Basic fibroblast growth factor slow release stent graft for endovascular aortic aneurysm repair: A canine model experiment

A canine model of aortic arch aneurysm created with autologous pericardium

Background

To establish a canine model of aortic arch aneurysm that is suitable for research on new devices and techniques applied to the aortic arch.

Materials and methods

Fifteen mongrel dogs underwent surgery. The autologous pericardial patch was sewn on the aortotomy site in the anterior wall of the aortic arch. The animals were followed up for 3 months postoperatively. Computed tomography angiography was used to visualize and measure the aneurysm model. Hematoxylin and eosin staining was used to observe the histological characteristics of the aneurysm model. Changes in aneurysm diameter over time were analyzed using analysis of variance.

Results

One dog died of hemorrhage during surgery. Fourteen dogs survived the surgical procedure. Two of them died on the first postoperative day because of ruptures at the suturing margin. The diameter of the aneurysm model was twice as large as that of the aortic arch. There was no significant change in the maximum diameter of the aneurysm model during the follow-up period.

Conclusions

We established a controllable and stable aortic arch aneurysm model created with an autologous pericardium patch. The aneurysm model can be used to research endoleaks after thoracic endovascular aortic repair and new endovascular techniques can be applied to the aortic arch.

Development of a stent capable of the controlled release of basic fibroblast growth factor and argatroban to treat cerebral aneurysms: In vitro experiment and evaluation in a rabbit aneurysm model

An ideal stent to treat cerebral aneurysms should have an antithrombotic effect on the inner stent blood-facing side and a tissue organization effect on the outer aneurysmal side of the stent. The objective of this study is to evaluate the feasibility of a drug containing stent in the in vivo treatment of cerebral aneurysms. Argatroban, an antithrombotic drug, is encapsulated in biodegradable poly (d,l-lactide-co-glycolide) (PLGA) microspheres for the controlled release with an in vitro study conducted to evaluate the drug release and anticoagulation behavior of released drug. Basic fibroblast growth factor (bFGF), an organization drug, is released from gelatin hydrogels. The stents are coated with gelatin hydrogels incorporating bFGF and PLGA microspheres containing argatroban, and applied to the carotid artery aneurysm of an elastase-induced rabbit model. Most of the aneurysm cavity is occupied by loose connective tissues in the group treated with drug-coated stents, whereas extensive massive hematomas are observed in the group treated with drug-free stents. The occurrence rate of in-stent thrombus is small in the drug-coated stents. The stent incorporating bFGF and PLGA microspheres containing argatroban is an effective device for cerebral aneurysm treatment. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2185-2194, 2019.

Animal Models in the Research of Abdominal Aortic Aneurysms Development

Abdominal aortic aneurysm (AAA) is a prevalent and potentially life threatening disease. Many animal models have been developed to simulate the natural history of the disease or test preclinical endovascular devices and surgical procedures. The aim of this review is to describe different methods of AAA induction in animal models and report on the effectiveness of the methods described in inducing an analogue of a human AAA. The PubMed database was searched for publications with titles containing the following terms “animal” or ‘‘animal model(s)’’ and keywords “research”, “aneurysm(s)’’, “aorta”, “pancreatic elastase’’, “Angiotensin”, “AngII” “calcium chloride” or “CaCl2”. Starting date for this search was set to 2004, since previously bibliography was already covered by the review of Daugherty and Cassis (2004). We focused on animal studies that reported a model of aneurysm development and progression. A number of different approaches of AAA induction in animal models has been developed, used and combined since the first report in the 1960’s. Although specific methods are successful in AAA induction in animal models, it is necessary that these methods and their respective results are in line with the pathophysiology and the mechanisms involved in human AAA development. A researcher should know the advantages/disadvantages of each animal model and choose the appropriate model.

Implantation study of a tissue-engineered self-expanding aortic stent graft (bio stent graft) in a beagle model

The use of stent grafts for endovascular aortic repair has become an important treatment option for aortic aneurysms requiring surgery. This treatment has achieved excellent outcomes; however, problems like type 1 endoleaks and stent graft migration remain. Bio stent grafts (BSGs), which are self-expanding stents covered with connective tissue, were previously developed using "in-body tissue architecture" technology. We assessed their early adaptation to the aorta after transcatheter implantation in a beagle model. BSGs were prepared by subcutaneous embedding of acryl rods mounted with self-expanding nitinol stents in three beagles for 4 weeks (n = 3/dog). The BSGs were implanted as allografts into infrarenal abdominal aortas via the femoral artery of three other beagles. After 1 month of implantation, aortography revealed no stenosis or aneurysmal changes. The luminal surface of the BSGs was completely covered with neointimal tissue, including endothelialization, without any thrombus formation. The cover tissue could fuse the luminal surface of the native aorta with tight conjunctions even at both ends of the stents, resulting in complete impregnation of the strut into the reconstructed vascular wall, which is expected to prevent endoleaks and migration in clinical applications.

Basic fibroblast growth factor gene transfection in repair of internal carotid artery aneurysm wall

Surgery or interventional therapy has some risks in the treatment of cerebral aneurysm. We established an internal carotid artery aneurysm model by dripping elastase in the crotch of the right internal and external carotid arteries of New Zealand rabbits. Following model induction, lentivirus carrying basic fibroblast growth factor was injected through the ear vein. We found that the longer the action time of the lentivirus, the smaller the aneurysm volume. Moreover, platelet-derived growth factor expression in the aneurysm increased, but smooth muscle 22 alpha and hypertension-related gene 1 mRNA expression decreased. At 1, 2, 3, and 4 weeks following model establishment, following 1 week of injection of lentivirus carrying basic fibroblast growth factor, the later the intervention time, the more severe the blood vessel damage, and the bigger the aneurysm volume, the lower the smooth muscle 22 alpha and hypertension-related gene 1 mRNA expression. Simultaneously, platelet-derived growth factor expression decreased. These data suggest that recombinant lentivirus carrying basic fibroblast growth factor can repair damaged cells in the aneurysmal wall and inhibit aneurysm dynamic growth, and that the effect is dependent on therapeutic duration.

Chondroitin sulfate and epidermal growth factor immobilization after plasma polymerization: a versatile anti-apoptotic coating to promote healing around stent grafts

Bioactive coatings constitute an interesting approach to enhance healing around implants, such as stent-grafts used in endovascular aneurysm repair. Three different plasma techniques, namely NH₃ plasma functionalization and atmospheric- or low-pressure plasma polymerization, are compared to create amino groups and covalently bind CS and EGF bioactive molecules on PET. The latter presents the greatest potential. CS + EGF coating is shown to strongly decrease cell apoptosis and cell depletion in serum-free medium, while increasing cell growth compared to unmodified PET. This versatile biomimetic coating holds promise in promoting vascular repair around stent-grafts, where resistance to apoptosis is a key issue.

A doxycycline loaded, controlled-release, biodegradable fiber for the treatment of aortic aneurysms

The pathogenesis of aortic aneurysm (AA) is characterized by degradation of extracellular matrix with increased matrix metalloproteinases (MMPs) and inflammatory reaction. Doxycycline (DOXY) has been reported to control the extension of AA by regulation of MMP. However, systemic administration may cause adverse side effects. In this study, we demonstrated the possibility of local administration of DOXY controlled-release biodegradable fiber (DCRBF) for AA in mice. DCRBF was fabricated by biodegradable polymer (polylactic acid; PLA) mixed with DOXY using an electrospinning technique. DCRBF was cocultured with SMCs, macrophages and aortic tissue, and placed on an abdominal aortic aneurysm which induced apolipoprotein E-deficient mice. We evaluated gene and protein expression of proteases, elastin and inflammatory markers. In the presence of DCRBF, MMP-12 was significantly decreased, TGF-β1 and Lox were significantly increased in SMC gene expression, MMP-9 and -12 significantly decreased gene expression of macrophages. The DCRBF preserved elastin content and decreased MMP-2 and -9 in aortic tissue. In addition, IGF-1 and TIMP-1 were significantly increased and IL-6 and TNF-α were significantly decreased with DCRBF in vivo. In conclusion, our results suggested that local administration of DCRBF may become a promising alternative therapeutic strategy for AA.

Animal models of abdominal aortic aneurysm and their role in furthering management of human disease

Abdominal aortic aneurysm is a common degenerative disorder associated with sudden death due to aortic rupture. Current therapy is limited to open surgical repair of the aorta or endovascular placement of covered stents to exclude the abdominal aortic aneurysm from the circulation. A number of different animal models have been developed in order to study abdominal aortic aneurysm in an effort to advance current management deficiencies. Large animal models have been mostly used to assist in developing novel methods to surgically treat abdominal aortic aneurysms. Small animal models, particularly those developed in rodents, have been employed to further the understanding of the mechanisms involved in abdominal aortic aneurysm in order to identify potential new medical treatments. It is expected that findings from these animal models will contribute importantly to new treatments for human abdominal aortic aneurysm. This review explores the animal models which are used in abdominal aortic aneurysm research and highlights their advantages and disadvantages.