Ultrastructural Study of Platelet Behavior and Interrelationship in Sprouting and Intussusceptive Angiogenesis during Arterial Intimal Thickening Formation

Platelets in atherosclerosis, bypass stenosis, and restenosis have been extensively assessed. However, a sequential ultrastructural study of platelets in angiogenesis during the early phases of these lesions has received less attention. Our objective was the study of platelets in angiogenesis and vessel regression during intimal thickening (IT) formation, a precursor process of these occlusive vascular diseases. For this purpose, we used an experimental model of rat occluded arteries and procedures for ultrastructural observation. The results show (a) the absence of platelet adhesion in the de-endothelialized occluded arterial segment isolated from the circulation, (b) that intraarterial myriad platelets contributed from neovessels originated by sprouting angiogenesis from the periarterial microvasculature, (c) the association of platelets with blood components (fibrin, neutrophils, macrophages, and eosinophils) and non-polarized endothelial cells (ECs) forming aggregates (spheroids) in the arterial lumen, (d) the establishment of peg-and-socket junctions between platelets and polarized Ecs during intussusceptive angiogenesis originated from the EC aggregates, with the initial formation of IT, and (e) the aggregation of platelets in regressing neovessels (‘transitory paracrine organoid’) and IT increases. In conclusion, in sprouting and intussusceptive angiogenesis and vessel regression during IT formation, we contribute sequential ultrastructural findings on platelet behavior and relationships, which can be the basis for further studies using other procedures.

Cryopreservation moderates the thrombogenicity of arterial allografts during storage

INTRODUCTION

Management of vascular infections represents a major challenge in vascular surgery. The use of cryopreserved vascular allografts could be a feasible therapeutic option, but the optimal conditions for their production and use are not precisely defined.

AIMS

To evaluate the effects of cryopreservation and the duration of storage on the thrombogenicity of femoral artery allografts.

METHODS

In our prospective study, eleven multi-organ-donation-harvested human femoral arteries were examined at five time points during storage at -80°C: before cryopreservation as a fresh native sample and immediately, one, twelve and twenty-four weeks after the cryopreservation. Cross-sections of allografts were perfused with heparin-anticoagulated blood at shear-rates relevant to medium-sized arteries. The deposited platelets and fibrin were immunostained. The thrombogenicity of the intima, media and adventitia layers of the artery grafts was assessed quantitatively from the relative area covered by fibrin- and platelet-related fluorescent signal in the confocal micrographs.

RESULTS

Regression analysis of the fibrin and platelet coverage in the course of the 24-week storage excluded the possibility for increase in the graft thrombogenicity in the course of time and supported the hypothesis for a descending trend in fibrin generation and platelet deposition on the arterial wall. The fibrin deposition in the cryopreserved samples did not exceed the level detected in any of the three layers of the native graft. However, an early (up to week 12) shift above the native sample level was observed in the platelet adhesion to the media.

CONCLUSIONS

The hemostatic potential of cryopreserved arterial allografts was retained, whereas their thrombogenic potential declined during the 6-month storage. The only transient prothrombotic change was observed in the media layer, where the platelet deposition exceeded that of the fresh native grafts in the initial twelve weeks after cryopreservation, suggesting a potential clinical benefit from antiplatelet therapy in this time-window.

Local vibration induced vascular pathological structural changes and abnormal levels of vascular damage indicators

BACKGROUND

The vascular component of the hand-arm-vibration syndrome (HAVS) is often characterized by vibration-induced white fingers (VWF). Active substances secreted by the vascular endothelial cells (VEC) maintain a dynamic balance but damage to the blood vessels may occur when the equilibrium is altered, thus forming an important pathological basis for VWF. This study was aimed at investigating vascular damage indicators as a basis for an early detection of disorders caused by vibration, using the rat tail model.

METHODS AND RESULTS

Experiments were conducted using a control group of rats not exposed to vibration while two exposed groups having different exposure durations of 7 and 14 days were randomly formed. Following exposure, the structural changes of tail tissue samples in anesthetized rats were observed. Enzyme-linked immunosorbent assay (ELISA) was used for analyzing four vascular damage indicators myosin regulatory light chain (MLC2), endothelin-1 (ET-1), vinculin (VCL) and 5-hydroxytryptamine (5-HT) in tail blood samples. We found that both vascular smooth muscle and endothelial cells displayed changes in morphology characterized by vacuolization and swelling in the vibration-exposed group. The levels of vascular damage indicators were altered under the vibration.

CONCLUSION

The degree of vascular pathology increased with the longer duration exposure. Furthermore, the levels of MLC2, ET-1 and 5-HT in rat plasma were associated with vascular injury caused by local vibration.

Resolving fine electromechanical structure of collagen fibrils via sequential excitation piezoresponse force microscopy

Collagen is the main protein in extracellular matrix that is found in many connective tissues, and it exhibits piezoelectricity that is expected to correlate with its hierarchical microstructure. Resolving fine electromechanical structure of collagen, however, is challenging, due to its weak piezoresponse, rough topography, and microstructural hierarchy. Here we adopt the newly developed sequential excitation strategy in combination with piezoresponse force microscopy to overcome these difficulties. It excites the local electromechanical response of collagen via a sequence of distinct frequencies, minimizing crosstalk with topography, followed by principal component analysis to remove the background noise and simple harmonic oscillator model for physical analysis and data reconstruction. These enable us to acquire high fidelity mappings of fine electromechanical response at the nanoscale that correlate with the gap and overlap domains of collagen fibrils, which show substantial improvement over conventional piezoresponse force microscopy techniques. It also embodies the spirit of big data atomic force microscopy that can be readily extended into other applications with targeted data acquisition.

Phenotypic Reversion of Smooth Muscle Cells in Hybrid Vascular Prostheses

Our purpose was to evaluate whether or not and when phenotypic modulation of smooth muscle cells (SMCs) in hybrid vascular prostheses preincorporated with SMCs occurs upon implantation. Two types of hybrid vascular grafts incorporated with vascular cells derived from canine jugular veins were prepared: grafts containing a collagen gel layer covered with an endothelial monolayer at the luminal surface (Model I graft) and those containing an endothelial monolayer and SMC multilayer (Model II graft). They were bilaterally implanted into carotid arteries of the same dogs from which the cells had been harvested for 2 wk (n = 3) and 12 wk (n = 3). The time-dependent changes in populations of three SMC phenotypes (synthetic, intermediate, and contractile) in the neoarterial layers were quantified by morphometric evaluation using a transmission electron microscope in hybrid vascular grafts. Before implantation, all the SMCs were of the synthetic phenotype. In Model II grafts at 2 wk, synthetic and intermediate SMCs were dominant especially in the luminal layer. On the other hand, neoarterial layers at 12 wk were dominated by contractile SMCs, which were evenly distributed throughout the entire neoarterial tissues. A markedly delayed phenotypic reversion was noted for the Model I grafts at 12 wk. In the hybrid grafts, during about 3 mo of implantation, neoarterial SMCs transformed from the synthetic to the contractile phenotypes, which was promoted by SMC incorporation.

Cavin-3 (PRKCDBP) deficiency reduces the density of caveolae in smooth muscle

Cavins belong to a family of proteins that contribute to the formation of caveolae, which are membrane organelles with functional roles in muscle and fat. Here, we investigate the effect of cavin-3 ablation on vascular and urinary bladder structure and function. Arteries and urinary bladders from mice lacking cavin-3 (knockout: KO) and from controls (wild type: WT) were examined. Our studies revealed that the loss of cavin-3 resulted in ∼40% reduction of the caveolae protein cavin-1 in vascular and bladder smooth muscle. Electron microscopy demonstrated that the loss of cavin-3 was accompanied by a reduction of caveolae abundance by 40-45% in smooth muscle, whereas the density of caveolae in endothelial cells was unchanged. Vascular contraction in response to an α₁-adrenergic agonist was normal but nitric-oxide-dependent relaxation was enhanced, in parallel with an increased relaxation on direct activation of soluble guanylyl cyclase (sGC). This was associated with an elevated expression of sGC, although blood pressure was similar in WT and KO mice. Contraction of the urinary bladder was not affected by the loss of cavin-3. The proteomic response to outlet obstruction, including STAT3 phosphorylation, the induction of synthetic markers and the repression of contractile markers were identical in WT and KO mice, the only exception being a curtailed induction of the Golgi protein GM130. Loss of cavin-3 thus reduces the number of caveolae in smooth muscle and partly destabilizes cavin-1 but the functional consequences are modest and include an elevated vascular sensitivity to nitric oxide and slightly disturbed Golgi homeostasis in situations of severe cellular stress.

Mice Lacking Platelet-Derived Growth Factor D Display a Mild Vascular Phenotype

Platelet-derived growth factor D (PDGF-D) is the most recently discovered member of the PDGF family. PDGF-D signals through PDGF receptor β, but its biological role remains largely unknown. In contrast to other members of the PDGF family of growth factors, which have been extensively investigated using different knockout approaches in mice, PDGF-D has until now not been characterized by gene inactivation in mice. Here, we present the phenotype of a constitutive Pdgfd knockout mouse model (Pdgfd^-/-), carrying a LacZ reporter used to visualize Pdgfd promoter activity. Inactivation of the Pdgfd gene resulted in a mild phenotype in C57BL/6 mice, and the offspring was viable, fertile and generally in good health. We show that Pdgfd reporter gene activity was consistently localized to vascular structures in both postnatal and adult tissues. The expression was predominantly arterial, often localizing to vascular bifurcations. Endothelial cells appeared to be the dominating source for Pdgfd, but reporter gene activity was occasionally also found in subpopulations of mural cells. Tissue-specific analyses of vascular structures revealed that NG2-expressing pericytes of the cardiac vasculature were disorganized in Pdgfd^-/- mice. Furthermore, Pdgfd^-/- mice also had a slightly elevated blood pressure. In summary, the vascular expression pattern together with morphological changes in NG2-expressing cells, and the increase in blood pressure, support a function for PDGF-D in regulating systemic arterial blood pressure, and suggests a role in maintaining vascular homeostasis.

[Juxtaglomerular blood flow pathway in the kidney (comparative-anatomical and age-related aspects)]

To observe the formation of blood flow in the juxtaglomerular pathway in comparative-anatomical and age-related aspects, 484 kidneys from the representatives of the five classes of vertebrates, 50 kidneys of human fetuses and 193 kidneys of normal individuals of different ages were studied. Macro-microscopic, histological and morphometric methods were used. In all the mammalian animal species, the significant development of vascular glomeruli and peritubular capillaries was observed. In human kidneys, the relative content of cortical and medullary arterial vessels was maximal in juvenile age. With age, this parameter was found to decrease both in renal cortex and medulla. The differentiation of renal tissue into the cortex and the medulla, that began in birds and was finally formed in mammals, explains the appearance of cortical and juxtamedullary blood flow pathways. During the antenatal period of human development, renal juxtaglomerular pathway of blood flow prevails over the cortical one. The diminished significance of juxtamedullary pathway of blood flow in elderly and senile age determines the decreased adaptive capacities of intraorgan renal arterial bed in the norm.

Effect of residual stress on peak cap stress in arteries

Vulnerable plaques are a subset of atherosclerotic plaques that are prone to rupture when high stresses occur in the cap. The roles of residual stress, plaque morphology, and cap stiffness on the cap stress are not completely understood. Here, arteries are modeled within the framework of nonlinear elasticity as incompressible cylindrical structures that are residually stressed through differential growth. These structures are assumed to have a nonlinear, anisotropic, hyperelastic response to stresses in the media and adventitia layers and an isotropic response in the intima and necrotic layers. The effect of differential growth on the peak stress is explored in a simple, concentric geometry and it is shown that axial differential growth decreases the peak stress in the inner layer. Furthermore, morphological risk factors are explored. The peak stress in residually stressed cylinders is not greatly affected by changing the thickness of the intima. The thickness of the necrotic layer is shown to be the most important morphological feature that affects the peak stress in a residually stressed vessel.

Autonomic innervation of the periglomerular arteries

OBJECTIVE

To explore spatial and volume relations of the calcitonine gene-related peptide (CGRP)-positive and tyrosine hydroxylase (TH)-positive nerve fibers in the wall of cortical blood vessels.

STUDY DESIGN

Kidney specimens from 10 rats were processed for confocal microscopy. Nerve fibers were stained with anti-CGRP and anti-TH antibodies and image stacks were collected. Three-dimensional reconstruction and quantification of labeled fibers were performed to reveal their distribution and spatial relations.

RESULTS

CGRP- and TH-immunoreactive nerve fibers were distributed throughout the kidney cortex. TH-positive fibers were dominant in the small periglomerular arteries (up to 4.6-fold). Examined nerves were finely intertwined in the wall of small blood vessels of the kidney and ran in the same nerve bundle but without co-localization. Extensive, web-like branching and varicosities of the TH nerves were observed. Sensory fibers prevailed in the wall of the larger arteries "embedded" into tubules near the medullary rays, and their endings can be verified in the muscularis layer of the interlobular arteries.

CONCLUSION

Characteristics of the investigated fibers emphasize their role in the regulation of kidney blood vessel diameter and their influence on hypertension onset.

The performance of cross-linked acellular arterial scaffolds as vascular grafts; pre-clinical testing in direct and isolation loop circulatory models

There is a significant need for small diameter vascular grafts to be used in peripheral vascular surgery; however autologous grafts are not always available, synthetic grafts perform poorly and allografts and xenografts degenerate, dilate and calcify after implantation. We hypothesized that chemical stabilization of acellular xenogenic arteries would generate off-the-shelf grafts resistant to thrombosis, dilatation and calcification. To test this hypothesis, we decellularized porcine renal arteries, stabilized elastin with penta-galloyl glucose and collagen with carbodiimide/activated heparin and implanted them as transposition grafts in the abdominal aorta of rats as direct implants and separately as indirect, isolation-loop implants. All implants resulted in high patency and animal survival rates, ubiquitous encapsulation within a vascularized collagenous capsule, and exhibited lack of lumen thrombogenicity and no graft wall calcification. Peri-anastomotic neo-intimal tissue overgrowth was a normal occurrence in direct implants; however this reaction was circumvented in indirect implants. Notably, implantation of non-treated control scaffolds exhibited marked graft dilatation and elastin degeneration; however PGG significantly reduced elastin degradation and prevented aneurismal dilatation of vascular grafts. Overall these results point to the outstanding potential of crosslinked arterial scaffolds as small diameter vascular grafts.

Protective effect of a fish egg homogenate marine compound on arterial ultrastructure in spontaneous hypertensive rats

We assessed the effect of a sturgeon eggs-based nutraceutical (LD-1227) versus eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA) on the ultrastructure of spontaneously hypertensive rat (SHR) aortas. Sixty SHR were randomly divided into three groups that were fed (1) rat chow, (2) rat chow plus 10 mg of EPA/DHA, or (3) rat chow plus 10 mg of LD-1227, for 18 weeks. Afterward, aortas of these rats were used for blind measurements of the thickened intima area and examination by electron microscopy. Control SHR showed an expanded subendothelial space and leukocyte infiltration of the intima that were reduced in LD-1227-fed rats (p<0.05) and less in EPA/DHA group. Transmission electron microscopy showed endothelial alteration with severe subcellular injury and, unlike the EPA/DHA-group, LD-1227-treated rats displayed a significant reduction in endothelial alteration with severe subcellular injury (p<0.05). These data suggest that LD-1227 has stronger arterial protective properties and deserves further investigation in view of a preventive medicine strategy.

Comparison of constitutive models of arterial layers with distributed collagen fibre orientations

Several constitutive models have been proposed for description of mechanical behaviour of soft tissues containing collagen fibres. The model with aligned fibres is modified in this paper to take the dispersion of fibre orientations into account through angular integration and it is compared with the model that is defined through generalized structure tensor. The paper is focused on the effect of fibre dispersion on the resulting stress-strain behaviour predicted by both models analyzed. Analytical calculations are used for the comparison of the mechanical behaviour under a specific biaxial tension mode. The two models have been implemented into commercial finite element code ANSYS via user subroutines and used for numerical simulation resulting in a non-homogeneous stress field. The effects of the fibre dispersion predicted by both models being compared differ significantly, e.g., the resulting stress difference between both models is lower than 10% only in the case of extremely small dispersion of collagen fibres orientation (κ< (0.01 to 0.03)). These results are consistent with those of other related literature. The applicability of the model defined through the generalized structure tensor is discussed.

Effects of changing physiologic conditions on the in vivo quantification of hemodynamic variables in cerebral aneurysms treated with flow diverting devices

Quantifying the hemodynamic environment within aneurysms and its change after deployment of flow diverting devices is important to assess the device efficacy and understand their long-term effects. The purpose of this study was to estimate deviations in the quantification of the relative change of hemodynamic variables during flow diversion treatment of cerebral aneurysms due to changing physiologic flow conditions. Computational fluid dynamics calculations were carried out on three patient-specific geometries. Three flow diverters were virtually implanted in each geometry and simulations were performed under five pulsatile flow conditions. Hemodynamic variables including aneurysm inflow rate, mean velocity, shear rate, and wall shear stress were quantified before and after stenting. Deviations in the relative change of these variables due to varying flow conditions were calculated. The results indicate that a change in the mean flow of the parent artery of approximately 30-50% can induce large deviations in the relative change of hemodynamic variables in the range of 30-80%. Thus, quantification of hemodynamic changes during flow diversion must be carried out carefully. Variations in the inflow conditions during the procedure may induce large deviations in the quantification of these changes.

[Vascular morphological and microdensity changes of corneal neovascularization induced by topical bevacizumab and sunitinib in an animal model]

OBJECTIVE

To evaluate the effects of topical bevacizumab and topical sunitinib on vascular microdensity and morphology of corneal neovascularization (NV).

METHODS

A total of 33 rabbits were distributed into 3 groups: group 1 (control; n=11): saline; group 2 (n=11): bevacizumab 5mg/ml; and group 3 (n=11): sunitinib 0.5mg/ml. A corneal NV model was used, based on sutures in the right eye of each rabbit. Each treatment was administered topically 3 times daily for 14 days. Corneas were then processed for the study of vascular microdensity (6 eyes) and vascular morphology analysis (5 eyes) using enzymatic staining histological techniques

RESULTS

The vascular response in group 3 was limited to small-sized tree formations with various vascular axes compared with the extensive, lush and directional corneal NV of group 1 and 2. In the histological sections near the limb, there were no differences in vascular microdensity studies between the three groups. However, the mean sectional area of vessels (MSAV) in group 3 was 41.88% lower than in group 1 and 19.19% lower than in group 2. In distal sections, there were no differences between groups 1 and 2. However, group 3 was characterized by absence of vessels.

CONCLUSIONS

Bevacizumab produced no changes in the morphology of the vessels or the vascular microdensity. Sunitinib reduced the size of the new vessels and induced changes in the vascular tree.

Plasmacytoid dendritic cells: biomarkers or potential therapeutic targets in atherosclerosis?

Plasmacytoid dendritic cells (pDCs) represent a unique subset of dendritic cells that play distinct and critical roles in the immune response. Importantly, pDCs play a pivotal role in several chronic autoimmune diseases strongly characterized by an increased risk of vascular pathology. Clinical studies have shown that pDCs are detectable in atherosclerotic plaques and others have suggested an association between reduced numbers of circulating pDCs and cardiovascular events. Although the causal relationship between pDCs and atherosclerosis is still uncertain, recent results from mouse models are starting to define the specific role(s) of pDCs in the disease process. In this review, we will discuss the role of pDCs in innate and adaptive immunity, the emerging evidence demonstrating the contribution of pDCs to vascular pathology and we will consider the possible impact of pDCs on the acceleration of atherosclerosis in chronic inflammatory autoimmune diseases. Finally, we will discuss how pDCs could be targeted for therapeutic utility.

[Functional and morphologic changes in the tendons and multimicrovacuolar collagen absorbing system of the three-phalanx fingers in disorder of arterial inflow]

Taking into account the fact, that unsatisfactory results of treatment of the thumbs traumatic damage are significantly caused by presence of anatomic disruption of the thumbs palm's own arteries with chronic tissue ischemia occurrence. One of consequences of damage of the three-phalanx thumbs interphalanx joints and the thumbs palm's own arteries is a formation of quickly progressing secondary flexing contracture of proximal interphalanx joints (PIPHJ). In the investigations accomplished there was established, that the changed tissues of the flexors tendons and their sheaths, forming cicatricial blockade distally to the primary trauma site, are taking part in a PIPHJ contracture development while arterial perfusion presence.The tissues damage severity, as well as a severity of clinical features of the tendons and their sheaths damage, depends on a degree of an arterial perfusion disorder present,

Comparative morphology of the hemolymph vascular system in krill (Euphausiacea; Crustacea)

The phylogenetic position of Euphausiacea within Malacostraca is still under debate. Either they are seen as sister group to a taxon comprising Pancarida and Peracarida or closer related to Decapoda. Both hypotheses can be supported by characters of the circulatory system. Therefore, a comparative re-evaluation of the circulatory system seems to be feasible. Here we present the first three-dimensional data of the circulatory system of three euphausiacean species based on semi-thin sections and micro computer tomography in combination with corrosion casting. We were also able to study for the first time representatives of Bentheuphausia amblyops, the suggested sister taxon to all other euphausiaceans. The main pumping structure in the open circulatory system of Euphausiacea is the globular heart in the rear thoracic segments. From the anterior and posterior end of the heart two unpaired and four pairs of arteries emanate. The unpaired anterior aorta runs below the carapace from the anterior part of the heart into the anterior cephalothorax, where it supplies the first antennae, the brain and the eyes. The paired posterior aortae run into the pleon supplying the pleopods, uropods and the telson. The four pairs of cardiac arteries supply appendages in the cephalic region and viscera in the trunk. The unpaired descending artery connects to the subneural vessel supplying the thoracopods. A myoarterial formation of the anterior aorta is described in Bentheuphausia amblyops. The observed pattern of a globular heart situated in the posterior cephalothorax and comprising a meshwork of muscular strands (also running through its lumen) is highly likely to be homologous in Euphausiacea and Decapoda. The data are compared with the scarce literature present to date.

Pulsatile shear and Gja5 modulate arterial identity and remodeling events during flow-driven arteriogenesis

In the developing chicken embryo yolk sac vasculature, the expression of arterial identity genes requires arterial hemodynamic conditions. We hypothesize that arterial flow must provide a unique signal that is relevant for supporting arterial identity gene expression and is absent in veins. We analyzed factors related to flow, pressure and oxygenation in the chicken embryo vitelline vasculature in vivo. The best discrimination between arteries and veins was obtained by calculating the maximal pulsatile increase in shear rate relative to the time-averaged shear rate in the same vessel: the relative pulse slope index (RPSI). RPSI was significantly higher in arteries than veins. Arterial endothelial cells exposed to pulsatile shear in vitro augmented arterial marker expression as compared with exposure to constant shear. The expression of Gja5 correlated with arterial flow patterns: the redistribution of arterial flow provoked by vitelline artery ligation resulted in flow-driven collateral arterial network formation and was associated with increased expression of Gja5. In situ hybridization in normal and ligation embryos confirmed that Gja5 expression is confined to arteries and regulated by flow. In mice, Gja5 (connexin 40) was also expressed in arteries. In the adult, increased flow drives arteriogenesis and the formation of collateral arterial networks in peripheral occlusive diseases. Genetic ablation of Gja5 function in mice resulted in reduced arteriogenesis in two occlusion models. We conclude that pulsatile shear patterns may be central for supporting arterial identity, and that arterial Gja5 expression plays a functional role in flow-driven arteriogenesis.

Accuracy of volumetric flow rate measurements: an in vitro study using modern ultrasound scanners

OBJECTIVE

Volumetric flow measurement with Doppler ultrasound is useful in assessing blood flow as part of an evaluation of arteriovenous fistula maturity in patients undergoing hemodialysis. In this study, we assessed both accuracy and variability in volumetric flow measurements obtained using modern and commercially available ultrasound systems and an in vitro experimental setup.

METHODS

Volumetric flow measurements using duplex ultrasound were obtained by 3 users operating 5 different systems for randomized flow in the range of 100 to 1000 mL/min. Users performed 3 consecutive measurements at a given flow rate. Data were analyzed using statistical techniques to assess measurement accuracy and variability.

RESULTS

Over the span of flow rates studied, the root mean square error (RMSE) for the 5 ultrasound systems ranged from 38.8 to 79.7, 36.8 to 52.0, 73.0 to 85.3, 26.7 to 44.6, and 43.9 to 93.5 mL/min. Corresponding average RMSE values were 60.3, 42.7, 81.1, 37.2, and 64.4 mL/min, respectively. A linear regression analysis of mean interobserver measurements revealed an excellent correlation for all ultrasound systems (r(2) > 99.1%). Assessment of intraobserver measurements revealed no statistically significant differences for any ultrasound system evaluated (P > .94). Comparison of interobserver measurements indicates no statistically significant differences between any of the 5 systems (P > .14).

CONCLUSIONS

Modern ultrasound systems are reasonably accurate in blood flow measurement in an experimental setup mimicking clinically relevant blood flow ranges in a hemodialysis fistula. Users need adequate training and experience to perform multiple measurements and use appropriate techniques to minimize errors in flow measurement.

Inhibition of Collateral Artery Growth by Mibefradil: Possible Role of Volume-Regulated Chloride Channels

Endothelial cell swelling is one of the earliest hallmarks of arteriogenesis, the growth and maturation of collaterals. Mibefradil was found to block endothelial Cl(-) channels that control the volume of endothelial cells. Thus the authors investigated whether the blockade of volume-controlling endothelial cell channels would translate into an inhibition of arteriogenesis. In BALB/c mice, the right femoral artery was ligated and the animals received either mibefradil or solvent (phosphate-buffered saline [PBS]) via osmotic minipumps. Laser Doppler perfusion ratio (R/L) of ligated versus nonligated distal hindlimb increased from 0.06 +/- 0.01 (immediately after ligation) to 0.25 +/- 0.02 (day 7) in the PBS group and only from 0.07 +/- 0.02 to 0.13 +/- 0.02 in the mibefradil group (p <.01). Collateral artery diameters were significantly smaller in the mibefradil group (61 +/- 4.7 microm) versus controls (77.3 +/- 0.9 microm) (p <.05). Relative hemoglobin oxygen saturation measurements confirmed these findings (p <.02). The inhibition of arteriogenesis in the mibefradil group suggests that endothelial Cl(-) channels are involved in the initiation of arteriogenesis.

Vascular Endothelial Growth Factor Response in Porcine Coronary and Peripheral Arteries Using Nonsurgical Occlusion Model, Local Delivery, and Liposome-Mediated Gene Transfer

Angiogenesis and arteriogenesis play an important role in advanced vascular occlusive diseases. Whether angiogenesis or arteriogenesis predominate depends on the preexisting collateral vessel network, the type and location of occlusion, and different developmental origin of the arteries. Angiogenesis and arteriogenesis were investigated following vascular endothelial growth factor (VEGF) treatment in different arteries important in occlusive arterial diseases using a newly developed porcine arterial occlusion model. Porcine coronary and peripheral arteries were occluded interventionally using blinded stent grafts. Gene transfer was performed using a needle injection catheter and cationic lipid DOCSPER as gene carrier. DNA and gene expression in arterial tissue was examined using polymerase chain reaction (PCR) and reverse transcriptase (RT)-PCR. Vessel development was determined by angiography, immunohistochemistry, and measurement of capillary density. The transfected gene and its expression were found 3 months following application. In tissue adjacent to coronary arteries, there was significantly enhanced capillary density but no increase in angiographic score. In contrast, tissue surrounding peripheral arteries demonstrated no enhancement of capillary density but an enhancement in angiographic score. These results demonstrate differential responses to VEGF treatment in coronary and peripheral arteries resulting predominantly in either angiogenesis or arteriogenesis. Further investigation of VEGF signaling pathway is necessary for better understanding of the processes of vascular development, which may have potential impact on the design of cardiovascular therapeutics.

A unique vascular configuration among the efferent branchial arteries and splanchnic arteries in the yellow stingray, Urobatis jamaicensis

With light and scanning electron microscopy of vascular corrosion casts, we have observed in Urobatis jamaicensis that the fourth epibranchial arteries do not merge completely with the dorsal aorta. Instead they form a brief anastomosis with a short vessel projecting ventrally from the dorsal aorta and maintain their integrity as separately distinct vessels. Posterior to the anastomosis, the right epibranchial becomes the celiac trunk and left epibranchial becomes the anterior mesenteric artery/posterior intestinal artery. This vascular configuration appears to be unique in elasmobranchs.

[Ultrastructure of the intima of human pial arteries in arterial hypertension]

Ultrastructure of the intima of human pial arteries obtained from 5 male cadavers of practically healthy individuals and from 8 cadavers of the patients with the intravitally diagnosed grade I arterial hypertension (AH) was studied by scanning and transmission electron microscopy. AH was found to be associated with the remodeling of the intimal structural elements in the pial arteries. In most arteries, the changes were detected in the microrelief of the luminal surface and in the permeability of the vascular endothelial lining and of the subendothelial layer. During this remodeling, some endothelial cells were found in the state of structural and functional adaptation to the elevated arterial pressure, while the others were undergoing the dystrophic changes. The latter include the cells containing lipid inclusions, as well as the endothelial cells presumably in the state of apoptosis. The destruction of the intercellular junctions, the disturbances in the endothelium permeability contributed to the development of subendothelial layer edema, resulting in its significant thickening. This layer became looser and contained abundant collagen fibrils.

Expression of heat shock proteins and stress fiber formation within the arterial vascular tree of adult rats under normal physiological conditions

In this study, we investigated heat shock protein (HSP) expression and stress fiber (SF) formation in endothelial cells (ECs) within the arterial vascular tree of adult rats under normal physiological conditions. Using quantitative immunofluorescence microscopy, we found no significant differences in expression of HSPs 25, 60, 70, and 90 among ECs in the straight portions of rat arteries. In these regions, ECs appeared spindle-shaped and contained short bundles of central SFs. In contrast, ECs in the curved portions or the branch sites of the arteries, exhibited striking differences in HSP expression. ECs with higher HSP expression were localized at the lesser curvature in the curved portions or the distal site of the branch ostia. Moreover, the ECs became polygonal and contained irregular central SFs at the lesser curvature. At the branch sites, downstream ECs became spear-shaped and contained long, thick bundles of central SFs. Curved portions or branch sites are the regions of disturbed flow at which early atherosclerotic lesions are often found. Our results demonstrate these positional differences in HSP expression associated with changes in SF formation within the arterial vascular tree under non-pathological conditions. Our study provides basic information for understanding stress responses via HSP expression and SF formation in vascular ECs and the pathogenesis of atherosclerotic disease.

Fetal and early post-natal development of the human spleen: from primordial arterial B cell lobules to a non-segmented organ

Immunohistological analysis of 31 human spleens from the 11th week of gestation to the early postnatal period suggested that fetal organ development may be preliminarily divided into four stages. At stage 0 the organ anlage contained erythrocyte precursors, few macrophages and almost no lymphocytes. Fetal spleens of stage I exhibited arterial vascular lobules and lymphocytes just began colonizing the organ. At stage II, B and T lymphocytes formed periarteriolar clusters. B cell clusters predominated, because B cells aggregated around the more peripheral branches of splenic arterioles, while T cells occupied the more centrally located parts of the vessels. The vascular lobules of stage I and II consisted of central arterioles surrounded by B cells, capillaries and peripheral venules. The lobular architecture slowly dissolved at late stage II when sinuses grew out from the peripheral venules into the centre of the lobule. Interestingly, the B cell accumulations around peripheral arterioles did not represent the precursors of follicles, but apparently persisted as periarteriolar B cell clusters in the adult splenic red pulp, while follicles containing FDCs developed at late stage II from B cells in direct contact to T cell clusters around larger arterial vessels. At stage III before birth the lobular architecture was no longer recognized. The chemokine CXCL13 was already present in vascular smooth muscle and adjacent stromal cells at stage I before B cells immigrated. CCL21, on the contrary, was only demonstrated in fibroblast-like cells supporting T cell clusters from stage II onwards.

Unique cellular structures in the parotid gland of an Old world fruit bat, Pteropus lylei (Lyle's flying fox)

Pteropus lylei (Lyle's flying fox), an Old World fruit bat, consumes only ripe fruit, which contains low protein and sodium. The carpophagous diet of P. lylei presents an adaptive challenge for salivary glands to conserve sufficient nutrition for living. Therefore, the parotid glands in both sexes were investigated by using light microscopy and transmission electron microscopy. No structural difference was observed in the parotid glands between sexes. The acinar cell contained dense serous secretory granules, prominent luminal microvilli and intercellular canaliculi. The intercalated duct exhibited simple cuboidal epithelium with no secretory granule. Striated duct consisted of simple columnar epithelium with basal striation, numerous elongated mitochondria, and apical vesicles. In the interlobular duct, simple tall columnar epithelium and apocrine secretion were found. The interlobar and excretory ducts surprisingly contained continuous capillaries that intervened in stratified cuboidal epithelium. In addition, there were several blood vessels around the interlobular, interlobar and excretory ducts. The morphological adaptation of the parotid gland observed in P. lylei enables this species to obtain sufficient nutrients from the preferred consumption of ripe fruit. Serous secretory granule was suitable for digestion of ripe fruit. A well-developed striated duct, continuous capillaries among the epithelial cells of interlobar and excretory ducts, and numerous blood vessels around these ducts enhanced the reabsorption of amino acids and ions. Structural variations in the parotid gland can indicate not only a correlation to diet and survival but also a close relationship of the Old World fruit bat to other kinds of bats.

Macrovascular changes in mice overexpressing human semicarbazide-sensitive amine oxidase in smooth muscle cells

BACKGROUND

The catalytic activity of semicarbazide-sensitive amine oxidase (SSAO) is increased in diabetes, as well as in other disorders of cardiovascular origin. Our hypothesis is that SSAO is involved in the synthesis or maturation of elastin in vascular tissue. An increased SSAO activity can thereby be involved in the development of vascular damage.

METHODS

Elastin quantification was performed in aorta of transgenic mice overexpressing the human form of SSAO, using electron microscopy. Furthermore, lung capacity was measured using a spirometry-mimicking method, developed for mice. The effect of vasoactive substances was estimated by measuring mean arterial pressure and pulse pressure under anesthesia.

RESULTS

No differences in elastin quantity or lung capacity could be observed between transgenic or nontransgenic littermates. Pulse pressure was higher in transgenic mice, and electron microscopy of aorta showed elastin fibers parallel with the aorta wall (ie, straight fibers instead of folded compared with control mice). No difference in the response to adrenaline or sodium chloride was observed between the transgenic and control mice. The control mice had a clear decrease in blood pressure (BP) with a longer duration as a response to injection of a nitric oxide (NO) donor, sodium nitroprusside, compared with transgenic mice where only a minor response was observed. The SSAO activity in serum of control mice was elevated in response to injection of the NO donor, but not in response to a ganglion blocker.

CONCLUSIONS

An elevated pulse pressure, together with an abnormal elastin structure in the aorta, suggests a rigidity of large arteries as a result of an elevated SSAO activity as well as a physiologic role for SSAO in elastin maturation.

An ultrastructural analysis of collagen in tissue engineered arteries

Collagen is the structural molecule that is most correlated with strength in blood vessels. In this study, we compared the properties of collagen in engineered and native blood vessels. Transmission electron microscopy (TEM) was used to image sections of engineered and native arteries. Band periodicities of engineered and native collagen fibrils indicated that spacing between collagen molecules was similar in engineered and native tissues. Engineered arteries, however, had thinner collagen fibrils and fibers than native arteries. Further, collagen fibrils were more loosely packed within collagen fibers in engineered arteries than in native arteries. The sensitivity of TEM analysis allowed measurement of the relative frequency of observation for alignment of collagen. These observations showed that collagen in both engineered and native arteries was aligned circumferentially, helically, and axially, but that engineered arteries had less circumferential collagen and more axial collagen than native arteries. Given that collagen is primarily responsible for dictating the ultimate mechanical properties of arterial tissue, future efforts should focus on using relative frequency of observation for alignment of collagen as a descriptive input for models of the mechanical properties of engineered or native tissues.

Transport in rat vessel walls. II. Macromolecular leakage and focal spot size growth in rat arteries and veins

Transendothelial lipid transport into and spread in the subendothelial intima of large arteries, and subsequent lipid accumulation, appear to start plaque formation. We experimentally examine transendothelial horseradish peroxidase (HRP) transport in vessels that are usually, e.g., pulmonary artery (PA), or almost always, e.g., inferior vena cava (IVC), atherosclerosis resistant vs. disease prone, e.g., aorta, vessels. In these vessels, HRP traverses the endothelium at isolated, focal spots, rather than uniformly, for short circulation times. For femoral vein HRP introduction, PA spots have 30-s radii [∼53.2 μm (SD10.4); compare aorta: 54.6 μm (SD8.75)] and grow quickly from 30 s to 1 min (40%, P < 0.05) and more slowly afterward ( P > 0.05). This trend resembles the aorta, suggesting the PA has a similarly sparse intima. With carotid artery (CA) HRP introduction, the 30-s spot (132.86 ± 37.32 μm) is far larger than the PAs, grows little (∼28%, P < 0.05) from 30 to 60 s, and is much flatter than the artery curves. Transverse electron microscopic sections after ∼10 min HRP circulation show thin, intense staining immediately beneath both vessels’ endothelia with an almost step change to diffuse staining beyond. This indicates the existence of a sparse, subendothelial intima, even when there is no internal elastic lamina (IVC). This motivates a simple model that translates growth rates into lower bounds for the flow through focal leaks. The model results and our earlier wall and medial hydraulic conductivity data explain these spot growth curves and point to differences in transport patterns that might be relevant in understanding the immunity of IVC to disease initiation.

Intraneural Topography of the Extratemporal Facial Nerve

The fascicular pattern is the most important component of a nerve when a microsurgical reconstruction is made. The intraneural topography of the extratemporal facial nerve does not have a reliable fascicular pattern, although our study in 25 extratemporal facial nerves showed a definite fascicular pattern in the different studied levels. The microanatomic intraneural investigation was made in four different levels; we studied the diameter of the trunk, number and diameter of each fascicle, fascicular pattern, characteristics of the epineurium, perineurium, and interfascicular connective tissue, and extra- and intraneural blood supply. In the proximal and distal facial trunk, most axons are included in one to three big funiculus surrounded by a small amount of connective, interfascicular tissue; both epineurium and perineurium are thin and slender. The principal arteries are placed between funiculus and epineurium. Either epineurial or interfascicular neurorrhaphy could be produced and mono- or polyfascicular nerve grafts can be used. In both temporofacial and cervicofacial primary branches, the fascicular distribution was from four to five fascicles in 64% of cases with abundant connective interfascicular tissue involving the principal arteries. The interfascicular surgical technique is of election, but the epineurial suture must not be discarded. Nerve graft must be polyfascicular. The goal of nerve repair is to obtain the restoration of anatomic continuity of the most of axons by means of a complete fascicular alignment, in which detailed knowledge of the intraneural topography of the facial nerve must be required for reliable microsurgical reparation.

Disruption of endothelial caveolae is associated with impairment of both NO- as well as EDHF in acetylcholine-induced relaxation depending on their relative contribution in different vascular beds

Caveolae represent an important structural element involved in endothelial signal-transduction. The present study was designed to investigate the role of caveolae in endothelium-dependent relaxation of different vascular beds. Caveolae were disrupted by cholesterol depletion with filipin (4x10(-6) g L(-1)) or methyl-beta-cyclodextrin (MCD; 1x10(-3) mol L(-1)) and the effect on endothelium-dependent relaxation was studied in rat aorta, small renal arteries and mesenteric arteries in the absence and presence of L-NMMA. The contribution of NO and EDHF, respectively, to total relaxation in response to acetylcholine (ACh) gradually changed from aorta (71.2+/-6.1% and 28.8+/-6.1%), to renal arteries (48.6+/-6.4% and 51.4+/-6.4%) and to mesenteric arteries (9.1+/-4.0% and 90.9+/-4.1%). Electron microscopy confirmed filipin to decrease the number of endothelial caveolae in all vessels studied. Incubation with filipin inhibited endothelium-dependent relaxation induced by cumulative doses of ACh (3x10(-9)-10(-4) mol L(-1)) in all three vascular beds. In aorta, treatment with either filipin or MCD only inhibited the NO component, whereas in renal artery both NO and EDHF formation were affected. In contrast, in mesenteric arteries, filipin treatment only reduced EDHF formation. Disruption of endothelial caveolae is associated with the impairment of both NO and EDHF in acetylcholine-induced relaxation.

[Effects of Astragalus polysaccharides and Cordyceps sinensis mycelium mixture on the transforming growth factor-beta1 expression in chronic rejection of artery transplantation: experiment with rats]

OBJECTIVE

To explore the effect of Astragalus polysaccharides (APS) and Cordyceps sinensis (CP) mycelium mixture on the chronic rejection of artery transplantation.

METHODS

The abdominal arteries of 180 Wistar rats were isolated and transplanted to 180 SD rats whose with their abdominal arteries resected. The 180 recipient SD rats were randomly divided into blank control group (n = 20), APS group (n = 40, receiving gastric perfusion of APS 1 mg/kg bid), APS + low-dose CP group (n = 40, receiving APS and CP mycelium powder 1.25 g/d), APS + medium-dose CP group (n = 40, receiving APS and CP mycelium powder 2.5 g/d), and APS + high-dose CP group (n = 40, receiving APS and CP mycelium powder 5 g/d). Thirty days later the SD rats were killed with the transplanted abdominal arteries taken out to undergo microscopy. The expression of transforming growth factor (TGF)-beta(1) in the transplanted artery was examined by immunohistochemistry.

RESULTS

In the control group, overexpression of TGF-beta(1) was observed in the intimal smooth muscle cells, monocytes, arterial endothelial cells, and arteriole, venule, and blood capillary endothelial cells in extima. However, the expression levels of TGF-beta(1) in the APS group and the 3 mixture administration groups were all significantly lower, especially in the medium- and high-dose groups (all P < 0.01). Severe edema of arterial endothelial cells and proliferation of monocytes were observed microscopically in the control group. Under electron microscope, rough endoplasmic reticulum and Golgi body were abundant in the control group. While in the mixture administration groups these changes were either weakened or absent.

CONCLUSION

Astragalus polysaccharides and Cordyceps sinensis mycelium polysaccharides mixture can decrease the expression of TGF-beta(1) and inhibit the synthesis of collagen in the transplanted arteries.

Rapid hyperspectral fluorescence lifetime imaging

We report a rapid hyperspectral fluorescence lifetime imaging (FLIM) instrument that exploits high-speed FLIM technology in a line-scanning microscope. We demonstrate the acquisition of whole-field optically sectioned hyperspectral fluorescence lifetime image stacks (with 32 spectral bins) in less than 40 s and illustrate its application to unstained biological tissue.

Effect of selenium compounds on the damage induced by oxysterol on rat arterial walls

Wistar rats were fed Se-deficient (0.017 +/- 0.002 mg Se/kg) and Seadequate (0.32 +/- 0.045 Se mg/kg) diets for 12 mo and then were given 5 mg/kg of cholestane-3beta,5alpha,6beta-triol (3-triol), intravenously. Se compounds (Na(2)SeO(3) and ebselen) were supplemented in different doses and times to the Se-deficient rats. Twenty-four hours after 3-triol infusion, the changes in ultrastructures of rat aorta were examined by scanning electron micrography (SEM) and transmission electron micrography (TEM). SEM examinations showed that 3-triol induced diffused injuries on arterial endothelial urfaces of long-term Se-deficient rat, and a large number of holes or craterlike defects were observed. TEM examinations further showed that 3-triol induced swelling, necrosis, and shedding of endothelial cells, which resulted in the destruction of endothelial integrity. Meanwhile, smooth muscle cells proliferated and migrated toward intimae; the breakage of internal elastic lamina benefited the migration of smooth muscle cells. Supplemented with Na(2)SeO(3) (40 microg/kg, 10 d per continuum) and ebselen (20 mg/kg), respectively, exhibited significant protection from damages induced by 3-triol. It seems that protecting mechanisms were different between Na(2)SeO(3) and ebselen. The present investigation gave visual evidence that both injuries induced by cholesterol oxides and the Se nutritional status contributed to the development of atherosclerosis.

The three-dimensional microvascular architecture of the human Kaposi sarcoma implanted in nude mice: a SEM corrosion casting study

The human Kaposi sarcoma represents one of the most common skin lesions associated with AIDS. Its clinical presentation and anatomopathological structure seem to demonstrate a particularly rich vascularity. The latest therapies aim to limit its intrinsic angiogenic activity in an attempt to reduce vascular density and the formation of new vessels. For these reasons, we decided to study the microvascular architecture of Kaposi sarcoma in three dimensions. We used a corrosion casting technique applied to nude mice previously transplanted subcutaneously with human modified neoplastic Kaposi sarcoma cells. The cooption of host vessels made by the tumor was demonstrated by three-dimensional scanning electron microscopy (SEM) images. At high magnification several angiogenic patterns were observed in the form of potato-shaped vessels, sprouts, intussusceptions and mouse tailed end tipped capillaries along with some ultrastructural features such as intercellular extravasations and endothelial cell modifications. Our investigation allowed us to build a detailed map of tumor vasculature in human Kaposi sarcoma. Furthermore, this study want to shed light on the sharp morphological three-dimensional conformation of angiogenic sprouts so to be able to better understand their modifications occurred during time and after antiangiogenic experimental therapies, by now observed only by immunohistochemical or immunofluorescent assays.

Hyperelastic modelling of arterial layers with distributed collagen fibre orientations

Constitutive relations are fundamental to the solution of problems in continuum mechanics, and are required in the study of, for example, mechanically dominated clinical interventions involving soft biological tissues. Structural continuum constitutive models of arterial layers integrate information about the tissue morphology and therefore allow investigation of the interrelation between structure and function in response to mechanical loading. Collagen fibres are key ingredients in the structure of arteries. In the media (the middle layer of the artery wall) they are arranged in two helically distributed families with a small pitch and very little dispersion in their orientation (i.e. they are aligned quite close to the circumferential direction). By contrast, in the adventitial and intimal layers, the orientation of the collagen fibres is dispersed, as shown by polarized light microscopy of stained arterial tissue. As a result, continuum models that do not account for the dispersion are not able to capture accurately the stress-strain response of these layers. The purpose of this paper, therefore, is to develop a structural continuum framework that is able to represent the dispersion of the collagen fibre orientation. This then allows the development of a new hyperelastic free-energy function that is particularly suited for representing the anisotropic elastic properties of adventitial and intimal layers of arterial walls, and is a generalization of the fibre-reinforced structural model introduced by Holzapfel & Gasser (Holzapfel & Gasser 2001 Comput. Meth. Appl. Mech. Eng. 190, 4379-4403) and Holzapfel et al. (Holzapfel et al. 2000 J. Elast. 61, 1-48). The model incorporates an additional scalar structure parameter that characterizes the dispersed collagen orientation. An efficient finite element implementation of the model is then presented and numerical examples show that the dispersion of the orientation of collagen fibres in the adventitia of human iliac arteries has a significant effect on their mechanical response.

A role for heterocellular coupling and EETs in dilation of rat cremaster arteries

OBJECTIVE

The authors probed endothelium-dependent dilation and endothelial cell Ca2+ handling in myogenically active resistance arteries.

METHODS

First-order arteries were removed from rat cremaster muscles, cannulated, and pressurized (75 mmHg). Vessel diameter and endothelial cell Ca2+ were monitored using confocal microscopy, and arterial ultrastructure was determined using electron microscopy.

RESULTS

Acetylcholine (ACh) stimulated elevations and oscillations in endothelial cell Ca2+, and concentration-dependently dilated arteries with myogenic tone. NO-independent dilation was blocked by 35 mM K+. Combined IK(Ca) (1 microM TRAM-34) and SK(Ca) (100 nM apamin) blockade partially inhibited NO-independent relaxations, with residual relaxations sensitive to BK(Ca) or cytochrome P-450 inhibition (100 nM iberiotoxin, and 20 microM 17-ODYA or 10 microM MS-PPOH). 11,12-EET stimulated iberiotoxin-sensitive dilation, but did not affect endothelial cell Ca2+. 15 mM K+ evoked dilation sensitive to inhibition of K(IR) (30 microM Ba2+) and Na+/K+-ATPase (10 microM ouabain), whereas these blockers did not affect ACh-mediated dilations. Homo- and heterocellular gap junctions were identified in radial sections through arteries.

CONCLUSION

These data suggest that rises in endothelial cell Ca2+ stimulate SK(Ca) and IK(Ca) channels, leading to hyperpolarization and dilation, likely due to electrical coupling. In addition, a component was unmasked following SK(Ca) and IK(Ca) blockade, attributable to activation of BK(Ca) channels by cytochrome P-450 metabolites.

Changes in extracellular matrix in subcutaneous small resistance arteries of patients with primary aldosteronism

CONTEXT AND OBJECTIVE

It has been previously demonstrated that aldosterone may possess a strong profibrotic action in vitro and in animal models of genetic or experimental hypertension. Our aim was to evaluate whether such a profibrotic action is present also in the human microcirculation.

DESIGN AND PATIENTS

We investigated 13 patients with primary aldosteronism, seven patients with essential hypertension, and 10 normotensive controls. All subjects were submitted to a biopsy of gluteal sc fat tissue. Small resistance arteries were dissected and mounted on an isometric myograph, and the tunica media to internal lumen ratio was measured.

MAIN OUTCOME MEASURES

The total collagen content within the tunica media was detected (Sirius red staining and image analysis), and collagen subtypes were evaluated using polarized light microscopy; under this condition thicker type I collagen fibers appear orange or red, whereas thinner type III collagen fibers are yellow or green.

RESULTS

Tunica media to internal lumen ratio was significantly increased in primary aldosteronism and in essential hypertension compared with normotensive controls. Clinic blood pressure values were similar in primary aldosteronism and in essential hypertension, and greater than in normotensive controls. Normotensive controls had less total and type III collagen (3.23 +/- 0.58 and 1.60 +/- 0.22%, respectively) in respect to the two hypertensive groups (P < 0.001). Total collagen and type III vascular collagen were significantly greater in primary aldosteronism (total collagen, 8.17 +/- 1.38%; type III collagen, 6.06 +/- 0.74%; P < 0.05) than in essential hypertension (total collagen, 6.84 +/- 1.15%; type III collagen, 5.25 +/- 0.80%).

CONCLUSIONS

Our results indicate that, in small resistance arteries of patients with primary aldosteronism, a pronounced fibrosis may be detected, even more evident than in blood-pressure-matched patients with essential hypertension.

New transgenic evidence for a system of sympathetic axons able to express tissue plasminogen activator (t-PA) within arterial/arteriolar walls

Sympathetic axons embedded in a few arterioles and vasa vasora were recently shown to store tissue plasminogen activator (t-PA) in vesicles. But the extension of such t-PA axons to arteries and arterioles throughout the organism has not been verified. Confirmation of this anatomy would identify a second significant source of vessel wall t-PA. To visualize fine embedded axons independent of endothelium, we created a transgenic mouse whose expressions of the t-PA promoter and enhanced green fluorescent protein are confined to sympathetic neurons and other neural crest derivatives. Confocal images reveal the extension of t-PA axons to arterioles serving heart, brain, kidney, lung, mesentery, and skin; plus aortic, carotid, and mesenteric artery walls. Ganglion neurons and adrenal chromaffin cells also show strong expressions. These new sightings confirm the existence of a system of t-PA axons that is prominent in arterioles, and compatible with the release of neural t-PA into their walls.

MT1-matrix metalloproteinase directs arterial wall invasion and neointima formation by vascular smooth muscle cells

During pathologic vessel remodeling, vascular smooth muscle cells (VSMCs) embedded within the collagen-rich matrix of the artery wall mobilize uncharacterized proteolytic systems to infiltrate the subendothelial space and generate neointimal lesions. Although the VSMC-derived serine proteinases, plasminogen activator and plasminogen, the cysteine proteinases, cathepsins L, S, and K, and the matrix metalloproteinases MMP-2 and MMP-9 have each been linked to pathologic matrix-remodeling states in vitro and in vivo, the role that these or other proteinases play in allowing VSMCs to negotiate the three-dimensional (3-D) cross-linked extracellular matrix of the arterial wall remains undefined. Herein, we demonstrate that VSMCs proteolytically remodel and invade collagenous barriers independently of plasmin, cathepsins L, S, or K, MMP-2, or MMP-9. Instead, we identify the membrane-anchored matrix metalloproteinase, MT1-MMP, as the key pericellular collagenolysin that controls the ability of VSMCs to degrade and infiltrate 3-D barriers of interstitial collagen, including the arterial wall. Furthermore, genetic deletion of the proteinase affords mice with a protected status against neointimal hyperplasia and lumen narrowing in vivo. These studies suggest that therapeutic interventions designed to target MT1-MMP could prove beneficial in a range of human vascular disease states associated with the destructive remodeling of the vessel wall extracellular matrix.

S100A8 and S100A9 in Human Arterial Wall

Atherogenesis is a complex process involving inflammation. S100A8 and S100A9, the Ca2+-binding neutrophil cytosolic proteins, are associated with innate immunity and regulate processes leading to leukocyte adhesion and transmigration. In neutrophils and monocytes the S100A8-S100A9 complex regulates phosphorylation, NADPH-oxidase activity, and fatty acid transport. The proteins have anti-microbial properties, and S100A8 may play a role in oxidant defense in inflammation. Murine S100A8 is regulated by inflammatory mediators and recruits macrophages with a proatherogenic phenotype. S100A9 but not S100A8 was found in macrophages in ApoE-/- murine atherosclerotic lesions, whereas both proteins are expressed in human giant cell arteritis. Here we demonstrate S100A8 and S100A9 protein and mRNA in macrophages, foam cells, and neovessels in human atheroma. Monomeric and complexed forms were detected in plaque extracts. S100A9 was strongly expressed in calcifying areas and the surrounding extracellular matrix. Vascular matrix vesicles contain high levels of Ca2+-binding proteins and phospholipids that regulate calcification. Matrix vesicles characterized by electron microscopy, x-ray microanalysis, nucleoside triphosphate pyrophosphohydrolase assay and cholesterol/phospholipid analysis contained predominantly S100A9. We propose that S100A9 associated with lipid structures in matrix vesicles may influence phospholipid-Ca2+ binding properties to promote dystrophic calcification. S100A8 and S100A9 were more sensitive to hypochlorite oxidation than albumin or low density lipoprotein and immunoaffinity confirmed S100A8-S100A9 complexes; some were resistant to reduction, suggesting that hypochlorite may contribute to protein cross-linking. S100A8 and S100A9 in atherosclerotic plaque and calcifying matrix vesicles may significantly influence redox- and Ca2+-dependent processes during atherogenesis and its chronic complications, particularly dystrophic calcification.

Tissue factor-dependent coagulation is preferentially up-regulated within arterial branching areas in a baboon model of Escherichia coli sepsis

Endothelium plays a critical role in the pathobiology of sepsis by integrating systemic host responses and local rheological stimuli. We studied the differential expression and activation of tissue factor (TF)-dependent coagulation on linear versus branched arterial segments in a baboon sepsis model. Animals were injected intravenously with lethal doses of Escherichia coli or saline and sacrificed after 2 to 8 hours. Whole-mount arterial segments were stained for TF, TF-pathway inhibitor (TFPI), factor VII (FVII), and markers for endothelial cells (ECs), leukocytes, and platelets, followed by confocal microscopy and image analysis. In septic animals, TF localized preferentially at branches, EC surface, leukocytes, and platelet aggregates and accumulated in large amounts in the subendothelial space. FVII strongly co-localized with TF on ECs and leukocytes but less so with subendothelial TF. TFPI co-localized with TF and FVII on endothelium and leukocytes but not in the subendothelial space. Focal TF increases correlated with fibrin deposition and increased endothelial permeability to plasma proteins. Biochemical analysis confirmed that aortas of septic baboons expressed more TF mRNA and protein than controls. Branched segments contained higher TF protein levels and coagulant activity than equivalent linear areas. These data suggest that site-dependent endothelial heterogeneity and rheological factors contribute to focal procoagulant responses to E. coli.

Evidence for frequency-dependent arterial damage in vibrated rat tails

The effects of single 4-hr bouts of continuous 30, 60, 120, and 800 Hz tail vibration (49 m/sec2, root mean squared) were compared to assess frequency-amplitude-related structural damage of the ventral caudal artery. Amplitudes were 3.9, 0.98, 0.24, and 0.0055 mm, respectively. Vibrated, sham-vibrated, and normal arteries were processed for light and electron microscopy. The Curry rat tail model of hand-arm vibration (Curry et al. Muscle Nerve 2002;25:527-534) proved well-suited for testing multiple frequencies. NFATc3 immunostaining, an early marker of cell damage, increased in smooth muscle and endothelial cells after 30, 60, and 120 Hz but not 800 Hz. Increased vacuolization, which is indicative of smooth muscle contraction, occurred for all frequencies except 800 Hz. Vacuoles increased in both endothelial and smooth muscle cells after 60 and 120 Hz. Only 30 Hz showed pronounced smooth muscle cell vacuolization along the internal and external elastic membranes, suggesting stretch-mediated contraction from the large amplitude shear stress. Discontinuities in toluidine blue staining of the internal elastic membrane (IEM) increased for all frequencies, indicating vibration-induced structural weakening of this structure. Patches of missing IEM and overlying endothelium occurred in approximately 5% of arteries after 60, 120, and 800 Hz. The pattern of damage after 800 Hz suggests that the IEM is disrupted because it resonates at this frequency. Vibration acceleration stress and smooth muscle contraction appear to be the major contributors to arterial damage. The pattern of vibration-induced arterial damage of smooth muscle and endothelial cells is frequency-amplitude-dependent.