Experimental saccular aneurysm models are necessary for testing novel surgical and endovascular treatment options and devices before they are introduced into clinical practice. Furthermore, experimental models are needed to elucidate the complex aneurysm biology leading to rupture of saccular aneurysms.
Several different kinds of experimental models for saccular aneurysms have been established in different species. Many of them, however, require special skills, expensive equipment, or special environments, which limits their widespread use. A simple, robust, and inexpensive experimental model is needed as a standardized tool that can be used in a standardized manner in various institutions.
The microsurgical rat abdominal aortic sidewall aneurysm model combines the possibility to study both novel endovascular treatment strategies and the molecular basis of aneurysm biology in a standardized and inexpensive manner. Standardized grafts by means of shape, size, and geometry are harvested from a donor rat's descending thoracic aorta and then transplanted to a syngenic recipient rat. The aneurysms are sutured end-to-side with continuous or interrupted 9-0 nylon sutures to the infrarenal abdominal aorta.
We present step-by-step procedural instructions, information on necessary equipment, and discuss important anatomical and surgical details for successful microsurgical creation of an abdominal aortic sidewall aneurysm in the rat.
14 Related JoVE Articles!
A Murine Model of Stent Implantation in the Carotid Artery for the Study of Restenosis
Institutions: RWTH Aachen University, RWTH Aachen University, Helmholtz-Institute of RWTH Aachen University, RWTH Aachen University, RWTH Aachen University.
Despite the considerable progress made in the stent development in the last decades, cardiovascular diseases remain the main cause of death in western countries. Beside the benefits offered by the development of different drug-eluting stents, the coronary revascularization bears also the life-threatening risks of in-stent thrombosis and restenosis. Research on new therapeutic strategies is impaired by the lack of appropriate methods to study stent implantation and restenosis processes. Here, we describe a rapid and accessible procedure of stent implantation in mouse carotid artery, which offers the possibility to study in a convenient way the molecular mechanisms of vessel remodeling and the effects of different drug coatings.
Medicine, Issue 75, Anatomy, Physiology, Biomedical Engineering, Mechanical Engineering, Cardiology, Surgery, Microsurgery, Animal Experimentation, Models, Animal, Cardiovascular Diseases, Stent implantation, atherosclerosis, restenosis, in-stent thrombosis, stent, mouse carotid artery, arteries, blood vessels, mouse, animal model, surgical techniques
Surgical Procedures for a Rat Model of Partial Orthotopic Liver Transplantation with Hepatic Arterial Reconstruction
Institutions: RWTH-Aachen University, Kyoto University .
Orthotopic liver transplantation (OLT) in rats using a whole or partial graft is an indispensable experimental model for transplantation research, such as studies on graft preservation and ischemia-reperfusion injury 1,2
, immunological responses 3,4
, hemodynamics 5,6
, and small-for-size syndrome 7
. The rat OLT is among the most difficult animal models in experimental surgery and demands advanced microsurgical skills that take a long time to learn. Consequently, the use of this model has been limited. Since the reliability and reproducibility of results are key components of the experiments in which such complex animal models are used, it is essential for surgeons who are involved in rat OLT to be trained in well-standardized and sophisticated procedures for this model.
While various techniques and modifications of OLT in rats have been reported 8
since the first model was described by Lee et al. 9
in 1973, the elimination of the hepatic arterial reconstruction 10
and the introduction of the cuff anastomosis technique by Kamada et al. 11
were a major advancement in this model, because they simplified the reconstruction procedures to a great degree. In the model by Kamada et al.
, the hepatic rearterialization was also eliminated. Since rats could survive without hepatic arterial flow after liver transplantation, there was considerable controversy over the value of hepatic arterialization. However, the physiological superiority of the arterialized model has been increasingly acknowledged, especially in terms of preserving the bile duct system 8,12
and the liver integrity 8,13,14
In this article, we present detailed surgical procedures for a rat model of OLT with hepatic arterial reconstruction using a 50% partial graft after ex vivo
liver resection. The reconstruction procedures for each vessel and the bile duct are performed by the following methods: a 7-0 polypropylene continuous suture for the supra- and infrahepatic vena cava; a cuff technique for the portal vein; and a stent technique for the hepatic artery and the bile duct.
Medicine, Issue 73, Biomedical Engineering, Anatomy, Physiology, Immunology, Surgery, liver transplantation, liver, hepatic, partial, orthotopic, split, rat, graft, transplantation, microsurgery, procedure, clinical, technique, artery, arterialization, arterialized, anastomosis, reperfusion, rat, animal model
Heterotopic Auxiliary Rat Liver Transplantation With Flow-regulated Portal Vein Arterialization in Acute Hepatic Failure
Institutions: University Hospital RWTH Aachen.
In acute hepatic failure auxiliary liver transplantation is an interesting alternative approach. The aim is to provide a temporary support until the failing native liver has regenerated.1-3
The APOLT-method, the orthotopic implantation of auxiliary segments- averts most of the technical problems. However this method necessitates extensive resections of both the native liver and the graft.4
In 1998, Erhard developed the heterotopic auxiliary liver transplantation (HALT) utilizing portal vein arterialization (PVA) (Figure 1). This technique showed promising initial clinical results.5-6
We developed a HALT-technique with flow-regulated PVA in the rat to examine the influence of flow-regulated PVA on graft morphology and function (Figure 2).
A liver graft reduced to 30 % of its original size, was heterotopically implanted in the right renal region of the recipient after explantation of the right kidney. The infra-hepatic caval vein of the graft was anastomosed with the infrahepatic caval vein of the recipient. The arterialization of the donor’s portal vein was carried out via the recipient’s right renal artery with the stent technique. The blood-flow regulation of the arterialized portal vein was achieved with the use of a stent with an internal diameter of 0.3 mm. The celiac trunk of the graft was end-to-side anastomosed with the recipient’s aorta and the bile duct was implanted into the duodenum. A subtotal resection of the native liver was performed to induce acute hepatic failure. 7
In this manner 112 transplantations were performed. The perioperative survival rate was 90% and the 6-week survival rate was 80%. Six weeks after operation, the native liver regenerated, showing an increase in weight from 2.3±0.8 g to 9.8±1 g. At this time, the graft’s weight decreased from 3.3±0.8 g to 2.3±0.8 g.
We were able to obtain promising long-term results in terms of graft morphology and function. HALT with flow-regulated PVA reliably bridges acute hepatic failure until the native liver regenerates.
Medicine, Issue 91, auxiliary liver transplantation, rat, portal vein arterialization, flow-regulation, acute hepatic failure
Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement
Institutions: Brigham and Women's Hospital/Harvard Medical School, CHUV University Hospital, University of Bordeaux, CHUV University Hospital.
The mainstay of contemporary therapies for extensive occlusive arterial disease is venous bypass graft. However, its durability is threatened by intimal hyperplasia (IH) that eventually leads to vessel occlusion and graft failure. Mechanical forces, particularly low shear stress and high wall tension, are thought to initiate and to sustain these cellular and molecular changes, but their exact contribution remains to be unraveled. To selectively evaluate the role of pressure and shear stress on the biology of IH, an ex vivo
perfusion system (EVPS) was created to perfuse segments of human saphenous veins under arterial regimen (high shear stress and high pressure). Further technical innovations allowed the simultaneous perfusion of two segments from the same vein, one reinforced with an external mesh. Veins were harvested using a no-touch technique and immediately transferred to the laboratory for assembly in the EVPS. One segment of the freshly isolated vein was not perfused (control, day 0). The two others segments were perfused for up to 7 days, one being completely sheltered with a 4 mm (diameter) external mesh. The pressure, flow velocity, and pulse rate were continuously monitored and adjusted to mimic the hemodynamic conditions prevailing in the femoral artery. Upon completion of the perfusion, veins were dismounted and used for histological and molecular analysis. Under ex vivo
conditions, high pressure perfusion (arterial, mean = 100 mm Hg) is sufficient to generate IH and remodeling of human veins. These alterations are reduced in the presence of an external polyester mesh.
Medicine, Issue 92, vein, human, intimal hyperplasia, neointima, perfusion, mesh, pressure, ex vivo
A New Murine Model of Endovascular Aortic Aneurysm Repair
Institutions: Hôpital X. Bichat, AP-HP, Paris, Institut Galilée - Université Paris 13, Paris, France, Université Paris-Est Creteil, Ecole de chirurgie de l'assistance publique des hôpitaux de Paris, Université René Descartes.
Endovascular aneurysm exclusion is a validated technique to prevent aneurysm rupture. Long-term results highlight technique limitations and new aspects of Abdominal aortic aneurysm (AAA) pathophysiology. There is no abdominal aortic aneurysm endograft exclusion model cheap and reproducible, which would allow deep investigations of AAA before and after treatment. We hereby describe how to induce, and then to exclude with a covered coronary stentgraft an abdominal aortic aneurysm in a rat. The well known elastase induced AAA model was first reported in 19901
in a rat, then described in mice2
. Elastin degradation leads to dilation of the aorta with inflammatory infiltration of the abdominal wall and intra luminal thrombus, matching with human AAA. Endovascular exclusion with small covered stentgraft is then performed, excluding any interactions between circulating blood and the aneurysm thrombus. Appropriate exclusion and stentgraft patency is confirmed before euthanasia by an angiography thought the left carotid artery. Partial control of elastase diffusion makes aneurysm shape different for each animal. It is difficult to create an aneurysm, which will allow an appropriate length of aorta below the aneurysm for an easy stentgraft introduction, and with adequate proximal and distal neck to prevent endoleaks. Lots of failure can result to stentgraft introduction which sometimes lead to aorta tear with pain and troubles to stitch it, and endothelial damage with post op aorta thrombosis. Giving aspirin to rats before stentgraft implantation decreases failure rate without major hemorrhage. Clamping time activates neutrophils, endothelium and platelets, and may interfere with biological analysis.
Medicine, Issue 77, Anatomy, Physiology, Biomedical Engineering, Bioengineering, Cardiology, Aortic Diseases, Aortic Aneurysm, Aortic Aneurysm, Disease Models, Animal, Vascular Surgical Procedures, Vascular Grafting, Microsurgery, animal models, Cardiovascular Diseases, Abdominal aortic aneurysm, rat, stentgraft exclusion, EVAR, animal model
Microsurgical Venous Pouch Arterial-Bifurcation Aneurysms in the Rabbit Model: Technical Aspects
Institutions: Hospital Rudolfstiftung, Kantonsspital Aarau, Medical University of Vienna, University of Berne, Medical University of Vienna, Paracelsus University Salzburg.
For ruptured human cerebral aneurysms endovascular embolization has become an equivalent alternative to aneurysm clipping.1
However, large clinical trials have shown disappointing long-term results with unacceptable high rates of aneurysm recanalization and delayed aneurysm rupture.2
To overcome these problems, animal experimental studies are crucial for the development of better endovascular devices.3-5
Several animal models in rats, rabbits, canines and swine are available.6-8
Comparisons of the different animal models showed the superiority of the rabbit model with regard to hemodynamics and comparability of the coagulation system and cost-effectiveness.9-11
The venous pouch arterial bifurcation model in rabbits is formed by a venous pouch sutured into an artificially created true bifurcation of both common carotid arteries (CCA). The main advantage of this model are true bifurcational hemodynamics.12
The major drawbacks are the sofar high microsurgical technical demands and high morbidity and mortality rates of up to 50%.13
These limitations have resulted in less frequent use of this aneurysm model in the recent years. These shortcomings could be overcome with improved surgical procedures and modified peri- and postoperative analgetic management and anticoagulation.14-16
Our techniques reported in this paper demonstrate this optimized technique for microsurgical creation of arterial bifurcation aneurysms.
Medicine, Issue 51, mental aneurysm, bifurcation, microsurgery, endovascular-coiling
Human Internal Mammary Artery (IMA) Transplantation and Stenting: A Human Model to Study the Development of In-Stent Restenosis
Institutions: TSI-Lab, Germany, University of Hamburg, University of Alberta, Stanford University School of Medicine , University of Veterinary Medicine, Vienna, Hechingen, Stanford University School of Medicine.
Preclinical in vivo
research models to investigate pathobiological and pathophysiological processes in the development of intimal hyperplasia after vessel stenting are crucial for translational approaches1,2
The commonly used animal models include mice, rats, rabbits, and pigs3-5
. However, the translation of these models into clinical settings remains difficult, since those biological processes are already studied in animal vessels but never performed before in human research models6,7
. In this video we demonstrate a new humanized model to overcome this translational gap. The shown procedure is reproducible, easy, and fast to perform and is suitable to study the development of intimal hyperplasia and the applicability of diverse stents.
This video shows how to perform the stent technique in human vessels followed by transplantation into immunodeficient rats, and identifies the origin of proliferating cells as human.
Biomedical Engineering, Issue 63, physiology, stent, Human Internal Mammary Artery (IMA) Transplantation, restenosis
Systemic Injection of Neural Stem/Progenitor Cells in Mice with Chronic EAE
Institutions: University of Cambridge, UK, University of Cambridge, UK.
Neural stem/precursor cells (NPCs) are a promising stem cell source for transplantation approaches aiming at brain repair or restoration in regenerative neurology. This directive has arisen from the extensive evidence that brain repair is achieved after focal or systemic NPC transplantation in several preclinical models of neurological diseases.
These experimental data have identified the cell delivery route as one of the main hurdles of restorative stem cell therapies for brain diseases that requires urgent assessment. Intraparenchymal stem cell grafting represents a logical approach to those pathologies characterized by isolated and accessible brain lesions such as spinal cord injuries and Parkinson's disease. Unfortunately, this principle is poorly applicable to conditions characterized by a multifocal, inflammatory and disseminated (both in time and space) nature, including multiple sclerosis (MS). As such, brain targeting by systemic NPC delivery has become a low invasive and therapeutically efficacious protocol to deliver cells to the brain and spinal cord of rodents and nonhuman primates affected by experimental chronic inflammatory damage of the central nervous system (CNS).
This alternative method of cell delivery relies on the NPC pathotropism, specifically their innate capacity to (i) sense the environment via
functional cell adhesion molecules and inflammatory cytokine and chemokine receptors; (ii) cross the leaking anatomical barriers after intravenous (i.v
.) or intracerebroventricular (i.c.v.
) injection; (iii) accumulate at the level of multiple perivascular site(s) of inflammatory brain and spinal cord damage; and (i.v.
) exert remarkable tissue trophic and immune regulatory effects onto different host target cells in vivo
Here we describe the methods that we have developed for the i.v
. and i.c.v.
delivery of syngeneic NPCs in mice with experimental autoimmune encephalomyelitis (EAE), as model of chronic CNS inflammatory demyelination, and envisage the systemic stem cell delivery as a valuable technique for the selective targeting of the inflamed brain in regenerative neurology.
Immunology, Issue 86, Somatic neural stem/precursor cells, neurodegenerative disorders, regenerative medicine, multiple sclerosis, experimental autoimmune encephalomyelitis, systemic delivery, intravenous, intracerebroventricular
Technique of Subnormothermic Ex Vivo Liver Perfusion for the Storage, Assessment, and Repair of Marginal Liver Grafts
Institutions: Toronto General Hospital, Toronto General Hospital, Toronto General Hospital.
The success of liver transplantation has resulted in a dramatic organ shortage. In most transplant regions 20-30% of patients on the waiting list for liver transplantation die without receiving an organ transplant or are delisted for disease progression. One strategy to increase the donor pool is the utilization of marginal grafts, such as fatty livers, grafts from older donors, or donation after cardiac death (DCD). The current preservation technique of cold static storage is only poorly tolerated by marginal livers resulting in significant organ damage. In addition, cold static organ storage does not allow graft assessment or repair prior to transplantation.
These shortcomings of cold static preservation have triggered an interest in warm perfused organ preservation to reduce cold ischemic injury, assess liver grafts during preservation, and explore the opportunity to repair marginal livers prior to transplantation. The optimal pressure and flow conditions, perfusion temperature, composition of the perfusion solution and the need for an oxygen carrier has been controversial in the past.
In spite of promising results in several animal studies, the complexity and the costs have prevented a broader clinical application so far. Recently, with enhanced technology and a better understanding of liver physiology during ex vivo
perfusion the outcome of warm liver perfusion has improved and consistently good results can be achieved.
This paper will provide information about liver retrieval, storage techniques, and isolated liver perfusion in pigs. We will illustrate a) the requirements to ensure sufficient oxygen supply to the organ, b) technical considerations about the perfusion machine and the perfusion solution, and c) biochemical aspects of isolated organs.
Medicine, Issue 90, ex vivo liver perfusion, marginal grafts, DCD
Monitoring the Wall Mechanics During Stent Deployment in a Vessel
Institutions: University of Nebraska-Lincoln.
Clinical trials have reported different restenosis rates for various stent designs1
. It is speculated that stent-induced strain concentrations on the arterial wall lead to tissue injury, which initiates restenosis2-7
. This hypothesis needs further investigations including better quantifications of non-uniform strain distribution on the artery following stent implantation. A non-contact surface strain measurement method for the stented artery is presented in this work. ARAMIS stereo optical surface strain measurement system uses two optical high speed cameras to capture the motion of each reference point, and resolve three dimensional strains over the deforming surface8,9
. As a mesh stent is deployed into a latex vessel with a random contrasting pattern sprayed or drawn on its outer surface, the surface strain is recorded at every instant of the deformation. The calculated strain distributions can then be used to understand the local lesion response, validate the computational models, and formulate hypotheses for further in vivo
Biomedical Engineering, Issue 63, Stent, vessel, interaction, strain distribution, stereo optical surface strain measurement system, bioengineering
Evaluation of a Novel Laser-assisted Coronary Anastomotic Connector - the Trinity Clip - in a Porcine Off-pump Bypass Model
Institutions: University Medical Center Utrecht, Vascular Connect b.v., University Medical Center Utrecht, University Medical Center Utrecht.
To simplify and facilitate beating heart (i.e.,
off-pump), minimally invasive coronary artery bypass surgery, a new coronary anastomotic connector, the Trinity Clip, is developed based on the excimer laser-assisted nonocclusive anastomosis technique. The Trinity Clip connector enables simplified, sutureless, and nonocclusive connection of the graft to the coronary artery, and an excimer laser catheter laser-punches the opening of the anastomosis. Consequently, owing to the complete nonocclusive anastomosis construction, coronary conditioning (i.e.,
occluding or shunting) is not necessary, in contrast to the conventional anastomotic technique, hence simplifying the off-pump bypass procedure. Prior to clinical application in coronary artery bypass grafting, the safety and quality of this novel connector will be evaluated in a long-term experimental porcine off-pump coronary artery bypass (OPCAB) study. In this paper, we describe how to evaluate the coronary anastomosis in the porcine OPCAB model using various techniques to assess its quality. Representative results are summarized and visually demonstrated.
Medicine, Issue 93, Anastomosis, coronary, anastomotic connector, anastomotic coupler, excimer laser-assisted nonocclusive anastomosis (ELANA), coronary artery bypass graft (CABG), off-pump coronary artery bypass (OPCAB), beating heart surgery, excimer laser, porcine model, experimental, medical device
Vascular Gene Transfer from Metallic Stent Surfaces Using Adenoviral Vectors Tethered through Hydrolysable Cross-linkers
Institutions: The Children's Hospital of Philadelphia, University of Pennsylvania.
In-stent restenosis presents a major complication of stent-based revascularization procedures widely used to re-establish blood flow through critically narrowed segments of coronary and peripheral arteries. Endovascular stents capable of tunable release of genes with anti-restenotic activity may present an alternative strategy to presently used drug-eluting stents. In order to attain clinical translation, gene-eluting stents must exhibit predictable kinetics of stent-immobilized gene vector release and site-specific transduction of vasculature, while avoiding an excessive inflammatory response typically associated with the polymer coatings used for physical entrapment of the vector. This paper describes a detailed methodology for coatless tethering of adenoviral gene vectors to stents based on a reversible binding of the adenoviral particles to polyallylamine bisphosphonate (PABT)-modified stainless steel surface via hydrolysable cross-linkers (HC). A family of bifunctional (amine- and thiol-reactive) HC with an average t1/2
of the in-chain ester hydrolysis ranging between 5 and 50 days were used to link the vector with the stent. The vector immobilization procedure is typically carried out within 9 hr and consists of several steps: 1) incubation of the metal samples in an aqueous solution of PABT (4 hr); 2) deprotection of thiol groups installed in PABT with tris(2-carboxyethyl) phosphine (20 min); 3) expansion of thiol reactive capacity of the metal surface by reacting the samples with polyethyleneimine derivatized with pyridyldithio (PDT) groups (2 hr); 4) conversion of PDT groups to thiols with dithiothreitol (10 min); 5) modification of adenoviruses with HC (1 hr); 6) purification of modified adenoviral particles by size-exclusion column chromatography (15 min) and 7) immobilization of thiol-reactive adenoviral particles on the thiolated steel surface (1 hr). This technique has wide potential applicability beyond stents, by facilitating surface engineering of bioprosthetic devices to enhance their biocompatibility through the substrate-mediated gene delivery to the cells interfacing the implanted foreign material.
Medicine, Issue 90, gene therapy, bioconjugation, adenoviral vectors, stents, local gene delivery, smooth muscle cells, endothelial cells, bioluminescence imaging
Mouse Models for Graft Arteriosclerosis
Institutions: Yale University School of Medicine , Yale University School of Medicine .
Graft arteriosclerois (GA), also called allograft vasculopathy, is a pathologic lesion that develops over months to years in transplanted organs characterized by diffuse, circumferential stenosis of the entire graft vascular tree. The most critical component of GA pathogenesis is the proliferation of smooth muscle-like cells within the intima. When a human coronary artery segment is interposed into the infra-renal aortae of immunodeficient mice, the intimas could be expand in response to adoptively transferred human T cells allogeneic to the artery donor or exogenous human IFN-γ in the absence of human T cells. Interposition of a mouse aorta from one strain into another mouse strain recipient is limited as a model for chronic rejection in humans because the acute cell-mediated rejection response in this mouse model completely eliminates all donor-derived vascular cells from the graft within two-three weeks. We have recently developed two new mouse models to circumvent these problems. The first model involves interposition of a vessel segment from a male mouse into a female recipient of the same inbred strain (C57BL/6J). Graft rejection in this case is directed only against minor histocompatibility antigens encoded by the Y chromosome (present in the male but not the female) and the rejection response that ensues is sufficiently indolent to preserve donor-derived smooth muscle cells for several weeks. The second model involves interposing an artery segment from a wild type C57BL/6J mouse donor into a host mouse of the same strain and gender that lacks the receptor for IFN-γ followed by administration of mouse IFN-γ (delivered via infection of the mouse liver with an adenoviral vector. There is no rejection in this case as both donor and recipient mice are of the same strain and gender but donor smooth muscle cells proliferate in response to the cytokine while host-derived cells, lacking receptor for this cytokine, are unresponsive. By backcrossing additional genetic changes into the vessel donor, both models can be used to assess the effect of specific genes on GA progression. Here, we describe detailed protocols for our mouse GA models.
Medicine, Issue 75, Anatomy, Physiology, Biomedical Engineering, Bioengineering, Cardiology, Pathology, Surgery, Tissue Engineering, Cardiovascular Diseases, vascular biology, graft arteriosclerosis, GA, mouse models, transplantation, graft, vessels, arteries, mouse, animal model, surgical techniques
Imaging In-Stent Restenosis: An Inexpensive, Reliable, and Rapid Preclinical Model
Institutions: Stanford University School of Medicine, Stanford University School of Medicine.
Preclinical models of restenosis are essential to unravel the pathophysiological processes that lead to in-stent restenosis and to optimize existing and future drug-eluting stents.
A variety of antibodies and transgenic and knockout strains are available in rats. Consequently, a model for in-stent restenosis in the rat would be convenient for pathobiological and pathophysiological studies.
In this video, we present the full procedure and pit-falls of a rat stent model suitable for high throughput stent research. We will show the surgical procedure of stent deployment, and the assessment of in-stent restenosis using the most elegant technique of OCT (Optical Coherence Tomography). This technique provides high accuracy in assessing plaque CSAs (cross section areas) and correlates well with histological sections, which require special and time consuming embedding and sectioning techniques. OCT imaging further allows longitudinal monitoring of the development of in-stent restenosis within the same animal compared to one-time snapshots using histology.
Medicine, Issue 31, stent, rats, restenosis, OCT, imaging