Elastase-induced Aneurysm Model Research Articles

Balloon neck-plasty to create a wide-necked aneurysm in the elastase-induced rabbit model.

The elastase-induced aneurysm (EIA) model in rabbits has been proposed for translational research; however, the adjustment of aneurysm neck size remains challenging. In this study, the technical feasibility and safety of balloon neck-plasty to create a wide-necked aneurysm in rabbit EIA model were investigated. Male New Zealand White rabbits (N = 15) were randomly assigned to three groups: group A, EIA creation without neck-plasty; group B, neck-plasty immediately after EIA creation; group C, neck-plasty 4 weeks after EIA creation. The diameter of balloon used for neck-plasty was determined 1 mm larger than origin carotid artery diameter. All rabbits were euthanized 4 weeks after their final surgery. Aneurysm neck, height, dome-to-neck (D/N) ratio, and histologic parameters were compared among the groups. Aneurysm creation was technically successful in 14 out of 15 rabbits (93.3%), with one rabbit experiencing mortality due to an adverse anesthetic event during the surgery. Saccular and wide-necked aneurysms were successfully created in all rabbits. Aneurysm neck was significantly greater in groups B and C compared to group A (all P < .05). D/N ratio was significantly lower in groups B and C compared to group A (all P < .05). Additionally, tunica media thickness, vessel area, and luminal area were significantly greater in groups B and C compared to group A (all P < .05). These variables were found to be significantly greater in group B compared to group C (all P < .05). The creation of a wide-necked aneurysm using balloon neck-plasty after elastase induction in rabbits has been determined to be technically feasible and safe.

Trehalose attenuates abdominal aortic aneurysm formation by inducing autophagy in smooth muscle cells.

Trehalose is a naturally occurring disaccharide, which has been identified as an autophagy inducer and exhibits protective effect in cardiovascular diseases such as myocardial infraction and atherosclerosis. However, the functional role of trehalose in abdominal aortic aneurysm (AAA) remains undefined. To study the effect of trehalose in AAA, trehalose (1 g/kg per day) were given for 14 continuous days in a mouse model of elastase-induced abdominal aortic aneurysm. On day 14, ultrasound was performed to measure aortic diameter before the abdominal aortas were harvested and processed for further analysis. Verhoeff-Van Gieson staining and TUNEL staining were performed on paraffin sections to evaluate vascular histology and apoptosis, immunofluorescence staining and Western-blot were performed to evaluate expression of autophagy markers. Echocardiography and in situ pictures demonstrated that trehalose attenuated infrarenal aorta dilation. Verhoeff-Van Gieson staining showed elastin degradation was improved in trehalose-treated group. Compared with vehicle-treated mice, trehalose treatment restored smooth muscle cell contractile phenotype with increased α-SMA, Calponin and Myh11 expression. Furthermore, trehalose also attenuated cell apoptosis and leukocytes infiltration. Importantly, trehalose induced autophagy with decrease SQSTM1/p62 accumulation, increased lamp2 expression and LC3B conversion. Trehalose attenuated AAA progression with decreased inflammation and restored SMC contractile phenotype by inducing autophagy. These results demonstrated the therapeutic potential of trehalose in AAA.

Murine model of elastase-induced proximal thoracic aortic aneurysm through a midline incision in the anterior neck.

This study was performed to develop a murine model of elastase-induced proximal thoracic aortic aneurysms (PTAAs). The ascending thoracic aorta and aortic arch of adult C57BL/6J male mice were exposed through a midline incision in the anterior neck, followed by peri-adventitial elastase or saline application. The maximal ascending thoracic aorta diameter was measured with high-resolution micro-ultrasound. Twenty-eight days after the operation, the aortas were harvested and analyzed by histopathological examination and qualitative polymerase chain reaction to determine the basic characteristics of the aneurysmal lesions. Fourteen days after the operation, the dilation rate (mean ± standard error) in the 10-min elastase application group (n = 10, 71.44 ± 10.45%) or 5-min application group (n = 9, 42.67 ± 3.72%) were significantly higher than that in the saline application group (n = 9, 7.37 ± 0.94%, P < 0.001 for both). Histopathological examination revealed aortic wall thickening, degradation of elastin fibers, loss of smooth muscle cells, more vasa vasorum, enhanced extracellular matrix degradation, augmented collagen synthesis, upregulated apoptosis and proliferation capacity of smooth muscle cells, and increased macrophages and CD4+ T cells infiltration in the PTAA lesions. Qualitative analyses indicated higher expression of the proinflammatory markers, matrix metalloproteinase-2 and -9 as well as Collagen III, Collagen I in the PTAAs than in the controls. We established a novel in vivo mouse model of PTAAs through a midline incision in the anterior neck by peri-adventitial application of elastase. This model may facilitate research into the pathogenesis of PTAA formation and the treatment strategy for this devastating disease.

An Improved Surgical Technique to Increase Neck Width of Elastase-Induced Aneurysm Model in Rabbits: A Prospective Study

BackgroundRabbit elastase-induced aneurysms have widely been used to test various endovascular materials over the past two decades. However, wide-necked aneurysms cannot be stably constructed.ObjectiveThe purpose of the study was to increase the neck width of the elastase-induced aneurysm model in rabbits via an improved surgical technique with two temporary clips.Materials and MethodsFifty-four elastase-induced aneurysms in rabbits were successfully created. Group 1 was (n = 34) composed of cases in which two temporary aneurysm clips were placed closely medially and laterally to the origin of the right common carotid artery (RCCA), respectively. Group 2 (n = 20) included cases in which a single temporary aneurysm clip was placed crossed the origin of RCCA. Digital subtraction angiography (DSA) was performed before and immediately after elastase incubation and 3 weeks later. The diameter of the origin of RCCA before and immediately after elastase incubation and aneurysm sizes of the two groups were measured and compared. Moreover, the correlation analysis was performed between the diameter of the origin of RCCA immediately after elastase incubation and aneurysm neck width.ResultsThe mean aneurysm neck and dome width of group 1 were both significantly larger than that of group 2 (p-value < 0.001 and p-value = 0.005, respectively). Moreover, the proportion of wide-necked aneurysms (neck width ≥4 mm) in group 1 was significantly larger than that in group 2 (p-value = 0.004) and the mean dome to neck ratio (D/N) of group 1 was smaller than that of group 2 (p-value = 0.008). Furthermore, there was a positive correlation between the diameter of the origin of RCCA immediately after elastase incubation and aneurysm neck width.ConclusionThe improved surgical technique with two temporary clips, focusing on the direct contact of elastase with the origin of RCCA, could increase the neck width of elastase-induced aneurysm models in rabbits.

A modified method of elastase-induced saccular aneurysm creation in rabbits: Schematic representation of the method.

The purpose of our study was to investigate the safety and effectiveness of a modified technique using a short guiding catheter for instillation of elastase in comparison with the previously described method of creating elastase-induced aneurysm in rabbits. Following right common carotid artery (RCCA) access using an arterial sheath and inflating the Fogarty balloon in the subclavian artery, a short guiding catheter was used for the instillation of the elastase in the experimental group (n = 5) while it was performed with a microcatheter in the control group (n = 5). The procedure duration was recorded from the RCCA puncture to the sheath removal. The histological changes were characterized using H&E and Masson's trichrome (MT) staining. The procedure time was 23 ± 2 min in the experimental group and 29 ± 2 min in the control group. All the rabbits (100%) in the experimental group survived without neurologic deficits, but two rabbits (40%) survived in the control group. All aneurysms were created in the saccular shape (100%) with a neck size of 2.3 ± 0.29 mm, a width of 2.75 ± 0.36 mm, and height of 6.37 ± 0.46 mm, and a dome to neck ratio of 1.21 ± 0.23. The aneurysm walls were partly thickened due to the degradation of the media tunica and adventitia proliferation with loss of the internal elastic lamina. By using a short guiding catheter, we could instill the elastase in a more effective and safe manner in the creation of the elastase-induced aneurysm model in rabbits.

Rabbit Elastase Aneurysm Model Mimics the Recurrence Rate of Human Intracranial Aneurysms following Platinum Coil Embolization.

Intracranial aneurysms treated with coils have been associated with incomplete occlusion, particularly in large or wide-neck aneurysms. This study aimed to validate the accuracy of the rabbit elastase model in predicting aneurysm recurrence in humans treated with platinum coils. Elastase-induced saccular aneurysms were induced in rabbits and embolized with conventional platinum coils. The recurrence rates of aneurysms were retrospectively analyzed. Morphologic characteristics of aneurysms, angiographic outcomes, and histologic healing were evaluated. A total of 28 (15.3%) of 183 aneurysms recurred. The aneurysm recurrence rate observed in this study (15.3%) is similar to those reported in multiple analyses of aneurysm recurrence rates in humans (7%-27%). The rate of recurrence was higher in aneurysms treated without balloon assistance (19/66, 28.8%) compared with those treated with balloon assistance (9/117, 7.7%). Aneurysms treated with balloon-assisted coiling had a lower recurrence rate (OR = 0.17; 95% CI, 0.05-0.47; P = .001) and higher occlusion rate (OR = 6.88; 95% CI, 2.58-20.37; P < .001) compared with those treated without balloon-assisted coiling. In this rabbit elastase-induced aneurysm model, packing density and aneurysm volume were weak predictors of aneurysm recurrence; however, the packing density was a good predictor of the occlusion rate (OR = 1.05; 95% CI, 1.02-1.10; P = .008). The rabbit elastase aneurysm model may mimic aneurysm recurrence rates observed in humans after platinum coil embolization. Moreover, balloon assistance and high packing densities were significant predictors of aneurysm recurrence and occlusion.

Hexarelin attenuates abdominal aortic aneurysm formation by inhibiting SMC phenotype switch and inflammasome activation.

Hexarelin, a synthetic growth hormone-releasing peptide, is shown to be protective in cardiovascular diseases such as myocardial infraction and atherosclerosis. However, the functional role of hexarelin in abdominal aortic aneurysm (AAA) remains undefined. The present study determined the effect of hexarelin administration (200μg/kg twice per day) in a mouse model of elastase-induced abdominal aortic aneurysm. Echocardiography and in situ pictures showed hexarelin decreased infrarenal aorta diameter. Histology staining showed elastin degradation was improved in hexarelin-treated group. Hexarelin rescued smooth muscle cell contractile phenotype with increased α-SMA and decreased MMP2. Furthermore, hexarelin inhibited inflammatory cell infiltration, NLRP3 inflammasome activation and IL-18 production. Particularly, hexarelin suppressed NF-κB signaling pathway which is a key initiator of inflammatory response. These results demonstrated that hexarelin attenuated AAA development by inhibiting SMC phenotype switch and NF-κB signaling mediated inflammatory response.

Temporal and Quantitative Analysis of Aortic Immunopathologies in Elastase-Induced Mouse Abdominal Aortic Aneurysms.

Objective Elastase-induced abdominal aortic aneurysm (AAA) model is widely used for aneurysmal pathogenesis and translational research. However, temporal alternations in aneurysmal histologies remain unknown. This study is aimed at analyzing temporal immunopathologies of aneurysmal aorta following experimental AAA induction. Methods Male C57BL/6J mice at the age of 10-14 weeks received intra-aortic infusion of elastase to induce AAAs. Aortic diameters at the baseline and indicated days after AAA induction were measured, and aortae were collected for histopathological analysis. Results Aorta diameters increased from 0.52 mm at the baseline levels to 0.99 mm, 1.34 mm, and 1.41 mm at days 7, 14, and 28, respectively, corresponding 90%, 158%, and 171% increases over the baseline level. Average aortic diameters did not differ between days 14 and 28. Severe elastin degradation and smooth muscle cell depletion were found at days 14 and 28 as compared to the baseline and day 7. No difference in the scores of medial elastin and SMC destruction was noted between days 14 and 28. Consistent results were found for leukocyte accumulation, neoangiogenesis, and matrix metalloproteinase expression. Twenty-eight days after AAA induction, all aneurysmal pathologies showed an attenuated trend, although most histopathological parameters did no differ between days 14 and 28. Conclusion Our data suggest that almost aneurysmal immunohistopathologies reach maximal 14 days following AAA induction. Analysis of day 14 histologies is sufficient for AAA pathogenesis and translational studies in elastase-induced mouse experimental AAAs.

Adaptive Remodeling in the Elastase-induced Rabbit Aneurysms.

Rupture of brain aneurysms is associated with high fatality and morbidity rates. Through remodeling of the collagen matrix, many aneurysms can remain unruptured for decades, despite an enlarging and evolving geometry. Our objective was to explore this adaptive remodeling for the first time in an elastase induced aneurysm model in rabbits. Saccular aneurysms were created in 22 New Zealand white rabbits and remodeling was assessed in tissue harvested 2, 4, 8 and 12 weeks after creation. The intramural principal stress ratio doubled after aneurysm creation due to increased longitudinal loads, triggering a remodeling response. A distinct wall layer with multi-directional collagen fibers developed between the media and adventitia as early as 2 weeks, and in all cases by 4 weeks with an average thickness of 50.6 ± 14.3 μm. Collagen fibers in this layer were multi-directional (AI = 0.56 ± 0.15) with low tortuosity (1.08 ± 0.02) compared with adjacent circumferentially aligned medial fibers (AI = 0.78 ± 0.12) and highly tortuous adventitial fibers (1.22 ± 0.03). A second phase of remodeling replaced circumferentially aligned fibers in the inner media with longitudinal fibers. A structurally motivated constitutive model with both remodeling modes was introduced along with methodology for determining material parameters from mechanical testing and multiphoton imaging. A new mechanism was identified by which aneurysm walls can rapidly adapt to changes in load, ensuring the structural integrity of the aneurysm until a slower process of medial reorganization occurs. The rabbit model can be used to evaluate therapies to increase aneurysm wall stability.

An Effective and Simple Way to Establish Elastase-Induced Middle Carotid Artery Fusiform Aneurysms in Rabbits.

Objective Elastase-induced aneurysms in rabbits have been proposed as a preclinical tool for device development, but there is still much deficiency in those aneurismal models. So we need to explore the efficient and convenient animal models for the investigation of intracranial aneurysms. Then, we compared and analyzed three methods of elastase-induced carotid artery aneurysms in rabbits and aimed to find a simple, effective, and reproducible method for creating elastase-induced aneurysms. Methods 42 standard feeding male adult Japanese white rabbits (3.05 ± 0.65 kg) were randomly divided into 3 groups and treated with elastase ablation to create common carotid artery (RCCA) aneurysm models: Group A (root-RCCA medication group, n = 12), Group B (mid-RCCA medication group, n = 18), and Group C (ligated RCCA+medication group, n = 12). For Group A, the origin of the RCCA was blocked by two temporary aneurysm clips, and the resulting 2 cm cavity was infused with elastase for 20 min, then the clip was removed and the RCCA was not ligated. For Group B, the middle part of RCCA was treated the same way as Group A and the RCCA was not ligated. For Group C, the middle part of RCCA was treated as Group B, but the distal RCCA was ligated. After the aneurysm models were created for 3 weeks, prior to sacrificing the animals, color Doppler ultrasound and angiography were performed for blood flow measurements inside the aneurysms. Histological analysis (such as SMA-α, CD31, CD34, CD68, collagen IV, and Ki67) and the other relevant indexes were compared between the ideal model's aneurysmal tissues and the human intracranial aneurysm's tissues to confirm whether we have successfully established elastase-induced aneurysm models. Results Compared with human intracranial aneurysm specimens by the color Doppler ultrasound, angiography, and changes in the inner diameter of arteries, all three methods have successfully established the elastase-induced aneurysm models. Histology showed that biological responses were similar to both human cerebral aneurysms and previously published elastase-induced rabbit aneurysm models. Group A and Group B had the same morphology, but Group A had a higher mortality rate than Group B. Group B and Group C had different morphology. The aneurysm of Group C was more similar to human cerebral aneurysms but had a higher mortality rate than Group B. Group B was confirmed not only as an alternative method but also as a more safe and effective method for creating elastase-induced aneurysm models. Conclusion Through analysis and comparison, the Group B is proven to be the simplest, reproducible, and most effective modeling method. The aneurysm model established by Group B can be used for basic research related to aneurysm mechanism. We have provided a new and effective method for basic research on aneurysm.

Tissue-engineered aneurysm models for in vitro assessment of neurovascular devices.

Preclinical testing of neurovascular devices is crucial for successful device design and is commonly performed using in vivo organisms such as the rabbit elastase-induced aneurysm model; however, simple in vitro models may help further refine this testing paradigm. The purpose of the current work was to evaluate, and further develop, tissue-engineered blood vessel mimics (BVMs) as simple, early-stage models to assess neurovascular devices in vitro prior to animal or clinical use. The first part of this work used standard straight-vessel BVMs to evaluate flow diverters at 1, 3, and 5 days post-deployment. The second part developed custom aneurysm-shaped scaffolds to create aneurysm BVMs. Aneurysm scaffolds were characterized based on overall dimensions and microstructural features and then used for cell deposition and vessel cultivation. It was feasible to deploy flow diverters within standard BVMs and cellular linings could withstand and respond to implanted devices, with increasing cell coverage over time. This provided the motivation and foundation for the second phase of work, where methods were successfully developed to create saccular, fusiform, and blister aneurysm scaffolds using a wax molding process. Results demonstrated appropriate fiber morphology within different aneurysm shapes, consistent cell deposition, and successful cultivation of aneurysm BVMs. It is feasible to use tissue-engineered BVMs for assessing cellular responses to flow diverters, and to create custom aneurysm BVMs. This supports future use of these models for simple, early-stage in vitro testing of flow diverters and other neurovascular devices.

Rabbit aortic aneurysm model with enlarging diameter capable of better mimicking human aortic aneurysm disease.

The self-healing phenomenon can be found in the elastase-induced abdominal aortic aneurysm (AAA) model, and an enlarging AAA model was successfully induced by coarctation. Unfortunately, aortic coarctation in these enlarging models is generally not found in human AAA disease. This study aimed to create an experiment model of enlarging AAA in rabbits to better mimic human aortic aneurysm disease. Eighty-four male New Zealand white rabbits were randomly divided into three equal groups: two aneurysm groups (A and B) and a SHAM group. Aneurysm group rabbits underwent extrinsic aortic stenosis below the right renal artery and received a 10-minute incubation of 60 μl elastase (1 unit/μl). Absorbable suture was used in Group A and nonabsorbable cotton thread was used in Group B. A sham operation was performed in the SHAM group. Aortic diameter was measured after 1, 3, 7, and 15 weeks; thereafter animals were sacrificed for histopathological, immunohistochemical and quantitative studies. Two rabbits died at 29 and 48 days, respectively, after operation in Group B. All aneurysms formed and enlarged progressively by 3 weeks in the Aneurysm groups. However, diameter enlargement in Group A was significantly lower than that in Group B at 7 weeks. Aneurysm groups developed intimal hyperplasia; intima-media thickness (IMT) increased significantly by week 7, and aortic media thickness and intima-media ratio (IMR) increased significantly by week 15. Marked destruction of elastin fibers and smooth muscle cells (SMCs) occurred 1 week later and increased progressively thereafter. Intimal hyperplasia and SMCs content in Group A increased significantly by week 15 compared with Group B. Aneurysm groups exhibited strong expression of matrix metalloproteinases 2 and 9 and RAM11 by week 1, and decreased progressively thereafter. In conclusion, this novel rabbit AAA model enlarges progressively without coarctation and is capable of better mimicking human aortic aneurysm disease.

Gamma Knife radiosurgery of saccular aneurysms in a rabbit model.

OBJECTIVEIntracranial aneurysms are vascular abnormalities associated with neurological morbidity and mortality due to risk of rupture. In addition, many aneurysm treatments have associated risk profiles that can preclude the prophylactic treatment of asymptomatic lesions. Gamma Knife radiosurgery (GKRS) is a standard treatment for trigeminal neuralgia, tumors, and arteriovenous malformations. Aneurysms associated with arteriovenous malformations have been noted to resolve after treatment of the malformation. The aim of this study was to determine the efficacy of GKRS treatment in a saccular aneurysm animal model.METHODSAneurysms were surgically produced using an elastase-induced aneurysm model in the right common carotid artery of 10 New Zealand white rabbits. Following initial observation for 4 years, each rabbit aneurysm was treated with a conformal GKRS isodose of 25 Gy to the 50% margin. Longitudinal MRI studies obtained over 2 years and terminal measures obtained at multiple time points were used to track aneurysm size and shape index modifications.RESULTSAneurysms did not rupture or involute during the observation period. Whole aneurysm and blood volume averages decreased with a linear trend, at rates of 1.7% and 1.6% per month, respectively, over 24 months. Aneurysm wall percent volume increased linearly at a rate of 0.3% per month, indicating a relative thickening of the aneurysm wall during occlusion. Nonsphericity of the average volume, aspect ratio, and isoperimetric ratio of whole aneurysm volume all remained constant. Histopathological samples demonstrated progressive reduction in aneurysm size and wall thickening, with subintimal fibrosis. Consistent shape indices demonstrate stable aneurysm patency and maintenance of minimal rupture risk following treatment.CONCLUSIONSThe data indicate that GKRS targeted to saccular aneurysms is associated with histopathological changes and linear reduction of aneurysm size over time. The results suggest that GKRS may be a viable, minimally invasive treatment option for intracranial aneurysm obliteration.

Rabbit aneurysm models mimic histologic wall types identified in human intracranial aneurysms

BackgroundSemiquantitative scales correlate histopathologic findings in the walls of human aneurysms with rupture status.ObjectiveTo apply a semiquantitative scale to the rabbit elastase-induced aneurysm model to determine whether rabbit histologic types...

Gingival fibroblasts protect against experimental abdominal aortic aneurysm development and rupture through tissue inhibitor of metalloproteinase-1 production.

Abdominal aortic aneurysm (AAA), frequently diagnosed in old patients, is characterized by chronic inflammation, vascular cell apoptosis and metalloproteinase-mediated extracellular matrix destruction. Despite improvement in the understanding of the pathophysiology of aortic aneurysm, no pharmacological treatment is yet available to limit dilatation and/or rupture. We previously reported that human gingival fibroblasts (GFs) can reduce carotid artery dilatation in a rabbit model of elastase-induced aneurysm. Here, we sought to investigate the mechanisms of GF-mediated vascular protection in two different models of aortic aneurysm growth and rupture in mice. In vitro, mouse GFs proliferated and produced large amounts of anti-inflammatory cytokines and tissue inhibitor of metalloproteinase-1 (Timp-1). GFs deposited on the adventitia of abdominal aorta survived, proliferated, and organized as a layer structure. Furthermore, GFs locally produced Il-10, TGF-β, and Timp-1. In a mouse elastase-induced AAA model, GFs prevented both macrophage and lymphocyte accumulations, matrix degradation, and aneurysm growth. In an Angiotensin II/anti-TGF-β model of aneurysm rupture, GF cell-based treatment limited the extent of aortic dissection, prevented abdominal aortic rupture, and increased survival. Specific deletion of Timp-1 in GFs abolished the beneficial effect of cell therapy in both AAA mouse models. GF cell-based therapy is a promising approach to inhibit aneurysm progression and rupture through local production of Timp-1.

Abstract 478: Altered Blood Flow and Anatomic Variations Increase the Translational Value of the PPE Murine Aneurysm Model

Introduction: Abdominal aortic aneurysm (AAA) is an individual and socioeconomic burden in the aging society. Treatment relies on surgical exclusion of the dilated aorta by open or endovascular repair only. For research purposes, animal models are necessary and the elastase induced aneurysm model (PPE) has gained much attention for it closely mimics endstage human aneurysm disease. However, to improve the translational value of this model we conducted a couple of modifications in relation to human aneurysm morphology. Materials and Methods: In 10-week-old male C57BL/6J wild-type mice the classic PPE procedure with local perfusion of porcine pancreatic elastase in order to induce aneurysm was modified using flow alteration by partial ligation of the iliac artery or the aorta. Additionally, careful exploration of the abdominal aortic branches allowed PPE induction at the suprarenal and iliac level. Molecular biology, ultrasound and immunistochemistry were used to evaluate the results. Results: Aortic blood flow restriction (PPE 2.0) significantly increases murine AAA diameter and affects the localization of vascular wall remodeling. Suprarenal aortic dissection allows inducing a more proximal aneurysm (PPE 3.0) similar to the angiotensin II induced aneurysm model. Separate investigation for canonical activation of transforming growth factor ß in these two embryologically distinct segments shows no difference. Creating an aorto-iliac bifurcated aneurysm (PPE 4.0) completes the mimicry of human aneurysm morphologies. Conclusion: PPE is the most important model for AAA research and the ß-versions PPE 2.0, 3.0 and 4.0 modifying its morphology further increase the translational value.

Inhibition of Receptor-Interacting Protein Kinase 1 with Necrostatin\u20131s ameliorates disease progression in elastase-induced mouse abdominal aortic aneurysm model

Abdominal aortic aneurysm (AAA) is a common aortic disease with a progressive nature. There is no approved pharmacological treatment to effectively slow aneurysm growth or prevent rupture. Necroptosis is a form of programmed necrosis that is regulated by receptor-interacting protein kinases (RIPs). We have recently demonstrated that the lack of RIP3 in mice prevented aneurysm formation. The goal of the current study is to test whether perturbing necroptosis affects progression of existing aneurysm using the RIP1 inhibitors Necrostatin-1 (Nec-1) and an optimized form of Nec-1, 7-Cl-O-Nec-1 (Nec-1s). Seven days after aneurysm induction by elastase perfusion, mice were randomly administered DMSO, Nec-1 (3.2 mg/kg/day) and Nec-1s (1.6 mg/kg/day) via intraperitoneal injection. Upon sacrifice on day 14 postaneurysm induction, the aortic expansion in the Nec-1s group (64.12 ± 4.80%) was significantly smaller than that of the DMSO group (172.80 ± 13.68%) (P < 0.05). The mean aortic diameter of Nec-1 treated mice appeared to be smaller (121.60 ± 10.40%) than the DMSO group, though the difference was not statistically significant (P = 0.1). Histologically, the aortic structure of Nec-1s-treated mice appeared normal, with continuous and organized elastin laminae and abundant αActin-expressing SMCs. Moreover, Nect-1s treatment diminished macrophage infiltration and MMP9 accumulation and increased aortic levels of tropoelastin and lysyl oxidase. Together, our data suggest that pharmacological inhibition of necroptosis with Nec-1s stabilizes pre-existing aneurysms by diminishing inflammation and promoting connective tissue repair.

Autologous adipose-derived mesenchymal stem cells improve healing of coiled experimental saccular aneurysms: an angiographic and histopathological study

PurposeLong-term occlusion of coiled aneurysms frequently fails, probably because of poor intrasaccular healing and inadequate endothelialization across the aneurysm neck. The purpose of this study was to determine if attachment...

Testing Stenting and Flow Diversion Using a Surgical Elastase-Induced Complex Fusiform Aneurysm Model.

Rabbit elastase-induced saccular aneurysms have been commonly used for preclinical testing of endovascular devices, including flow diverters. However, all tested devices have been shown to be capable of aneurysm occlusion with this model. We aimed to create a more challenging model to test and discriminate among neurovascular devices of varying efficacies. With a surgical approach that included elastase infusion and balloon dilation, we attempted the creation of complex fusiform aneurysms in 16 rabbits, with standard saccular carotid aneurysms created in 15 other animals. Aneurysms were randomly allocated to one of the following treatments: flow diversion (n = 8), high-porosity stent (n = 6), double high-porosity stent (n = 5), and control (n = 6). Angiographic assessment and pathologic analyses were performed at 3 months. Creation of complex fusiform and standard saccular aneurysms was successful in 12/16 and 13/15 attempts, respectively. All saccular (n = 4) or complex fusiform (n = 4) aneurysms treated with flow diverters were successfully occluded. Three of 3 saccular compared with 0/2 complex fusiform aneurysms were occluded by double high-porosity stents. One of 3 saccular and 0/3 complex fusiform aneurysms were occluded by a single high-porosity stent. Both aneurysm types shared the same pathologic findings when untreated: The aneurysm wall lacked an elastic layer and smooth muscle cells, while the lumen was lined with neointima of varying thickness. Neointimal coverage of the devices was complete when aneurysms were occluded, while leaks were always associated with aneurysm remnants. Challenging fusiform aneurysms can be created in rabbits by using a surgical modification of the elastase method.

Experimental testing of the dual-layer Woven EndoBridge device using an elastase-induced aneurysm model in rabbits.

The dual-layer Woven EndoBridge (WEB) device (WEB II) is designed to improve the performance of the first-generation WEB device. This study was performed to evaluate the acute and chronic performance of WEB II for aneurysm occlusion in an elastase-induced aneurysm model in rabbits. We implanted WEB II devices in 36 elastase-induced aneurysms and followed up for one, three, six, and 12 months. Degree of aneurysm occlusion at follow-up was graded on the Web Occlusion Scale (WOS): Grade A, complete aneurysm occlusion; Grade B, complete occlusion with recess filling; Grade C, residual neck filling; and Grade D, residual aneurysm filling. Hematoxylin and eosin staining was performed for histological assessment of aneurysm healing. Grades A, B, C, and D aneurysm occlusion at one-month follow-up were noted in three (17%), three (17%), eight (44%), and four (22%) of 18 cases, respectively. At the three-month time point Grades A, B, C, and D were shown in two (33%), two (33%), one (17%), and one (17%) aneurysms. Six months after treatment, one (17%), two (33%), two (33%), and one (17%) cases demonstrated Grades A, B, C, and D occlusion. At the 12-month time point, Grades B, C, and D were shown in three (50%), two (33%), and one (17%) aneurysms. Histologic evaluation showed progressive thrombus organization within aneurysm lumen from one to 12 months. These results indicated that the WEB II device can achieve high rates of aneurysm occlusion over time in experimental aneurysms.