Metformin Inhibits Abdominal Aortic Aneurysm Formation through the Activation of the AMPK/mTOR Signaling Pathway.

BACKGROUND AND OBJECTIVE: Epidemiological evidence suggests that the antidiabetic drug metformin (MET) can also inhibit abdominal aortic aneurysm (AAA) formation. However, the underlying protective mechanism remains unknown. It has been reported that phosphorylated AMP-activated protein kinase (AMPK) levels are significantly lower in AAA tissues than control aortic tissues. AMPK activation can inhibit the downstream signaling molecule called mechanistic target of rapamycin (mTOR), which has also been reported be upregulated in thoracic aneurysms. Thus, blocking mTOR signaling could attenuate AAA progression. MET is a known agonist of AMPK. Therefore, in this study, we investigated if MET could inhibit formation of AAA by activating the AMPK/mTOR signaling pathway. MATERIALS AND METHODS: The AAA animal model was induced by intraluminal porcine pancreatic elastase (PPE) perfusion in male Sprague Dawley rats. The rats were treated with MET or compound C (C.C), which is an AMPK inhibitor. AAA formation was monitored by serial ultrasound. Aortas were collected 4 weeks after surgery and subjected to immunohistochemistry, Western blot, and transmission electron microscopy analyses. RESULTS: MET treatment dramatically inhibited the formation of AAA 4 weeks after PPE perfusion. MET reduced the aortic diameter, downregulated both macrophage infiltration and matrix metalloproteinase expression, decreased neovascularization, and preserved the contractile phenotype of the aortic vascular smooth muscle cells. Furthermore, we detected an increase in autophagy after MET treatment. All of these effects were reversed by the AMPK inhibitor C.C. CONCLUSION: This study demonstrated that MET activates AMPK and suppresses AAA formation. Our study provides a novel mechanism for MET and suggests that MET could be potentially used as a therapeutic candidate for preventing AAA.

Effect of resveratrol combined with atorvastatin on re-endothelialization after drug-eluting stents implantation and the underlying mechanism.

AIMS: To explore whether the combination of atorvastatins and resveratrol is superior to each individual drug alone regarding re-endothelialization after drug-eluting stents (DESs) implantation. MATERIALS AND METHODS: Ninety-four rabbits were randomized into control, atorvastatin, resveratrol, and combined medication groups. Abdominal aorta injury was induced via ballooning, followed by DES implantation. Neointimal formation and re-endothelialization after stent implantation were assessed via optical coherence tomography and scanning electron microscopy. The effects of resveratrol and atorvastatin on bone marrow-derived mesenchymal derived stem cells (BMSCs) were assessed. KEY FINDINGS: Compared with the findings in the resveratrol and atorvastatin groups, the neointimal area and mean neointimal thickness were greater in the combined medication group, which also exhibited improved re-endothelialization. Compared with the effects of monotherapy, combined treatment further protected BMSCs against rapamycin-induced apoptosis and improved cell migration. Combined medication significantly upregulated Akt, p-Akt, eNOS, p-eNOS, and CXCR4 expression in BMSCs compared with the effects of monotherapy, and these effects were abolished by the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002. SIGNIFICANCE: The combination of atorvastatin and resveratrol has the potential of accelerating re-endothelialization after stent implantation, reducing the risk of thrombosis and improving the safety of DESs.

Excessive Methionine Supplementation Exacerbates the Development of Abdominal Aortic Aneurysm in Rats.

OBJECTIVE: The relationship between methionine (Met) and abdominal aortic aneurysm (AAA) has been previously demonstrated, but the mechanisms controlling this association remain unclear. This study investigated the potential contribution of hypermethioninemia (HMet) to the development of AAA. METHODS: A model of AAA was induced by intraluminal porcine pancreatic elastase (PPE) infusion in 60 male Sprague-Dawley rats divided into 4 groups (n = 15 per group). Met was supplied by intragastric administration (1 g/kg body weight/day) from 1 week before surgery until 4 weeks after surgery. The aortic diameter was measured by ultrasound. Aortas were collected 4 weeks after surgery and subjected to biochemical analysis, histological assays, and transmission electron microscopy. RESULTS: After 5 weeks of Met supplementation, HMet increased the dilation ratio of the HMet + PPE group, and hyperhomocysteinemia was also induced in HMet and HMet + PPE rats. Increased matrix metalloproteinase-2 (MMP-2), osteopontin, and interleukin-6 expression was detected in HMet + PPE rats. Furthermore, increased autophagy was detected in the HMet + PPE group. CONCLUSION: This study demonstrates that HMet may exacerbate the formation of AAA due to the increased dilation ratio partially via enhancing MMP-2 and inflammatory responses.

On the influence of wall calcification and intraluminal thrombus on prediction of abdominal aortic aneurysm rupture.

OBJECTIVE: Parameters other than maximum diameter that predict rupture of abdominal aortic aneurysms (AAAs) may be helpful for risk-benefit analysis in individual patients. The aim of this study was to characterize the biomechanical-structural characteristics associated with AAA walls to better identify the related mechanistic variables required for an accurate prediction of rupture risk. METHODS: Anterior AAA wall (n = 40) and intraluminal thrombus (ILT; n = 114) samples were acquired from 18 patients undergoing open surgical repair. Biomechanical characterization was performed using controlled circumferential stretching tests combined with a speckle-strain tracking technique to quantify the spatial heterogeneity in deformation and localized strains in the AAA walls containing calcification. After mechanical testing, the accompanying microstructural characteristics of the AAA wall and ILT types were examined using electron microscopy. RESULTS: No significant correlation was found between the AAA diameter and the wall mechanical properties in terms of Cauchy stress (rs = -0.139; P = .596) or stiffness (rs = -0.451; P = .069). Quantification of significant localized peak strains, which were concentrated in the tissue regions surrounding calcification, reveals that peak strains increased by a mean of 174% as a result of calcification and corresponding peak stresses by 18.2%. Four ILT types characteristic of diverse stages in the evolving tissue microstructure were directly associated with distinct mechanical stiffness properties of the ILT and underlying AAA wall. ILT types were independent of geometric factors, including ILT volume and AAA diameter measures (ILT stiffness and AAA diameter [rs = -0.511; P = .074]; ILT stiffness and ILT volume [rs = -0.245; P = .467]). CONCLUSIONS: AAA wall stiffness properties are controlled by the load-bearing capacity of the noncalcified tissue portion, and low stiffness properties represent a highly degraded vulnerable wall. The presence of calcification that is contiguous with the inner wall causes severe tissue overstretching in surrounding tissue areas. The results highlight the use of additional biomechanical measures, detailing the biomechanical-structural characteristics of AAA tissue, that may be a helpful adjunct to improve the accuracy of rupture prediction.

Structural analysis of adventitial collagen to feature aging and aneurysm formation in human aorta.

OBJECTIVE: Adventitial collagen structure provides the aorta with tensile strength. Like other collagen-rich tissues, it can be affected by internal factors including aging and location. We determined whether the structural characteristics of human aortic adventitial collagen change with aging, location, and aneurysm formation. METHODS: Nonatherosclerotic nonaneurysmal (NANA) human abdominal aortas were collected from 15 individuals who had died of noncardiovascular diseases (<40 years old, NANA young, n = 5; >60 years old, NANA old, n = 5). The architecture of adventitial collagen in the aortas was assessed by scanning electron microscopy, and fiber orientation was assessed by polarized microscopy with two-dimensional fast Fourier transform. We then analyzed retardation as an anisotropic property of adventitial collagen by polarized light microscopy. The orientation and retardation of NANA aortas were compared with those of abdominal aortic specimens from patients who were surgically treated for abdominal aortic aneurysm (AAA) (>60 years old, n = 11). RESULTS: Adventitial collagen of the abdominal aortas on scanning electron microscopy images appeared as wavy, ropy fibers in aortas from young individuals (NANA young, n = 5) and were essentially flattened in those from older patents (NANA old, n = 5) and from those with AAA. Collagen fibers were thicker but sparser in the adventitia of aortas with AAA. Orientation maintained in the collagen fibers of NANA aortas (n = 15) on two-dimensional fast Fourier transform analysis was unrelated to either location or age and did not differ between NANA aortas and those with AAA. However, collagen fibrils in NANA aortas (n = 15) were significantly less retarded only at the level of the inferior mesenteric artery compared with other aortic locations. In addition, retardation was significantly reduced in abdominal aortas with AAA at the level of the inferior mesenteric artery. CONCLUSIONS: The basic structure of adventitial collagen fiber was maintained in abdominal aortas regardless of location or age. Because the molecular structure at the subfibril level changed at abdominal aorta and enhanced in aortas with AAA, alterations in the molecular structure of adventitial collagen might be associated with aneurysmal formation.

Segmental and age differences in the elastin network, collagen, and smooth muscle phenotype in the tunica media of the porcine aorta.

The porcine aorta is often used in studies on morphology, pathology, transplantation surgery, vascular and endovascular surgery, and biomechanics of the large arteries. Using quantitative histology and stereology, we estimated the area fraction of elastin, collagen, alpha-smooth muscle actin, vimentin, and desmin within the tunica media in 123 tissue samples collected from five segments (thoracic ascending aorta; aortic arch; thoracic descending aorta; suprarenal abdominal aorta; and infrarenal abdominal aorta) of porcine aortae from growing domestic pigs (n=25), ranging in age from 0 to 230 days. The descending thoracic aorta had the greatest elastin fraction, which decreased proximally toward the aortic arch as well as distally toward the abdominal aorta. Abdominal aortic segments had the highest fraction of actin, desmin, and vimentin positivity and all of these vascular smooth muscle markers were lower in the thoracic aortic segments. No quantitative differences were found when comparing the suprarenal abdominal segments with the infrarenal abdominal segments. The area fraction of actin within the media was comparable in all age groups and it was proportional to the postnatal growth. Thicker aortic segments had more elastin and collagen with fewer contractile cells. The collagen fraction decreased from ascending aorta and aortic arch toward the descending aorta. By revealing the variability of the quantitative composition of the porcine aorta, the results are suitable for planning experiments with the porcine aorta as a model, i.e. power test analyses and estimating the number of samples necessary to achieving a desirable level of precision. The complete primary morphometric data, in the form of continuous variables, are made publicly available for biomechanical modeling of site-dependent distensibility and compliance of the porcine aorta.

Perigraft seroma with minute observations after Gore-Tex graft implantation.

Perigraft seroma is a very rare postoperative complication following abdominal aortic aneurysm repair. A 74-year-old man with history of esophageal cancer surgery, underwent Gore-Tex graft replacement for an abdominal aortic aneurysm. A 50-mm perigraft seroma was noted one year later, increasing to over 70 mm in the next 6 months. We resected the Gore-Tex graft and replaced it with a Dacron graft via a repeat laparotomy. We observed the resected Gore-Tex graft in detail using electron microscopy to investigate the mechanism of perigraft seroma.

Experimental noninferiority trial of synthetic small-caliber biodegradable versus stable vascular grafts.

OBJECTIVE: Long-term evolution of polycaprolactone vascular prostheses has been investigated recently. The goal of this study was to evidence a noninferiority of such grafts compared with expanded polytetrafluoroethylene (ePTFE) implants in an aortic replacement model in the rat. METHODS: Fourteen anesthetized Sprague-Dawley rats received an infrarenal aortic graft (biodegradable, n = 8; expanded polytetrafluoroethylene, n = 6) replacement (end to end; inner diameter, 2 mm). Biodegradable grafts (polycaprolactone) were produced by random micro-/nanofiber electrospinning. After a median survival of 16.5 months, in vivo ultrasonography and angiography as well as postexplantation microcomputed tomography, histomorphometry, immunohistochemistry, and scanning electron microscopy were performed. RESULTS: Patency was 100% for polycaprolactone and 67% for ePTFE. No aneurysmal dilatation or stenoses were found in either group. Compliance was significantly higher for polycaprolactone compared with ePTFE (8.2 ± 1.0%/100 mm Hg vs 5.7 ± 0.7%/100 mm Hg; P < .01), but markedly reduced compared with adjacent native aortas and the control group. Histologically, low cellular in-growth was found in ePTFE whereas polycaprolactone showed significantly greater homogenous cellularity, producing an autologous extracellular matrix (10.8% ± 4.0% vs 32.1% ± 9.2%, P < .0001). Morphometry showed 100% neo-endothelialization for both grafts with a totally confluent endothelial coverage for polycaprolactone grafts by scanning electron microscope. More intimal hyperplasia was found in ePTFE compared with polycaprolactone grafts. Calcification was higher in ePTFE than in polycaprolactone grafts (15.8% vs 7.0%, P = .04) and was absent in controls. CONCLUSIONS: Outcomes of synthetic biodegradable nanofiber polycaprolactone grafts are not inferior compared with the clinically used expanded polytetrafluoroethylene grafts after long-term implantation in the rat aorta. Moreover, these implants show better patency, compliance, endothelialization, and cell in-growth, and less intimal hyperplasia and calcification than their counterparts.

Novel mechanism of aortic aneurysm development in mice associated with smoking and leukocytes.

OBJECTIVE: The purpose of this study was to evaluate potential mechanisms promoting abdominal aortic aneurysm development with tobacco smoke (TS) exposure. METHODS AND RESULTS: Experiments used the elastase perfusion model of abdominal aortic aneurysms with smoke-free controls. The effect of TS exposure was evaluated in C57/Bl6 mice, after broad-spectrum matrix metalloproteinase inhibition with doxycycline and in mice deficient in matrix metalloproteinase-9, matrix metalloproteinase-12, Cathepsin-S, and Neutrophil Elastase. Preparations of washed marrow, spleen, and peripheral blood leukocytes were transferred to smoke-free mice from 6-week TS-exposed mice or smoke-free mice. All mice were euthanized 14 days after elastase perfusion, and the percentage of change in aortic diameter (%Δ aortic diameter) was calculated. Electron microscopy of aortic tissue from animals exposed to TS without elastase exposure did not demonstrate any ultrastructural changes. Neither doxycycline nor any specific elastase deficiency was effective at preventing an increase in %Δ aortic diameter in TS-exposed animals. Smoke exposure for 6 weeks increased the %Δ aortic diameter after a smoke-free interval of up to 6 weeks before elastase perfusion. Leukocyte preparations from TS-exposed mice localized to abdominal aortic aneurysms and increased the %Δ aortic diameter in smoke-free mice. CONCLUSIONS: The effect of TS on the development of abdominal aortic aneurysms is not dependent on the activity of elastolytic enzymes and persists for long periods despite cessation of TS. Alterations in leukocyte response to aortic injury appear to mediate this effect.

Evaluation of the humoral and cellular immune responses after implantation of a PTFE vascular prosthesis.

INTRODUCTION: The experiment was designed in order to determine the immunological processes that occur during the healing in synthetic vascular grafts, especially to establish the differences in the location of the complement system proteins between the proximal and distal anastomosis and the differences in the arrangement of inflammatory cells in those anastomoses. The understanding of those processes will provide a true basis for determining risk factors for complications after arterial repair procedures. MATERIAL/METHODS: The experiment was carried out on 16 dogs that underwent implantation of unilateral aorto-femoral bypass with expanded polytetrafluoroethylene (ePTFE). After 6 months all animals were euthanized to dissect the vascular grafts. Immunohistochemical assays and electron microscopic examinations were performed. RESULTS: Immunohistochemical findings in the structure of neointima between anastomoses of vascular prostheses demonstrated significant differences between humoral and cellular responses. The area of proximal anastomosis revealed the presence of fibroblasts, but no macrophages were detected. The histological structure of the proximal anastomosis indicates that inflammatory processes were ended during the prosthesis healing. The immunological response obtained in the distal anastomosis corresponded to the chronic inflammatory reaction with the presence of macrophages, myofibroblasts and deposits of complement C3. DISCUSSION: The identification of differences in the presence of macrophages and myofibroblasts and the presence of the C3 component between the anastomoses is the original achievement of the present study. In the available literature, no such significant differences have been shown so far in the humoral and cellular immune response caused by the presence of an artificial vessel in the arterial system.

A complex variation of the parietal and visceral branches of the abdominal aorta / Una compleja variación de las ramas parietales y viscerales de la parte abdominal de la aorta

Variations in the branches of the abdominal aorta were determined during a routine abdominal region dissection of a 70-year-old male cadaver. Left gastric artery arose as the first root from antero-lateral of aorta. Coeliacomesenteric trunk occurred as a thick root. After 29.9mm, coeliacomesenteric trunk bifurcated as coeliac trunk and superior mesenteric artery. Coeliac trunk bifurcated as splenic artery and common hepatic artery. These multiple variations which change the normal anatomic structure of the abdominal aorta have to be kept in mind by surgeons, radiologists and anatomists.

Fueron encontradas, en un cadáver de sexo masculino de 70 años de edad durante una disección de rutina de la cavidad abdominal, variaciones de las ramas en la parte abdominal de la aorta. La arteria gástrica izquierda se originaba como la la primera rama antero-lateral de la aorta. El tronco celiacomesénterico se originó desde la aorta como una raíz gruesa. Después de 29,9mm, el tronco celiacomesentérico se dividió en el tronco celíaco y la arteria mesentérica superior. El tronco celíaco se dividió en las arterias esplénica y hepática común. Estas variaciones múltiples que cambian la estructura anatómica normal de la parte abdominal de la aorta tienen que ser tomada en consideración por los cirujanos, radiólogos y anatomistas.

Ultrastructural changes in atherosclerotic plaques following the instillation of airborne particulate matter into the lungs of rabbits.

BACKGROUND: Epidemiological studies have established that cardiovascular events account for the greatest number of air pollution-related deaths. However, the underlying structural changes are still unknown. OBJECTIVE: To investigate changes in the ultrastructure of atherosclerotic plaques in Watanabe heritable hyperlipidemic (WHHL) rabbits following the instillation of ambient particulate matter air pollution (particles smaller than 10 µm in diameter) into the lungs. METHODS: WHHL rabbits (n=8) exposed to 5 mg of ambient particles (Environmental Health Centre - 1993 [EHC-93]; suspended in saline and instilled in the airway) twice per week for four weeks were compared with control WHHL rabbits (n=8) treated with saline alone. RESULTS: All abdominal aortic plaques were examined using light and electron microscopy, which showed the following: increased accumulation of macrophage-derived foam cells immediately below the endothelial plaque surface (P=0.04); increased contact between these foam cells and the dense subendothelial extracellular matrix (P<0.005) with reduction (P<0.0001) and fragmentation (P<0.0001) of this matrix; and emigration of macrophage- derived foam cells from the plaques in exposed rabbits. In addition, immunohistochemistry verified the presence of type IV collagen in the thickened extracellular matrix material subtending the endothelium. CONCLUSIONS: The ultrastructure of atherosclerotic plaques in EHC-93- instilled rabbits differed from the ultrastructure observed in rabbits that did not receive EHC-93. These ultrastructural differences are consistent with greater endothelial instability in the plaques of atherosclerosis-prone rabbits.

Morphological and mechanical changes in juxtarenal aortic segment and aneurysm before and after open surgical repair of abdominal aortic aneurysms.

OBJECTIVE: The aim of study was to assess how the ultrastructure of the wall of aortic aneurysms, sac and neck influences aortic wall distensibility and proximal dilatation 2 years after open repair. METHODS: Biopsies for electron microscopy were taken from aneurysmal sac and neck of 30 patients. Patients were assessed by computed tomography (CT) and ultrasound for aneurysm diameter and distensibility (M-mode ultrasonography). RESULTS: Postoperative CT of the aortic stump distinguished two groups. Group I (n = 11) with little enlargement, median 1 mm (1-3 mm) and group II (n = 19) with significant aortic enlargement, median 5.2 mm (4-12 mm). In group II, changes in elastic fibres in the aneurysm neck were comparable to, but as extreme as in the aneurysm sac. For group I, the distensibility of the aneurysmal sac was significantly lower than in the neck or at the renal arteries. For group II, the distensibility in both the neck and sac was significantly lower than at the juxtarenal segment (p = 0.01). The biopsies of group II patients showed the extensive degeneration of normal architecture, which was associated with altered wall distensibility in both the aneurysmal neck and sac. CONCLUSIONS: Disorganisation and destruction of normal aortic architecture at the ultrastructural level are associated with decreasing aortic distensibility. Low aortic neck distensibility is associated with proximal aortic dilatation at 2 years postoperatively.

Histopathological comparison of vascular wall damage created by external cross-clamp and endoluminal balloon occlusion techniques.

AIM: Almost all cross-clamps utilized in vascular surgery, even atraumatic clamps, have been shown to cause mechanical damage to the vascular wall. In recent years, surgical procedures using an endoluminal balloon technique have been reported as an alternative occlusion strategy. This study discusses the histopathological characteristics and comparison between vascular wall damage secondary to the two occlusion techniques in the early postoperative period. METHODS: Twelve adult rabbits were divided into two experimental groups: the clamp group (N. = 6) and the balloon group (N. = 6). External cross-clamp occlusion was applied to the abdominal aorta for 30 minutes via laparotomy in the clamp group. In the balloon group, occlusion was applied for 30 minutes by inflating the catheter balloon, which was inserted through the iliac artery and advanced into the abdominal aorta. The appropriate aortic segments were subsequently extracted in both groups and tissue samples were examined by light and electron microscopy. Finally, the samples were scored for grade of tissue damage. RESULTS: In both experimental groups, tissue damage was apparent. In the investigations carried out under light microscopy, it was observed that the damage caused by balloon occlusion was remarkably less than the damage caused by the cross-clamp technique. In the balloon group, eight tissue samples (66.7%) had grade 1 damage. On the other hand, five tissue samples had grade 3 damage, all of which were in the clamp group. Investigation by electron microscopy revealed that greater intimal, medial, and adventitial damage occurred in the vascular walls of the clamp group samples, and this also corresponded with an increase in immune response and intraluminal thrombosis. CONCLUSION: External clamp and internal balloon occlusion techniques applied to the aorta were compared, and widespread intimal and medial damage were observed in both techniques. However, endoluminal occlusion of the aorta should be the technique of choice in properly selected cases, since it results in lower damage grades, and it should also be used if application of an external clamp is technically difficult.

Características ultraestruturais do segmento abdominal da aorta de rato albino / Mural features of the abdominal aortic segment of albino rat

O objetivo da presente pesquisa foi investigar as peculiaridades ultraestruturais da parede da aorta de rato. Foram utilizados sete ratos albinos, adultos jovens, dos quais foram coletados fragmentos da aorta abdominal infra-renal. Após a coleta, os segmentos asculares foram fixados e encaminhados para a rotina de microscopia eletrônica de transmissão e varredura. As lamelas elásticas aparecem interpostas às fibras musculares lisas, sendo essa disposição principalmente notada na túnica média da parede vascular. Entre as fibras musculares lisas e as lamelas elásticas, observa-se um inter-relacionamento aparentemente estreito, feito por conexão e ancoramento entre ambos os elementos murais por meio de lamelas de colágeno. A túnica íntima da aorta abdominal do rato mostra algumas peculiaridades ultraestruturais marcantes, tais como a interrupção, em certos locais da parede, de continuidade da lâmina elástica interna, interrupção acompanhada por poros endoteliais, de certa extensão, suprajacentes à falha na estrutura elástica intimal. Este padrão de constituição mural, com destaque aos ancoramentos elástico-musculares, via o colágeno, parece garantir propriedades fundamentais da parede vascular, concernentes à hemodinâmica, tal como o cisalhamento, normalmente notado entre os estratos superpostos da parede vascular, bem como a contratilidade e a visco-elasticidade da parede arterial.

The objective of the present research was to investigate the ultrastructural peculiarities of the aortic wall of the rat. Seven young adult rats were used, from which fragments of the infrarenal abdominal aorta were collected. After collection, the vascular segments were fixed and sent for analysis by scanning electron microscope. The elastic lamellae appear interposed with smooth muscular fibers; this pattern was verified mainly at the medial layer structure. Among the mural elements a well defined interrelationship was established through connective lamellae of the arterial wall. The collagen lamellae mainly provided anchoring among the elastic and smooth muscular constituents. The intimal layer showed special ultrastructural features, such as a non-continuous inner elastic lamina presented in certain sites of the vascular wall, followed by endothelial pores. This mural pattern of the abdominal aorta provided support to vascular functions such as shrinkage among the laminar composition of the arterial layers, also acting in mechanical properties of the vascular wall, such as viscoelasticity and contractility – essential actions to blood vessel hemodynamics.

Localization to atherosclerotic plaque and biodistribution of biochemically derivatized superparamagnetic iron oxide nanoparticles (SPIONs) contrast particles for magnetic resonance imaging (MRI).

Annexin V recognizes apoptotic cells by specific molecular interaction with phosphatidyl serine, a lipid that is normally sequestered in the inner leaflet of the cell membrane, but is translocated to the outer leaflet in apoptotic cells, such as foam cells of atherosclerotic plaque. Annexin V could potentially deliver carried materials (such as superparamagnetic contrast agents for magnetic resonance imaging) to sites containing apoptotic cells, such as high grade atherosclerotic lesions, so we administered biochemically-derivatized (annexin V) superparmagnetic iron oxide particles (SPIONs) parenterally to two related rabbit models of human atherosclerosis. We observe development of negative magnetic resonance imaging (MRI) contrast in atheromatous lesions and but not in healthy artery. Vascular targeting by annexin V SPIONs is atheroma-specific (i.e., does not occur in healthy control rabbits) and requires active annexin V decorating the SPION surface. Targeted SPIONs produce negative contrast at doses that are 2,000-fold lower than reported for non-specific atheroma uptake of untargeted superparamagnetic nanoparticles in plaque in the same animal model. Occlusive and mural plaques are differentiable. While most of the dose accumulates in liver, spleen, kidneys and bladder, annexin V SPIONs also partition rapidly and deeply into early apoptotic foamy macrophages in plaque. Contrast in plaque decays within 2 months, allowing MRI images to be replicated with a subsequent, identical dose of annexin V SPIONs. Thus, biologically targeted superparamagnetic contrast agents can contribute to non-invasive evaluation of cardiovascular lesions by simultaneously extracting morphological and biochemical data from them.

Experimental study of one-shot vascular anastomostic device for proximal vein graft anastomoses.

PURPOSE: A new type of sutureless aortic-vein-graft vascular anastomostic device, One-Shot Vascular Anastomostic Device (Horologe Factory of Jinan City, Shandong Province, China) has been recently designed to create a one-shot anastomosis between the aorta and vein grafts for coronary artery bypass grafting surgery. DESCRIPTION: Twelve pigs were scheduled for the test of the feasibility of the One-Shot Vascular Anastomostic Device for artery to vein graft anastomosis. In each animal one proximal anastomosis was performed by means of the One-Shot Vascular Anastomostic Device and the distal end was sutured in a conventional manner to serve as the animal own control. The anastomosis incorporating the abdominal main artery to the segment of a free external carotid vein to the external iliac artery is for the simulation of the aorta-vein anastomosis. EVALUATION: The mean duration of the completion of the proximal anastomosis was 1.2 +/- 1.2 minutes (range, 0.3-5.0 minutes). There was a significant difference between the control groups (p < 0.01). All vein grafts were still functioning at the end of the procedure. Pathologic studies and angiography demonstrated that the results were satisfactory. CONCLUSIONS: This device enables rapid and safe completion of vascular anastomostic procedure. The vein graft was functioning well and incorporated into the vessel intima smoothly.

Upregulation of connexin43 gap junctions between neointimal smooth muscle cells.

Increased expression of connexin43 gap junctions in smooth muscle cells (SMC) is implicated in the response to primary arterial injury and in the early stages of human coronary atherosclerosis, but the relevance of these findings to restenosis is unknown. Here we investigated the expression of connexin43 gap junctions in restenotic aortas of cholesterol-fed double injured rabbits. Immunofluorescence confocal microscopy was used to evaluate temporal and spatial expression patterns and to characterize the major expressing cell type. Parallel studies were conducted by electron microscopy, in situ hybridization and Northern blot analysis. Connexin43 gap junctions- and connexin43 mRNA-expressing cells were abundant in the media of non-injured control aorta. Following primary injury and 6 weeks cholesterol diet, connexin43 gap junctions were found distributed throughout the primary intimal layer; although medial expression was reduced, the overall mRNA expression level remained similar to that of non-injured controls. After secondary injury, no major change in distribution pattern of connexin43 gap junctions occurred up to day 10, when marked neointimal labeling was observed. This overall pattern persisted, though with some diminution, at later stages. On the mRNA level total connexin43 mRNA expression declined to about 40% of control values within 4 days after secondary injury (P < 0.05), but subsequently increased four-fold, attaining levels double that of non-injured controls in the 10-day group (P < 0.005 versus control and 4 days). At later stages mRNA expression levels returned to values similar to those of non-injured controls. At all stages, connexin43 gap junctions were localized to the SMC, not to macrophages. We conclude that the enhanced gap junction formation may contribute to the coordination of the response of SMC after secondary injury, particularly in the early phase of restenosis.

Arteriosclerosis in rat aortic allografts: early changes in endothelial integrity and smooth muscle phenotype.

BACKGROUND: Transplant arteriosclerosis remains a limiting factor for the long-term survival of transplanted organs and effective treatment is lacking. A rat model of aortic allografts was used to analyze this process by electron microscopy and further characterize the phenotypic properties of the cells involved. METHODS: A segment of abdominal aorta was transplanted orthotopically from Fischer to Lewis rats. The animals were killed 1-12 weeks after the operation (four to six rats/group), and the grafts were removed and processed for microscopy. RESULTS: The first changes (1 week) included detachment of endothelial cells, adhesion of degranulating platelets to the subendothelial matrix, and modification of smooth muscle cells in the media. The latter process was distinguished by loss of myofilaments and formation of a prominent endoplasmic reticulum and Golgi complex (shift from contractile to synthetic phenotype). Subsequently, modified smooth muscle cells invaded the intima. In parallel, lymphocytes and monocytes/macrophages infiltrated the intima and adventitia. The neointima grew in size by cell proliferation and production of extracellular matrix (4-8 weeks). Smooth muscle cells and monocytes/macrophages in the neointima and media were also noted to accumulate cytoplasmic lipid droplets and eventually turn into foam cells and die. Within the lipid-rich cell remnants, calcification occurred. Finally (12 weeks), the growth in mass of the intimal lesions ceased and in some places reformation of an endothelial lining was detected. Few viable smooth muscle cells remained in the media and the inflammatory infiltrate in the adventitia was reduced. CONCLUSIONS: These observations highlight the importance of early changes in endothelial integrity and smooth muscle phenotype in the development of allograft vascular disease and form the basis for a partly modified model of the cellular mechanisms in this process.