Initial steps in the unifying theory of the pathogenesis of artery aneurysms

Apolipoprotein E (ApoE) Rescues the Contractile Smooth Muscle Cell Phenotype in Popliteal Artery Aneurysm Disease

Popliteal artery aneurysm (PAA) is the most frequent peripheral aneurysm, primarily seen in male smokers with a prevalence below 1%. This exploratory study aims to shed light on cellular mechanisms involved in PAA progression. Sixteen human PAA and eight non-aneurysmatic popliteal artery samples, partially from the same patients, were analyzed by immunohistochemistry, fluorescence imaging, Affymetrix mRNA expression profiling, qPCR and OLink proteomics, and compared to atherosclerotic (n = 6) and abdominal aortic aneurysm (AAA) tissue (n = 19). Additionally, primary cell culture of PAA-derived vascular smooth muscle cells (VSMC) was established for modulation and growth analysis. Compared to non-aneurysmatic popliteal arteries, VSMCs lose the contractile phenotype and the cell proliferation rate increases significantly in PAA. Array analysis identified APOE higher expressed in PAA samples, co-localizing with VSMCs. APOE stimulation of primary human PAA VSMCs significantly reduced cell proliferation. Accordingly, contractile VSMC markers were significantly upregulated. A single case of osseous mechanically induced PAA with a non-diseased VSMC profile emphasizes these findings. Carefully concluded, PAA pathogenesis shows similar features to AAA, yet the mechanisms involved might differ. APOE is specifically higher expressed in PAA tissue and could be involved in VSMC phenotype rescue.

Magnetic resonance imaging study of safe needling depth and angulation for acupuncture at BL40

OBJECTIVES

The objectives of this study were to identify the mean safe needling depth and angle at BL40 between subjects, taking into account variables including sex and body mass index (BMI).

METHODS

One hundred and twenty-four participants who had undergone magnetic resonance imaging (MRI) examination of the knee region for clinical indications were included in this study. BL40 needling sites were localized by World Health Organization (WHO) standards and were measured by MRI. As much as 70% of the value of AN (from the needle insertion point to the popliteal artery) was considered to represent the safe depth, and angle alpha between the BL40 straight line and the AN line was regarded as the safe angle.

RESULTS

Overall, mean safe depth regardless of BMI and sex was 18.51 ± 3.56 mm (95% confidence interval (CI), 17.88%-19.14%). Mean safe depth was 17.24 ± 3.14 mm in the low and normal BMI group, 18.76 ± 2.90 mm in the overweight group, and 22.01 ± 3.71 mm in the obese group. Thirteen patients (10.5%) had internal deviation of angle alpha (95% CI, 5.6%-15.3%), while 111 patients (89.5%) had external deviation (95% CI, 84.7%-94.4%). The mean internal and external deviations of angle alpha were 8.78° ± 2.92° (95% CI, 7.01°-10.55°) and 9.75° ± 3.46° (95% CI, 9.10°-10.41°), respectively.

CONCLUSION

We would suggest that, when using a straight needle insertion at BL40, it is safe to advance a 25-mm needle approximately 12.5 mm, and 17.5 mm should be safe for patients with BMI greater than 28 kg/m². Practitioners should decrease the depth of penetration when treating patients of low body weight or height.

High serum thrombospondin-1 concentration is associated with slower abdominal aortic aneurysm growth and deficiency of thrombospondin-1 promotes angiotensin II induced aortic aneurysm in mice

Abdominal aortic aneurysm (AAA) is a common age-related vascular disease characterized by progressive weakening and dilatation of the aortic wall. Thrombospondin-1 (TSP-1; gene Thbs1) is a member of the matricellular protein family important in the control of extracellular matrix (ECM) remodelling. In the present study, the association of serum TSP-1 concentration with AAA progression was assessed in 276 men that underwent repeated ultrasound for a median 5.5 years. AAA growth was negatively correlated with serum TSP-1 concentration (Spearman's rho -0.129, P=0.033). Men with TSP-1 in the highest quartile had a reduced likelihood of AAA growth greater than median during follow-up (OR: 0.40; 95% confidence interval (CI): 0.19-0.84, P=0.016, adjusted for other risk factors). Immunohistochemical staining for TSP-1 was reduced in AAA body tissues compared with the relatively normal AAA neck. To further assess the role of TSP-1 in AAA initiation and progression, combined TSP-1 and apolipoprotein deficient (Thbs1-/-ApoE-/-, n=20) and control mice (ApoE-/-, n=20) were infused subcutaneously with angiotensin II (AngII) for 28 days. Following AngII infusion, Thbs1-/- ApoE-/- mice had larger AAAs by ultrasound (P=0.024) and ex vivo morphometry measurement (P=0.006). The Thbs1-/-ApoE-/- mice also showed increased elastin filament degradation along with elevated systemic levels and aortic expression of matrix metalloproteinase (MMP)-9. Suprarenal aortic segments and vascular smooth muscle cells (VSMCs) isolated from Thbs1-/-ApoE-/- mice showed reduced collagen 3A1 gene expression. Furthermore, Thbs1-/-ApoE-/- mice had reduced aortic expression of low-density lipoprotein (LDL) receptor-related protein 1. Collectively, findings from the present study suggest that TSP-1 deficiency promotes maladaptive remodelling of the ECM leading to accelerated AAA progression.

Role of molecular imaging with positron emission tomographic in aortic aneurysms

Aortic aneurysms (AA) are often asymptomatic before the occurrence of acute, potentially fatal complications including dissection and/or rupture. Beyond aortic size, the ability to assess aortic wall characteristics and processes contributing to aneurysm development may allow improved selection of patients who may benefit from prophylactic surgical intervention. Current risk stratification for aneurysms relies upon routine noninvasive imaging of aortic size without assessing the underlying pathophysiologic processes, including features such as inflammation, which may be associated with aneurysm development and progression. The use of molecular imaging modalities with positron emission tomographic (PET) scan allows characterization of aortic wall inflammatory activity. Elevated uptake of Fuorine-2-deoxy-D-glucose (FDG), a radiotracer with elevated avidity in highly-metabolic cells, has been correlated with the development and progression of both abdominal and thoracic AA in a number of animal models and clinical studies. Other novel PET radiotracers targeting matrix metalloproteinases (MMPs), mitochondrial translocator proteins (TSPO) and endothelial cell adhesion molecules are being investigated for clinical utility in identifying progression of disease in AA. By further defining the activation of molecular pathways in assessing aortic regions at risk for dilatation, this imaging modality can be integrated into future clinical decision-making models.

Role of Apoptosis and Proteolysis in the Pathogenesis of Iliac Artery Aneurysms

The objective of this study was to investigate the role of inflammation, programmed cell death, its molecular modulators, and proteolysis in the pathogenesis of iliac artery aneurysms (IAAs). Nineteen IAA specimens were obtained from patients undergoing elective surgical repair. All were males with ages ranging from 55 to 85 years (mean 73 years). Controls were iliac arteries ( n = 6) retrieved from surgical patients without aneurysmal disease. Standard histochemical techniques were used to assess elastic lamellae fragmentation and inflammatory infiltrate in aneurysmal and normal tissues. Identification of different types of cells in the aneurysm wall and detection of death-promoting molecules, Fas, p53, perforin, apoptosis-mediating bcl-2 family proteins, apoptotic death substrate, and poly(adenosine diphosphate–ribose) polymerase were performed immunohistochemically. Apoptosis was detected by terminal deoxynucleotidyl transferase–mediated digoxigenin–deoxyuridine triphosphate nick end-labeling (TUNEL) assay and caspase activity. Proteolytic activity was determined by 10% gelatin gel zymography. There is a conspicuous disruption and fragmentation of elastic lamellae in IAAs compared with normal arteries. Increased gelatinolytic activity was observed at 92, 72, and 67 kDa in the aneurysmal tissues. There was a significant loss of vascular smooth muscle cells (VSMCs) in the IAA walls compared with normal arteries ( p < .02). Large numbers of inflammatory cells were observed in the IAA specimens ( p = .01). Only aneurysmal arteries showed CD8+ T cells expressing death-promoting molecules. CD3+, CD8+, CD20+, CD30+, and CD68+ immunoreactive cells were significantly more prominent in the aneurysmal tissues than in the control arteries. There was a significant increase in the number of cells undergoing apoptosis in aneurysmal tissue than in the normal vessels ( p < .02), as well as in the expression of bax, p53, CPP-32, and Fas. Apoptotic cells and proapoptotic molecules predominantly localized to the inflammatory infiltrate. VSMC apoptosis was significant in IAAs. The data confirm the architectural disruption of the IAA wall and illustrate an apparent biologic response involving inflammatory infiltrate, apoptosis, and signaling molecules capable of initiating cell death. In addition to compromising the mechanical integrity of the vessel wall, VSMC loss may contribute to imbalance in the protein profile, accelerating extracellular matrix degradation that could favor IAA development.

Novel Evidence of PLC δ2 Involvement in the Regulation of the Differential Evolution of Aneurysms

The biological and molecular mechanisms which are responsible for the formation and possible evolution of human aneurysms are unknown. Previous investigations have pointed to the possible involvement of inositol specific-phospholipase C (PLC) in the mechanisms related to the formation or evolution of intracranial aneurysms, but, thus far, a relationship of one or more PLC isoforms with the biological signals influencing the fate of this lesion has not been demonstrated. The aim of this study was to investigate the expression, activity and possible modification of PLC isoforms in intracranial aneurysms in patients undergoing elective surgical repair after casual identification of unruptured aneurysms, or during emergency surgical repair of ruptured aneurysms. PLC and proliferating cell nuclear antigen (PCNA) expressions were detected by immunoistochemical analysis; PLC activity was obtained by measuring its hydrolytic activity on labelled PIP2; PKC activity was measured by total kinase activity assay. Results indicated no substantial differences between controls and aneurysms, with the only exception being PLC 52 which was nearly absent in controls and ruptured aneurysms, while strongly expressed and functionally active in almost all unruptured aneurysms. In addition, its expression always correlated with the proliferation cell marker PCNA, while its specific activity always correlated to PKC activity. PLC δ2 distribution, regulation and role in human tissues are still unknown Therefore, although preliminary, these data provide a novel insight into the signalling machinery influencing the aneurismal progression.

(18)F-FDG PET scanning of abdominal aortic aneurysms and correlation with molecular characteristics: a systematic review

Purpose

The purpose of this study is to give an overview of studies investigating the role of fludeoxyglucose F18 (¹⁸F-FDG) positron emission tomography (PET) scanning in patients with aortic aneurysms with a focus on molecular characteristics of the aneurysm wall.

Methods

MEDLINE, EMBASE, and the Cochrane database were searched for relevant articles. After inclusion and exclusion, we selected 18 relevant articles reporting on ¹⁸F-FDG PET scanning of aortic aneurysms.

Results

The sample size of studies is limited, and there are no standardized imaging protocols and quantification methods. ¹⁸F-FDG PET scanning was shown to display molecular characteristics of the aortic wall. Different studies showed contradictory findings of aortic ¹⁸F-FDG uptake in aneurysm patients compared to controls.

Conclusions

Non-invasively determining molecular characteristics of aortic wall weakening might lead to better rupture and growth prediction. This might influence the decision of the surgeon between conservative and surgical treatment of aneurysms. To date, there is conflicted evidence regarding the use of ¹⁸F-FDG PET scanning to predict aneurysm rupture and growth. The role of ¹⁸F-FDG PET scanning in rupture risk prediction needs to be further investigated, and standardized imaging protocols and quantification methods need to be implemented.

Electronic supplementary material

The online version of this article (doi:10.1186/s13550-015-0153-8) contains supplementary material, which is available to authorized users.

Autoradiography screening of potential positron emission tomography tracers for asymptomatic abdominal aortic aneurysms

OBJECTIVE

The aetiology and early pathophysiological mechanisms of aortic aneurysm formation are still unknown and challenging to study in vivo. Positron emission tomography (PET) is a potentially valuable instrument for non-invasive in vivo pathophysiological studies. No specific tracer to identify the pathophysiological process of aneurysmal dilatation is yet available, however. The aim of this study was to explore if different PET tracers could be useful to image aneurysmal disease.

METHODS AND RESULTS

Human aneurysmal aortic tissue, collected during elective resection of abdominal aortic aneurysm (AAA) of asymptomatic patients, was investigated in vitro by means of autoradiography with [(68)Ga]CRP-binder targeting C-reactive protein, [(11)C]DAA1106 targeting translocator protein (18 kDa), [(11)C]D-deprenyl with unknown target receptor, [(11)C]deuterium-L-deprenyl targeting astrocytes, [(18)F]fluciclatide targeting integrin αVβ3, [(68)Ga]IMP461 and bi-specific antibody TF2 052107 targeting carcinoembryonic antigen, [(18)F]F-metomidate targeting mitochondrial cytochrome P-450 species in the adrenal cortex, and [(18)F]vorozole targeting aromatase. Of the investigated tracers, only [(18)F]fluciclatide exhibited specific binding, whereas the other PET tracers failed to show specific uptake in the investigated tissue and are probably not useful for the intended purpose.

CONCLUSION

It seems likely that αVβ3 integrin expression in AAA can be visualized with PET and that the αVβ3 selective tracer, [(18)F]fluciclatide, may be suitable for in vivo molecular imaging of asymptomatic AAA. Additional evaluation of [(18)F]fluciclatide and αVβ3 integrin expression in AAA will be performed in vitro as well as in vivo.

Age-related telomere uncapping is associated with cellular senescence and inflammation independent of telomere shortening in human arteries

Arterial telomere dysfunction may contribute to chronic arterial inflammation by inducing cellular senescence and subsequent senescence-associated inflammation. Although telomere shortening has been associated with arterial aging in humans, age-related telomere uncapping has not been described in non-cultured human tissues and may have substantial prognostic value. In skeletal muscle feed arteries from 104 younger, middle-aged, and older adults, we assessed the potential role of age-related telomere uncapping in arterial inflammation. Telomere uncapping, measured by p-histone γ-H2A.X (ser139) localized to telomeres (chromatin immunoprecipitation; ChIP), and telomeric repeat binding factor 2 bound to telomeres (ChIP) was greater in arteries from older adults compared with those from younger adults. There was greater tumor suppressor protein p53 (P53)/cyclin-dependent kinase inhibitor 1A (P21)-induced senescence, measured by P53 bound to P21 gene promoter (ChIP), and greater expression of P21, interleukin 8, and monocyte chemotactic protein 1 mRNA (RT-PCR) in arteries from older adults compared with younger adults. Telomere uncapping was a highly influential covariate for the age-group difference in P53/P21-induced senescence. Despite progressive age-related telomere shortening in human arteries, mean telomere length was not associated with telomere uncapping or P53/P21-induced senescence. Collectively, these findings demonstrate that advancing age is associated with greater telomere uncapping in arteries, which is linked to P53/P21-induced senescence independent of telomere shortening.

Hybrid Approach for Treatment of Behind the Knee Popliteal Artery Aneurysms

We describe herein a combined approach to the treatment of popliteal artery aneurysms (PAA) that averts extensive dissections and potential blood loss particularly in cases of behind-the-knee aneurysms. Over the last 4 years, 13 patients (12 males) with mean age of 75 ± 8 years were treated for PAAs at our institution with a combined surgical and endovascular approach. The mean size of popliteal aneurysms was 2.9 cm ± 1.7 cm. One of the 13 cases (8%) was performed for acute ischemia and an additional 5 (38%) for claudication. All operations were performed under general anesthesia in supine position. Vein conduits (eight ipsilateral great saphenous veins, two contralateral great saphenous veins and one arm vein) were utilized for 11 bypasses. Of these, eight were from superficial femoral artery (SFA) to below the knee popliteal artery, two popliteal to popliteal and one SFA to posterior tibial artery. In addition, two expanded polytetrafluoroethylene femoral popliteal bypasses were performed. The distal anastomosis was performed after the popliteal artery was ligated distal to the aneurysm. Next, coil embolization of the aneurysmal sac was performed under fluoroscopic or ultrasound guidance. Coils were embolized through a 5F sheath. Lastly, the popliteal artery was ligated distal to the proximal anastomosis. Completion studies were obtained with duplex in six cases and arteriography in the remaining five cases. Mean follow-up was 11.6 months ± 9.6. One bypass occluded in 2 months after surgery. One patient demonstrated continued growth of his aneurysm despite coil embolization twice and underwent an open ligation of the branches perfusing the aneurysm from within the sac through a posterior approach. This approach may be particularly useful for PAAs located behind the knee where optimal surgical exposure is often difficult and the collateral circulation is abundant. The proposed technique is simple, effective and averts extensive dissections required to minimize blood loss.

Enhanced expression and activation of pro-inflammatory transcription factors distinguish aneurysmal from atherosclerotic aorta: IL-6- and IL-8-dominated inflammatory responses prevail in the human aneurysm

Inflammation plays a key role in the pathogenesis of an AAA (abdominal aortic aneurysm); however, the nature of the inflammatory factors and cellular response(s) involved in AAA growth is controversial. In the present study, we set out to determine the aortic levels of inflammatory cytokines in relation to downstream inflammatory transcription factors and cellular responses. A comparison of AAA wall samples with atherosclerotic wall samples taken from the same aortic region allowed AAA-specific inflammatory parameters to be identified that distinguish AAAs from ASD (aortic atherosclerotic disease). RT-PCR (real-time PCR), ELISA, Western blotting and immunohistochemistry were combined to assess cytokines and transcription factors at the mRNA and protein level, and their activation status. Compared with ASD, inflammatory parameters associated with Th1-type [T-bet, IL (interleukin)-2, IFN-gamma (interferon-gamma), TNF-alpha (tumour necrosis factor-alpha), IL-1alpha and cytotoxic T-cells] and Th2-type [GATA3, IL-4, IL-10, IL-13 and B-cells] responses were all increased in AAA samples. Evaluation of major downstream inflammatory transcription factors revealed higher baseline levels of C/EBP (CCAAT/enhancer-binding protein) alpha, beta and delta in the AAA samples. Baseline p65 NF-kappaB (nuclear factor kappaB) and c-Jun [AP-1 (activator protein-1)] levels were comparable, but their activated forms were strongly increased in the AAA samples. Downstream target genes of p65 NF-kappaB, c-Jun, IL-6 and IL-8 were hyperexpressed. Molecular and cellular processes associated with IL-6 and IL-8 hyperactivation were enhanced in the AAA samples, i.e. the expression of phospho-STAT-3 (signal transducer and activator of transcription-3) and perforin were elevated, and the content of plasma cells, neutrophils and vasa vasorum was increased. In conclusion, our findings demonstrate that an AAA is a general inflammatory condition which is characterized by enhanced expression and activation of pro-inflammatory transcription factors, accompanied by IL-6 and IL-8 hyperexpression and exaggerated downstream cellular responses, which together clearly distinguish an AAA from ASD.

Nitrogen-rich coatings for promoting healing around stent-grafts after endovascular aneurysm repair

Complications following endovascular aneurysm repair (EVAR) are related to deficient healing around the stent-graft (SG). New generations of SG with surface properties that foster vascular repair could overcome this limitation. Our goal was to evaluate the potential of a new nitrogen-rich plasma-polymerised biomaterial, designated PPE:N, as an external coating for polyethylene terephtalate (PET)- or polytetrafluoro-ethylene (PTFE)-based SGs, to promote healing around the implant. Thin PPE:N coatings were deposited on PET and PTFE films. Then, adhesion, growth, migration and resistance to apoptosis of vascular smooth muscle cells (VSMCs) and fibroblasts, as well as myofibroblast differentiation, were assessed in vitro. In another experimental group, chondroitin sulphate (CS), a newly described mediator of vascular repair, was added to normal culture medium, to search for possible additional benefit. PPE:N-coatings, especially on PET, increased and accelerated cell adhesion and growth, compared with control PET and with standard polystyrene culture plates (PCP). PPE:N was also found to increase the resistance to apoptosis in VSMC, an important finding as aneurysms are characterised by VMSC depletion caused by a pro-apoptotic phenotype. Addition of CS in solution further increased migration and resistance to apoptosis. In conclusion, PPE:N-coating and/or CS could promote vascular repair around SGs following EVAR.

Implant Degradation and Poor Healing After Endovascular Repair of Abdominal Aortic Aneurysms: An Analysis of Explanted Stent-Grafts

PURPOSE

To study explanted stent-grafts to achieve a better understanding of the mechanisms of failure after endovascular treatment of abdominal aortic aneurysms (AAA).

METHODS

Twelve stent-grafts were harvested at autopsy (n=3) or during surgical conversion (n=9). Device alterations were investigated by macroscopic examination, radiography, and surface analysis techniques. Healing around the implants was studied via histology and immunohistochemistry, with particular attention to the stent-graft/tissue interface.

RESULTS

Degradation was more important with Vanguard stent-grafts (off the market) than with AneuRx and Talent stent-grafts, but rupture of nitinol wires and poor surface finish in Talent stent-grafts raise concern about their corrosion resistance and long-term stability. Poor healing was observed around stent-grafts even after several years of implantation, with absence of vascular smooth muscle cells, fibroblasts, and collagen formation. In addition to the well-known foreign body reaction around the graft, numerous polymorphonuclear cells characteristic of the first step of healing were present in tissues around stent-grafts retrieved at surgical conversion. Factors explaining the lack of tissue organization around stent-grafts are discussed.

CONCLUSION

The long-term stability of implants remains a concern and requires more transparency from manufacturers regarding the surface properties of their devices. Lack of neointima formation impairs biological fixation of the implant to the vessel wall, leading to possible endoleaks and migration. New-generation stent-grafts promoting biological fixation should be developed to improve clinical outcomes of this minimally invasive treatment.

Popliteal Artery Aneurysms: Tried, True, and New Approaches to Therapy

Popliteal artery aneurysms are the most common peripheral aneurysm. They are associated with concomitant contralateral popliteal aneurysms and abdominal aortic aneurysms. Patients with unrecognized aneurysms may present with acute limb ischemia and potential for limb loss. Use of preoperative lytic therapy to improve distal runoff prior to exclusion and bypass has significantly improved the outcome from acute thrombosis. Long-term follow-up has shown that both proximal and distal ligation of the aneurysm are important because a thrombosed aneurysm may begin to enlarge after a long period of quiescence. Popliteal aneurysms are now being treated with covered stents. This article delineates the current evaluation, preoperative planning, and surgical and endovascular approaches to this disease. With proper diagnosis and repair, excellent limb salvage and postoperative function has become the norm.

Mycotic Aneurysm of the Celiac Trunk: From Early CT Sign to Rupture

We present a case of the rapid development and rupture of a mycotic celiac trunk aneurysm. Initially on multislice computed tomography (ms-CT) there was a normal celiac trunk with minimal haziness of the surrounding fat. Only 2 weeks later the patient went into hypovolemic shock due to a ruptured celiac aneurysm. Although aneurysms of the visceral arteries are rare, they are of major clinical importance as they carry a life-threatening risk of rupture. This case illustrates the use of ms-CT in detecting and evaluating visceral aneurysms, in order to prevent emergency operation.

Fasudil, a Rho-kinase inhibitor, attenuates angiotensin II-induced abdominal aortic aneurysm in apolipoprotein E-deficient mice by inhibiting apoptosis and proteolysis

BACKGROUND

Angiotensin II (Ang II) accelerates atherosclerosis and induces abdominal aortic aneurysm (AAA) in an experimental mouse model. Agonism of a G protein-coupled receptor by Ang II activates Rho-kinase and other signaling pathways and results in activation of proteolysis and apoptosis. Enhanced proteolysis and smooth muscle cell apoptosis are important mechanisms associated with AAA. In this study, we tested the hypothesis that fasudil, a Rho-kinase inhibitor, could attenuate Ang II-induced AAA formation by inhibiting vascular wall apoptosis and extracellular matrix proteolysis.

METHODS AND RESULTS

Six-month-old apolipoprotein E-deficient mice were infused with Ang II (1.44 mg x kg(-1) x d(-1)) for 1 month. Animals were randomly assigned to treatment with fasudil (136 or 213 mg x kg(-1) x d(-1) in drinking water) or tap water. Ang II infusion induced AAA formation in 75% of the mice, which was accompanied by an increase in proteolysis detected by zymographic analysis and quantified by active matrix metalloproteinase-2 activity, as well as apoptosis detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and quantified by both caspase-3 activity and histone-associated DNA fragmentation. The level of DNA fragmentation in the suprarenal aorta correlated with AAA diameter. Ang II also increased atherosclerotic lesion area and blood pressure. Fasudil treatment resulted in a dose-dependent reduction in both the incidence and severity of AAA. At the higher dose, fasudil decreased AAA by 45% while significantly inhibiting both apoptosis and proteolysis, without affecting atherosclerosis or blood pressure.

CONCLUSIONS

These data demonstrate that inhibition of Rho-kinase by fasudil attenuated Ang II-induced AAA through inhibition of both apoptosis and proteolysis pathways.

Popliteal aneurysm as a cause of leg pain in a geriatric patient

OBJECTIVE

To discuss the management of a patient with unilateral lower extremity pain as a consequence of a popliteal aneurysm.

CLINICAL FEATURES

An 85-year-old male had difficulty in ambulating due to low back and lower extremity pain. Standard tests demonstrated and reproduced pain at the lower back while inspection, palpation, and auscultation revealed a pulsatile mass in the popliteal fossa of the right knee.

INTERVENTION AND OUTCOME

Specific joint manipulation for relief of low back pain was performed. Comanagement of the patient with a vascular surgeon and subsequent surgical intervention resulted in relief of lower extremity pain.

CONCLUSION

Resolution of pain and guarded gait was accomplished by a multidisciplinary approach combining conservative care and invasive techniques.

Ultrasound evaluation of abdominal aortic and iliac aneurysms and mesenteric ischemia

The role of US in imaging of the abdominal vasculature has broadened over recent years. Long considered the modality of choice in the detection of AAA, its use has expanded to diagnosing and monitoring IAAs and PAAs, screening for mesenteric ischemia, and posttreatment monitoring of endovascular stents.

Influence of intraluminal thrombus on structural and cellular composition of abdominal aortic aneurysm wall

INTRODUCTION

It has been suggested that the intraluminal thrombus of abdominal aortic aneurysm (AAA) affects the underlying vessel wall. Aneurysm enlargement has been associated with growth of thrombus, and rupture has been proposed to occur after bleeding into the thrombus. To examine how thrombus affects the vessel wall, we compared the morphology of aneurysm wall covered with thrombus with wall segments exposed to flowing blood. Material and methods Sixteen patients (14 men, 2 women; age range, 56-79 years) undergoing elective repair of AAA, where computed tomography scans showed thrombus and segments of the aneurysm wall exposed to flowing blood, were included in the study. Specimens from the aneurysm were taken for light and electron microscopy. Masson trichrome staining was performed for wall thickness determination and demonstration of collagen, and Weigert-van Gieson staining for elastin. The cellular composition was analyzed by immunohistochemistry with antibodies against CD3 for T cells, CD4 for T helper cells, CD8 for T cytotoxic cells, CD20 for B cells, CD68 for macrophages, and smooth muscle alpha-actin for smooth muscle cells (SMCs). Caspase-3 staining and TUNEL analysis were performed to evaluate apoptosis.

RESULTS

The aneurysm wall covered with thrombus was thinner and contained fewer elastin fibers, and the few that were found were often fragmented. This part of the wall also contained fewer SMCs and more apoptotic nuclei than the wall exposed to flowing blood. Clusters of inflammatory cells were detected in the media of the aneurysm wall and in higher numbers in the parts covered with thrombus. Electron microscopy showed that the aneurysm wall without thrombus contained a dense collagenous matrix with differentiated SMCs. In the segment covered with thrombus, SMCs were more dedifferentiated (synthetic) and apoptotic or necrotic. There were also an increased number of inflammatory cells located in close contact with SMCs in various stages of apoptosis.

CONCLUSION

The aneurysm wall covered with thrombus is thinner and shows more frequent signs of inflammation, apoptosis of SMCs, and degraded extracellular matrix. These findings suggest that thrombus formation and accumulation of inflammatory cells may perturb the structural integrity and stability of the vessel wall and thereby increase the risk for aneurysm rupture.

Differential expression of YAMA/CPP-32 by T lymphocytes in popliteal artery aneurysm

BACKGROUND

We have previously demonstrated that programmed cell death, proteolytic activity, and inflammatory infiltrate in the aneurysmal wall may have a role in the pathogenesis of popliteal artery aneurysms (PAA). This investigation examines the expression of a cell death-promoting molecule, a cysteine protease, YAMA/CPP-32 in a series of PAA specimens.

METHODS

Twenty PAA specimens were obtained from patients undergoing elective surgical repair. Normal controls were popliteal arteries obtained from patients without PAA who were undergoing infrainguinal bypass surgery (n = 8). Standard histochemistry techniques were used to assess inflammatory infiltrates in PAA. Expression of apoptosis-promoting molecule, CPP-32, vascular smooth muscle cells (VSMC), macrophages, and T lymphocytes was detected by immunohistochemistry.

RESULTS

There is a conspicuous disruption and fragmentation of elastic lamellae and increased inflammatory infiltrate in the PAA as compared with normal arteries. As compared with normal popliteal artery tissues, the PAA demonstrated large number of cells immunopositive for CPP-32 (60.45 +/- 4.25% P < 0.05). This study revealed significantly increased expression of CPP-32 in the T-cell population of the PAA as compared with the other cells (P < 0.01). Dual immunolabeling and investigation of serial sections demonstrated that co-expression of CPP-32 was maximum in the CD8+ subset (37 +/- 3.3% of the total CPP-32 immunoreactive cells identified).

CONCLUSIONS

The data emphasize that the inflammatory infiltrate in the PAA walls has a significant role in the pathogenesis of this vascular disorder. Cells expressing death-promoting molecules are present in large numbers and are predominantly T lymphocytes in PAA. In addition to compromising the mechanical integrity of the vessel wall, apoptosis in the inflammatory infiltrate may contribute to the production of cytokines, activation of other signaling molecules such as stress proteins that could eventually favor PAA development.

Small popliteal artery aneurysms: are they clinically significant?

OBJECTIVE

We undertook this study to determine whether popliteal artery aneurysm diameter correlates with initial symptoms and presence of associated occlusive disease.

METHODS

Duplex arteriography before infrainguinal revascularization in 500 lower extremities enabled diagnosis of 34 popliteal aneurysms in 25 patients (24 male, 1 female) over the last 4 years. Fourteen patients (41%) had no symptoms (group 1) and 20 (59%) had symptoms (group 2) of severe claudication (n = 8), acute ischemia (n = 6), rest pain (n = 2), and tissue loss (n = 4). We compared clinical presentation with popliteal artery diameter, prevalence of thrombosis, and presence of associated occlusive disease.

RESULTS

Popliteal artery aneurysm diameter averaged 2.8 +/- 0.7 cm (range, 1.8-4.5 cm) in group 1 and 2.2 +/- 0.8 cm (range, 1.3-4.0 cm) in group 2 (P <.03). Popliteal aneurysm thrombosis was present in 7 of 20 limbs in group 2. Four of these patients also had ipsilateral superficial femoral artery thrombosis. Evaluation of the infrapopliteal arteries in group 1 showed three-vessel runoff in 7 limbs, two-vessel runoff in 3 limbs, one-vessel runoff in 2 limbs, and no vessel runoff in 2 limbs. However, all infrapopliteal arteries were either occluded or significantly stenotic in 14 limbs (70%). In group 2, one-vessel runoff was observed in 5 limbs, and two-vessel runoff in 1 limb.

CONCLUSIONS

Smaller popliteal artery aneurysm was associated with higher incidence of thrombosis, clinical symptoms, and distal occlusive disease. Liberal use of duplex scanning in this setting may have accounted for the increased awareness that small popliteal artery aneurysms can thrombose and present with severe ischemia.