Development Of Intimal Hyperplasia Research Articles

Regulation of vascular smooth muscle cell expression and function of matrix metalloproteinases is mediated by estrogen and progesterone exposure

Postmenopausal women receiving hormone replacement therapy (HRT) have been reported to have more adverse outcomes after vascular reconstructions, including increased intimal hyperplasia development and bypass graft failure. HRT may be affecting the pathway contributing to intimal hyperplasia. An important component of this pathway involves matrix metalloproteinases (MMPs), implicated in vascular remodeling due to their ability to degrade components of the extracellular matrix. We hypothesize that estrogen (Est) and progesterone (Prog) upregulate the MMP pathway in vascular smooth muscle cells (VSMCs) thereby increasing MMP activity and function. VSMCs were incubated with Est (5 ng/mL), Prog (50 ng/mL), Est + Prog combination (Est/Prog), and/or doxycycline (40 microg/mL; Doxy). Using reverse transcriptase polymerase chain reaction (RT-PCR) analysis we have previously shown membrane type 1-MMP (MT1-MMP) messenger ribonucleic acid (mRNA) levels are significantly increased by Est. Here, Western blot analyses indicated MT1-MMP and MMP-2 protein levels, not tissue inhibitor of MMP-2 (TIMP-2), were increased in response to Est and Est/Prog (P < .05 vs control). In-gel zymography revealed that Est and Est/Prog resulted in increased MMP-2 activity (hormone groups, P < .05 vs control) with no significant difference among the hormone groups. VSMC migration was increased by 45 +/- 14% in response to Est (P < .05 vs control), as measured using a modified Boyden chamber assay. Doxycycline significantly inhibited basal and Est/Prog-stimulated increases in MMP-2 activity (P < .05 vs control; P < .05 vs hormone groups), and partially blocked basal and hormonally stimulated migration (P < .05 vs control and Est). Estrogen and progesterone affects the MMP pathway by increasing MMP-2 enzymatic activity, possibly via the upregulation of MT1-MMP expression without a corresponding increase in TIMP expression. This increased collagenase activity increases VSMC motility and their ability to migrate through a collagen type IV lattice. Est/Prog upregulation of MT1-MMP may contribute to the adverse effect of HRT on vascular interventions.

Inhibition of allograft inflammatory factor-1 expression reduces development of neointimal hyperplasia and p38 kinase activity

Allograft inflammatory factor-1 (AIF-1) is a calcium-binding, scaffold-signalling protein expressed in vascular smooth muscle cells (VSMCs) in response to injury. The effects of AIF-1 attenuation on development of intimal hyperplasia are unknown, and the molecular mechanisms of these effects remain uncharacterized. The goals of the present study were to determine whether AIF-1 knockdown reduced VSMC proliferation, migration, and intimal hyperplasia, and determine AIF-1 effects on signal transduction in VSMCs. Balloon angioplasty-injured rat carotid arteries transduced with adenovirus to overexpress AIF-1 (AdAIF-1) significantly increased, and adenovirus to knock down AIF-1 (AdsiRNA) expression significantly decreased neointimal formation compared with green fluorescent protein (AdGFP) and Adscrambled controls (P < 0.05 and P < 0.01, n = 6). Primary rat VSMCs transduced with AdAIF-1 displayed a significant increase in proliferation, and AdsiRNA-transduced VSMCs proliferated significantly more slowly than controls (P < 0.05). VSMCs transduced with AdAIF-1 show increased migration when compared with control VSMCs (P < 0.01). Rat VSMCs transduced with AdAIF-1 showed constitutive and prolonged activation of the mitogen-activated protein kinase p38, whereas AdsiRNA-treated VSMCs showed decreased p38 activation compared with AdGFP (P < 0.05). Immunohistochemical analysis of AdAIF-1-transduced carotid arteries showed increased staining with a phospho-specific p38 antibody compared with AdGFP-transduced arteries. A specific p38 inhibitor abrogated AIF-1-induced VSMC proliferation, but not AIF-1-induced migration. Taken together, AIF-1 expression plays a key role in the development of neointimal hyperplasia. AIF-1 expression enhances the activation of p38 MAP kinase. AIF-1-enhanced proliferation is p38 kinase dependent, but AIF-1-enhanced VSMC migration is p38 independent.

Expression and Suppressive Effects of Interleukin-19 on Vascular Smooth Muscle Cell Pathophysiology and Development of Intimal Hyperplasia

Anti-inflammatory cytokines may play a protective role in the progression of vascular disease. The purpose of this study was to characterize interleukin (IL)-19 expression and function in the development of intimal hyperplasia, and discern a potential mechanism of its direct effects on vascular smooth muscle cells (VSMCs). IL-19 is an immunomodulatory cytokine, the expression of which is reported to be restricted to inflammatory cells. In the present study, we found that IL-19 is not expressed in quiescent VSMCs or normal arteries but is induced in human arteries by injury and in cultured human VSMCs by inflammatory cytokines. Recombinant IL-19 significantly reduced VSMC proliferation (37.1 +/- 4.8 x 10(3) versus 72.2 +/- 6.1 x 10(3) cells/cm(2)) in a dose-dependent manner. IL-19 adenoviral gene transfer significantly reduced proliferation and neointimal formation in balloon angioplasty-injured rat carotid arteries (0.172 +/- 29.9, versus 0.333 +/- 71.9, and 0.309 +/- 56.6 microm(2)). IL-19 induced activation of STAT3 as well as the expression of the suppressor of cytokine signaling 5 (SOCS5) in VSMCs. IL-19 treatment significantly reduced the activation of p44/42 and p38 MAPKs in stimulated VSMCs. Additionally, SOCS5 was found to interact with both p44/42 and p38 MAPKs in IL-19-treated human VSMCs. This is the first description of the expression of both IL-19 and SOCS5 in VSMCs and of the functional interaction between SOCS5 and MAPKs. We propose that through induction of SOCS5 and inhibition of signal transduction, IL-19 expression in VSMCs may represent a novel, protective, autocrine response of VSMCs to inflammatory stimuli.

Lysophosphatidic Acid Receptors 1 and 2 Play Roles in Regulation of Vascular Injury Responses but Not Blood Pressure

Phenotypic modulation of vascular smooth muscle cells (SMCs) is essential for the development of intimal hyperplasia. Lysophosphatidic acid (LPA) is a serum component that can promote phenotypic modulation of cultured SMCs, but an endogenous role for this bioactive lipid as a regulator of SMC function in vivo has not been established. Ligation injury of the carotid artery in mice increased levels in the vessel of both autotaxin, the lysophospholipase D enzyme responsible for generation of extracellular LPA, and 2 LPA responsive G protein-coupled receptors 1 (LPA1) and 2 (LPA2). LPA1(-/-)2(-/-) mice were partially protected from the development of injury-induced neointimal hyperplasia, whereas LPA1(-/-) mice developed larger neointimal lesions after injury. Growth in serum, LPA-induced extracellular signal-regulated protein kinase activation, and migration to LPA and serum were all attenuated in SMCs isolated from LPA1(-/-)2(-/-) mice. In contrast, LPA1(-/-) SMCs exhibited enhanced migration resulting from an upregulation of LPA3. However, despite their involvement in intimal hyperplasia, neither LPA1 nor LPA2 was required for dedifferentiation of SMCs following vascular injury or dedifferentiation of isolated SMCs in response to LPA or serum in vitro. Similarly, neither LPA1 nor LPA2 was required for LPA to elicit a transient increase in blood pressure following intravenous administration of LPA to mice. These results identify a role for LPA1 and LPA2 in regulating SMC migratory responses in the context of vascular injury but suggest that additional LPA receptor subtypes are required for other LPA-mediated effects in the vasculature.

Effect of serum concentration on adhesion of monocytic THP-1 cells onto cultured EC monolayer and EC-SMC co-culture

The adhesion of monocytes to the endothelium following accumulation of low-density lipoprotein (LDL) in subendothelial spaces is an important step in the development of intimal hyperplasia in arterially implanted vein grafts and atherosclerosis in both animals and humans. However, it is not well known how serum factors affect the adhesion of monocytes. We have studied the effect of fetal calf serum (FCS), which we considered a source of LDL, on the adhesion of monocytes to endothelial cells (ECs) by using human monocytic THP-1 cells and both a monolayer of cultured bovine aortic endothelial cells (EC monoculture) and a co-culture with bovine aortic smooth muscle cells (EC-SMC co-culture). It was found that the addition of FCS to the medium greatly affected the adhesion of THP-1 cells, and the higher the concentration of FCS in the medium, the greater the adhesion of THP-1 cells to endothelial cells. Adhesion of THP-1 cells to an EC-SMC co-culture was approximately twofold greater than that to an EC monoculture, and after adhering to endothelial cells, many THP-1 cells transmigrated into the layer of smooth muscle cells. The results suggest that the elevation of the LDL (cholesterol) level in blood provides a favorable condition for the development of intimal hyperplasia and atherosclerosis by promoting the adhesion of monocytes to the endothelium and their subsequent migration into subendothelial spaces.

FLOW CHARACTERIZATION INSIDE A COMPLEX AV GRAFT TO VEIN CONNECTION

Flow field characterization inside a complex arteriovenous (AV) graft to vein connection using laser Doppler anemometry (LDA) under steady flow conditions is done in this study. The objective of the current study is to find the critical flow regions and to understand the importance of biomechanical forces in the development of intimal hyperplasia (IH) within these grafts. In vivo studies were done by [Fillinger, 1990]. They correlated Reynolds number characterizing the flow with the fluctuations inside anastomosis. Loth, 2003 analyzed the flow field inside AV graft to vein connection and found the turbulence level inside the connection region

Differential association between human prostacyclin receptor polymorphisms and the development of venous thrombosis and intimal hyperplasia: a clinical biomarker study

The role of prostacyclin in the development of venous thrombosis and vascular dysfunction in humans is unclear. In patients with deep vein thrombosis (DVT, n=34) and controls (matched for age, sex, indexes of systemic inflammation and metabolic status, n=20), we studied (i) differences on systemic markers of vascular disease and platelet activation and (ii) the influence of prostacyclin receptor gene (PTGIR) polymorphisms. Enhanced levels of urinary 11-dehydro-thromboxane (TX)B2 and plasma [soluble(s)] P-selectin, mostly platelet derived, were detected in DVT patients, whereas plasma von Willebrand factor levels and intima-media thickness of the common carotid arteries were not significantly different. In all patients' cohorts, we identified five PTGIR polymorphisms (three nonsynonymous: P226T, R212C, V196L; two synonymous: V53V, S328S). In the four individuals carriers of R212C polymorphism (three in DVT, one in controls), intima-media thickness values were significantly (P=0.0043) higher than those detected in individuals of all cohorts [1.68+/-0.38, 1.55 (1.4-2.2) vs. 1.05+/-0.33, 1.08 (0.01-1.68) mm, respectively, mean+/-SD, median (range)]. Moreover, enhanced sP-selectin and 11-dehydro-TXB2, in DVT versus controls, were statistically significant only in carriers of both synonymous PTGIR polymorphisms V53V/S328S. Only the PTGIR mutant R212C was dysfunctional when examined in an in vitro overexpression system. Our results suggest a propensity of enhanced platelet activation in DVT patients with PTGIR polymorphisms V53V/S328S. Moreover, we identified a dysfunctional PTGIR polymorphism (R212C) associated with intimal hyperplasia.

Impaired graft healing due to hypercholesterolemia is prevented by dietary supplementation with α-tocopherol

The patency of prosthetic grafts is partly limited by incomplete endothelial cell coverage and development of anastomotic intimal hyperplasia. The goal of this study was to determine the effect of elevated cholesterol on prosthetic graft healing and the ability of alpha-tocopherol to improve healing. Rabbits were placed on one of four diets: chow, chow plus 1% cholesterol, chow plus alpha-tocopherol, or chow plus 1% cholesterol and alpha-tocopherol. After 2 weeks, expanded polytetrafluoroethylene grafts (12-cm long, 4-mm internal diameter) were implanted in the abdominal aorta. Grafts were removed after 6 weeks and analyzed for cholesterol and alpha-tocopherol content, endothelial coverage, anastomotic intimal thickness, and cellular composition of the neointima. At the time of graft implantation, plasma cholesterol was 34 +/- 4 mg/dL in the chow group and 689 +/- 30 mg/dL in the 1% cholesterol group (P < .05). Grafts removed from hypercholesterolemic rabbits had marked intimal thickening, with an intima/graft thickness ratio of 0.76 +/- 0.29 compared with 0.14 +/- 0.06 in chow animals (P < .05). Macrophage infiltrate was increased to 45 +/- 11 macrophages/0.625 mm(2) in grafts from hypercholesterolemic rabbits compared with 0 +/- 0.4 in controls (P < .05). Endothelialization of grafts was lower in hypercholesterolemic rabbits than in the chow group, with endothelial cells covering 46% +/- 7% and 62% +/- 7% of the graft surface, respectively (P = .05). When alpha-tocopherol was added to the 1% cholesterol diet, the macrophage count decreased to 12 +/- 8, the intimal/graft thickness ratio decreased to 0.17 +/- 0.09, and endothelial coverage increased to 70% +/- 7% (P < .05 compared with the high-cholesterol group). Anastomotic intimal hyperplasia is dramatically increased and endothelialization is reduced in rabbits on a high-cholesterol diet, but alpha-tocopherol supplementation blocks the augmented neointimal thickening and improves endothelial cell coverage.

Numerical simulations of pulsatile non-Newtonian flow in an end-to-side anastomosis model

A potential interaction between the local hemodynamics and the artery wall response has been suggested for vascular graft failure by intimal hyperplasia (IH). Among the various hemodynamic factors, wall shear has been implicated as the primary factor responsible for the development of IH. In order to explore the role of hemodynamics in the formation of IH in end-to-side anastomosis, computational fluid dynamics is employed. To validate the numerical simulations, comparisons with existing experimental data are performed for both steady and pulsatile flows. Generally, good agreement is observed with the velocity profiles whereas some discrepancies are found in wall shear stress (WSS) distributions. Using the same end-to-side anastomosis geometry, numerical simulations are extended using a femoral artery waveform to identify the possible role of unsteady hemodynamics. In the current simulations, Carreau–Yasuda model is used to account for the non-Newtonian nature of the blood. Computations indicated a disturbed flow field at the artery-graft junction leading to locally elevated shear stresses on the vascular wall. Furthermore, the shear stress distribution followed the same behavior with oscillating magnitude over the entire flow cycle. Thus, distal IH observed in end-to-side artery-graft models may be caused by the fluctuations in WSS’s along the wall.

Aneurysmorrhaphy is an Easy Technique for Arteriovenous Fistula Salvage

The life-saving procedures for patients in chronic renal failure (CRF) are hemodialysis (HD) or successful kidney transplantation. HD requires a properly placed and functioning vascular access, most often obtained by creating an arteriovenous fistula (AVF). The long-term patency of AVFs is limited, in addition to other factors, by the development of intimal hyperplasia and the process results in venous wall thickening and progressive fistula occlusion. Another problem is limited patency, due to the development of pseudoaneurysm, which is associated with an increased risk of thrombosis, infection and bleeding, difficult cannulation for dialysis, pain and cosmetic defects. Treatment is focused on rapidly progressing pseudoaneurysms, which can predispose to rupture, technical problems during cannulation because of pseudoaneurysm size or a growing intraluminal thrombus. Most of these patients are scheduled for pseudoaneurysm removal and new fistula construction or, occasionally, an endovascular procedure involving stent graft implantation. This paper describes a simple and inexpensive technique of managing an AVF pseudoaneurysm, i.e. aneurysmorrhaphy. To offset the weakening of the venous wall by suture following aneurysmorrhaphy, an external polyethylene terephthalate (PET) prosthesis was implanted in the vein to prevent the development of intimal hyperplasia in the de novo created AVF.

Asymmetric Dimethylarginine and Cardiac Allograft Vasculopathy Progression: Modulation by Sirolimus

Cardiac allograft vasculopathy (CAV) is a major cause of death after heart transplantation (HT). The reduced bioavailability of endothelium-derived nitric oxide may play a role in endothelial vasodilator dysfunction and thus in the structural changes characterizing CAV. A potential contributor to endothelial pathobiology is asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor. It was hypothesized that ADMA concentrations may influence CAV progression during the first postoperative year. Thirty-two consecutive HT recipients underwent intravascular ultrasound evaluation at month 1 and year 1 after HT. Immunosuppression included mycophenolate mofetil (MMF, n=16) and sirolimus (n=16). Change in intimal volume greater than the median and vascular remodeling were major outcome measures. Plasma ADMA levels were associated with subsequent development of intimal hyperplasia (risk ratio [95% confidence interval] =2.72 [1.06-6.94]; P=0.038), and plasma ADMA levels greater than 0.70 micromol/L most accurately identified patients who would have developed intimal hyperplasia. However, ADMA levels did not correlate with negative coronary remodeling. Treatment with sirolimus, as compared with MMF, was associated with significantly lower ADMA levels (0.65+/-0.12 vs. 0.77+/-0.10 micromol/L; P<0.01) and less intimal hyperplasia (risk ratio [95% confidence interval] = 0.08 [0.01-0.56]; P=0.01). Elevated plasma ADMA is associated with coronary intimal hyperplasia, supporting the importance of nitric oxide synthase inhibition in CAV pathogenesis. Treatment with sirolimus (rather than MMF) is associated with lower ADMA levels and reduced risk of accelerated CAV.

Involvement of connexin 43 in angiotensin II-induced migration and proliferation of saphenous vein smooth muscle cells via the MAPK-AP-1 signaling pathway

Proliferation and migration of vascular smooth muscle cells (VSMCs) lead to intimal thickening and influence the long-term patency of venous graft post coronary arterial bypass graft. There is increasing evidence that connexins are involved in the development of intimal hyperplasia and restenosis. We assessed connexin 43 (Cx43) expression and its role in angiotensin II-induced proliferation and migration of smooth muscle cells and the signal pathways involved in human saphenous vein bypass conduits. Angiotensin II significantly increased gap junctional intercellular communication and induced the expression of Cx43 in human saphenous vein SMCs in a dose- and time-dependent manner through angiotensin II type 1 receptor. The effect of angiotensin II was blocked by siRNA of ERK 1/2, p38 MAPK and JNK, respectively. Overexpression of Cx43 markedly increased the proliferation of saphenous vein SMCs. However, siRNA for Cx43 inhibited angiotensin II-induced proliferation, cyclin E expression and migration of human saphenous vein SMCs. In dual-luciferase reporter assay, angiotensin II markedly activated AP-1 transcription factor, which was significantly attenuated by a dominant-negative AP-1 (A-Fos) with subsequent inhibition of angiotensin II-induced transcriptional expression of Cx43. These data demonstrate the role of Cx43 in the proliferation and migration of human saphenous vein SMCs and angiotensin II-induced Cx43 expression via mitogen-activated protein kinases (MAPK)-AP-1 signaling pathway.

Reduction of heat shock protein 27 phosphorylation inhibits the development of intimal hyperplasia

Development of intimal hyperplasia involves smooth muscle cell proliferation, migration as well as extracellular matrix deposition. These responses require dynamic reorganization of the actin cytoskeleton, a process known to involve HSP27expression and phosphorylation. In this study, we evaluated the ability of a cell permeant peptide inhibitor of the MAPKAP kinase II (MK2i) to decrease the phosphorylation of HSP27 and its effect on the development of intimal hyperplasia in vitro. Human saphenous vein (HSV) rings were placed in 8‐well chamber slides, and maintained in RPMI 1640 medium with 30% FBS for 14 days at 37°C /5% CO2. They were either untreated or treated with MK2i (5 or 10 μM), SB 203580 (25 μM, an inhibitor of the upstream kinase, P38 MAPK), or recombinant HSP27 (3μM). The rings were sectioned, stained, and the intimal thickness was measured. HSP27 phosphorylation was evaluated by Western blot. MK2i and SB reduced the phosphorylation of HSP27 by 39±17% and 58±22% respectively (p &lt; 0.05). MK2i at 10 μM, but not at 5 μM, significantly (p &lt;; 0.05) reduced the intimal thickness by 43±15%; a reduction of 51±10% was observed after treatment with SB. On the other hand, treatment with recombinant HSP27 increased the intimal thickness by 39±27%. These results demonstrate that reduction of HSP27 phosphorylation by MK2i treatment is a potential strategy to inhibit the development of intimal hyperplasia. Support: NIH RO1 70715

Particle image velocimetry measurements of three proximal anastomosis models under a pulsatile flow condition

This study was designed to examine the effects of the anastomotic angle on the flow and haemodynamic parameter distribution patterns of the proximal anastomoses, with emphasis on identifying site-specific haemodynamic features that could reasonably be expected to trigger the initiation and further development of anastomotic intimal hyperplasia. Particle image velocimetry measurements were carried out with three simplified glass proximal models under a physiological flow condition. The results revealed that the disturbed flow and the induced shear stress patterns including low recirculation flow, stagnation point, high wall shear stress, high temporal wall shear stress gradient, low time-averaged wall shear stress (TAWSS), and high oscillating shear index (OSI) occurred around the anastomotic joints and the flow field at proximal anastomosis was strongly affected by the anastomotic angle. Among the three models investigated, the 45 degrees backward anastomosis is found to have a smaller low-recirculation-flow region along the graft inner wall, non-stationary stagnation, and separation points, a higher TAWSS and smaller high-OSI low-TAWSS and low-OSI high-TAWSS regions.

96. Intermittent Inhaled Carbon Monoxide Mediates the Regression of Established Neointimal Lesions

Introduction: Angioplasty and surgical bypass are limited by the development of intimal hyperplasia (IH) which is mediated by inflammation and proliferation. Carbon monoxide (CO) is both antiproliferative and anti-inflammatory and has been previously shown to inhibit IH when administered prior to injury. However, no therapy to date has been effective in mediating the regression of an established neointimal lesion. Recently, inhaled CO has been reported to reverse the vascular remodeling that occurs in pulmonary hypertension.

Elevated mature macrophage expression of human ABHD2 gene in vulnerable plaque

We previously reported that the mouse α/β hydrolase domain containing 2 (Abhd2) was expressed in smooth muscle cells (SMCs) which suppressed their migration and inhibited the development of intimal hyperplasia by cuff placement; however, the role of ABHD2 in human remains to be elucidated. In this study, we examined ABHD2 expression in the human coronary atherosclerotic lesions of the patients with unstable angina (UA) and stable angina (SA). Our results showed that the ABHD2 was expressed in atherosclerotic lesions, and that the ABHD2 expression was significantly higher in the patients with UA than with SA. Immunohistochemistry analysis revealed abundant expression of ABHD2 in macrophages, but low expression in SMCs of atherosclerotic lesions. Using human vascular primary culture cell lines, we also demonstrated that the expression of ABHD2 was significantly higher in macrophages than in SMCs, and that the expression of ABHD2 significantly increased proportionally with differentiation from monocyte into macrophage.

The Effects of Toradol on Postoperative Intimal Hyperplasia in a Rat Carotid Endarterectomy Model: Laboratory Research

Carotid endarterectomy (CEA) and more recently carotid artery stenting are the treatments of choice for atherosclerotic disease of the extracranial carotid arteries; however, early restenosis caused by neointimal hyperplasia confounds surgical therapy. Oxidative stress has been implicated in the progression of intimal hyperplasia. The authors hypothesized that ketorolac tromethamine (Toradol), a nonsteroidal antiinflammatory drug that is a potent cyclooxygenase inhibitor, would decrease oxidative stress and thereby reduce intimal hyperplasia in a rat CEA model. Twenty-nine male Sprague-Dawley rats underwent CEA and were divided into 3 treatment groups as follows: (1) control (placebo), (2) 7.5 mg/kg Toradol, and (3) 10 mg/kg Toradol. Toradol treatment began 2 days before CEA and continued for 2 weeks. Two weeks after endarterectomy, carotid arteries were fixed, harvested, and examined for platelet activity (platelet reactive units), oxidative stress (malondialdehyde and glutathione), and intimal hyperplasia (measured as percentage of luminal stenosis). Platelet activity, malondialdehyde and glutathione, and intimal hyperplasia were all significantly lowered in both 7.5- and 10-mg/kg doses of Toradol versus control. Toradol given daily beginning 2 days before CEA and ending 2 weeks after the procedure was effective at significantly reducing platelet activity, oxidative stress, and intimal hyperplasia development in the rat without any increase in bleeding. Although the mechanism of action of this reduction is not completely understood, one possible explanation may be through the inhibition of reactive oxygen species production.

Risk factors for atherosclerosis and the development of preatherosclerotic intimal hyperplasia

Intimal hyperplasia or thickening is considered to be the precursor lesion for atherosclerosis in humans; however, the factors governing its formation are unclear. To gain insight into the etiology of preatherosclerotic intimal hyperplasia, we correlated traditional risk factors for atherosclerosis with the intimal hyperplasia in an atherosclerosis-resistant vessel, the internal thoracic artery. Paired internal thoracic arteries were obtained from 89 autopsies. Multivariate logistic regression and multiple regression models were used to examine the association of preatherosclerotic intimal hyperplasia with traditional risk factors for atherosclerosis: age, gender, hypertension, smoking, body mass index, diabetes, and hypercholesterolemia. Atherosclerotic lesions consisting of fatty streaks and/or type III intermediate lesions were identified in 19 autopsies. Only age >75 years was found to be significantly correlated with atherosclerotic lesion development (P=.01). Multiple regression model of the intima/media ratio in all 89 cases revealed age >75 years (P<.0001), age 51-75 years (P=.0012), smoking (P=.008), and hypertension (P=.02) to be significantly correlated with intimal thickness. In the 70 cases without atherosclerosis, only age 51-75 years (P=.006) and smoking (P=.028) were found to be significantly associated with preatherosclerotic intimal thickening. In the atherosclerosis-resistant internal thoracic artery, preatherosclerotic intimal hyperplasia routinely forms during adulthood after the fourth decade and is associated with at least two traditional risk factors for atherosclerosis: age and smoking. These observations indicate that in some settings, intimal hyperplasia may be part of the disease process of atherosclerosis and that its formation may be influenced by traditional risk factors for atherosclerosis.

Aspirin

Dependence on an expanded polytetrafluoroethylene graft for provision of pulmonary blood flow is a common yet precarious interval through which a population of patients with congenital heart disease must pass. The goals of the systemic-to–pulmonary artery shunt are to relieve cyanosis and to provide time before establishing in-series circulation by either complete repair of 2-ventricle lesions or, in the case of the single-ventricle patient, a bidirectional Glenn shunt. In the case of patients with single-ventricle anatomy, this period of parallel circulation is necessary to permit the lung maturation and the reduction in pulmonary vascular resistance that are necessary for subsequent palliation. For patients who will ultimately achieve a 2-ventricle repair, the goals of a preliminary shunt may include increasing the size of the pulmonary artery size or having a larger, older patient at the time of repair. This period of parallel circulation is tenuous, and the patient remains at increased risk during this period of altered circulation. Article p 293

The cyclolignan picropodophyllin attenuates intimal hyperplasia after rat carotid balloon injury by blocking insulin-like growth factor-1 receptor signaling

Smooth muscle cell proliferation (SMC) is a pivotal factor in the development of intimal hyperplasia after vascular injury. A number of growth factors, including insulin-like growth factor-1 (IGF-1), have been shown to be involved in SMC proliferation. We evaluated the effect of picropodophyllin (PPP), a new IGF-1 receptor inhibitor, in the prevention of SMC proliferation and development of intimal hyperplasia after vascular injury. The effects of systemic administration of PPP on intimal hyperplasia were studied in a balloon rat carotid injury model. Lesions were quantified by morphometry and SMC proliferation and apoptosis was studied by immunohistochemical staining for proliferating cell nuclear antigen (PCNA) and activated caspase 3, respectively. The effect of PPP on rat aortic SMC proliferation and apoptosis was studied in vitro by using cell counting, 3[H]-thymidine incorporation, and a flow cytometry assay for annexin V. Phosphorylation of the IGF-1 receptor, protein kinase B (Akt), and extracellular signal-regulated kinase 1/2 (ERK1/2) in vitro and in vivo were analyzed by using Western blotting. PPP inhibited IGF-1-mediated SMC proliferation in vitro but no significant increase in apoptosis was detected. In rats treated with PPP, a more than a twofold reduction in carotid intima area was observed 2 weeks after balloon injury, a significant decrease in PCNA staining was demonstrated in early lesions, but activated caspase 3 was not detected. In addition, PPP attenuated phosphorylation of the IGF-1 receptor, Akt, and ERK1/2 in IGF-1-stimulated SMCs in vitro, and a reduced phosphorylation of the IGF-1 receptor and Akt was found in balloon-injured carotid arteries in rats treated with PPP. These results show that PPP potently blocks IGF-1-mediated phosphorylation of the IGF-1 receptor in SMCs, decreases downstream Akt and ERK1/2 activation, inhibits SMC replication, and subsequently attenuates intimal hyperplasia after balloon injury of rat carotid arteries.