Pamela Somers

Three‐dimensional and quantitative analysis of atherosclerotic plaque composition by automated differential echogenicity

To validate automated and quantitative three‐dimensional analysis of coronary plaque composition using intracoronary ultrasound (ICUS).

Influence of convolution filtering on coronary plaque attenuation values: observations in an ex vivo model of multislice computed tomography coronary angiography

Attenuation variability (measured in Hounsfield Units, HU) of human coronary plaques using multislice computed tomography (MSCT) was evaluated in an ex vivo model with increasing convolution kernels. MSCT was performed in seven ex vivo left coronary arteries sunk into oil followingthe instillation of saline (1/∞) and a 1/50 solution of contrast material (400xa0mgI/ml iomeprol). Scan parameters were: slices/collimation, 16/0.75xa0mm; rotation time, 375xa0ms. Four convolution kernels were used: b30f-smooth, b36f-medium smooth, b46f-medium and b60f-sharp. An experienced radiologist scored for the presence of plaques and measured the attenuation in lumen, calcified and noncalcified plaques and the surrounding oil. The results were compared by the ANOVA test and correlated with Pearson’s test. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The mean attenuation values were significantly different between the four filters (pu2009<u20090.0001) in each structure with both solutions. After clustering for the filter, all of the noncalcified plaque values (20.8u2009±u200939.1, 14.2u2009±u200935.8, 14.0u2009±u200932.0, 3.2u2009±u200932.4 HU with saline; 74.7u2009±u200966.6, 68.2u2009±u200963.3, 66.3u2009±u200966.5, 48.5u2009±u200960.0 HU in contrast solution) were significantly different, with the exception of the pair b36f–b46f, for which a moderate-high correlation was generally found. Improved SNRs and CNRs were achieved by b30f and b46f. The use of different convolution filters significantly modifief the attenuation values, while sharper filtering increased the calcified plaque attenuation and reduced the noncalcified plaque attenuation.

The histopathology of varicose vein disease.

Varicosity is a complex venous pathology affecting the lower extremities. The exact etiology and physiopathology of varicose vein disease remain, however, unclear. Several theories exist from incompetence of the valves to a disturbance of the smooth muscle cells (SMC) and extra-cellular matrix (ECM) organization providing a weakness of the venous wall. Multiple studies have been performed to explain the underlying mechanisms of varicosity inducing alterations in the expression patterns of the endothelium, SMC, and ECM. In that respect, most attention has been focused on the alteration of the endothelium due to blood stasis and hypoxia inducing migration/proliferation of the medial SMC into the intima. Also, studies in the deformation of the ECM induced by alterations of the expression patterns of the metalloproteinases (MMP) and their inhibitors (TIMPs) have been put forward to explain the etiology of varicosity. However, less attention has been paid to the hormonal changes that occur during pregnancy and menopause, crucial factors to be involved in the etiology of varicosity. Since alteration of the estrogen receptor-b (ERb) expression could enhance directly the cellular volume of SMC and thus the disorganization of the contractile-elastic units, hypertrophy of SMC must be accounted a pivotal role that could induce the weakness of the venous wall. Altogether, this review summarizes an overview of the latest findings of varicosity with respect to the histopathological changes of the different cellular components of the varicose vein wall related to functional and morphologic alterations.

Shear stress and VEGF enhance endothelial differentiation of human adipose-derived stem cells

Abstract Herein we combine chemical and mechanical stimulation to investigate the effects of vascular endothelial growth factor (VEGF) and physiological shear stress in promoting the differentiation human adipose derived stem cells (ADSCs) into endothelial cells. ADSCs were isolated and characterized; endothelial differentiation was promoted by culturing confluent cells in 50u2009ng/ml VEGF under physiological shear stress for up to 14 days. Afterwards, endothelial cells were seeded onto collagen or acellular aortic valve matrices and exposed to four culture conditions: shear stress + VEGF; shear stress − VEGF; static + VEGF and static − VEGF. After 7 days, phenotype was investigated. ADSCs subjected to shear stress and VEGF express a comprehensive range of specific endothelial markers (vWF, eNOS and FLT-1 after 7 days and CD31, FLk-1 and VE-cadherin after 14 days) and maintain the phenotype when seeded onto scaffolds. Our protocol proved to be an efficient source of endothelial-like cells for tissue engineering based on autologous ADSC.

Impact of Detergent-Based Decellularization Methods on Porcine Tissues for Heart Valve Engineering

To date an optimal decellularization protocol of heart valve leaflets (HVL) and pericardia (PER) with an adequate preservation of the extracellular matrix (ECM) is still lacking. This study compares a 4 day Triton X-100-based protocol with faster SDC-based protocols for the decellularization of cardiac tissues. Decellularized and non-treated HVL and PER were processed for histological, biochemical and mechanical analysis to determine the effect of these agents on the structure, ECM components, and biomechanical properties. Tissues treated with SDC-based protocols still showed nuclear material, whereas tissues treated with Triton X-100 1%xa0+xa0ENZxa0±xa0TRYP were completely cell free. For both decellularized tissues, an almost complete washout of glycosaminoglycans, a reduction of soluble collagen and an alteration of the surface ultrastructure was observed. Interestingly, only the elastic fibers of pericardial tissue were affected and this tissue had a decreased maximum load. This study showed that both detergents had a similar impact on the ECM. However, Triton X-100 1% +DNase/RNase (ENZ)xa0±xa0Trypsin (TRYP) is the only protocol that generated completely cell free bioscaffolds. Also, our study clearly demonstrated that the decellularization agents have more impact on pericardial tissues than on heart valve leaflets. Thus, for the purpose of tissue engineering of heart valves, it is advisable to use valvular rather than pericardial matrices.

Decellularization of Heart Valve Matrices: Search for the Ideal Balance

Abstract: Objective: Currently used decellularization procedures have negative effects on extracellular matrix (ECM) integrity. The objective of this study is to evaluate four decellularization methods and their effect on the collagen ultrastructure, mechanical behavior and antigenicity of porcine aortic valves. Methods: Aortic valves were placed in a trypsin, osmotic, trypsin-osmotic or detergent-osmotic solution. Leaflets were processed for histology and mechanical testing. Matrices were implanted subdermally in rats to evaluate immune reaction and calcification. Results: Trypsin-osmotic methodology effected near-complete decellularization. Trypsin treatment resulted in cell removal only in the spongiosa layer. Osmotic and detergent-osmotic treatments did not remove any cells from the cusps. Mechanical strength was significantly inferior in the trypsin (p50,03) and trypsin-osmotic treated group (p50,04). Trypsin and trypsin-osmotic decellularized matrices evoked a strong CD31 inflammatory cell infiltration. Conclusion: Enzymatic-osmotic decellularization appears to be the only effective method to remove cellular components. However, the near cell free scaffolds still evokes a strong CD31 T-cell inflammatory reaction.

Lumen enhancement influences absolute noncalcific plaque density on multislice computed tomography coronary angiography: Ex-vivo validation and in-vivo demonstration

Aim The purpose of this study was to define the in-vitro and in-vivo effects of intracoronary enhancement on the absolute density values of coronary plaques during multislice computed tomography. Methods We studied seven ex-vivo left coronary artery specimens surrounded by olive oil and filled with isotonic saline and four solutions with decreasing dilutions of contrast material: control (isotonic saline), 1/200, 1/80, 1/50, and 1/20. The multislice computed tomography protocol was: slice/collimation 32 × 2 × 0.6 mm and rotation time 330 ms. The attenuation (Hounsfield units) value of atherosclerotic plaques was measured for each dilution in lumen, plaque (noncalcified coronary wall thickening), calcium, and surrounding oil. In-vivo assessment was performed in 12 patients (nine men; mean age 58.7 ± 9.9 years) who underwent two subsequent multislice computed tomography scans (arterial and delayed) after intravenous administration of a single bolus of contrast material. The attenuation values of lumen and plaques during arterial and delayed computed tomography were compared. The results were compared with one-way analysis of variance and correlated with Pearsons test. Results Mean lumen (45 ± 38–669 ± 151 HU) and plaque (11 ± 35–101 ± 72 HU) attenuation differed significantly (P < 0.001) among the different dilutions. The attenuation of lumen and plaque of coronary plaques showed moderate correlation (r = 0.54, P < 0.001). The mean attenuation value in vivo for the arterial and delayed phase scans differed significantly (P < 0.001) for lumen (325 ± 70 and 174 ± 46 HU, respectively) and plaque (138 ± 71 and 100 ± 52 HU, respectively). Conclusion Coronary plaque attenuation values are significantly modified by differences in lumen contrast densities both ex vivo and in vivo. This should be taken into account when considering the distinction between lipid and fibrous plaques.

Acute and chronic effects of dysfunction of right ventricular outflow tract components on right ventricular performance in a porcine model: implications for primary repair of tetralogy of fallot

OBJECTIVESnThis study investigates the contribution of infundibular versus pulmonary valve (PV) dysfunction on right ventricular (RV) function in a porcine model.nnnBACKGROUNDnClinical outcome after repair of tetralogy of Fallot is determined by the adaptation of the right ventricle to the physiological sequelae of the right ventricular outflow tract (RVOT) reconstruction. Recent surgical techniques are pursuing a PV-versus infundibulum-sparing approach.nnnMETHODSnIn a porcine model, 3 types of RVOT dysfunction were created and compared with sham-operated controls: infundibular dysfunction (INF), PV insufficiency (PI), and combined infundibular-PV dysfunction (TAP). Both acute and chronic effects on RV function were studied by using conductance technology and magnetic resonance imaging.nnnRESULTSnIn animals with PI, pulmonary regurgitant fraction progressed more in the presence of concomitant INF (54% in TAP versus 14% in PI; p = 0.03). Subsequently, RV end-systolic and end-diastolic volume increased more in both groups, resulting in decreased ejection fraction after 3 months. Preload-independent systolic indices showed acute impairment of RV contractility in all treatment groups but most in animals with infundibular scarring (INF and TAP). Further chronic deterioration was observed in animals of the TAP group. RV compliance improved proportionally most in the PI and TAP groups in relation to the extent of RV dilation.nnnCONCLUSIONSnSurgical RVOT dysfunction, whether it includes the infundibulum and/or the PV, has an immediate effect on RV performance. Although impaired RV contractility is due to intrinsic myocardial damage by infundibular distortion, it is chronically furthered by PI-related RV dilation. These findings support the adoption of a RVOT-sparing strategy to treat tetralogy of Fallot.

An optimized growth factor cocktail for ovine mesenchymal stem cells

Growth factors that regulate proliferation, migration, and invasion of ovine mesenchymal stem cells (oMSCs) are not well defined. In this study, we have evaluated five growth factors for their ability to initiate and support in vitro proliferation, migration, and invasion of oMSCs. oMSCs were exposed to different doses and combinations of the growth factors: basic fibroblast growth factor (bFGF), transforming growth factor-β (TGF-β), epidermal growth factor (EGF), insulin growth factor-I (IGF-I), connective tissue growth factor, and platelet-derived growth factor-AB (PDGF-AB). Cellular proliferation, motility, and invasiveness were assayed. The most proliferative stimulating growth factors are PDGF-AB+TGF-β and PDGF-AB+IGF-I. Combinations EGF+bFGF and EGF+bFGF+PDGF-AB demonstrated the greatest ability to stimulate migration. Moreover, the triple cocktail EGF+bFGF+TGF-β has the most significant effect on invasion. Different growth factor cocktails are required to enhance proliferation, migration, and invasion. These results may be useful for the development of a tissue-engineered heart valve by stimulating cellular repopulation.

Role of myocardial hypertrophy on acute and chronic right ventricular performance in relation to chronic volume overload in a porcine model: relevance for the surgical management of tetralogy of Fallot.

OBJECTIVESnThe age for correction of tetralogy of Fallot has progressively declined to the postnatal period, often despite an increased rate of transannular patch repair. However, the long-term effect of premature exposure to chronic pulmonary insufficiency on the right ventricle remains unknown. On the basis of the relationship between the duration of pressure overload and age, the role of previous pressure load-related hypertrophy on right ventricular (RV) performance after chronic volume overload was investigated in a porcine model.nnnMETHODSnRV hypertrophy (RVH), induced by pulmonary artery banding, was studied in pigs with (RVH plus pulmonary insufficiency [PI]) and without (RVH) subsequent PI. The effect of volume overload was compared between these 2 groups and pigs without RVH but with PI and controls (sham). Both acute and chronic effects on RV function were studied using conductance technology and validated using echocardiography.nnnRESULTSnAfter chronic volume overload, the end-systolic and end-diastolic volumes were smaller in the RVH+PI group than in the PI group, including a lower pulmonary regurgitation fraction (25% ± 5% vs 35% ± 5%; P = .002). RVH resulted in better preserved systolic function, confirmed by an increased preload recruitable stroke work slope (14.7 ± 1.8 vs 9.3 ± 1.3 Mw.s/mL; P = .025) and higher RV ejection fraction (51% ± 3% vs 45% ± 4%; P = .05). Myocardial stiffness was impaired in the RVH+PI group versus the PI group (β, 0.19 ± 0.03 vs 0.12 ± 0.02 mL(-1); P = .001), presenting restrictive physiology only in the condition associating RVH and PI.nnnCONCLUSIONSnThe results of the present study have demonstrated that RVH attenuates the RV remodeling process related to chronic PI. It enables better preservation of contractility but at the cost of sustained diastolic impairment. These findings might help to determine the timing and strategy for repair of tetralogy of Fallot when RV outflow tract morphology indicates a definite need for transannular reconstruction.