A novel hollow and perforated flexible wire allows the safe and effective local application of thrombolytic therapy in a mouse model of deep vein thrombosis

We tested the feasibility of local thrombolytic therapy via a novel hollow flexible and perforated wire in a mouse model of deep vein thrombosis. Inferior vena cava (IVC) thrombosis was induced by vessel wall exposure to ferric chloride after laparotomy in anesthetized C57Bl/6 mice. Thrombus formation was visualized by intravital microscopy of rhodamine-labeled platelets and leukocytes. A nitinol hypotube coronary wire with perforated tip was inserted via a 0.8 × 40 mm canula into the IVC lumen distal to the site of ferric chloride exposure. Either tissue plasminogen activator (tPA, alteplase) or saline (control) was administered via the platinum wire distal to the thrombus, avoiding mechanical fragmentation. Thrombus size was assessed by immunohistochemistry (platelet CD41 staining). Intravital microscopy of the IVC demonstrated platelet-containing thrombus growth starting 1 min after ferric chloride exposure. Alteplase administration resulted in significant thrombus size reduction within 10–20 min observed by intravital microscopy and confirmed by histological assessment of IVC cross-sections. Saline-treated mice (n = 4) demonstrated near total IVC occlusion with thrombotic material (84 ± 8 % of cross-sectional area in serial sections), whereas alteplase-treated mice showed a dose-dependent decrease of thrombotic area [56 ± 5 % with 1.5, 39 ± 4 % with 15 and 21 ± 6 % with 150 mg/kg, respectively (n = 4)]. We demonstrate that a flexible hollow and perforated wire enables the successful application of thrombolytic therapy to IVC thrombi in mice without vessel wall perforation. Flexible wire-based thrombolytic therapy appears to be a safe and reliable method for thrombus dissolution even in fragile small veins and may become a promising strategy for targeted therapy of small vessel thrombosis.     

Early and Rapid Identification of COVID-19 Patients with Neutralizing Type I Interferon Auto-antibodies

Journal of Clinical Immunology - Six to 19% of critically ill COVID-19 patients display circulating auto-antibodies against type I interferons (IFN-AABs). Here, we establish a clinically applicable...     

Simplified contrast ultrasound accurately reveals muscle perfusion deficits and reflects collateralization in PAD

BackgroundSimplified contrast-enhanced ultrasound (CEUS) can be used to evaluate muscle perfusion in peripheral arterial disease (PAD). Here, we report its diagnostic accuracy for detecting symptomatic PAD. Additionally, we hypothesize that the extent of collateral formation is reflected by CEUS.MethodsUltrasound contrast agent was injected into an antecubital vein of 58 control subjects and 52 symptomatic PAD patients and its appearance in the calf muscle was evaluated. Interreader variability was tested using 118 raw data films. Arterial collateralization of PAD patients was assessed by angiographic imaging.ResultsPAD patients showed a significantly longer median time to peak intensity (TTP, 36.9 s) than control subjects (19.4 s, p < 0.001) with longer TTPs in advanced PAD stages. The area under the receiver operating characteristic curve was 0.942 and the mean TTP difference between two blinded readers was 0.28 s. A TTP cut off at 30.5 s was associated with 91% positive predictive value. PAD patients with good collateralization showed a significantly shorter TTP (34.1 s) than patients with poor collateralization (44.0 s, p = 0.008) but not a higher ankle–brachial index (ABI).ConclusionsCEUS accurately displays perfusion deficits of the calf muscle in symptomatic PAD patients. The degree of arterial collateralization is reflected by CEUS and not by ABI.     

Platelet granule secretion continuously prevents intratumor hemorrhage

Cancer is associated with a prothrombogenic state capable of platelet activation. Platelets, on the other hand, can support angiogenesis, a process involved in the progression of tumor growth and metastasis. However, it is unclear whether platelet/tumor interactions substantially contribute to tumor physiology. We investigated whether platelets stabilize tumor vessels and studied the underlying mechanisms. We induced severe acute thrombocytopenia in mice bearing s.c. Lewis lung carcinoma or B16F10 melanoma. Intravital microscopy revealed that platelet depletion led to a rapid destabilization of tumor vessels with intratumor hemorrhage starting as soon as 30 min after induction of thrombocytopenia. Using an inhibitor of glycoprotein Ibalpha (GPIbalpha) and genetically engineered mice with platelet adhesion defects, we investigated the role of platelet adhesion receptors in stabilizing tumor vessels. We found that a single defect in either GPIbalpha, von Willebrand factor, P-selectin, or platelet integrin activation did not lead to intratumor hemorrhage. We then compared the ability of transfused resting and degranulated platelets to prevent intratumor hemorrhage. Whereas resting platelets prevented thrombocytopenia-induced tumor bleeding, circulating degranulated platelets did not. This suggests that the prevention of intratumor hemorrhage by platelets relies on the secretion of the content of platelet granules. Supporting this hypothesis, we further found that thrombocytopenia dramatically impairs the balance between propermeability and antipermeability factors in tumor-bearing animals, in particular depleting blood of angiopoietin-1 and serotonin. Our results show a crucial contribution of platelets to tumor homeostasis through continuous prevention of severe intratumor hemorrhage and consequent cell death. The study also suggests platelet function as a reasonable target for specific destabilization of tumor vessels.