Performance of a modified rabbit model of abdominal aortic aneurysm induced by topical application of porcine elastase: 5-month follow-up study

A Novel Method for the Rat Model of Abdominal Aortic Aneurysm Induced by Retroperitoneal Implantation of an Osmotic Pump System With Lipopolysaccharide

BACKGROUND

Few methods can cocurrently mimic the pathological characteristics and nature history of human abdominal aortic aneurysms (AAAs), especially for the exist of the self-healing tendency of rodents. This study tested a novel method for the AAA rat model induced by retroperitoneal implantation of an osmotic pump system with lipopolysaccharide (LPS) based on the hypothesis that chronic inflammation of perivascular adipose tissue directly influenced the development and progression of AAAs.

METHODS

20 male Sprague-Dawley rats (10-month-old) fed with the Paigen diet were randomly divided into 4 groups: the blank group ×2, the sham group ×4, the empty capsule group ×4, and the LPS capsule group ×10. The LPS capsule group received implantations of the ALZET® osmotic pump capsule with LPS (3.6 μg/day) parallel to the abdominal aorta through a retroperitoneal approach. Two weeks later, 6 rats were randomly selected from the LPS capsule group to form the anti-inflammatory group and received implantations of another osmotic pump capsule with interleukin (IL)-10 (75 ng/day) through the same approach. The changes in abdominal aortic diameter were observed by ultrasound every 2 weeks, and samples were harvested for histopathologic and immunohistochemical analysis 6 weeks later.

RESULTS

Within the 6 weeks after modeling, the LPS capsule group showed sustained and significant aortic dilatation (P < 0.01), while the anti-inflammatory group showed a rapid and obvious shrinkage 2 weeks after the IL-10 osmotic pump capsule implantation (P < 0.01). The LPS capsule group presented excellent pathological mimicking of human AAAs and showed severe medial degeneration with the least elastic content among the 5 groups at the end of the sixth week (P < 0.05). Notably, the anti-inflammatory group showed perfect medial preservation with the most elastic content (P < 0.05) and the highest elastin/collagen ratio (P < 0.01) at the end of the study. Matrix metalloproteinases (MMP) 2 and 9 and toll-like receptor 2 showed strong expression in the LPS capsule group at the end of the sixth week, which was significantly higher than that in the blank group and sham group. Interestingly, the anti-inflammatory group showed a slightly higher MMP9 expression than the LPS capsule group though there was no statistical difference between them.

CONCLUSIONS

This novel method for the rat AAA model induced by retroperitoneal implantation of an osmotic pump capsule with LPS can concurrently mimic the histological characteristics and natural history of human AAAs. Further studies were needed to improve the osmotic pump system.

A novel rabbit model of abdominal aortic aneurysm: Construction and evaluation

Prior research has indicated that animal models of abdominal aortic aneurysm (AAA) utilizing porcine pancreatic elastase (PPE) exhibit a perfusion duration of 30 min, and extended perfusion durations are associated with elevated mortality rates. Similarly, the AAA model, which relies solely on balloon dilation (BD), is limited by the occurrence of self-healing aneurysms. Consequently, we constructed a novel AAA model by PPE combined with balloon expansion to shorten the modeling time and improve the modeling success rate. The findings indicated that 5 min was the optimal BD time for rabbits, 3 min BD was ineffective for aneurysm formation, and 10 min BD had a high mortality rate. The model, constructed in combination with PPE and 5 min BD, exhibited a 100% model formation rate and a 244.7% ± 9.83% dilation rate. HE staining exhibited that severe disruption of the inner, middle, and outer membranes of the abdominal aorta, with a marked decrease in smooth muscle cells and elastase, and a marked increase in fibroblasts of the middle membrane, and many infiltrating inflammatory cells were seen in all three layers, especially in the middle membrane. EVG staining displayed that the elastic fibers of the abdominal aortic wall were fractured and degraded, and lost their normal wavy appearance. The protein expression of inflammatory factor (IL-1β, IL-6 and TNF-α) as well as extracellular matrix components (MMP-2 and MMP-9) were significantly increased compared to PPE and 5 min BD alone. In conclusion, PPE combined with BD allows the establishment of a novel AAA model that closely mimics human AAA in terms of histomorphology, inflammatory cell infiltration, and vascular stromal destruction. This model provides an ideal animal model for understanding the pathogenesis of AAA.

Degeneration and Regeneration of Smooth Muscle Cells in Two Different Abdominal Aortic Aneurysm Models in Rabbits

BACKGROUND

We aimed to investigate the formation and self-healing process of rabbit abdominal aortic aneurysm (AAA) by focus on the degeneration and regeneration of smooth muscle cells (SMCs) in elastase-induced AAA model and enlarging AAA model in rabbits.

METHODS

Sixty rabbits were equally divided into 2 aneurysm groups (Group A and Group B). Rabbits received a 10-min incubation of elastase in Group A (10 units/µL) and Group B (1 unit/µL). Rabbits underwent aortic stenosis above the incubated segment in Group B. Aortic diameter was measured and rabbits were sacrificed for histopathological and immunohistochemical studies.

RESULTS

The incubated aorta dilated immediately and ran up to maxima by day 21 in Group A. All aneurysms formed by day 21 and enlarged progressively in Group B. SMCs content, elastin content and intima-media thickness decreased significantly by day 0 in Group A. SMCs and elastic fibers were destroyed gradually in Group B, however, SMCs content was significantly lower than Group A by day 70. Intimal thickness increased significantly by day 70 in the Aneurysm groups. MMP2 maintained moderate expression in Group A, which decreased significantly by day 3 in Group B. MMP9 and RAM11 expressions were higher by day 1, but decreased significantly by day 3 in Group B.

CONCLUSIONS

Irreversible degeneration of SMCs is critical to a rapid formation of elastase-induced rabbit AAA model, and SMCs excessive regeneration accounts for the selfhealing process. SMCs degradation and regeneration remain relatively stable in an enlarging AAA model. SMCs should be the key target for studying the mechanism of AAA and intervention therapy.

Mechanisms of abdominal aortic aneurysm progression: A review

Abdominal aortic aneurysm (AAA) is a common disease associated with significant cardiovascular morbidity and mortality. Up to now, there is still controversy on the choice of treatment method of AAA. Even so, the mechanisms of AAA progression are poorly defined, making targeting new therapies problematic. Current evidence favors an interaction of the hemodynamic microenvironment with local and systemic immune responses. In this review, we aim to provide an update of mechanisms in AAA progression, involving hemodynamics, perivascular adipose tissue, adventitial fibroblasts, vasa vasorum remodeling, intraluminal thrombus, and distribution of macrophage subtypes.

Photochemical Collagen Cross-Linking Reverses Elastase-Induced Mechanical Degradation of Upper Eyelid Tarsus

INTRODUCTION

The floppy eyelid syndrome describes an eyelid disorder characterized by floppy tarsal plates that may be caused by a loss of elastin. The authors attempted to create floppy eyelids by digesting elastin from cadaveric tarsus and then treated them with cross-linking using ultraviolet A and riboflavin.

METHODS

Nine right and 9 left upper eyelids were excised from cadavers. Four vertical strips of central tarsus were removed from each eyelid. One strip of tarsus from each eyelid was treated with 10 units/ml of elastase for 2 hours. Another tarsal strip from each eyelid was immersed in normal saline for 2 hours (control). A third strip from the same eyelid was cross-linked using ultraviolet A at 6 mW/cm for 18 minutes. Finally, a fourth strip of tarsus was cross-linked in the same manner following treatment with elastase for 2 hours. A microtensile load cell was used to measure the Young modulus (stiffness) of each tissue.

RESULTS

Mean (standard deviation) Young modulus for controls (18.9 ± 3.6 MPa) was significantly higher than samples treated with elastase alone (6.6 ± 3.8 MPa, p <0.01). Samples that were treated with cross-linking after elastase had a mean (standard deviation) Young modulus of 26 ± 2.3 MPa, while those treated with cross-linking alone had a mean (standard deviation) Young modulus of 34 ± 0.15 MPa. The differences in stiffness between all groups were significant (p <0.01).

DISCUSSION

Treatment with elastase significantly reduces the stiffness of tarsal plates. This effect is reversed by cross-linking, raising the possibility of using this modality for the treatment of FES.

Mechanisms underlying the inhibitory effects of probucol on elastase-induced abdominal aortic aneurysm in mice

BACKGROUND AND PURPOSE

Abdominal aortic aneurysm (AAA) is a degenerative disease with irreversible and progressive dilation of the artery. But there are few options for efficacious treatment except for traditional surgery. Probucol has been widely applied to treat hyperlipidaemia and atherosclerosis in clinic, but whether it can protect against AAA remains unknown. In this study, the protective effects of probucol against AAA and its related mechanisms were explored.

EXPERIMENTAL APPROACH

The model of AAA was induced in mice by periaortic application of elastase (40 min) to the abdominal aorta. Probucol at different doses was administered by daily gavage, starting on the same day as AAA was induced, for 14 days. In vitro, cultures of rat vascular smooth muscle cells (VSMCs) were stimulated with TNF-α. Haem oxygenase (HO)-1 siRNA and HO-1 plasmid were used to regulate the expression or activity of HO-1 in the VSMCs and to clarify the effects of HO-1.

KEY RESULTS

Probucol dose-dependently prevented the development of AAA, reflected by decreased incidence of AAA, diameter of aortic dilation, elastin degradation, and infiltration of inflammatory cells. Probucol also protected VSMCs from oxidative injury and enhanced elastin biosynthesis. This anti-inflammatory effects of probucol on VSMCs were significantly decreased when HO-1 was inhibited by siRNA.

CONCLUSION AND IMPLICATIONS

Probucol protected against AAA through inhibiting the degradation of elastin induced by inflammation and oxidation and by facilitating the biosynthesis of elastin. HO-1 played a crucial role in the anti-inflammatory effects of probucol in VSMCs.

Long-Term Effects of the Abdominal Aortic Aneurysm Model in Rabbits Prepared by Pancreatic Elastase Combined With Angiotensin II

OBJECTIVE:

This study aimed to observe the effect of pancreatic elastase combined with angiotensin II on a stable rabbit abdominal aortic aneurysm model.

METHODS:

A total of 20 male New Zealand rabbits were randomly divided into groups A and B, with 10 rabbits per group. The rabbits in group A were given an intraperitoneal perfusion of pancreatic elastase, and the rabbits in group B were given continuous pumping of angiotensin II in addition to the operation of group A. Before the operation and at 2, 4, and 16 weeks postoperation, vascular color Doppler ultrasonography was performed, and blood samples were collected to measure the serum matrix metalloproteinase 9 (MMP9) and MMP2 levels. At 16 weeks postoperation, all rabbits in both groups were killed, and hematoxylin and eosin, Elastic-van-Gieson, Masson's, and immunohistochemical staining were performed for the vessel specimens.

RESULTS:

At 2 weeks postoperation, the aneurysm formation rates of the 2 groups were both 100%, and the average expansion rates of the aneurysm diameters were 85% and 93%, respectively; these differences were not significant ( P = .150 and P = .280, respectively). At 4 weeks postoperation, the aneurysm formation rates of the 2 groups were 71.4% and 100%, and the average expansion rates of the aneurysm diameter were 68% and 99%, respectively; the differences between the groups were significant ( P = .031 and P = .022, respectively). At 16 weeks postoperation, the aneurysm formation rates of the 2 groups were 14.3% and 100%, and the average expansion rates of the aneurysm diameter were 12% and 108%, respectively; the differences between the groups were significant ( P = .026 and P = .014, respectively).

CONCLUSION:

Compared to the abdominal aortic aneurysm modeling method in rabbits based on pancreatic elastase alone, the abdominal aortic aneurysm modeling method in rabbits using pancreatic elastase combined with angiotensin II maintained the morphology of the abdominal aortic aneurysm for a longer time, showing an important application value for the long-term observation of changes in abdominal aortic aneurysms.

Hemodynamics and pathology of an enlarging abdominal aortic aneurysm model in rabbits

Hemodynamics may play an essential role in the initiation and progression of abdominal aortic aneurysm (AAA). We aimed to study the mechanism of self-healing process by the changes of hemodynamics and pathology in an enlarging AAA in rabbits. Seventy-two rabbits were randomly divided into three groups. Rabbits underwent extrinsic coarctation and received a 10-minute elastase incubation in Group A and Group B. Absorbable suture used in Group A was terminated by balloon dilation at week 4. Diameter was measured after 1, 3, 5, and 15 weeks, computational fluid dynamics analysis was performed at week 3 and week 15. Rabbits were sacrificed after 1, 5, and 15 weeks for pathological and quantitative studies. The higher velocity magnitude, intensified bulk flow and obvious vortex formation were observed in Group A at week 3 instead of week 15. Both low wall shear stress and high relative residence time increased in Group B, however, high oscillatory shear index had relatively less increase compared with Group A. Aortic diameter reached a plateau at 5 weeks in Group A, which was significantly lower than in week 15 in Group B. Intimal hyperplasia, intima-media thickness increased significantly in Group A at week 5, significantly higher than in week 15 in Group B. Marked destruction of elastin fibers and smooth muscle cells occurred at week 1, and increased significantly at week 15 in Group A. Aneurysm exhibited strong expression of matrix metalloproteinase 9 and mouse anti-rabbit macrophage 11 at week 1, and showed a tendency to decrease. Matrix metalloproteinase 2 expression decreased significantly in Group B at week 15 compared with week 5 and Group A. In conclusion, the self-healing of rabbit AAA may attributed to the regeneration of smooth muscle cells. The turbulence flow caused by coarctation is associated with continuous growth of rabbit AAA and prevents the self-healing phenomenon.

TIMP‑3 suppresses the proliferation and migration of SMCs from the aortic neck of atherosclerotic AAA in rabbits, via decreased MMP‑2 and MMP‑9 activity, and reduced TNF‑α expression

The present study investigated the role of tissue inhibitor of matrix metalloproteinase‑3 (TIMP‑3) in regulating the proliferation, migration, apoptosis and activity of matrix metalloproteinase (MMP)‑2 and ‑9, during the development of an atherosclerotic abdominal artery aneurysm (AAA). Experiments were conducted using rabbit AAA neck (NA) smooth muscle cells (SMCs), to investigate the potential for TIMP‑3 to be used as a novel stent coating in preventing aortic dilation adjacent to the AAA. The atherosclerotic AAA model was induced in New Zealand white rabbits via a 6‑week high‑cholesterol diet, followed by incubation of the targeted aortic region with elastase. SMCs were isolated from the aorta adjacent to the aneurysm 30 days after AAA model induction, and stimulated with 3, 10, 30 or 100 ng/ml TIMP‑3. Cell proliferation was investigated using Cell Counting Kit‑8 reagent, migration was examined using a Boyden chamber assay and apoptotic rate was analyzed using the Annexin V‑fluorescein isothiocyanate Apoptosis Detection kit. Gelatin zymography and ELISA were used to measure the activity of MMP‑2 and MMP‑9, and the expression of tumor necrosis factor‑α (TNF‑α), respectively. Analysis of cell proliferation indicated that 10, 30 and 100 ng/ml TIMP‑3 reduced cell viability. Cell migration was decreased by 10, 30 and 100 ng/ml TIMP‑3. MMP‑2 activity was inhibited by 10, 30 and 100 ng/ml TIMP‑3, and MMP‑9 activity was suppressed by 30 and 100 ng/ml TIMP‑3. The protein levels of secreted TNF‑α were reduced by 10, 30 and 100 ng/ml TIMP‑3. The present study demonstrated the ability of 30 and 100 ng/ml TIMP‑3 to attenuate migration and proliferation, and to inhibit the activity of MMP‑2, MMP‑9 and TNF‑α secretion of NA SMCs. In conclusion, TIMP‑3 may be considered a potential therapeutic drug for use in a novel drug‑eluting stent, to attenuate the progressive dilation of the aortic NA.

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.

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.

Thermosensitive Hydrogel Containing Doxycycline Exerts Inhibitory Effects on Abdominal Aortic Aneurysm Induced By Pancreatic Elastase in Mice

Doxycycline (DOX) is reported to exert therapeutic effects against abdominal aortic aneurysm (AAA), a severe degenerative disease. In this study, a DOX hydrogel formulation of DOX/PECT^gel is studied, and its phase transition behavior and in vitro release profiles are explored. In addition, the anti-AAA effects and bioavailability of DOX/PECT^gel are evaluated in an elastase induced AAA mouse model. The results show that the phase transition temperature of 30% poly(e-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-undecanone) (PECT) solution is above 34 °C. In vitro release profiles of DOX/PECT^gel indicate a fast release of DOX at the first two days, followed by a slow and sustained release for 14 d. In vivo single-dose single subcutaneous injection of DOX/PECT^gel containing 8.4 or 4.2 mg mL^-1 DOX presents comparatively preventive effects on AAA, compared to intraperitoneal injections of DOX alone at a dose of 15 mg kg^-1 for seven injections, while DOX bioavailability of the DOX/PECT^gel treated groups is 1.39 times or 1.19 times of the DOX alone treated group, respectively.

Transauricular intra-arterial and intravenous digital subtraction angiography for abdominal aortic aneurysm imaging in a rabbit model

Aim

The aim of this study was to evaluate transauricular digital subtraction angiography (DSA) as an alternative to conventional intra-arterial DSA for rabbit abdominal aortic aneurysm (AAA).

Materials and methods

AAA models were created in 8 New Zealand white rabbits by sewing vein patch. The diameters of aortic arteries were measured by DSA via ear vein and ear central artery. The common carotid artery (CCA) was exposed and cannulated for DSA as conventional angiography. Diameter size was measured and compared.

Results

Aortic diameters, tested by DSA via ear vein, ear central artery and CCA were 7.9 ± 1.2 mm, 7.8 ± 1.0 mm and 7.9 ± 1.1 mm respectively, with no significant differences. Angiography via CCA as standard procedure, correlation in aneurysm neck diameter was r = 0.93 for IVDSA and r = 0.96 for angiography via central artery (P < 0.01); Correlation in AAA diameter was r = 0.99 for IVDSA and r = 0.99 for angiography via central artery (P < 0.0001).

Conclusions

Transauricular DSA shows good correlation to conventional DSA, can be used repeatedly with less invasiveness, and suitable for rabbit AAA follow-up study.

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Correlations of DSA via ear vein and ear central artery to conventional DSA were good.

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Transauricular DSA shows good correlation to conventional DSA.

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Transauricular DSA can be used repeatedly with less invasiveness, and suitable for rabbit AAA follow-up study.

A Novel Modification of the Murine Elastase Infusion Model of Abdominal Aortic Aneurysm Formation

BACKGROUND

To create a novel procedure that will decrease the mortality of experimental animals in the intraarterial infusion of elastase abdominal aortic aneurysm (AAA) model.

METHODS

Novel models were created by means of direct puncture in the infrarenal abdominal aortic aorta, intraluminal elastase in the 1-cm segment of abdominal aorta. Femoral artery cannula approach and infusing with elastase was considered as the traditional group and that infusing with saline solution as the control group. Survival rate, morphology and histology of aneurysms, and inflammation mediators were calculated.

RESULTS

Among the 36 rats, the average length from testicular arteries to left iliolumbar artery was 1.18 ± 0.22 cm, and 77.8% of them were longer than 1 cm. Procedure time was significantly shorter in novel group than that in 2 other groups (P = 0.006; P < 0.0001). During 24 hr postoperation, no death was observed in the novel group. Within 4 wk, survival rate in the control group was 60.6% and 80.8% in the novel group whereas 41.0% in the traditional group. Till the second week, all rats in the traditional and novel group had formed AAAs. And then, the survival rates and rupture rates of AAA between the 2 groups were similar within the following 2 wk (P = 0.487; P = 0.539). Inflammation degree and elastase content in intima media of aneurysms were similar (P = 0.720). However, Tumor necrosis factor alpha and Interleukin-1 beta levels were significantly lower in the novel group than those in the traditional group (P < 0.0001; P < 0.0001).

CONCLUSIONS

A novel rat AAA model was created by intraluminal elastase infusion through direct puncture the infrarenal aorta. This model is efficient and reliable, with a high survival rate and with similar morphology and histology of aortic aneurysms.

Effect of Low-Pressurized Perfusion with Different Concentration of Elastase on the Aneurysm Formation Rate in the Abdominal Aortic Aneurysm Model in Rabbits

Establishing an animal model of abdominal aortic aneurysm (AAA) is the key to study the pathogenesis and the pathophysiological features of AAAs. We investigated the effects of low-pressurized perfusion with different concentrations of elastase on aneurysm formation rate in the AAA model. Fifty male New Zealand white rabbits were randomly divided into A, B, C, D, and E groups. 10 μL of normal saline was perfused into the abdominal aorta in group A and 1 U/mL, 10 U/mL, 100 U/mL, or 200 U/mL of elastase was, respectively, perfused for the other four groups. All the animals were perfused for 7 min. Doppler ultrasound examinations of the abdominal aorta were performed before surgery and on day 14 after surgery. The rabbits were sacrificed and the perfused segment of the abdominal aorta was observed visually and after staining. The aneurysm formation rate of group A, group B, group C, group D, and group E was, respectively, 0%, 0%, 33.3%, 102.5–146.8%, and 241.5–255.2%. The survival rate of five groups was 90%, 90%, 90%, 90%, and 40%, respectively. So, we concluded that low-pressurized perfusion with 100 U/mL of elastase can effectively establish AAAs in rabbits with a high aneurysm formation rate.

Human Adipose-Derived Stem Cells Suppress Elastase-Induced Murine Abdominal Aortic Inflammation and Aneurysm Expansion Through Paracrine Factors

Abdominal aortic aneurysm (AAA) is a potentially lethal disease associated with immune activation-induced aortic degradation. We hypothesized that xenotransplantation of human adipose-derived stem cells (hADSCs) would reduce aortic inflammation and attenuate expansion in a murine AAA model. Modulatory effects of ADSCs on immune cell subtypes associated with AAA progression were investigated using human peripheral blood mononuclear cells (hPBMNCs) cocultured with ADSCs. Murine AAA was induced through elastase application to the abdominal aorta in C57BL/6 mice. ADSCs were administered intravenously, and aortic changes were determined by ultrasonography and videomicrometry. Circulating monocytes, aortic neutrophils, CD28- T cells, FoxP3+ regulatory T cells (Tregs), and CD206+ M2 macrophages were assessed at multiple terminal time points. In vitro, ADSCs induced M2 macrophage and Treg phenotypes while inhibiting neutrophil transmigration and lymphocyte activation without cellular contact. Intravenous ADSC delivery reduced aneurysmal expansion starting from day 4 [from baseline: 54.8% (saline) vs. 16.9% (ADSCs), n = 10 at baseline, n = 4 at day 4, p < 0.001], and the therapeutic effect persists through day 14 (from baseline: 64.1% saline vs. 24.6% ADSCs, n = 4, p < 0.01). ADSC administration increased aortic Tregs by 20-fold (n = 5, p < 0.01), while decreasing CD4+CD28- (-28%), CD8+CD28- T cells (-61%), and Ly6G/C+ neutrophils (-43%, n = 5, p < 0.05). Circulating CD115+CXCR1-LY6C+-activated monocytes decreased in the ADSC-treated group by day 7 (-60%, n = 10, p < 0.05), paralleled by an increase in aortic CD206+ M2 macrophages by 2.4-fold (n = 5, p < 0.05). Intravenously injected ADSCs transiently engrafted in the lung on day 1 without aortic engraftment at any time point. In conclusion, ADSCs exhibit pleiotropic immunomodulatory effects in vitro as well as in vivo during the development of AAA. The temporal evolution of these effects systemically as well as in aortic tissue suggests that ADSCs induce a sequence of anti-inflammatory cellular events mediated by paracrine factors, which leads to amelioration of AAA progression.

Inhibition of early AAA formation by aortic intraluminal pentagalloyl glucose (PGG) infusion in a novel porcine AAA model

Background

The vast majority of abdominal aortic aneurysms found in screening programs are small, and as no effective treatment exits, many will expand until surgery is indicated. Therefore, it remains intriguing to develop a safe and low cost treatment of these small aneurysms, that is able to prevent or delay their expansion.

In this study, we investigated whether intraluminal delivered pentagalloyl glucose (PGG) can impair the early AAA development in a porcine model.

Methods

The infrarenal aorta was exposed in thirty pigs. Twenty underwent an elastase based AAA inducing procedure and ten of these received an additional intraluminal PGG infusion. The final 10 were sham operated and served as controls.

Results

All pigs who only had an elastase infusion developed macroscopically expanding AAAs. In pigs treated with an additional PGG infusion the growth rate of the AP-diameter rapidly returned to physiological values as seen in the control group. In the elastase group, histology revealed more or less complete resolution of the elastic lamellae in the media while they were more abundant, coherent and structurally organized in the PGG group. The control group displayed normal physiological growth and histology.

Conclusion

In our model, intraluminal delivered PGG is able to penetrate the aortic wall from the inside and impair the early AAA development by stabilizing the elastic lamellae and preserving their integrity. The principle holds a high clinical potential if it can be translated to human conditions, since it, if so, potentially could represent a new drug for stabilizing small abdominal aneurysms.

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Pentagalloyl glucose impairs the early AAA development in a porcine model.

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Pentagalloyl glucose stabilizes arterial elastic lamellae and preserves their integrity.

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Pentagalloyl glucose can penetrate the arterial wall in large AAA prone arteries from the inside.

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Pentagalloyl glucose, a potential new drug for stabilizing small abdominal aneurysms.

Recent Advances in the Development of Experimental Animal Models Mimicking Human Aortic Aneurysms

Aortic aneurysm is a common and life-threatening disease that can cause death from rupture. Current therapeutic options are limited to surgical or endovascular procedures because no pharmacological approaches have been proven to decrease the chance of expansion or rupture. The best approach to the management of aortic aneurysm would be the understanding and prevention of the processes involved in disease occurrence, progression, and rupture. There is a need for animal models that can reproduce the pathophysiological features of human aortic aneurysm, and several such models have been studied. This review will emphasize recent advances in animal models used in the determination of mechanisms and treatments of aortic aneurysms.

Different long-term outcomes of abdominal aortic aneurysm and intracranial aneurysm models: hemodynamic change may also play an essential role in the initiation and progression of abdominal aortic aneurysm in rabbits

Self-healing phenomenon was found in the periarterial elastase-induced abdominal aortic aneurysm (AAA) in rabbit. This kind of aneurysm model does not progress and heals spontaneously in the long term, which is quite different from the performance of AAA disease in human. In order to better mimic human AAA and overcome this shortcoming of traditional AAA model in rabbit, we studied the pathogenesis of cerebral aneurysm (CA) model in small animal, which shows an excellent long-term patency and progressive enlargement. We found that hemodynamic conditions, such as turbulence flow, high blood flow, and shear stress, play an important role in the formation and progression of CA. So, we hypothesize that hemodynamic change may also play an essential role in the initiation and progression of rabbit AAA, and self-healing will be overcome if hemodynamic condition changes by coarctation of infra-renal aorta after elastase incubation.