Review: Clinical aspects of vascular remodeling

A study on the ultimate mechanical properties of middle-aged and elderly human aorta based on uniaxial tensile test

Background

The mechanical properties of the aorta are particularly important in clinical medicine and forensic science, serving as basic data for further exploration of aortic disease or injury mechanisms.

Objective

To study the influence of various factors (age, gender, test direction, anatomical location, and pathological characteristics) on the mechanical properties and thickness of the aorta.

Methods

In this study, a total of 24 aortas (age range: 54-88 years old) were collected, one hundred and seventy-four dog-bone-shaped samples were made, and then the uniaxial tensile test was run, finally, pathological grouping was performed through histological staining.

Results

Atherosclerotic plaques were mainly distributed near the openings of blood vessel branches. The distribution was most severe in the abdominal aorta, followed by the aortic arch. Aortic atherosclerosis was a more severe trend in the male group. In the comparison of thickness, there were no significant differences in age (over 50 years) and test direction, the average thickness of the aorta was greater in the male group than the female group and decreased progressively from the ascending aorta to the abdominal aorta. Comparing the mechanical parameters, various parameters are mainly negatively correlated with age, especially in the circumferential ascending aorta (εp "Y = -0.01402*X + 1.762, R2 = 0.6882", εt "Y = -0.01062*X + 1.250, R2 = 0.6772"); the parameters of males in the healthy group were larger, while the parameters of females were larger in atherosclerosis group; the aorta has anisotropy, the parameters in the circumferential direction were greater than those in the axial direction; the parameters of the ascending aorta were the largest in the circumferential direction, the ultimate stress [σp "1.69 (1.08,2.32)"] and ultimate elastic modulus [E2"8.28 (6.67,10.25)"] of the abdominal aorta were significantly larger in the axial direction; In the circumferential direction, the stress [σp "2.2 (1.31,3.98)", σt "0.13 (0.09,0.31)"] and ultimate elastic modulus (E2 "14.10 ± 7.21") of adaptive intimal thickening were greater than those of other groups, the strain (εp "0.82 ± 0.17", εt "0.53 ± 0.14") of pathological intimal thickening was the largest in the pathological group.

Conclusion

The present study systematically analyzed the influence of age, sex, test direction, anatomical site, and pathological characteristics on the biomechanical properties of the aorta, described the distribution of aortic atherosclerosis, and illustrated the characteristics of aortic thickness changes. At the same time, new insights into the grouping of pathological features were presented.

A Triplex Ultrasound Evaluation of Preclinical Changes in Type 2 Diabetes in Foot Arteries

Background and objective: Type 2 diabetes mellitus (T2DM) is a significant health problem that is becoming more prevalent worldwide. This study aimed to assess hemodynamic and morphological parameters in diabetic patients' foot arteries and compare them to those obtained in asymptomatic control group.

Materials and methods: This is a cross-sectional case-control study. B-mode ultrasound, color Doppler, and pulse wave Doppler were conducted to assess the dorsalis pedis arteries (DPAs) and posterior tibial arteries (PTAs). The morphological, total vascular diameter, wall thickness, and flow Doppler indices were measured. A total of 200 hundred participants were selected randomly using a random sampling technique. One hundred diabetic patients and 100 non-diabetic persons were determined.

Results: In diabetic patients, the overall grayscale diameter and wall thickness of foot arteries were statistically significantly larger than the asymptomatic group in the right DPA (p<0.01), left DPA (p<0.001), right PTA (p<0.001), and left PTA (p<0.001). In the diabetic group, the level of hemoglobin A1c (HbA1c) was positively correlated with blood flow resistive index (RI) in the right DPA (r=0.839; p<0.001), left DPA (r=0.801; p<0.001), right PTA (r=0.801; p<0.001), and left PTA (r=0.801; p<0.001). No significant differences were noted in both groups in blood flow Doppler parameters - pulsatility index (PI) and resistive index (RI).

Conclusion: Overall grayscale diameters of foot arteries are larger in the diabetes group than in the control group, indicating arterial wall thickening as an early indicator of diabetes-related alterations. PI of both DPA and RI of right DPA were increased in diabetic patients more than the control group. The level of glycosylatedhemoglobin A1c (HbA1c) was strongly linked with the blood flow resistive index in diabetes patients.

Outcomes of Lower Extremity Endovascular Revascularization: Potential Predictors and Prevention Strategies

Peripheral artery disease (PAD) is a manifestation of atherosclerosis, which may affect arteries of the lower extremities. The most dangerous PAD complication is chronic limb-threatening ischemia (CLTI). Without revascularization, CLTI often causes limb loss. However, neither open surgical revascularization nor endovascular treatment (EVT) ensure long-term success and freedom from restenosis and revascularization failure. In recent years, EVT has gained growing acceptance among all vascular specialties, becoming the primary approach of revascularization in patients with CLTI. In clinical practice, different clinical outcomes after EVT in patients with similar comorbidities undergoing the same procedure (in terms of revascularization technique and localization of the disease) cause unsolved issues that need to be addressed. Nowadays, risk management of revascularization failure is one of the major challenges in the vascular field. The aim of this literature review is to identify potential predictors for lower extremity endovascular revascularization outcomes and possible prevention strategies.

The Society for Vascular Surgery practice guidelines on follow-up after vascular surgery arterial procedures

Although follow-up after open surgical and endovascular procedures is generally regarded as an important part of the care provided by vascular surgeons, there are no detailed or comprehensive guidelines that specify the optimal approaches with regard to testing methods, indications for reintervention, and follow-up intervals. To provide guidance to the vascular surgeon, the Clinical Practice Council of the Society for Vascular Surgery appointed an expert panel and a methodologist to review the current clinical evidence and to develop recommendations for follow-up after vascular surgery procedures. For those procedures for which high-quality evidence was not available, recommendations were based on observational studies, committee consensus, and indirect evidence. Recognizing that there are numerous published reports on the role of duplex ultrasound for surveillance of infrainguinal vein bypass grafts, the Society commissioned a systematic review and meta-analysis on this topic. The panel classified the strength of each recommendation and the corresponding quality of evidence on the basis of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system: recommendations were graded either strong or weak, and the quality of evidence was graded high, moderate, or low. The resulting recommendations represent a wide variety of open surgical and endovascular procedures involving the extracranial carotid artery, thoracic and abdominal aorta, mesenteric and renal arteries, and lower extremity arterial revascularization. The panel also identified many areas in which there was a lack of high-quality evidence to support their recommendations. This suggests that there are opportunities for further clinical research on testing methods, threshold criteria, and the role of surveillance as well as on the modes of failure and indications for reintervention after vascular surgery procedures.

Common carotid artery intima-media thickness increases throughout the pregnancy cycle: a prospective cohort study

Background

High parity is associated with greater cardiovascular disease (CVD) among mid-life and older women. Prospective studies of arterial change throughout pregnancy are needed to provide insight into potential mechanisms. This study assessed vascular adaptation across pregnancy in healthy first-time pregnant women.

Methods

The Maternal Vascular Adaptation to Healthy Pregnancy Study (Pittsburgh, PA, 2010–2015) assessed 37 primigravid women each trimester, 6–8 weeks after delivery and 1–5 years postpartum, with B-mode ultrasound imaging of common carotid artery (CCA) intima-media thickness (IMT) and inter-adventitial diameter (IAD) to assess associations with physical and cardiometabolic measures.

Results

Thirty-seven women (age 28.2 ± 4.5 years, pre-pregnant BMI 24.4 ± 3.2 kg/m²) experienced uncomplicated pregnancies. After adjustment for age and pre-pregnancy BMI, mean (SE) IAD (mm) increased each trimester, from 6.38 (0.08) in the 1st trimester to 6.92 (0.09) in the 3rd trimester, and then returned to 1st trimester levels postpartum (6.35 [0.07], P <  0.001). In contrast, mean (SE) CCA IMT (mm) increased from the 2nd trimester (i.e., 0.546 [0.01]) onward, and remained higher at an average of 2.7 years postpartum (0.581 [0.02], P = 0.03). Weight partially explained changes in IAD.

Conclusions

In uncomplicated first pregnancies, IAD increased and returned to 1st trimester levels postpartum. In contrast, CCA IMT remained increased 2 years postpartum. Maternal weight explained vascular changes better than did metabolic changes. Increased postpartum CCA IMT may persist and contribute to long-term CVD risk.

Electronic supplementary material

The online version of this article (10.1186/s12884-018-1841-y) contains supplementary material, which is available to authorized users.

Exosomes in mesenchymal stem cells, a new therapeutic strategy for cardiovascular diseases?

Cardiovascular diseases (CVDs) are still a major cause of people deaths worldwide, and mesenchymal stem cells (MSCs) transplantation holds great promise due to its capacity to differentiate into cardiovascular cells and secrete protective cytokines, which presents an important mechanism of MSCs therapy for CVDs. Although the capability of MSCs to differentiate into cardiomyocytes (CMCs), endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) has been well recognized in massive previous experiments both in vitro and in vivo, low survival rate of transplanted MSCs in recipient hearts suggests that therapeutic effects of MSCs transplantation might be also correlated with other underlying mechanisms. Notably, recent studies uncovered that MSCs were able to secret cholesterol-rich, phospholipid exosomes which were enriched with microRNAs (miRNAs). The released exosomes from MSCs acted on hearts and vessels, and then exerted anti-apoptosis, cardiac regeneration, anti-cardiac remodeling, anti-inflammatory effects, neovascularization and anti-vascular remodeling, which are considered as novel molecular mechanisms of therapeutic potential of MSCs transplantation. Here we summarized recent advances about the role of exosomes in MSCs therapy for CVDs, and discussed exosomes as a novel approach in the treatment of CVDs in the future.

Doppler ultrasound detection of preclinical changes in foot arteries in early stage of type 2 diabetes

BACKGROUND

There are few reports regarding the changes within the vessels in the initial stage of type 2 diabetes. The aim of this study was to estimate the hemodynamic and morphological parameters in foot arteries in type 2 diabetes subjects and to compare these parameters to those obtained in a control group of healthy volunteers.

MATERIAL/METHODS

Ultrasound B-mode, color Doppler and pulse wave Doppler imaging of foot arteries was conducted in 37 diabetic patients and 36 non-diabetic subjects to determine their morphological (total vascular diameter and flow lumen diameter) and functional parameters (spectral analysis).

RESULTS

In diabetic patients, the overall vascular diameter and wall thickness were statistically significantly larger when compared to the control group in the right dorsalis pedis artery (P=0.01; P=0.001), left dorsalis pedis artery (P=0.007; P=0.006), right posterior tibial artery (P=0.005; P=0.0005), and left posterior tibial artery (P=0.007; P=0.0002). No significant differences were observed in both groups in flow lumen diameters and blood flow parameters (PSV, EDV, PI, RI). In the diabetic group, the level of HbA1c positively correlated with flow resistance index in the right dorsalis pedis artery (r=0.38; P=0.02), right posterior tibial artery (r=0.38; P=0.02) and left posterior tibial artery (r=0.42; P=0.009). The pulsatility index within the dorsalis pedis artery decreased with increased trophic skin changes (r=-0.431, P=0.009).

CONCLUSIONS

In the diabetic group, overall artery diameters larger than and flow lumina comparable to the control group suggest vessel wall thickening occurring in the early stage of diabetes. Doppler flow parameters are comparable in both groups. In the diabetic group, the level of HbA1c positively correlated with flow resistance index and negative correlation was observed between the intensity of trophic skin changes and the pulsatility index.

Influence of temporal variation in wall shear stress on intima-media thickening in arteriovenous fistulae

Arteriovenous fistula (AVF) failure is mainly due to venous stenosis characterized by significant amount of intima-media thickening (IMT), probably in the presence of negative (inward) remodeling. Our hypothesis is that the longitudinal changes in wall shear stress (WSS) within different configurations of AVF can influence remodeling factors (changes in luminal diameter (ΔDh ) and IMT) during its maturation process. Dh is an equivalent diameter for a noncircular conduit. A total of six AVFs with curved (C-AVF; n = 3) and straight (S-AVF; n = 3) configurations were created between the femoral artery and vein of three pigs, bilaterally. CT scans and ultrasounds were utilized to calculate local WSS at 2D (D: days), 7D, and 28D postsurgery. For each AVF, IMT was measured at four regions along the vein using morphometric analyses. At these regions, repeated measurements of WSS and luminal diameter of each AVF were obtained over time. The ΔD(h) between 7D and 28D was significantly larger for C-AVF than for S-AVF (2.27 ± 0.67 mm vs. 0.02 ± 0.55 mm; p < 0.05). Also, at 28D the amount of IMT in C-AVF (77.46 ± 7.10 units) was significantly greater (p < 0.05) when compared with S-AVF (53.71 ± 8.23 units). These structural changes were accompanied by significantly different gradients of WSS over time (τ') for C-AVF (-0.56 ± 0.60 dyne/cm(2)/day) in comparison with S-AVF (0.71 ± 0.39 dyne/cm(2)/day). Negative τ' for C-AVF corresponded to reduction in WSS level over time resulting in a physiological level of WSS at 28D (4.08 ± 5.08 dyne/cm(2)). In contrast, a positive τ' for S-AVF was associated with the increase in WSS levels over time causing high levels of WSS at 28D (36.68 ± 5.32 dyne/cm(2)). The decrease in WSS levels for the C-AVF over time was associated with outward remodeling of the venous wall (favorable to maturation). In contrast, for S-AVF, the increase in WSS levels over time was associated with inward remodeling and subsequently, venous stenosis. Thus, temporal gradients of WSS, which could be altered by the surgical configuration of AVF, may provide important information on the remodeling behavior of AVFs. Identification of an optimal AVF configuration, which results in a temporal decrease in WSS and an outward remodeling of the venous wall, may reduce AVF maturation failure.

Induction of endothelial nitric oxide synthase expression by IL-17 in human vascular endothelial cells: implications for vascular remodeling in transplant vasculopathy

IL-17 is a signature cytokine of Th17 cells, a recently described subset of effector CD4 T cells implicated in the development of several pathologies. We have examined the role of IL-17 in regulating endothelial NO synthase (eNOS) expression in human vascular endothelial cells (ECs) because of the key role of eNOS in determining the pathological outcome of immune-mediated vascular diseases. In cultured ECs, IL-17 increased expression of eNOS, eNOS phosphorylation at Ser(1177), and NO production. The induction of eNOS expression by IL-17 was prevented by the pharmacological inhibition of NF-κB, MEK, and JNK, as well as by small interfering RNA-mediated gene silencing of these signaling pathways. The expression of IL-17 was then examined by immunohistochemistry in human arteries affected by transplant vasculopathy (TV), a vascular condition that is a leading reflection of chronic heart transplant rejection. IL-17 was expressed by infiltrating leukocytes in the intima of arteries with TV, and the majority of IL-17-positive cells were T cells. The number of IL-17-positive cells was not correlated with the intima/media ratio, but was negatively correlated with the amount of luminal occlusion. There was also a significant positive correlation between the number of IL-17-positive cells and the density of eNOS-expressing luminal ECs in arteries with TV. Altogether, these findings show that IL-17 induces the expression of eNOS in human ECs and that this may facilitate outward expansion of arteries afflicted with TV.

Regional distribution of collagen and haemosiderin in the lungs of horses with exercise-induced pulmonary haemorrhage

REASONS FOR PERFORMING STUDY

Regional veno-occlusive remodelling of pulmonary veins in EIPH-affected horses, suggests that pulmonary veins may be central to pathogenesis. The current study quantified site-specific changes in vein walls, collagen and haemosiderin accumulation, and pleural vascular profiles in the lungs of horses suffering EIPH.

HYPOTHESIS

In the caudodorsal lung regions of EIPH-affected horses, there is veno-occlusive remodelling with haemosiderosis, angiogenesis and fibrosis of the interstitium, interlobular septa and pleura.

METHODS

Morphometric methods were used to analyse the distribution and accumulation of pulmonary collagen and haemosiderin, and to count pleural vascular profiles in the lungs of 5 EIPH-affected and 2 control horses.

RESULTS

Vein wall thickness was greatest in the dorsocaudal lung and significantly correlated with haemosiderin accumulation. Increased venous, interstitial, pleural and septal collagen; lung haemosiderin; and pleural vascular profiles occurred together and changes were most pronounced in the dorsocaudal lung. Further, haemosiderin accumulation colocalised with decreased pulmonary vein lumen size. Vein wall thickening, haemosiderin accumulation and histological score were highly correlated and these changes occurred only in the caudodorsal part of the lung.

CONCLUSION

The colocalisation of these changes suggests that regional (caudodorsal) venous remodelling plays an important role in the pathogenesis of EIPH.

POTENTIAL RELEVANCE

The results support the hypothesis that repeated bouts of venous hypertension during strenuous exercise cause regional vein wall remodelling and collagen accumulation, venous occlusion and pulmonary capillary hypertension. Subjected to these high pressures, there is capillary stress failure, bleeding, haemosiderin accumulation and, subsequently, lung fibrosis.

Arachidonic Acid metabolites in the cardiovascular system: the role of lipoxygenase isoforms in atherogenesis with particular emphasis on vascular remodeling

Vascular remodeling refers to lasting structural alterations in the vessel wall that are initiated in response to external and internal stimuli. These changes are distinct from acute functional responses of blood vessels when challenged by increased blood pressure, altered hemodynamics, or vasoactive mediators. In early atherogenesis, when lesion formation is starting to impact local hemodynamics, the vessel wall responds with outward vascular remodeling to maintain normal blood flow. However, inward remodeling may also occur during the time course of plaque formation, contributing to vascular stenosis. Lipoxygenases form a heterogeneous family of lipid-peroxidizing enzymes, which have been implicated in atherogenesis. Several lines of in vitro and in vivo evidence indicated their involvement in disease development, but the precise function of different lipoxygenase isoforms is still a matter of discussion. Vascular remodeling is an early response during plaque development; therefore, lipoxygenases may be involved in this process. Unfortunately, little is known about the potential role of lipoxygenase isoforms in vascular remodeling. This review will briefly summarize our knowledge of the role of lipoxygenases in vascular biology and will critically review the activities of the 3 most athero-relevant lipoxygenase isoforms in atherogenesis, with particular emphasis on vascular remodeling.

Urokinase-type plasminogen activator and metalloproteinase-2 are independently related to the carotid atherosclerosis in haemodialysis patients

INTRODUCTION

Matrix metalloproteinases (MMPs), their tissue inhibitors (TIMPs) system, and fibrinolytic system, have been implicated as important factors in atherosclerosis and vascular remodeling. However, no data are yet available on the associations between these two systems in relation to carotid atherosclerosis in hemodialysis (HD) patients.

MATERIAL AND METHODS

We compared plasma levels of MMP-2, MMP-9, TIMP-1, TIMP-2; the parameters of fibrinolytic system: tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPAR) and its soluble receptor (suPAR), plasminogen activator inhibitor-1 (PAI-1), plasmin-alpha2-antiplasmin (PAP) complexes; high sensitivity C-reactive protein (hs CRP) as a marker of inflammation and a surrogate of atherosclerotic disease-intima media thickness (IMT) in HD patients and in healthy controls.

RESULTS

The values of the uPA, suPAR, PAP, MMP-2, TIMPs, hs CRP and IMT in the patients significantly exceeded those in controls. The concentrations of MMP-9, tPA and PAI-1 were similar in both investigated groups. uPA, uPAR and PAP were positively associated with MMP-2/TIMPs system; all mentioned above parameters (except TIMP-2) and hsCRP were associated with IMT. Multivariate analysis showed that uPA, MMP-2 and age were the strong independent variables linked to IMT values in HD patients.

CONCLUSIONS

The patients on haemodialysis treatment have evidence of disordered fibrinolysis/proteolysis balance in the plasma, independently associated with IMT on multivariate analysis. These data suggest the importance of uPA and MMP-2 levels in the developing of atherosclerosis in these patients.

Human coronary artery remodeling, beginning and end of the atherosclerotic process

Background, Aims of the Study

The objective of the study was to relate the progress of coronary artery remodeling to the earliest stages of the atherosclerotic process. For this purpose, a mathematical model for description of dimensional change of the coronary artery wall and its constituent components was developed and applied.

Materials and Methods

The study used coronary artery samples randomly taken from each of 83 consecutive, unselected postmortems. All samples were routinely fixed and processed to paraffin for the preparation of right-angled, 5-micron sections, routinely stained and mounted for subsequent analysis. Computer assisted image analysis, using 32 systematic random, radial sampling lines, was used for interactive measurements of distance from centre of lumen to points defining intima, media and adventitia thickness along the radial intercept, which were subsequently tabled for analysis of variance, calculations of (group –vessel) means, and related to stage of pathology.

Results

Pre-atherosclerotic changes, before any localised changes in especially intima dimensions, are found, consisting of a process of gradual vascular widening, associated with temporally at least partly dissociated increases in width, which as a fraction of total vessel radius show a phased process. In these, the intima first increases, subsequently remains stable, and finally reduces in width proportionally to the increasing diameter. The media shows a similar initial increase, on average stabilising in the third phase after reaching a plateau value in the second. The adventitia, already increasing in phase 1, continues to increase in phase 2, accelerating in phase 3. The complex process, as found, occurs systematically in all vessels, is distributed circumferentially, and precedes the development of localised lesions of the intima.

Conclusions

The findings suggest the existence of a diffuse complex of changes, consisting of a gradual vascular widening followed by narrowing, with associated mural changes reflecting the atherosclerotic process.

Metalloproteinases in Development and Progression of Vascular Disease

Remodeling of the vascular wall plays a role in many physiological processes, but also in the pathogenesis of major cardiovascular diseases such as restenosis and atherosclerosis. Remodeling requires proteolytic activity to degrade components of the extracellular matrix; this can be generated by the matrix metalloproteinase(MMP) system alone or in concert with the fibrinolytic (plasminogen/plasmin) system. Several lines of evidence suggest that the MMP system plays a role in vascular smooth muscle cell migration and neointima formation after vascular injury. In atherosclerotic lesions, active MMPs may contribute to plaque destabilisation by degrading extracellular matrix components, but may also promote aneurysm formation by proteolytic degradation of the elastic lamina. The MMP system may therefore represent a potential therapeutic target for treatment of restenosis or atherosclerosis.

Vascular endothelin-B receptor system in vivo plays a favorable inhibitory role in vascular remodeling after injury revealed by endothelin-B receptor-knockout mice

BACKGROUND

Two subtypes of endothelin (ET) receptors, ET(A) and ET(B), are distributed in vascular smooth muscle cells to cause contraction and proliferation. Vascular endothelial cells express only ET(B) receptors, which cause NO release. Although ET(A) receptor blockade is reported to be effective in ameliorating vascular remodeling, there is no report on the long-term effect of ET(B) receptor blockade on vascular remodeling after injury.

METHODS AND RESULTS

ET(B) receptor-knockout (KO) mice, which were genetically rescued from lethal intestinal aganglionosis, and wild-type (WT) mice underwent complete ligation of the right common carotid artery, ie, a blood flow cessation model of vascular remodeling. Fourteen days after ligation, the intimal area, the ratio of intimal to medial areas, and the stenotic ratio in the ligated artery of KO mice were significantly increased compared with those of WT mice. The expression level of ET-1 mRNA in the ligated artery of KO mice was increased similarly to that of WT mice, whereas tissue NO(x) levels in lesions of KO mice were significantly lower than those of WT mice. Long-term treatment with the ET(A) receptor antagonist TA-0201 (0.5 mg x kg(-1) x d(-1)) significantly ameliorated vascular stenosis in both groups. Long-term treatment with the ET(B) receptor antagonist A-192621 (30 mg x kg(-1) x d(-1)) worsened vascular remodeling in WT mice.

CONCLUSIONS

We demonstrated that inhibition of the ET(B) receptor system is harmful for vascular remodeling after injury, the mechanism of which is partly attributed to decreased NO release, in KO mice. These results suggest that the overall effect of vascular ET(B) receptors is antiproliferative in the injured artery.

Shear stress and vascular remodeling: study of cardiac allograft coronary artery disease as a model of diffuse atherosclerosis

BACKGROUND

The assessment of remodeling in diffuse atherosclerosis by intravascular ultrasound is hampered by the lack of an appropriate reference segment. Transplant coronary artery disease is an accepted model of diffuse atherosclerosis. Flow-dependent remodeling is regulated by shear stress. Thus, normal levels of shear stress at baseline flow reflect adequate regulation and provide a functional assessment of flow-dependent remodeling.

METHODS

The approach was evaluated in 91 patients with transplant coronary artery disease and in 9 non-transplanted controls and 16 control transplant recipients. Quantitative coronary angiography, intracoronary ultrasound and intracoronary velocity studies were performed at baseline and after pharmacologic intervention. Calculated shear stress was compared between these groups and a sub-group with coronary angioplasty at follow-up (8 of 60 patients with control angiography after 23 +/- 8 months). The relation of shear stress to flow, diameter, flow/area ratio and endothelial function was analyzed.

RESULTS

Normal shear stress was found in non-transplanted controls and transplant recipients without coronary artery disease. Patients with coronary angioplasty at follow-up had elevated shear stress and enhanced endothelial dysfunction on the initial investigation. Shear stress was not correlated with flow (r = 0.062, non-significant), but with diameter (r = -0.654), flow/area ratio (r = 0.814) and endothelial dysfunction (r = 0.722).

CONCLUSION

Calculated local shear stress appears to be useful for the assessment of the adequacy of flow-dependent macrovascular remodeling in diffuse atherosclerosis. Elevated blood flow/area ratio is a potential clinical marker of increased shear stress that reflects inadequate flow-dependent remodeling.

Intrapericardial paclitaxel delivery inhibits neointimal proliferation and promotes arterial enlargement after porcine coronary overstretch

BACKGROUND

Catheter-based intrapericardial (IPC) delivery of therapeutic agents has recently been demonstrated. Paclitaxel is known to inhibit vascular smooth muscle cell proliferation. This study examined the effect of IPC instillation of paclitaxel on neointimal proliferation after balloon overstretch of porcine coronary arteries.

METHODS AND RESULTS

Overstretch injury of coronary arteries was followed by IPC administration of micellar paclitaxel at low dose (LD, 10 mg; n=6) or high dose (HD, 50 mg; n=7) or of control micelles (50 mg, n=5). Animals were euthanized 28 days after balloon dilation. Arterial injury indices were no different among the groups. The neointimal area, maximal intimal thickness, and adventitial thickness were significantly reduced in both LD (0.47+/-0.04 mm(2), 0.43+/-0.03 mm, and 0.35+/-0.02 mm, respectively) and HD (0.51+/-0.06 mm(2), 0.42+/-0.03 mm, and 0. 38+/-0.03 mm, respectively) paclitaxel groups compared with the control group (0.79+/-0.07 mm(2), 0.56+/-0.02 mm, and 0.47+/-0.02 mm, respectively; P:<0.001). Meanwhile, the vessel circumference measured at the external elastic lamina of paclitaxel-treated vessels was significantly larger than the control circumference. Apoptotic cells were found in the neointima. The apoptotic cell percentage was not different between the control (1.72%) and LD (2. 31%) groups but was higher in the HD group (7.07%, P:<0.0001 versus control and LD groups). Immunostaining for matrix metalloproteinase-2 revealed concurrent reduction in the HD group compared with the control and LD groups.

CONCLUSIONS

IPC space delivery of a single dose of paclitaxel significantly reduces vessel narrowing in this balloon-overstretch model. This effect is mediated by reduction of neointimal mass as well as positive vascular remodeling.

Endothelial cell delivery for cardiovascular therapy

Obstructive atherosclerotic vascular disease stands as one of the greatest public health threats in the world. While a number of therapies have been developed to combat vascular disease, endothelial cell delivery has emerged as a distinct therapeutic modality. In this article, we will review the anatomy of the normal blood vessel and the biology of the intact endothelium, focusing upon its centrality in vascular biology and control over the components of the vascular response to injury so as to understand better the motivation for a cell-based form of therapy. Our discussion of cell delivery for cardiovascular therapy will be divided into surgical and interventional approaches. We will briefly recount the development of artificial grafts for surgical vascular bypass before turning our attention towards endothelial cell seeded vascular grafts, in which endothelial cells effectively provide local delivery of endogenous endothelial secretory products to maintain prosthetic integrity after surgical implantation. New techniques in tissue and genetic engineering of vascular grafts and whole blood vessels will be presented. Methods for percutaneous interventions will be examined as well. We will evaluate results of endoluminal endothelial cell seeding for treatment of restenosis and gene therapy approaches to enhance endogenous re-endothelialization. Finally, we will examine some innovations in endothelial cell delivery that may lead to the development of endothelial cell implants as a novel therapy for controlling proliferative vascular arteriopathy.