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Frank W G Leebeek

Publications and source records attributed to Frank W G Leebeek.

At least 19 recordsLinked to original sources
PubMed2025

Rewriting the script: gene therapy and genome editing for von Willebrand Disease.

In recent years gene therapy has emerged as a powerful technology for treatment of a large variety of inherited disorders. With the FDA approval of in vivo gene therapy of hemophilia A and B using AAV-mediated transgene delivery to hepatocytes, the path towards a new treatment era seemed paved. Also, CRISPR-Cas based approaches have reached the clinic, as in the ex vivo treatment of hematopoietic stem cells for sickle cell disease and thalassemia patients. The question arises whether these innovative strategies will also be suitable for patients with von Willebrand Disease (VWD). Whilst in and ex vivo delivery to endothelial cells (ECs) has been demonstrated, and CRISPR-Cas9 gene editing has been successful in ECs, there are currently no gene therapy options available for VWD. The wide variety of pathogenic VWF mutations makes development of broadly applicable, cost-effective gene therapies challenging. While delivery of von Willebrand factor (VWF) as a therapeutic transgene would be optimal, the size of VWF challenges efficient delivery. Therefore, treatment of VWD requires targeted, personalized gene therapy; for instance by using the newest CRISPR-Cas technologies which can be tailored to facilitate alteration and restoration of various pathogenic VWD variants. This review describes the inherited bleeding disorder VWD and potential gene therapy approaches for management of the disease. Thereby we are exploring different CRISPR-Cas technologies and recent developments in the field. Moreover, we will discuss the ongoing advances of in vivo delivery systems, all with the scope on ECs.

CRISPR-Cas, in vivo delivery↗
PubMed2006

High von Willebrand factor levels increase the risk of first ischemic stroke: influence of ADAMTS13, inflammation, and genetic variability.

BACKGROUND AND PURPOSE: Elevated von Willebrand factor (vWF) concentrations are associated with an increased risk of ischemic heart disease. Several factors influence vWF antigen levels and activity, including blood group, genetic variability, acute-phase response, and proteolysis by A Disintegrin and Metalloprotease with ThromboSpondin motif (ADAMTS13), a determinant of proteolytic cleavage of vWF. We assessed how these factors affect the relation between vWF and the occurrence of stroke to understand the underlying mechanism. METHODS: In a case-control study of 124 first-ever ischemic stroke patients and 125 age- and sex-matched controls, we studied vWF antigen (vWF:Ag), vWF ristocetin cofactor activity (vWF:RCo), ADAMTS13 activity, the -1793C/G polymorphism in the vWF gene, and C-reactive protein. RESULTS: vWF antigen and activity levels were significantly higher in cases than in controls. The relative risk of ischemic stroke was highest in individuals in the upper quartile of vWF:Ag (odds ratio, 3.2; 95% CI, 1.4 to 7.5) and vWF:RCo (odds ratio, 2.1; 95% CI, 0.9 to 4.8) compared with individuals in the lowest quartiles. In individuals with ADAMTS13 in the lowest quartile, the relative risk of stroke was 1.7 (95% CI, 0.7 to 3.9) compared with the highest quartile. C-reactive protein, ADAMTS13, and genetic variation did not affect the association between vWF and the relative risk of stroke, whereas blood group did affect the association. CONCLUSIONS: vWF antigen and activity are associated with the occurrence of acute ischemic stroke. This relation is unaffected by the severity of the acute-phase response or by genetic variation or degradation.

ADAM Proteins↗
PubMed2006

Effectiveness of managing suspected pulmonary embolism using an algorithm combining clinical probability, D-dimer testing, and computed tomography.

CONTEXT: Previous studies have evaluated the safety of relatively complex combinations of clinical decision rules and diagnostic tests in patients with suspected pulmonary embolism. OBJECTIVE: To assess the clinical effectiveness of a simplified algorithm using a dichotomized clinical decision rule, D-dimer testing, and computed tomography (CT) in patients with suspected pulmonary embolism. DESIGN, SETTING, AND PATIENTS: Prospective cohort study of consecutive patients with clinically suspected acute pulmonary embolism, conducted in 12 centers in the Netherlands from November 2002 through December 2004. The study population of 3306 patients included 82% outpatients and 57% women. INTERVENTIONS: Patients were categorized as "pulmonary embolism unlikely" or "pulmonary embolism likely" using a dichotomized version of the Wells clinical decision rule. Patients classified as unlikely had D-dimer testing, and pulmonary embolism was considered excluded if the D-dimer test result was normal. All other patients underwent CT, and pulmonary embolism was considered present or excluded based on the results. Anticoagulants were withheld from patients classified as excluded, and all patients were followed up for 3 months. MAIN OUTCOME MEASURE: Symptomatic or fatal venous thromboembolism (VTE) during 3-month follow-up. RESULTS: Pulmonary embolism was classified as unlikely in 2206 patients (66.7%). The combination of pulmonary embolism unlikely and a normal D-dimer test result occurred in 1057 patients (32.0%), of whom 1028 were not treated with anticoagulants; subsequent nonfatal VTE occurred in 5 patients (0.5% [95% confidence interval {CI}, 0.2%-1.1%]). Computed tomography showed pulmonary embolism in 674 patients (20.4%). Computed tomography excluded pulmonary embolism in 1505 patients, of whom 1436 patients were not treated with anticoagulants; in these patients the 3-month incidence of VTE was 1.3% (95% CI, 0.7%-2.0%). Pulmonary embolism was considered a possible cause of death in 7 patients after a negative CT scan (0.5% [95% CI, 0.2%-1.0%]). The algorithm was completed and allowed a management decision in 97.9% of patients. CONCLUSIONS: A diagnostic management strategy using a simple clinical decision rule, D-dimer testing, and CT is effective in the evaluation and management of patients with clinically suspected pulmonary embolism. Its use is associated with low risk for subsequent fatal and nonfatal VTE.

Adult↗
PubMed2006

Elevated levels of von Willebrand Factor in cirrhosis support platelet adhesion despite reduced functional capacity.

Cirrhosis of the liver is frequently accompanied by complex alterations in the hemostatic system, resulting in a bleeding tendency. Although many hemostatic changes in liver disease promote bleeding, compensatory mechanisms also are found, including high levels of the platelet adhesive protein von Willebrand Factor (VWF). However, conflicting reports on the functional properties of VWF in cirrhosis have appeared in literature. We have measured a panel of VWF parameters in plasma from patients with cirrhosis of varying severity and causes. Furthermore, we assessed the contribution of VWF to platelet adhesion, by measuring the ability of plasma from patients with cirrhosis to support adhesion of normal or patient platelets under flow conditions. VWF antigen levels were strongly increased in patients with cirrhosis. In contrast, the relative collagen binding activity, as well as the relative ristocetin cofactor activity, was significantly lower in patients as compared with controls, indicating loss of function. Accordingly, patients had a reduced fraction of high-molecular-weight VWF multimers. Both strongly elevated and reduced activity and antigen levels of the VWF cleaving protease ADAMTS13 were found in individual patients. Adhesion of either normal or patient platelets to a collagen surface was substantially increased when these platelets were resuspended in plasma of patients with cirrhosis, as compared with control plasma. In conclusion, highly elevated levels of VWF in patients with cirrhosis contribute to the induction of primary hemostasis despite reduced functional properties of the molecule. This phenomenon might compensate for defects in platelet number and function in patients with cirrhosis.

Biomarkers↗
PubMed2006

Acquired lysosomal storage caused by frequent plasmapheresis procedures with hydroxyethyl starch.

BACKGROUND: Hydroxyethyl starch (HES) solutions have largely replaced conventional plasma expanders such as human albumin and colloidal fluids. Only a few side effects have been reported and mainly concern pruritus or blood coagulation disorders. Excessive HES exposure can result in diffuse tissue storage and accumulation with foamy appearing macrophages which produce the enzyme chitotriosidase (CT). In case of massive tissue storage, this enzyme activity can reach levels comparable to those of Gaucher disease. STUDY DESIGN AND METHODS: In this single-center retrospective analysis of 11 consecutive patients receiving large amounts of HES for chronic plasmapheresis, plasma CT activity was investigated. Five patients receiving chronic intermittent plasmapheresis with conventional plasma expanders served as controls. Plasma CT activity was measured and plotted against creatinine clearance. Where available, marrow aspirate was analyzed with light microscopy to detect foamy macrophages. One patient developed a lysosomal storage disease and was examined extensively. RESULTS: Conventional plasma expanders did not alter plasma CT activity. In patients with impaired renal function, frequent plasma replacement with HES resulted in an increase in plasma CT activity. In the patient with the acquired lysosomal storage disease, massive tissue infiltration with activated foamy macrophages was observed. The phagocytic capacity in this patient, however, did not seem to be altered. CONCLUSION: Patients with impaired renal function receiving large amounts of HES exhibit an increase in plasma CT activity. Because excessive HES exposure can result in an acquired lysosomal storage disease, this should be avoided in chronic plasmapheresis procedures.

Adult↗
PubMed2006

Myeloproliferative disease in the pathogenesis and survival of Budd-Chiari syndrome.

We studied the etiology, diagnosis and natural course of myeloproliferative disease (MPD) in 40 consecutive patients with Budd-Chiari syndrome (BCS). In 38% of the BCS patients with MPD another etiological factor was found. JAK2 mutation was present in 41% of the tested BCS patients. Survival was not significantly affected by the presence of MPD.

Adult↗
PubMed2004

What is the lowest dose of aspirin for maximum suppression of in vivo thromboxane production after a transient ischemic attack or ischemic stroke?

BACKGROUND: There is still worldwide disagreement about the optimal lowest dose of aspirin to be used in patients after a transient ischemic attack (TIA) or nondisabling stroke. We measured the urinary 11-dehydro-thromboxane-B(2) (uTXB(2)) excretion to compare the degree of suppression of in vivo platelet activation by various low doses of aspirin. METHODS: 60 patients were randomly allocated to treatment with either 30, 50, 75 or 325 mg of aspirin. All patients received a 413-mg loading dose of carbasalate calcium (equivalent to 325 mg of aspirin) on day 0. The study population was stratified into a subgroup with acute ischemic stroke (AIS; n = 20; onset of symptoms <48 h) and a subgroup with a recent TIA or minor stroke (TIA/mS; n = 40) with onset of symptoms beyond 30 days, but less than a year previously. Urine samples were collected on day 0, 1, 5, 11 and 28 in patients with AIS, and on day 0, 11 and 28 in the patients with a TIA/mS. RESULTS: On day 28, mean uTXB(2) levels were 241, 130, 217 and 187 pmol/mmol creatinine in the four treatment groups (ANOVA, p = 0.43). In the AIS subgroup, uTXB(2) remained suppressed on days 5 and 11 in all except the patients with the lowest dose (mean uTXB(2) on days 5 and 11: 475 and 392 pmol/mmol creatinine; log-transformed ANOVA, p = 0.05). CONCLUSION: In patients with a TIA or nondisabling stroke, a daily dose of 30 mg of aspirin provides sufficient suppression of thromboxane synthesis. No indication of a dose-effect relationship was found. However, whether such a low dose adequately suppresses thromboxane synthesis in patients with acute stroke is uncertain.

Adult↗
PubMed2004

Successful treatment of systemic amyloidosis with hepatic involvement and factor X deficiency by high dose melphalan chemotherapy and autologous stem cell reinfusion.

Systemic amyloidosis with hepatic involvement is a rare disorder, which is characterized by the deposits of amyloid fibrils in the liver. The prognosis is poor and the median survival is 13 months. Bleeding problems resulting from coagulopathy frequently complicates systemic amyloidosis. We present two patients with a severe factor X deficiency and hepatomegaly as the presenting abnormalities of systemic amyloidosis. One of the patients was treated with high dose melphalan chemotherapy and autologous stem cell reinfusion, resulting in a normalization of the liver enzyme tests and the factor X level. The diagnosis and treatment of systemic amyloidosis with hepatic involvement and the management of the multifactorial coagulopathy in these cases is discussed.

Alkaline Phosphatase↗
PubMed2004

Genetic variability of von Willebrand factor and risk of coronary heart disease: the Rotterdam Study.

The von Willebrand factor (VWF) may be causally associated with coronary heart disease (CHD) or merely be a marker of endothelial damage. The G allele of the -1793 C/G promoter polymorphism in the VWF gene has been associated with higher plasma levels of VWF. To investigate whether VWF has a causal role in CHD, we designed a case-cohort study, including 352 subjects with CHD and a random cohort (n = 736), and prospectively examined the association of the -1793 C/G polymorphism with CHD in subjects with and without advanced atherosclerosis. All subjects were </=75 years of age and participating in the population-based Rotterdam Study. Atherosclerosis was assessed by the ankle-arm index. Among subjects with advanced atherosclerosis, heterozygous and homozygous carriers of the G allele had a 3.5 (1.2-10.2) and 1.5 (0.4-5.7) fold increased risk of CHD respectively, compared with C/C homozygotes. The hazard ratio was 2.6 (1.0-6.8) for carriers of at least one copy of the G allele versus non-carriers. No associations were found in the absence of advanced atherosclerosis. In conclusion, this study suggests that the G allele of the -1793 C/G polymorphism in the VWF gene is associated with an increased risk of CHD, but only in subjects with advanced atherosclerosis.

Aged↗
PubMed2004

Functional characteristics of photochemically treated platelets.

BACKGROUND: A photochemical treatment (PCT) process using the psoralen compound amotosalen HCL (S59) and long wavelength UVA light was developed for inactivation of infectious pathogens and WBCs. In this study the effect of PCT on functional characteristics of the platelets was evaluated in vitro. STUDY DESIGN AND METHODS: Platelet concentrates were treated photochemically using the experimental clinical processing system T-bag S59 Reduction Device (SRD) (n = 4) or the commercially available integral processing system Wafer SRD (n = 4) and compared with control platelet concentrates in plasma/PAS III alone (n = 4). The evaluation included variables with respect to the overall quality of the product (e.g., HSR, pH), the function (aggregation and activation tests), apoptosis (annexin V and caspase 3), and lysis. RESULTS: No differences were found in the product quality variables, in P-selectin expression, and the apoptosis variables. PCT using the T-bag SRD led to a significant decrease in aggregation capacity with collagen and thrombin and a significant increase in plasma LDH, whereas no differences for the Wafer SRD were found. CONCLUSION: PCT using the experimental T-bag SRD led to a significant decrease in platelet function. However, the commercially available Wafer SRD had only minor in vitro effects on the quality of the platelets.

Apoptosis↗
PubMed2004

In vitro studies, pharmacokinetic studies and clinical use of a high purity double virus inactivated FVIII/VWF concentrate (Immunate) in the treatment of von Willebrand disease.

Patients with type 2 and 3 von Willebrand disease (VWD) are treated with factor VIII/VWF concentrate in case of bleeding or surgery. Immunate (Baxter, Vienna, Austria) is a double virus inactivated FVIII/VWF concentrate and is registered in several countries for patients with VWD with reduced FVIII levels. We performed an in vitro, a pharmacokinetic and a clinical study to evaluate Immunate in VWD. In vitro studies showed a significant variation in VWF levels in 9 different batches. The median (range) values (in IU/mL) were 1.10 (0.98-1.30) for FVIII:C, 1.34 (0.95-1.61) for VWF:Ag, 0.60 (0.27-1.08) for VWF:CBA and 0.73 (0.59-0.94) for VWF:RCo. The relatively low VWF activity is mainly due to the lack of high molecular weight multimers (HMWM), as determined by electrophoresis. A pharmacokinetic study showed, based on a content of FVIII:C of 1 U/mL, in vivo recoveries (%) of 106 (56-150) (median and range) for FVIII:C, 105 (62-187) for VWF:Ag, 25 (7-41) for VWF:CBA and 43 (11-76) for VWF:RCo. Half-lives were 14.1 h (7.4-36.9) for FVIII:C, 10.8 h (7.7-26.2) for VWF:Ag, 15.3 h (7.8-44.6) for VWF:CBA and 16.4 h (4.2-26.5) for VWF:RCo. In a clinical study efficacy was determined after infusion given before surgery or dental extractions in ten patients. In two patients the hemostatic response was classified as inadequate. In conclusion, there is a wide variability in VWF concentration and activity in various batches of Immunate. In the clinical study in which the dosage was based on FVIII:C contents of the concentrate, two out of ten patients had an insufficient haemostatic response. Therefore dosing of Immunate dosing should not be based on FVIII:C levels, but should be based on VWF activity of the individual batches. Future studies using a VWF activity-guided dosage regimen have to be performed to establish the efficacy of Immunate in the treatment of von Willebrand disease.

Adolescent↗
PubMed2003

Association between thrombin-activatable fibrinolysis inhibitor (TAFI) and clinical outcome in patients with unstable angina pectoris.

Decrease of fibrinolytic potential is considered to be a risk factor for arterial thrombosis. The recently described thrombin-activatable fibrinolysis inhibitor (TAFI) attenuates fibrinolysis by cleaving of the C-terminal lysine residues from fibrin, thereby inhibiting tPA mediated plasminogen activation. The role of plasma TAFI antigen (Ag) levels and gene polymorphisms in arterial thrombosis is still not elucidated. In this prospective study, the association between plasma TAFI Ag levels and the TAFI gene polymorphisms, Ala147Thr, Thr325Ile and -438A/G, with refractory unstable angina pectoris (UAP) was determined. The study population consisted of 209 patients with UAP of whom 76 were refractory and 133 non-refractory to medical treatment. In the same study population the contribution of these polymorphisms to plasma TAFI Ag levels was determined. Plasma TAFI Ag levels were significantly higher in non-refractory patients compared to refractory patients (geometric mean 114.4 and 105.6 U/dl respectively, p=0.042). Plasma TAFI Ag levels in the lowest quartile resulted in a 2.6 fold (95% confidence interval 1.2-5.9) increased risk for refractory UAP compared to plasma TAFI Ag levels in the upper quartile. The three studied TAFI polymorphisms had an independent and additive effect on plasma TAFI Ag levels. However, no significant association between the individual TAFI polymorphisms and refractiveness was observed. In conclusion, in this study population plasma TAFI Ag levels are significantly correlated with refractiveness in patients with UAP. Furthermore, all three polymorphisms contribute independently to plasma TAFI Ag levels, but not to refractiveness.

Aged↗
PubMed2002

PLA1/A2 polymorphism of the platelet glycoprotein receptor IIb/IIIa in young patients with cryptogenic TIA or ischemic stroke.

BACKGROUND: The relationship between the PIA2 allele of the Leu(33)Pro polymorphism of glycoprotein IIb/IIIa receptor (GPIIb/IIIa) and ischemic stroke is uncertain. The purpose of this study was to investigate a possible association between the GPIIb/IIIa PIA1/A2 polymorphism and the occurrence of cryptogenic stroke in young patients. METHODS: From a consecutive series of 80 patients aged 45 or less with a recent ischemic stroke or TIA, we selected 45 patients with stroke due to small vessel occlusion or stroke of undetermined etiology (according to the TOAST criteria). Controls were 60 healthy blood donors with a similar age distribution. All patients underwent CT of the brain and were screened for cardiovascular risk factors, cardiac disorders and large vessel disease. The frequency of the PIA2 allele was determined by PCR and Msp1 restriction analysis. RESULTS: Eight patients (16%) and 16 controls (27%) were heterozygous for PIA2 allele. Two patients (4%) were homozygous for PIA2. The relative risk of ischemic stroke associated with PIA2 allele was estimated at 0.8 (95% CI: 0.3-1.9). CONCLUSION: This study does not support the association between the PIA1/A2 polymorphism and cryptogenic stroke or TIA in patients aged 45 or less.

Adult↗
PubMed2002

Recombinant factor VIIa improves clot formation but not fibrolytic potential in patients with cirrhosis and during liver transplantation.

Cirrhosis is associated with a bleeding tendency, which is particularly pronounced during orthotopic liver transplantation (OLT). A novel approach to treating the bleeding diathesis of patients with cirrhosis is administration of recombinant factor VIIa (rFVIIa). This study examined whether the efficacy of rFVIIa in cirrhosis might be explained in part by enhanced down-regulation of fibrinolysis by thrombin-activatable fibrinolysis inhibitor (TAFI). Addition of therapeutic or supratherapeutic doses of rFVIIa to plasma of 12 patients with stable cirrhosis did not result in a prolongation of clot lysis time, though clotting times were significantly reduced. Also, clot lysis assays of plasma samples taken during and after OLT, which was performed with or without a single bolus dose of rFVIIa, did not show any effect of rFVIIa on plasma fibrinolytic potential. In conclusion, this study shows no evidence for an antifibrinolytic effect of rFVIIa in cirrhotic patients or in patients undergoing OLT.

Antifibrinolytic Agents↗