Development of a new model of transvenous thrombosis in the pig superior sagittal sinus using thrombin injection and balloon occlusion

Aluminium Chloride instead of Ferric chloride for inducing superior sagittal sinus thrombosis to reduce ferromagnetic artifacts on MRI-imaging in experimental models

Using ferric chloride (FeCl3) to induce experimental superior sagittal sinus (SSS) thrombosis might interfere with magnetic resonance imaging (MRI)-assisted visualization and evaluation of the thrombus, the brain parenchyma, and the quality of the occlusion. The aim of this study was to investigate whether aluminum chloride (AlCl3)-induced thrombosis of the SSS has comparable properties to those of FeCl3 without causing artifacts in MRI. SSS thrombosis was induced in 14 male Wistar rats by exposure of the SSS and subsequent topical application of a filter paper strip soaked in AlCl3 (n = 7) or FeCl3 (n = 7) over a period of 15 min. The animals with AlCl3-induced SSS thrombosis showed a constant and complete occlusion with in histological analysis large thrombi. Blood flow measurements indicated a significant reduction on the first and seventh postoperative day compared to preoperative measurements. MRI enabled visualization and subsequent evaluation of the thrombus and the surrounding parenchyma. In comparison, FeCl3-induced SSS thrombosis could not be evaluated by MRI due to artifacts caused by the paramagnetic properties and increased susceptibility of FeCl3. The occluded sinus and the surrounding area appeared hypointense. The quality of SSS occlusion by AlCl3 was comparable to that of FeCl3. AlCl3 therefore represents a significant alternative substance in experimental SSS thrombosis ideally suited for studies using MRI.

A novel severe cerebral venous thrombosis rat model based on semi-ligation combined with ferric chloride and thrombin

AIMS

An applicable cerebral venous sinus thrombosis (CVST) model is imperative for exploring its pathophysiology. We established a novel severe CVST model using semi-ligation, ferric chloride, and thrombin.

METHODS

A total of 138 male Sprague-Dawley rats were randomly divided into semi-ligation (n = 75) and non-semi-ligation (n = 63) groups. A sham group (n = 46) was also included. We compared short-term and long-term neurological and cognitive dysfunction, mortality rates, thrombus load, venous infarction volume, the blood-brain barrier permeability, brain water content, and microglia activation among the three groups.

RESULTS

Thrombi involving multiple venous sinuses appeared in all semi-ligation rats within 2 days postoperatively. Compared with the non-semi-ligation group, short-term and long-term neurological dysfunction were more severe (p < 0.05), and thrombus weight, venous infarction volumes, and microglia activation were more significant (p < 0.05) in the semi-ligation group. Further, the cognitive function of the semi-ligation group significantly decreased (p < 0.05) on postoperative day 21. Cumulative mortality rates between the semi-ligation and non-semi-ligation groups did not differ significantly.

CONCLUSION

Semi-ligation combined with ferric chloride and thrombin can produce a severe CVST model with multiple venous sinus involvement, which is suitable for short- and long-term neurological and cognitive dysfunction assessment.

Canine Intracranial Venous System: A Review

The intracranial venous system (ICVS) represents in mammals a complex three-dimensional structure, which provides not only for adequate brain perfusion, but has also a significant impact on: cerebrospinal fluid (CSF) resorption, maintaining of the intracranial pressure (ICP), and brain thermoregulation. An intimate understanding of the anatomy and physiology of ICVS is fundamental for neurological diagnostics, selection of therapeutic options, and success of neurosurgical procedures in human and veterinary medicine. Since the intracranial interventions in dogs are recently performed more frequently than twenty or thirty years ago, the authors decided to review and report on the basic knowledge regarding the complex topic of morphology and function of the canine ICVS. The research strategy involved an NCBI/NLM, PubMed/MED-LINE, and Clarivate Analytics Web of Science search from January 1, 1960, to December 31, 2021, using the terms “canine dural venous sinuses” and “intracranial venous system in dogs” in the English language literature; also references from selected papers were scanned and relevant articles included.

Mechanical thrombectomy and intravascular imaging for cerebral venous sinus thrombosis: a preclinical model

OBJECTIVE

Although the majority of patients with cerebral venous sinus thrombosis (CVST) will improve with anticoagulation therapy, a portion of patients will either present in a comatose state or continue to deteriorate clinically despite early anticoagulation. In these cases, along with treating the underlying thrombophilia, timely thrombolysis may be beneficial. Repurposed arterial thrombectomy devices may not perform as expected in the cerebral venous sinus, and there are currently no preclinical endovascular thrombectomy (EVT) models for CVST. Contrary to arterial stroke research, preclinical models utilized to test various endovascular techniques and devices are lacking. The purpose of this research was to develop a reliable preclinical animal model for the testing of endovascular strategies to treat CVST.

METHODS

Five consecutive male Yorkshire swine weighing 45 kg were utilized. Thrombosis of the superior sagittal sinus was induced with a bovine thrombin injection via a microcatheter under distal balloon occlusion for 15 minutes. Combined arterial injections and superselective sinus injections confirmed the extent of thrombosis. EVT was subsequently performed using a second-generation stent retriever, followed by intravascular optical coherence tomography (OCT) imaging to assess the luminal environment after thrombectomy.

RESULTS

Thrombosis of the superior sagittal sinus, EVT, and subsequent OCT imaging were technically successful in 4 of the 5 swine. Recanalization of the sinus with a second-generation stent retriever was successful after one attempt in 3 of 4 swine (75%), and 1 swine required two attempts. OCT imaging after thrombectomy revealed regions of residual sinus luminal thrombus despite complete angiographic recanalization. Thrombosed bridging cortical veins were also observed before draining into the sinus, along with patent cortical veins.

CONCLUSIONS

The authors describe a preclinical model to assess endovascular techniques and devices for the treatment of CVST. Repurposed devices from arterial stroke may not perform as expected, given the unique features of venous sinus thrombosis. Residual bridging cortical vein thrombus and residual sinus thrombus, visualized on intravascular OCT, may be present despite complete sinus recanalization on angiography, and this may be the etiology of the poor clinical outcome despite technical success. In the setting of bridging cortical vein thrombus after successful sinus thrombectomy, direct chemical thrombolysis may be warranted to dissolve the remaining clot. This model may be helpful in developing and testing a new generation of devices designed specifically for CVST treatment.

A Novel Mouse Model for Cerebral Venous Sinus Thrombosis

Cerebral venous sinus thrombosis (CVST) is an uncommon cause of stroke resulting in parenchymal injuries associated with heterogeneous clinical symptoms and prognosis. Therefore, an experimental animal model is required to further study underlying mechanisms involved in CVST. This study is aimed at developing a novel murine model suitable and relevant for evaluating injury patterns during CVST and studying its clinical aspects. CVST was achieved in C57BL/6J mice by autologous clot injection into the superior sagittal sinus (SSS) combined with bilateral ligation of external jugular veins. Clot was prepared ex vivo using thrombin before injection. On days 1 and 7 after CVST, SSS occlusion and associated-parenchymal lesions were monitored using different modalities: in vivo real-time intravital microscopy, magnetic resonance imaging (MRI), and immuno-histology. In addition, mice were subjected to a neurological sensory-motor evaluation. Thrombin-induced clot provided fibrin- and erythrocyte-rich thrombi that lead to reproducible SSS occlusion at day 1 after CVST induction. On day 7 post-CVST, venous occlusion monitoring (MRI, intravital microscopy) showed that initial injected-thrombus size did not significantly change demonstrating no early spontaneous recanalization. Microscopic histological analysis revealed that SSS occlusion resulted in brain edema, extensive fibrin-rich venular thrombotic occlusion, and ischemic and hemorrhagic lesions. Mice with CVST showed a significant lower neurological score on post-operative days 1 and 7, compared to the sham-operated group. We established a novel clinically CVST-relevant model with a persistent and reproducible SSS occlusion responsible for symptomatic ischemic and hemorrhagic lesions. This method provides a reliable model to study CVST physiopathology and evaluation of therapeutic new regimens.

Endoplasmic reticulum stress and oxidative stress contribute to neuronal pyroptosis caused by cerebral venous sinus thrombosis in rats: Involvement of TXNIP/peroxynitrite-NLRP3 inflammasome activation

Cerebral venous sinus thrombosis (CVST) is a rare type of stroke, which is life-threatening in severe cases. However, considerably less attention has been concentrated on the mechanism of neural cell damage after CVST. This study aims to investigate the role of endoplasmic reticulum stress, oxidative stress, and pyroptosis in a well-established rodent model of CVST. Rat brains were harvested at 0 h, 6 h, days 1, days 3, days 7, and days 14 post-CVST for measurement of corresponding indexes. Endoplasmic reticulum stress sensors (including protein kinase RNA-like ER kinase (PERK) and inositol-requiring enzyme-1α (IRE1α)), oxidative stress markers (thioredoxin-interacting protein (TXNIP) and peroxynitrite), NLRP3, caspase p20, IL-1β, and gasdermin D (GSDMD, an indicator of pyroptosis) were separately evaluated by Western-blot and Immunohistochemistry/Immunofluorescence. Co-immunoprecipitation and Fluorescent double-labeling were employed to probe into the relationship between TXNIP/peroxynitrite and NLRP3 inflammasome. In the damaged cortex region, profuse p-PERK, p-IRE1α, TXNIP were produced and predominantly localized in neurons accompanied by a small amount expressed in microglia and astrocytes. The levels of 3-nitrotyrosine (3-NT, as a footprint of peroxynitrite), NLRP3, caspase p20, IL-1β, and GSDMD were distinctly elevated post-CVST and cellular localization of peroxynitrite, NLRP3, caspase p20, and IL-1β was largely observed in neurons and/or microglia. Importantly, sites of enhanced TXNIP and 3-NT immunoreactivity were colocalized with increased NLRP3 staining, indicating the involvement of TXNIP and peroxynitrite in NLRP3 inflammasome activation and subsequent pyroptosis. Besides, co-immunoprecipitation also hinted that there might be an interaction or causality between TXNIP/peroxynitrite and NLRP3 inflammasome. We concluded that endoplasmic reticulum stress and oxidative stress may jointly lead to neuronal NLRP3 inflammasome activation and pyroptosis after CVST.

The characteristics of brain injury following cerebral venous infarction induced by surgical interruption of the cortical bridging vein in mice

Cerebral venous infarction (CVI) caused by the injury of cortical bridging veins (CBVs), is one of the most serious complications following neurosurgical craniotomy. Different from cerebral artery infarction, this CVI pathological process is more complicated, accompanied by acute venous hypertension, brain edema, cerebral ischemia and hemorrhage in the veins bridged brain area. Therefore, a reliable and stable small animal model is particularly important for the pathological study of CVI induced by surgical CBV interruption (CBVi). A mouse model established by cutting off the right CBVs from bregma to lambda with microsurgical technique is used for the assessment of the pathological process. Adult male mice underwent craniotomy after transection of the parietal skin under anesthesia. The right CBVs were exposed by removing the right skull along the right lateral edge of the sagittal sinus (forming a 4 mm × 3 mm bone window from bregma to lambda) with a drill under the operating microscope. Following the final inspection of the cerebral veins, the CBVs (30% one, 60% two, 10% none) were sacrificed using bipolar coagulation technique. Intracranial pressure (ICP) monitoring, motor function examination, brain edema assessment and brain histopathological observation after perfusion were performed at different time points (6 h, 12 h, 24 h, and 48 h) in the postoperative mice. Cerebral hemisphere swelling, midline shift and subcortical petechial hemorrhage were found on histological sections 6 h after CBVs dissection. The change of ICP was consistent with cerebral edema and peaked at 12 h after surgery, as well as the disruption of the blood-brain barrier assessed by Evans Blue staining. Tissue necrosis, nerve cell loss and monocytes infiltration were also dynamically increased in the postoperative hemispheric cortex. Behavioral tests showed obvious somato- and forelimb-motor dysfunction, and severe somatosensory disorder on the operative mice at 12 h, which were substantially recovered at 48 h. Our study provided a novel mouse model of CVI caused by surgical CBVi that was close to clinical practice, and preliminarily confirmed its pathological process. This model might become an important tool to study the clinical pathology and the molecular mechanism of nerve injury following CVI.

Animal models of venous thrombosis

Venous thrombosis (VT) is a prevalent clinical condition with significant adverse sequela or mortality. Anticoagulation and pharmacologic or pharmacomechanical thrombolytic therapies are the mainstays of VT treatment. An understanding of thrombosis biology will allow for more effective VT-tailored diagnosis and therapy. In vivo models of thrombosis provide indispensable tools to study the pathogenesis of thrombus formation and to evaluate novel therapeutic or preventive adjuncts for VT management or prevention. In this article, we review the most prominent in vivo models of VT created in rodents and swine species and outline how each model can serve as a useful tool to promote our understanding of VT pathogenesis and to examine novel therapies.

A rabbit model of cerebral venous sinus thrombosis established by ferric chloride and thrombin injection

OBJECTIVE

Cerebral venous sinus thrombosis (CVST) is a life-threatening disease with high misdiagnosis and mortality rates due to its complex etiology and unknown pathophysiology. The present study aimed to establish an animal model suitable for assessing the pathophysiology of CVST and develop treatment methods.

METHODS

40% ferric chloride (FeCl3) was administered for 5min followed by thrombin injection to induce superior sagittal sinus thrombosis (SSST). Digital subtraction angiography (DSA) was performed to ensure thrombosis and evaluate the recanalization rate 7days post-CVST. Neurological evaluation, Evans blue injection, 2,3,5-Triphenyltetrazolium chloride (TTC), and hematoxylin-eosin (H&E) staining were used to assess thrombosis and the accompanying brain parenchyma.

RESULTS

SSST was detected in all model rabbits, with a thrombus recanalization rate of 10%. Brain infarction, hemorrhage, cell edema, and disruption of the blood-brain barrier (BBB) were also observed.

CONCLUSION

The method of inducing cerebral venous sinus thrombosis by applying 40% FeCl3 and injecting thrombin is feasible and efficient. This experimental model mimics the pathogenesis and pathophysiology of actual CVST.

Sinus thrombosis-do animal models really cover the clinical syndrome?

Cerebral venous sinus thrombosis (CVST) is an important cause of stroke in young patients. CVST represents with 0.5-3% of stroke cases a relatively rare disease. CVST affects 3-4 cases per 1 million overall and 7 cases per 1 million children and neonates. Typical clinical symptoms include headache, visual deficits and seizures. Beside the main condition associated with CVST in women in pregnancy and puerperium, the most frequently identified risk factors are oral hormonal contraceptives in combination with coagulation disorders. The initial treatment contains heparin and its efficacy is based on two randomized placebo-controlled trials including 79 patients together. A lack of understanding of the pathophysiology of CSVT makes animal models of this disease indispensable. Previously developed animal models of sinus sagittalis superior contributes to further clarify the pathophysiologic mechanisms and surrounding circumstances in the topic of cerebral venous thrombosis.