated with ticagrelor requires careful consideration. In conclusion, these findings underscore the importance of a personalized approach in managing coagulation and thrombotic risks. The studies show that genetic variability, specific medical conditions, and medication effects are crucial in thrombotic risk. Therefore, customized strategies based on individual patient profiles and contexts are essential for effectively managing and preventing thrombotic events.
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| 4. |
- Boknäs, Niklas, 1979-
(author)
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Studies on interfaces between primary and secondary hemostasis
- 2016
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Doctoral thesis (other academic/artistic)abstract
- Our conceptual understanding of hemostasis is still heavily influenced by outdated experimental models wherein the hemostatic activity of platelets and coagulation factors are understood and studied in isolation. Although perhaps convenient for researchers and clinicians, this reductionist view is negated by an ever increasing body of evidence pointing towards an intimate relationship between the two phases of hemostasis, marked by strong interdependence. In this thesis, I have focused on factual and proposed interfaces between primary and secondary hemostasis, and on how these interfaces can be studied.In my first project, we zoomed in on the mechanisms behind the well-known phenomenon of thrombin-induced platelet activation, an important event linking secondary to primary hemostasis. In our study, we examined how thrombin makes use of certain domains for high-affinity binding to substrates, called exosite I and II, to activate platelets via PAR4. We show that thrombin-induced platelet activation via PAR4 is critically dependent on exosite II, and that blockage of exosite II with different substances virtually eliminates PAR4 activation. Apart from providing new insights into the mechanisms by which thrombin activates PAR4, these results expand our knowledge of the antithrombotic actions of various endogenous proteins such as members of the serpin superfamily, which inhibit interactions with exosite II. Additionally, we show that inhibition of exosite II could be a feasible pharmacological strategy for achieving selective blockade of PAR4.In my second project, we examined the controversial issue of whether platelets can initiate the coagulation cascade by means of contact activation, a hypothesis which, if true, could provide a direct link between primary and secondary hemostasis. In contrast to previous results, our findings falsify this hypothesis, and show that some of the erroneous conclusions drawn from earlier studies can be explained by inappropriate experimental models unsuitable for the study of plateletcoagulation interfaces.My third project comprised an assessment of the methodological difficulties encountered when trying to measure the ability of platelets to initiate secondary hemostasis by the release of microparticles expressing tissue factor. Our study shows that the functional assays available for this purpose are highly susceptible to error caused by artificial contact activation. These results could help to improve the methodology of future research and thus pave the way for new insights into the roles of tissue factor-bearing microparticles in the pathophysiology of various thrombotic disorders.From a personal perspective, my PhD project has been a fascinating scientific odyssey into the largely unexplored interfaces between primary and secondary hemostasis. Looking forward, my ambition is to continue our work exploring platelet-coagulation interactions and to translate these insights into clinically meaningful information, which may someday improve the treatment of patients with bleeding and/or thrombosis.
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| 5. |
- Faxälv, Lars, 1977-
(author)
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Imaging methods for haemostasis research
- 2009
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Doctoral thesis (other academic/artistic)abstract
- Blood is a vital part of the human physiology; a transport system that brings nutrients and oxygen to sustain living cells and simultaneously facilitates the removal of carbon dioxide and other waste products from the body. To assure the continuity of these functions, it is of uttermost importance to keep the flowing blood inside the vascular system at any cost. The principal components of the haemostatic system are the blood platelets and the plasma coagulation system, both working in concert to create a blood stopping haemostatic plug when a vessel is ruptured. In modern health care, methods for treatment and diagnostics often implicate the contact between blood and artificial materials (biomaterials). Biomaterial surfaces may activate platelets and the coagulation cascade by exposing a surface that during blood contact shares certain characteristics with surfaces found at the site of vascular injury. Therefore it is of great importance that the mechanisms behind the interactions between foreign surfaces and blood are studied in order to minimize, and if possible, prevent unnecessary reactions that may lead to thrombosis.This thesis describes two important methods to study blood – surface interactions in terms of surface induced plasma coagulation and platelet adhesion/aggregation. The method ‘Imaging of coagulation’, a coagulation assay based on time-lapse image capture of the coagulation process was developed during the course of this work. The use of images enables the method to answer questions regarding where coagulation was initiated and how fast coagulation propagates. Such questions are highly relevant in the study of blood-biomaterial interactions but also in general haemostasis research. In vivo, platelet adhesion and aggregation are events that always proceed under flow conditions. Therefore we also developed a cone-and-plate flow model to study these mechanisms under similar conditions in vitro. The cone-and-plate setup was found to be a flexible platform and was used for both blood compatibility testing of potential biomaterials as well as for general haemostasis research.With the above mentioned methods we tested the haemocompatibility of glycerol monooleate (GMO), a proposed substance for use in biomaterial applications. It was found that GMO did not activate coagulation to any great extent either in plasma or in whole blood.Surface induced coagulation and platelet adhesion was also studied on PEG-containing hydrogels and compared with hydrogels constructed from three different non-PEG-containing monomers. It was concluded that all the grafted hydrogels, in particular those produced from the monomers 2-hydroxyethyl methacrylate (HEMA) and/or PEG- methacrylate (PEGMA), demonstrated good haemocompatibility.Supported phospholipid bilayers were used to investigate the relationship between surface charge and procoagulant activity. The coagulation process was studied in a straightforward manner using the imaging of coagulation setup. We concluded that the content of negatively charged 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-L-serine] (POPS) in the bilayer must exceed ~ 6% for the bilayer to exert procoagulant activity.The physiological role of factor XII in human haemostasis and thrombosis was investigated in the imaging of coagulation setup and the cone and plate setup by the use of surfaces with thrombogenic coatings. We found that tissue factor initiated coagulation could be greatly accelerated by the presence of contact activating agents in a platelet dependent manner.In conclusion, the method ‘Imaging of coagulation’ and platelet adhesion/aggregation in the cone-and-plate flow model are both versatile methods with many possible applications. The combination of the two methods provides a solid foundation for biomaterial and haemostasis research.
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| 6. |
- Karlsson, Anna, 1985-, et al.
(author)
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The effect of tinzaparin on biomarkers in FIGO stages III-IV ovarian cancer patients undergoing neoadjuvant chemotherapy – the TABANETOC trial: study protocol for a randomized clinical multicenter trial
- 2024
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In: Acta Oncologica. - Uppsala : Medical Journals Sweden. - 0284-186X .- 1651-226X. ; 63, s. 580-585
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Journal article (peer-reviewed)abstract
- Background: Tinzaparin, a low-molecular weight heparin (LMWH), has shown anti-neoplastic properties in animal models and in in vitro studies of human cancer cell lines. The reduction of CA-125 levels during neoadjuvant chemotherapy (NACT) in patients with epithelial ovarian cancer (EOC) co-varies with the prognosis; the larger the decrease in CA-125, the better the prognosis.Purpose: This study aims to evaluate the potential anti-neoplastic effects of tinzaparin by investigating changes in serum CA-125 levels in advanced EOC patients who receive NACT.Material and methods: This is an open randomized multicenter pilot trial. Forty patients with EOC selected to receive NACT will be randomized 1:1 to receive daily addition of tinzaparin or no tinzaparin. The processing and treatment of the patients will otherwise follow the recommendations in the Swedish National Guidelines for Ovarian Cancer. Before every cycle of chemotherapy, preoperatively, and 3 weeks after the last cycle of chemotherapy, a panel of biomarkers, including CA-125, will be measured.Patients: Inclusion criteria are women aged 18 years or older, World Health Organization performance status 0–1, histologically confirmed high-grade serous, endometrioid or clear cell EOC, International Federation of Gynecology and Obstetrics (FIGO) stages III-IV. In addition, a CA-125 level of ≥ 250 kIE/L at diagnosis. Exclusion criteria are contraindications to LMWH, ongoing or recent treatment with unfractionated heparin, LMWH, warfarin or non-vitamin K antagonist oral anticoagulants.Interpretation: This study will make an important contribution to the knowledge of the anti-neoplastic effects of tinzaparin in EOC patients and may thus guide the planning of a future study on the impact of tinzaparin on survival in EOC.
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| 7. |
- Milovanovic, Micha, 1966-
(author)
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Platelets : with special reference to platelet density subpopulations, stable coronary heart disease and atrial fibrillation
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The current thesis was divided into two parts. Basic platelet research is the topic of the first section. The subsequent clinical part examines platelet reactivity in stable angina pectoris (AP) and in atrial fibrillation.Platelet heterogeneity was investigated in the first section (papers 1 and 2). The cells were separated according to density using linear Percoll™ (a density medium) gradients. The latter contained EDTA, prostaglandin E1 and theophylline to prevent platelet in vitro activity. The platelet population was then divided into density subpopulations (n = 16 - 20). Membrane attached fibrinogen was determined with a flow cytometer technique and used as a marker reflecting platelet in vivo activity. Platelet P-Selectin content was employed to estimate the quantity of platelet α-granules. Paper I examined healthy blood donors (n = 3). The second report (paper II) compared healthy volunteers (n = 2) and subjects with essential thrombocythemia (ET) (n = 2). The latter is a clonal disease being characterized by an excessive platelet production. Platelet counts were determined in all fractions. In manuscripts I and II determination of surface bound fibrinogen and intracellular P-Selectin was carried out in 12 and 16 platelet density fractions, respectively.High density platelets displayed more surface bound fibrinogen indicating in vivo activity. They also contained less P-Selectin. The latter finding implies platelet in vivo release reactions. Low density platelets circulated with more surface bound fibrinogen as well. Compared with peak density platelets, lighter cells contained more P-Selectin. ET was characterized by a similar platelet density pattern in that high and low density platelets displayed more surface bound fibrinogen. The similarity may explain why severe bleedings do not occur more frequently in ET. It is also obvious from the current thesis that the significance of platelet heterogeneity remains unclear and stimulates to further research. In particular, future work must involve more patients.The second part (papers III-VI) of the thesis was devoted to stable AP and atrial fibrillation. Determination of platelet reactivity i.e. platelet bound fibrinogen after stimulation was carried out in whole blood. A flow cytometer technique was employed (papers III-VI). Adenosine diphosphate (ADP) (1.7 and 8.5 μmol/L) and a thrombin-receptor activating peptide (TRAP-6) (57 and 74 μmol/L) were used as stimulating agents. Determination of peak platelet density (kg/L) was utilized as a further measure reflecting platelet reactivity (paper V). Surface bound and soluble P-Selectin were employed as platelet activity markers (paper VI).Gender differences with respect to platelet reactivity were investigated in paper III. Paper IV examined platelets in stable AP without significant coronary flow obstruction(s) as determined by coronary angiography. In a following study platelet reactivity was analysed in diabetes type II complicated by stable AP (paper V). Finally, long-term (more than 2 years) outcome of atrial fibrillation was related to platelet reactivity and activity (paper VI). In this study the subjects were investigated at the initial electrical cardioversion and the analysis were repeated after more than 2 years.Postmenopausal women with stable AP demonstrated more reactive platelets when stimulating with TRAP-6. They had higher platelet counts (paper III) as well. Stable AP without significant coronary flow obstruction(s) was associated with elevated platelet reactivity (paper IV). Diabetes type II was linked to higher peak platelet density and elevated platelet reactivity (paper V). Augmented platelet reactivity proved to be a feature of subjects remaining in atrial fibrillation more than 2 years after the electrical cardioversion (paper VI). In contrast, the irregular heart rhythm did not affect platelet activity.It is to assume that platelets at least partly are responsible for the sometimes atypical symptoms of females with stable AP. It is also conceivable to speculate that platelets contribute to chest pain in AP free from significant coronary flow obstruction(s). Theoretically, enhanced platelet reactivity could at least partly explain why diabetes type II affects the prognosis of coronary heart disease. The thesis further shows a possible theoretical link between atrial fibrillation, increased platelet reactivity and clot formation.
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| 8. |
- Nylander, Martina, 1980-
(författare)
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The thrombin receptors PAR1 and PAR4 and their relative role in platelet activation
- 2009
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many blood cell mechanisms in the human body are working all the time to maintain haemostasis in the blood vessels. Once a wound arises platelets are alerted via different substances to cover the wound and prevent loss of blood. Most of the times these mechanisms do stop the blood, and further heal the wound. During other circumstances the platelet-covering continues to form a thrombus, preventing the blood to flow and instead causes myocardial infarction or stroke. There are several risk factors triggering development of circulatory diseases such as obesity, lack of exercise, smoking, infection and stress.This thesis describes the interaction between the two platelet thrombin receptors PAR1 and PAR4, together with the interaction of the oral pathogen Porphyromonas gingivalis (with thrombin-like gingipains), and the cross talk with the stress hormone epinephrine and its α2A adrenergic receptor. Until now PAR1 is thought to be the most important thrombin receptor due to its high affinity for thrombin. From a phylogenetical and patophysiological point of view there must be a reason why platelets express two different thrombin receptors. Today PAR4 is considered less important, but this thesis implies that PAR4 plays an important role in platelet signaling and haemostasis.The results show that bacteria pre-stimulated platelets, followed by epinephrine gives a strong and full aggregation and calcium mobilization, in both aspirinated and non-aspirinated human platelets. The amount of bacteria does not itself, or epinephrine alone give aggregation or calcium mobilization. This mechanism is dependent on both Rgp type gingipain released from P. gingivalis, and PARs in an interaction with the α2A adrenergic receptor.Further, results reveal that PAR4 interacts and cross talks with the platelet α2A-adrenergic receptor in aspirinated platelets. Neither of the two platelet purinergic P2Y-receptors (P2Y12 and P2Y1) contribute to this action, but the purinergic P2X1 does. In aggregation studies a low dose of PAR4 activating peptide (AP), but not PAR1-AP, followed by epinephrine results in a strong aggregation and in a calcium mobilization. ATP secretion measurements did reveal that ATP was released during epinephrine stimulation, which indicate that ATP and P2X1 have a key role in this event. By blocking P2X1 both aggregation and calcium mobilization were abolished, but not by blocking P2Y12 and P2Y1. Inhibition of PI3-kinase, both epinephrine-induced calcium mobilization and aggregation were significant reduced. In non-aspirinated platelets PAR1 synergizes with the α2A adrenergic receptor and P2X1.In conclusion, this thesis suggests that PAR4 plays an intriguing and important role in platelets with inactived cyclooxygenase 1. The results described in this thesis contribute to an increased knowledge of the platelet thrombin receptors.
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| 9. |
- Rajani, Rupesh, 1973-
(författare)
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Hepatic and Portal Vein Thrombosis : studies on epidemiology and risk factors
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Budd-Chiari syndrome (BCS) i.e. thrombosis in the hepatic veins and/or inferior vena cava, and portal vein thrombosis (PVT) are rare disorders. Epidemiological data are scarce and previous reports have been from highly specialised referral centres.The aims of the thesis were: (i) to investigate the epidemiology, clinical features and survival of Swedish patients with BCS or PVT, and to (ii) determine common underlying risk factors i.e. thrombophilic factors and genetic markers of myeloproliferative disorders (MPD).In the first two papers we retrospectively reviewed the medical records of all BCS (1986-2003) and PVT (1995-2004) patients identified by searching the computerized patient registers of 11 hospitals including all university hospitals and liver transplantation units. In the following two papers we excluded patients with malignancy and included new cases diagnosed during the years 2004-2009; blood samples were collected and compared with controls and other patient groups.A total of 43 patients with BCS were identified (median age 40 years, 24 women). The mean agestandardised incidence and prevalence rates were 0.8 per million per year and 1.4 per million inhabitants respectively. Two or more risk factors were present in 44%. The overall transplantationfree survival at 1, 5 and 10 years was 47%, 28% and 17% respectively.173 patients (median age 57 years, 93 men) with portal vein thrombosis were identified. The incidence and prevalence rates were 0.7 per 100 000 per year and 3.7 per 100 000 inhabitants, respectively. In the absence of cirrhosis and malignancy, being the most common risk factors, the survival at 1 year and 5 years was 92% and 76%, respectively.We observed an increased plasma level of the procoagulant factor VIII in BCS (mean 1.63 kIE/L), PVT without cirrhosis (1.87 kIE/L), PVT with cirrhosis (1.97 kIE/L), deep vein thrombosis (1.41 kIE/L) and cirrhosis patients alone (2.22 kIE/L), all p <0.001 compared to healthy controls (1.04 kIE/L). Elevated factor VIII levels were found in 50% of BCS and in 85% of PVT patients without previously identified prothrombotic risk factors.The somatic JAK2 V617F-mutation, a marker of MPD, was present in 63% of BCS and 14% of PVT patients. The frequency of the germline JAK2 46/1 haplotype was significantly higher in BCS (53%) and PVT (36%) patients compared to controls (27%) (p=0.02). However, the enrichment was only observed in JAK2 V617F positive patients.Conclusions: The incidence and prevalence rates of BCS in Sweden were calculated to be 0.8/million inhabitants per year and 1.4/million inhabitants, respectively. The rates of PVT were higher; 0.7/100 000 inhabitants per year and 3.7/100 000 inhabitants, respectively. In BCS the transplantation-free survival was poor, whereas in PVT the survival was variable and highly dependent on the presence of underlying disease. Concurrent prothrombotic risk factors are common in both disorders. High plasma levels of procoagulant factor VIII was observed in a majority of idiopathic BCS and PVT. The prevalence of the somatic JAK2 V617F mutation was high in our cohort and associated with the presence of a germline JAK2 46/1 haplotype.
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| 10. |
- Vretenbrant Öberg, Karin, 1979-
(författare)
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The role of platelet thrombin receptors PAR1 and PAR4 in platelet activation
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Platelets play a pivotal role in coagulation and haemostasis. Their most prominent task is to seal damaged blood vessels by the formation of a platelet plug at the damaged area. Once the injury is covered, platelets retract the coagulum to close the wound and allow the blood to flow freely in the vessel. Platelets are strongly activated by the essential enzyme thrombin, formed in the coagulation cascade. Activation of the platelet thrombin receptors PAR1 and PAR4 leads to shape change, secretion of granule content, and aggregation, all of which can be accomplished by each receptor individually. However more and more findings indicate that there are differences between the receptors and that they have different physiological functions. This thesis presents studies performed to elucidate the relative role of PAR1 and PAR4 in platelet activation and coagulation. We have studied the effects on platelet activation and coagulation, and revealed a possible physiological role for PAR4 in the stabilisation of the coagulum. We also investigated the relative role of PAR1 and PAR4 in the cross-talk between thrombin and epinephrine with and without inhibition of COX-1. We demonstrated that PAR4 interacts with adrenergic receptors and causes an aggregation of platelets dependent on released ATP and its receptor P2X1, thereby circumventing the inhibition by aspirin. Not only is this an interesting specific role for PAR4, but it may also be of clinical importance considering that COX-1 inhibition is the most common treatment for patients with cardiovascular disease to prevent thrombosis. We show that the number of PAR1 receptors varied between donors and that this variation was correlated to the response on receptor activation. The number of PAR1 receptors on the platelet surface was decreased after PAR1 stimulation but increased after stimulation of other receptors. In a final attempt to elucidate the nature of PAR1 and PAR4 we used mathematics to evaluate the effect of co-stimulation of the receptors. We found a strong synergistic effect for both platelet activation and aggregation. This indicates that PAR1 and PAR4 interact in a yet unknown way to regulate or amplify the effect of each other rather than merely transmitting the incoming signal the same way.
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