Imaging aspects of cardiovascular disease at the cell and molecular level

Cell and molecular imaging has a long and distinguished history. Erythrocytes were visualized microscopically by van Leeuwenhoek in 1674, and microscope technology has evolved mightily since the first single-lens instruments, and now incorporates many types that do not use photons of light for image formation. The combination of these instruments with preparations stained with histochemical and immunohistochemical markers has revolutionized imaging by allowing the biochemical identification of components at subcellular resolution. The field of cardiovascular disease has benefited greatly from these advances for the characterization of disease etiologies. In this review, we will highlight and summarize the use of microscopy imaging systems, including light microscopy, electron microscopy, confocal scanning laser microscopy, laser scanning cytometry, laser microdissection, and atomic force microscopy in conjunction with a variety of histochemical techniques in studies aimed at understanding mechanisms underlying cardiovascular diseases at the cell and molecular level.

Microvascular oxygen quantification using two-photon microscopy

An instrument is demonstrated that is capable of three-dimensional (3D) vasculature imaging and pO(2) quantification with high spatial resolution. The instrument combines two-photon (2P) microscopy with phosphorescence quenching to measure pO(2). The instrument was demonstrated by performing depth-resolved microvascular pO(2) measurements of rat cortical vessels down to 120 microm below the surface. 2P excitation of porphyrin was confirmed, and measured pO(2) values were consistent with previously published data for normoxic and hyperoxic conditions. The ability to perform 3D pO(2) measurements using optical techniques will allow researchers to overcome existing limitations imposed by polarographic electrodes, magnetic resonance techniques, and surface-only pO(2) measurement techniques.

Perindopril, atenolol, and amlodipine prevent aortic ultrastructural changes in rats exposed to ethanol

BACKGROUND

The effects of perindopril, an angiotensin-converting enzyme inhibitor, atenolol, a beta adrenergic receptor blocker, and amlodipine, a calcium channel blocker, were investigated in chronic alcohol administered rats.

MATERIAL/METHODS

Adult male Wistar rats (240-320 g) were used in the present study. Alcohol was given to rats on a modified liquid diet for 21 days. Perindopril (2.5 and 5 mg/kg), atenolol (5 and 10 mg/kg), and amlodipine (5 and 10 mg/kg) were injected into rats in different groups intraperitoneally for 21 days. Control rats were pair fed an isocaloric liquid diet containing sucrose as a caloric substitute for alcohol. Saline was injected into the control rats for 21 days. The hearts were removed after the rats were anesthetized by ether, and 1-mm3 samples from the ascending aortas were fixed. Five fields per aorta were examined and photographed with a transmission electron microscope. Blood alcohol levels were also measured spectrophotometrically.

RESULTS

Daily alcohol consumption of the rats was in the range of 12.09-15.50 g/kg. Blood alcohol concentrations were 145.63 mg/dl on the 21st day of alcohol consumption. Chronic alcohol consumption caused some marked aortic wall injuries. Perindopril, atenolol, and amlodipine at high doses, but not low doses, produced some significant beneficial effects on alcohol-induced aortic wall damage.

CONCLUSIONS

These results imply that perindopril, atenolol, and amlodipine may have protective effects on heavy chronic alcohol consumption-induced aortic wall injury in rats only in high doses.

Increased Protein Nitration Burden in the Atherosclerotic Lesions and Plasma of Apolipoprotein A-I–Deficient Mice

Apolipoprotein A-I (apoA-I), the major protein constituent within high-density lipoprotein (HDL), has been associated with antiatherogenic protection by mechanisms that include reverse cholesterol transport and antiinflammatory functions. To evaluate the proposed protective function of apoA-I, proteins modified by nitrating oxidants were evaluated in the aortic tissue and plasma of mice lacking the low-density lipoprotein receptor and apobec (LA) and LA mice with genetic deletion of apoA-I (LA–apoA-I −/− ). The levels of nitrated proteins in aortic tissue quantified by liquid chromatography with online electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS) were 6-fold higher in the LA–apoA-I −/− as compared with the LA mice. The quantitative analyses were corroborated by immunohistochemical and high-resolution immunoelectron microscopic evaluation of the lesions, which revealed abundant staining for nitrated proteins in the aortic root lesions of LA–apoA-I −/− as compared with the LA mice. Proteomic approaches based on affinity enrichment and site-specific adduct mapping identified unique specific protein targets for nitration in the plasma of LA–apoA-I −/− that were not present in the plasma of LA mice. In particular the nitration of fibrinogen was shown to accelerate fibrin clot formation. Another consequence of the augmented levels of nitrated proteins was the induction of humoral responses documented by the increased circulating immunoglobulins that recognize nitrotyrosine in LA–apoA-I −/− as compared with the LA mice. These data collectively support a protective function of apoA-I diminishing the burden of nitrative oxidants in these mice models of atherosclerosis.

Dietary iron deficiency compromises normal development of elastic fibers in the aorta and lungs of chicks

Elastic fibers play a key role in the structure and function of numerous organs that require elasticity. Elastogenesis is a complex process in which cells first produce a microfibrillar scaffold, composed of numerous structural proteins, upon which tropoelastin assembles to be cross-linked into polymeric elastin. Recently, it was demonstrated that low concentrations of free iron upregulate elastin gene expression in cultured fibroblasts. The present studies were conducted to assess whether low-iron diets would affect the deposition of elastic fibers in an in vivo model. One-day-old chicks were fed semipurified diets containing 1.3 (low), 12 (moderate), and 24 (control) mg/kg of iron. After 3 wk, chicks in the low-iron group were underweight and anemic. Their aortas were smaller with significantly thinner walls than control chicks, yet elastin or collagen content did not decrease relative to total protein. They also demonstrated a significantly lower stress-strain resistance than the controls. Electron microscopy demonstrated that aortic and lung smooth muscle cells were vacuolated and surrounded by loose extracellular matrix and disorganized elastic lamellae with diffuse and fragmented networks of elastic fibers and microfibrils. Immunohistology demonstrated that fibrillin-3 (FBN3) was disorganized and markedly reduced in amount in aortas of the low-iron chicks. Elastin messenger RNA levels were not downregulated in the tissues from the low-iron-fed chicks; however, there was a significant reduction in expression of the FBN1 and FBN3 genes compared with control chicks. The studies indicate that iron deficiency had a pronounced negative effect on elastic fiber development and suggests that fibrillin may have an important role in this pathology.

Time-dependent biaxial mechanical behavior of the aortic heart valve leaflet

Despite continued progress in the treatment of aortic valve (AV) disease, current treatments continue to be challenged to consistently restore AV function for extended durations. Improved approaches for AV repair and replacement rests upon our ability to more fully comprehend and simulate AV function. While the elastic behavior the AV leaflet (AVL) has been previously investigated, time-dependent behaviors under physiological biaxial loading states have yet to be quantified. In the current study, we performed strain rate, creep, and stress-relaxation experiments using porcine AVL under planar biaxial stretch and loaded to physiological levels (60 N/m equi-biaxial tension), with strain rates ranging from quasi-static to physiologic. The resulting stress-strain responses were found to be independent of strain rate, as was the observed low level of hysteresis ( approximately 17%). Stress relaxation and creep results indicated that while the AVL exhibited significant stress relaxation, it exhibited negligible creep over the 3h test duration. These results are all in accordance with our previous findings for the mitral valve anterior leaflet (MVAL) [Grashow, J.S., Sacks, M.S., Liao, J., Yoganathan, A.P., 2006a. Planar biaxial creep and stress relaxatin of the mitral valve anterior leaflet. Annals of Biomedical Engineering 34 (10), 1509-1518; Grashow, J.S., Yoganathan, A.P., Sacks, M.S., 2006b. Biaxial stress-stretch behavior of the mitral valve anterior leaflet at physiologic strain rates. Annals of Biomedical Engineering 34 (2), 315-325], and support our observations that valvular tissues are functionally anisotropic, quasi-elastic biological materials. These results appear to be unique to valvular tissues, and indicate an ability to withstand loading without time-dependent effects under physiologic loading conditions. Based on a recent study that suggested valvular collagen fibrils are not intrinsically viscoelastic [Liao, J., Yang, L., Grashow, J., Sacks, M.S., 2007. The relation between collagen fibril kinematics and mechanical properties in the mitral valve anterior leaflet. Journal of Biomechanical Engineering 129 (1), 78-87], we speculate that the mechanisms underlying this quasi-elastic behavior may be attributed to inter-fibrillar structures unique to valvular tissues. These mechanisms are an important functional aspect of native valvular tissues, and are likely critical to improve our understanding of valvular disease and help guide the development of valvular tissue engineering and surgical repair.

Comparative morphology of the hemolymph vascular system in scorpions--a survey using corrosion casting, MicroCT, and 3D-reconstruction

Although scorpions are one of the better known groups of Arthropoda, detailed knowledge of their anatomy remains superficial. This contribution presents the first comprehensive investigation of the gross morphology of the scorpion vascular system, based on a survey of species representing all major lineages of the order, using classical and modern non-destructive techniques in combination with three-dimensional reconstruction. The investigation reveals that the hemolymph vascular system (HVS) of Scorpiones comprises a central pumping heart which extends the entire length of the mesosoma and is enclosed in a pericardium. Several arteries branch off the heart to supply different organs and body regions. Two different anterior aorta major branching patterns are identified among the species investigated. Arteries that branch off the anterior aorta system supply the appendages (chelicerae, pedipalps, and walking legs) and the central nerve mass with a complex arterial network. This study of the HVS of scorpions provides further evidence that the vascular systems of euarthropods can be highly complex. Use of the term "open circulatory system" within arthropods is re-emphasized, as it refers to the general organization of the body cavity (i.e. mixocoely) rather than to the complexity of the circulatory system.

A novel method for quantification of the folding of elastic laminae in elastic arteries

A transgenic mouse overexpressing the human form of semicarbazide-sensitive amine oxidase (SSAO) is known to have an abnormal structure of the elastic laminae and the elastic fibres in the aorta. Compared to the non-transgenic littermates, the elastic laminae are less folded. In order to quantify the undulation of this structure, an image analysis program that identified the elastic laminae was developed. The program measures the area fraction in different sectors from a plane parallel to the aorta wall. Images were taken from unstained aorta specimens where the elastic laminae were visualised with phase contrast microscopy. A contextual operation of the images produced a local orientation estimation for every linear structure. The image was then thresholded in eight sectors from 0 degrees to 180 degrees , with different orientation angles. The results show that the area fraction of the elastic laminae was significantly lower for the transgenic mouse in all sectors measured except for two. At 0-25 degrees , no difference was seen. In the sector at 160-180 degrees , parallel to the aorta wall, the area fraction of elastic laminae was instead significantly higher in the transgenic mouse. A novel method is presented, developed for detection and quantification of pathological changes in the elastic laminae in the aorta wall. The method gave reliable results and is considered to be a useful tool for morphometric studies of aorta with this kind of altered morphology concerning the elastic laminae. When compared with tangent count, the control group had a significantly larger mean curvature.

Cardiac cells implanted within the outer aortic wall of rats generate measurable contractile force

PURPOSE

To determine whether neonatal cardiomyocytes grafted into the aortic wall contract, develop pressure, and can be paced.

METHODS AND RESULTS

Medium only (n = 9) or neonatal cardiomyocytes (n = 12, 5 x 10(6) cells each) were injected into the outer aortic wall in adult female Fischer rats. At 6 weeks after implantation, 11 out of 12 cardiomyocyte-treated aortas showed spontaneous rhythmic beating at the grafted site following excision of the heart. The spontaneous beating rate changed with pacing frequency. Five out of the 11 beating aortas had intra-aortic pressure generated by the spontaneously contracting cardiomyocytes. The pulse pressure generated by the grafted cardiomyocytes was 0.36 +/- 0.05 mmHg without pacing; during pacing it was 0.78 +/- 0.21 mmHg with systolic pressure up to 3.8 mmHg. Hematoxylin and eosin staining showed viable grafts in the outer wall of the cardiomyocyte-treated aortas in 12 out of 12 aortas. Neonatal cardiomyocytes in the graft matured with cross striations. Immunohistochemical staining of the aorta for sacromeric actin was positive in 12 out of 12 aortas. Staining of connexin 43 showed that some grafted cardiomyocytes formed gap junctions. The above examinations were negative in nine out of nine medium-treated aortas.

CONCLUSION

The results show for the first time that cardiomyocytes engrafted into the foreign environment of an extracardiac vascular structure can be paced and generate measurable intravascular pressure. This study may serve as a useful model for studying the growth and response of the grafted cardiomyocytes to various stimuli in an extra-cardiac environment in vivo.

Improving biocompatibility of heart valve and vascular transplants by their devitalization and repopulation by recipient cells

Inoculation of cells derived from the aorta of Wistar rats on devitalized porcine aortic walls 2-4-fold reduced their calcinosis after subcutaneous implantation to Wistar rats. Inoculation of Wistar rat bone marrow mesenchymal cells selected by adhesion activity did not reduce tissue calcinosis. The results indicate good prospects of repopulation of devitalized heart valve and vessel transplants by recipient vascular cells for reducing transplant calcinosis and improvement of their biocompatibility.

Knockout mice: is it just genetics? Effect of enriched housing on fibulin-4(+/-) mice

BACKGROUND

Fibulin-4 is an extracellular matrix protein expressed by vascular smooth muscle cells that is essential for maintaining arterial integrity. Fibulin-4(-/-) mice die just before birth due to arterial hemorrhage, but fibulin-4(+/-) mice appear to be outwardly normal. Experiments were therefore performed to determine whether fibulin-4(+/-) mice display arterial pathologies on a microscopic scale. After preliminary experiments were performed, a second purpose developed, which was to test the hypothesis that any observed pathologies would be ameliorated by housing the animals in enriched cages.

METHODOLOGY

Fibulin-4(+/-) and wild-type mice were housed either four/cage in standard cages or two per cage in larger cages, each cage containing a tunnel and a wheel. After three weeks the mice were sacrificed, and the aortas perfusion-fixed and excised for light and electron microscopy.

PRINCIPLE FINDINGS

When the mice were in standard cages, localized regions of disorganized extracellular matrix and collagen fibers consistently appeared between some of the medial smooth muscle cells in the fibulin-4(+/-) mice. In the wild-type mice, the smooth muscle cells were closely connected to each other and the media was more compact. The number of disorganized regions per square mm was significantly greater for fibulin-4(+/-) mice (172+/-43 (SEM)) than for wild-type mice (15+/-8) (p<0.01, n = 8). When the mice were in enriched cages, the fibulin-4(+/-) mice showed significantly fewer disorganized regions than those in standard cages (35+/-12) (p<0.05, n = 8). The wild type mice also showed fewer disorganized regions (3+/-2), but this difference was not significant.

CONCLUSIONS

These results indicate that arterial pathologies manifested in fibulin-4(+/-) mice can be reduced by enriching the housing conditions, and imply that appropriate environments may counteract the effects of some genetic deficiencies.

Severe endothelial dysfunction in the aorta of a mouse model of Fabry disease; partial prevention by N-butyldeoxynojirimycin treatment

OBJECTIVE

Fabry disease results from alpha-gala-ctosidase A deficiency and is characterized by the lysosomal accumulation of globotriaosylceramide. Globotriaosylceramide storage predominantly affects endothelial cells, altering vascular wall morphology and vasomotor function. Our objective was to investigate aortic globotriaosylceramide levels, morphology and function in a mouse model of Fabry disease, and the effect of substrate reduction therapy, using the glycosphingolipid biosynthesis inhibitor N-butyldeoxynojirimycin.

METHODS AND RESULTS

Mice used were C57BL/6J and alpha-galactosidase A knockout (Fabry). We show progressive accumulation of aortic globotriaosylceramide throughout the lifespan of untreated Fabry mice (55-fold elevation at 2 months increasing to 187-fold by 19 months), localized to endothelial and vascular smooth-muscle cells; there was no effect on vascular wall morphology in young Fabry mice. In old mice, storage resulted in intimal thickening. Endothelial function declined with age in Fabry mouse aorta. Aortae from N-butyldeoxynojirimycin-treated Fabry mice at 19 months of age had reduced endothelial globotriaosylceramide storage, fewer morphological abnormalities and less severe vasomotor dysfunction compared with untreated littermates.

CONCLUSION

We provide evidence of a novel vascular phenotype in the Fabry mouse that has relevance to vascular disease in Fabry patients. N-Butyldeoxynojirimycin treatment partially prevented the phenotype in the Fabry mouse by reducing endothelial globotriaosylceramide storage.

Caveolae in smooth muscles: nanocontacts

Smooth muscle cell (SMC) caveolae have been investigated by quantitative and qualitative analysis of transmission electron microscopy (TEM) images of rat stomach, bladder and myometrium, guinea pig taenia coli, human ileum, and rat aortic SMCs. Ultrathin (below 30 nm) serial sections were used for examination of caveolar morphology and their connections with SMC organelles. Average caveolar diameter was smaller in vascular SMCs (70 nm, n=50) than in visceral SMCs (77 nm, n=100), but with the same morphology. Most of the caveolae, featured as flask-shaped plasma membrane (PM) invaginations, opened to the extracellular space through a 20 nm stoma (21, 3nm) having a 7 nm thick diaphragm. A small percentage of caveolae (3%), gathered as grape-like clusters, did not open directly to the extracellular space, but to irregular PM pockets having a 20-30 nm opening to the extracellular space. In visceral SMCs, caveolae were disposed in 4 - 6 rows, parallel to myofilaments, whilst aortic SMCs caveolae were arranged as clusters. This caveolar organization in rows or clusters minimizes the occupied volume, providing more space for the contractile machinery. The morphometric analysis of relative volumes (% of cell volume) showed that caveolae were more conspicuous in visceral than in vascular SMCs (myometrium - 2.40%; bladder - 3.66%, stomach - 2.61%, aorta - 1.43%). We also observed a higher number of caveolae per length unit of cell membrane in most visceral SMCs compared to vascular SMCs (myometrium - 1.06/μm, bladder - 0.74/μm, aorta - 0.57/μm, stomach - 0.48/μm). Caveolae increase the cellular perimeter up to 15% and enlarge the surface area of the plasma membrane about 80% in SMCs. Three-dimensional reconstructions (15μ³) showed that most caveolae, in both visceral and vascular SMCs, have nanocontacts with SR (87%), or with mitochondria (10%), and only 3%, apparently, have no contact with these organelles. Usually, 15 nm wide junctional spaces exist between caveolae and SR, some of them with nanostructural links between each other or with mitochondria: direct contacts (space < 2 nm or none) and molecular links, so called ‘feet’ (about 12 nm electron dense structures between organellar membranes). Direct contacts possibly allow molecular translocation between the two membranes. Electron-dense ‘feet’-like structures suggest a molecular link between these organelles responsible for intracellular Ca²⁺ homeostasis (excitation-contraction coupling or pharmaco-mechan-ical coupling). Close appositions (∼15 nm) have also been observed between caveolae and perinuclear SR cisterna, suggesting that caveolae might be directly implicated in excitation-transcription coupling.

Changes in the activity of Cu/Zn superoxide dismutase, lipid profile and aorta morphology of spontaneously hypertensive rats on zinc diet

The aim of the present study was to investigate the effect of zinc on the activity of copper-zinc superoxide dismutase (Cu/Zn SOD), the lipid profile, the arterial blood pressure and the morphological changes of the aorta in male spontaneously hypertensive rats (SHR).

MATERIALS AND METHODS

The study included 52 male SHR animals. The animals were randomly asigned into three groups to be fed one of three zink diets--in group one animals (G1, control group) the zinc content was 50 mg/kg, in group two (G2)--155 mg/kg and in group three (G3) 250 mg/kg. The laboratory chow zinc content and the zinc and copper serum levels were measured by a direct flame atomic-absorption spectrophotometry. The Cu/Zn SOD activity was measured in the erythrocytes using a reagent from RANSOD (RANDOX Laboratories). Systolic arterial blood pressure was measured on the rat's tail (tail cuff) by an indirect method without anesthesia (Ugo Basile). The lipid profile was determined with ABX reagents (France). Histological investigations of the aortas were performed using histochemical and electron microscopic methods.

RESULTS

Statistically significant increase of Cu/Zn SOD activity (p < 0.05) was found in G2 (2276.88 +/- 145.53) and G3 (2337.31 +/- 146.25) in comparison with the control group of animals (2099.46 +/- 111.73). There was significant decrease of serum LDL levels (p < 0.05) in G3 (1.09 +/- 0.32) compared with G2 (1.19 +/- 0.42) and G1 (1.62 +/- 0.28). Increased number of migrated smooth muscle cells was found in G1 animals. Lipid drops were increased in the aortic wall of SHR animals and then decreased after zinc diet was applied.

CONCLUSIONS

The results indicate that high zinc content in the diet has a protective effect as it increases Cu/Zn SOD activity, decreases the LDL serum levels and the lipid infiltration of the aorta in male SHR animals.

Localization of lipids in the aortic wall with imaging TOF-SIMS

Time-of-flight secondary-ion-mass-spectrometry (TOF-SIMS) was utilized to address the issue of localization of lipids and inorganic ions in healthy rat aorta and human atherosclerotic plaque. Pieces of rat aorta were high pressure frozen, freeze-fractured and freeze dried. The samples were analyzed by imaging TOF-SIMS equipped with a Bi(1-7)(+)-source. Reference lipid samples were analyzed and compared to data obtained by analysis of the rat aorta samples. Fatty acids, cholesterol, oxysterol and diacylglycerols were detected and localized. A heterogeneous lipid distribution could be shown in the aorta, where the lamellae of the aorta, distinguished by imaging of CN(-), appeared enriched in cholesterol, oxysterol and diacylglycerols, while the smooth muscle tissue, identified by imaging of PO(3), appeared enriched in phosphocholine. Palmitic/palmitoleic acid and stearic/oleic acid appeared to be heterogeneously distributed over the aorta with high concentration areas located especially in the tunica media region of the aorta. Human atherosclerotic plaque showed an irregular cholesterol distribution mainly located in spots in the intima region with elongated diacylglycerol regions located mainly in the media region.

Morphological differences between guinea pig aortic and venous endothelial cells in situ

Endothelial cells (ECs) respond to fluid shear stress. They reveal shear stress related morphological changes in both their cell shape and cytoskeletal organization. Little is known about the cytoskeletal organization of ECs in situ. We studied, together with the living ultrasound high resolution imaging system, the distribution of stress fibers (SFs), certain focal adhesion (FA) and signal transduction associated proteins in guinea pig aortic and venous ECs. Although SFs present in the basal portion of venous ECs ran along the direction of the blood flow, their size was smaller and their number was fewer than those of aortic ECs. Venous ECs were elongated to the direction of flow than in aortic ECs exposed over normal shear stress (SS). Since fluid SS in the vein is low, a sustained and uni-directional low SS over a long period might thus cause these structural features observed in venous ECs.

[Anti-atherosclerotic effects of divided functional recipes of Dahang Zhechong pill in rabbits]

OBJECTIVE

To study the effects of the divided functional recipes of Dahuang Zhechong pill( DHZCP) on atherosclerosis in rabbits.

METHOD

The atherosclerotic model was established by the combination of hypercholesterol feeding and immune-injured endothelium in rabbits. Male New Zealand rabbits were randomly divided into nine groups: normal group, model group, Danshen group (0. 5 g x kg(-1) ), the low-dose(0. 5 g x kg(-1) ) and high-dose( 1.0 g - kg(-1) ) groups of the first divided recipe, the low-dose(0. 75 g x kg-' ) and high-dose(1. 5 g x kg(-1)) groups of the second divided recipe, the low-dose(0. 8 g x kg(-1) ) and high-dose( 1.6 g x kg(-1) ) groups of the third divided recipe. The effects of the divided functional recipes of DHZCP were observed in macropathology, histopathology and ultrastructure. Image analyzing system was used to determine atherosclerotic plaque area, intima thickness(IT) and intima-media thickness(IMT) in rabbit aorta.

RESULT

The divided functional recipes of DHZCP could significantly decreased the deposit of lipid and the atherosclerotic plaque area in aorta intima, relieve the histopathological changes of atherosclerosis, and inhibited the proliferation of vascular smooth muscle cells and collagen to reduce pachynsis of vascular intima. The divided functional recipes of DHZCP also reduced IT, IMT and IT/MT and reversed the contractive vascular remodeling.

CONCLUSION

The divided functional recipes of DHZCP produce the different anti-atherosclerotic action, among which the first divided functional recipe exhibits more effective action.

Cellular mechanisms and signalling pathways activated by high glucose and AGE-albumin in the aortic endothelium

This review summarizes evidence on the effect of excess circulating glucose concentration and AGE-albumin on the aortic endothelial cells (ECs) phenotype, transport function, and expression of signalling molecules. The recent reports on the ECs dysfunction in diabetes are briefly reviewed, to provide a broader view on the link between ECs structural changes, functional alterations, and the underlying biochemical mechanisms. The original results emerging from streptozotocin-injected mice and human aortic endothelial cells grown in high (25 mM) glucose concentration are presented. Compared to physiological condition, in diabetes aortic ECs switch to a biosynthetic phenotype, present an increased number of caveolae, and enhance (by approximately 20%) transcytosis of AGE-albumin (AGE-Alb). In cultured ECs, 25 mM glucose induces approximately 2.6 fold increase in pSTAT-3 and pERK1 and approximately 1.8 fold increase in pERK2; further exposure to 5 microM AGE-Alb causes approximately 4.3 fold increase in pERK1/2 (vs. 5 mM glucose). Together, these data may explain the phenotypic change, enhanced permeability, and proliferation of aortic ECs in diabetic conditions.

Phenotypic heterogeneity is an evolutionarily conserved feature of the endothelium

Mammalian endothelial cells (ECs) display marked phenotypic heterogeneity. Little is known about the evolutionary mechanisms underlying EC heterogeneity. The last common ancestor of hagfish and gnathostomes was also the last common ancestor of all extant vertebrates, which lived some time more than 500 million years ago. Features of ECs that are shared between hagfish and gnathostomes can be inferred to have already been present in this ancestral vertebrate. The goal of this study was to determine whether the hagfish endothelium displays phenotypic heterogeneity. Electron microscopy of the aorta, dermis, heart, and liver revealed ultrastructural heterogeneity of the endothelium. Immunofluorescent studies demonstrated marked differences in lectin binding between vascular beds. Intravital microscopy of the dermis revealed histamine-induced adhesion of leukocytes in capillaries and postcapillary venules, but no such adhesion in arterioles. Together, these data suggest that structural, molecular, and functional heterogeneity of the endothelium evolved as an early feature of this cell lineage.

Ascending aorta dilatation in aortic valve disease: morphological analysis of medial changes

We investigated whether and how the severity of medial degeneration lesions varies along the circumference of the dilated intrapericardial aorta. Two groups of aortic wall specimens, respectively harvested in the convexity and concavity of ascending aorta in 72 patients undergoing surgery for dilatation of the intrapericardial aorta associated with aortic valve disease, were separately sent for pathology, morphometry, and ultrastructural examination. Cystic medial necrosis, fibrosis, and elastic fiber fragmentation were classified into three degrees of severity; their mean degree and morphometric findings in the convexity and in the concavity specimens were compared by paired t-test. Correlation between echocardiographic degree of aortic dilatation and severity of medial degeneration was assessed separately for each of the two groups of specimens. Morphologically, medial degeneration was found in all cases; a higher mean degree was found in the convexity group (2.39 +/- 0.58 vs 1.44 +/- 0.65 in the concavity group; P < 0.001). At morphometry normal smooth muscle cells in the convexity specimens were significantly reduced (P = 0.007); the length (P = 0.012) and number (P = 0.009) of elastic fibers reduced and increased, respectively. Moreover, in the convexity specimens a significantly smaller amount of smooth muscle cells and an increase of immunohistochemical labeling of apoptosis-associated proteins in the subintimal layer of the media was noticed. Correlation between aortic ratio and medial degeneration degree was significant in the convexity group (P < 0.001), but not in the concavity group (P = 0.249). Scanning electron microscopy analysis confirmed morphological results and allowed us to better distinguish the early pathological cavities from the microvessels, which were in the outer media in normal aorta and ubiquitous in aortitis or atherosclerosis. Electron transmission microscopy analysis showed changes in the extracellular matrix and smooth muscle cells, and these changes increased from the intima to the adventitial layer of the media. In dilated intrapericardial aorta, medial degeneration changes and expression of apoptosis-associated proteins are more marked in the ascending aorta convexity, likely due to hemodynamic stress asymmetry. Ultrastructural findings allow us to distinguish the early medial changes not yet evident on light microscopy.

Possible role of Akt to improve vascular endothelial dysfunction in diabetic and hyperhomocysteinemic rats

The study has been designed to investigate the effect of demethylasterroquinone B1 (DAQ B1), an activator of Akt, in diabetes mellitus (DM) and hyperhomocysteinemia (HHcy)-induced vascular endothelial dysfunction. Streptozotocin (55 mg kg(-1), i.v.) and methionine (1.7% w/w, p.o., 4 weeks) were administered to rats to produce DM (serum glucose >140 mg dl(-1)) and HHcy (serum homocysteine >10 microM), respectively. Vascular endothelial dysfunction was assessed using isolated aortic ring preparation, electron microscopy of thoracic aorta and serum concentration of nitrite/nitrate. The expression of messenger RNA for p22phox and eNOS was assessed by reverse transcription-polymerase chain reaction. Serum thiobarbituric acid reactive substances (TBARS) and aortic superoxide anion were estimated to assess oxidative stress. DAQ B1 (5 mg kg(-1), p.o.) or atorvastatin (30 mg kg(-1), p.o.) in diabetic and hyperhomocysteinemic rats significantly reduced serum glucose and homocysteine concentration. DAQ B1 or atorvastatin markedly improved acetylcholine-induced endothelium-dependent relaxation, vascular endothelial lining, serum nitrite/nitrate concentration and serum TBARS in diabetic and hyperhomocysteinemic rats. However, this ameliorative effect of DAQ B1 has been prevented by L-NAME (25 mg kg(-1), i.p.), an inhibitor of eNOS. Therefore, it may be concluded that DAQ B1-induced activation of Akt may activate eNOS and consequently reduce oxidative stress to improve vascular endothelial dysfunction.

Ultrastructural pathology of aortic dissections in patients with Marfan syndrome:

Despite the discovery in 1990 that mutations in the fibrillin-1 gene cause the Marfan syndrome, the pathogenesis of the life-threatening dissections associated with this disease is far from elucidated. Both the massive number of known fibrillin-1 mutations that result in a heterogeneous patient population and the strongly heterogeneous histology of patients' aortae presumably contribute to this lack of knowledge. We performed a detailed ultrastructural immunoelectron microscopic and histochemical analysis of the dissected media of ascending aortae of 10 patients with Marfan syndrome and compared them with those of 6 patients without Marfan syndrome and 77 individuals without known aortic disease. Relatively similar abnormalities were found in both patient groups, although they were more numerous and more diffusely spread in the patients with Marfan syndrome than in the patients without Marfan syndrome. The most conspicuous ultrastructural defects were the formation of abrupt transverse tears in thick and compact elastic lamellae and the local breaking up of smooth muscle cell-elastic lamella connections (that largely consist of microfibrils and elastic extensions, protruding from the elastic lamellae). This breaking up was characterized by a strongly reduced number of microfibrils and a severe shortening of the elastic extensions. Finally, the elastic extensions detached from the lamellae to ultimately degenerate and disappear. These changes were found mainly in the oldest group of patients with Marfan syndrome, indicating that they represented a loss of previously normally developed structures. We also compared our findings with those from a recently developed murine Marfan model (Pereira L, Lee SY, Gayraud B, Andrilopoulos K, Shapiro SD, Bunton T, Biery NJ, Dietz HC, Sakai LY, Ramirez F. Pathogenetic sequence for aneurysm revealed in mice underexpressing fibrillin-1. Proc Natl Acad Sci. U. S. A. 1999: 96: 3819-3823). Next to similarities, several striking differences existed, demonstrating that this model is not fully representative of the human Marfan syndrome.

In-vitro analysis of normal and aneurismal human ascending aortic tissues using FT-IR microspectroscopy

FTIR microspectroscopy has shown to be a proven tool in the investigation of many tissue types. We have used this spectroscopic approach to analyse structural differences between normal and aneurismal aortic tissues and also aortas from patients with congenital anomalies like aortic bicuspid valves. Spectral analysis showed important variations in amide I and II regions, related to changes in alpha-helix and beta-sheet secondary structure of proteins that seem to be correlated to structural modifications of collagen and elastin. These proteins are the major constituents of the aortic wall associated to smooth muscular cells. The amide regions have thus been identified as a marker of structural modifications related to these proteins whose modifications can be associated to a given aortic pathological situation. Both univariate (total absorbance image and band ratio) and multivariate (principal components analysis) analyses of the spectral information contained in the infrared images have been performed. Differences between tissues have been identified by these two approaches and allowed to separate each group of aortic tissues. However, with univariate band ratio analysis, the pathological group was found to be composed of samples from aneurismal aortas associated or not with an aortic bicuspid valve. In contrast, PCA was able to separate these two types of aortic pathologies. For other groups, PCA and band ratio analysis can differentiate between normal, aneurismal, and none dilated aortas from patients with a bicuspid aortic valve.

Ultrastructural damage in vascular endothelium in rats treated with paclitaxel and doxorubicin

Endothelium is the first physiological barrier between blood and tissues and can be injured by physical or chemical stress, particularly by the drugs used in the cancer therapy. Paclitaxel and doxorubicin are frequently used anticancer drugs and their cardiac side effects are well observed in clinical setting. Their side effects on the endothelium are still not clear enough. There are few investigations assessing the damages elicited by the combination use of chemotherapy agents in animal experimental models. The purpose of this study was to examine and compare the side effects of doxorubicin and paclitaxel on endothelium in vivo. The drugs were administered weekly to rats via intraperitoneal injections singly or in combinations. Lastly, aorta endothelium was examined. The most familiar parts of the aorta endothelium are the nucleus, free ribosomes, Weibel-Palada granules, plasmalemmal vesicles, and clear basement membrane. Examination of the endothelium and the related structures revealed some clear degenerative findings. Notably, administration of a paclitaxel and doxorubicin combinations caused the most dramatic change in ultrastructure, which may disrupt many functions of the endothelium.

Direct innervation of the Drosophila melanogaster larval aorta

The heart rate of larval Drosophila is modulated by various biogenic amines and peptides. The actions have always been assumed to be due to direct action on the heart since the larval heart was not known to be innervated. A recent study showed a difference in the sensitivity of the larval heart to serotonin when the CNS was ablated, thus suggesting a direct neural input. Here, we show that GFP tagged motor neurons and nerve terminals are present on the aortic region of the heart. Motor neuron cell bodies also exist outside the CNS. Transmission electron microscopy reveals the direct innervation in the aortic tissue. Thus, developmental and regulatory questions in this genetic model can now be addressed in relation to heart development and neural control.