Significant Intimal Hyperplasia Research Articles

Peritoneal pre-conditioning impacts long-term vascular graft patency and remodeling.

There are questions about how well small-animal models for tissue-engineered vascular grafts (TEVGs) translate to clinical patients. Most TEVG studies used grafting times ≤6months where conduits from generally biocompatible materials like poly(ε-caprolactone) (PCL) perform well. However, longer grafting times can result in significant intimal hyperplasia and calcification. This study tests the hypothesis that differences in pro-inflammatory response from pure PCL conduits will be consequential after long-term grafting. It also tests the long-term benefits of a peritoneal pre-implantation strategy on rodent outcomes. Electrospun conduits with and without peritoneal pre-implantation, and with 0% and 10% (w/w) collagen/PCL, were grafted into abdominal aortae of rats for 10months. This study found that viability of control grafts without pre-implantation was reduced unlike prior studies with shorter grafting times, confirming the relevance of this model. Importantly, pre-implanted grafts had a 100% patency rate. Further, pre-implantation reduced intimal hyperplasia within the graft. Differences in response between pure PCL and collagen/PCL conduits were observed (e.g., fewer CD80+ and CD3+ cells for collagen/PCL), but only pre-implantation had an effect on the overall graft viability. This study demonstrates how long-term grafting in rodent models can better evaluate viability of different TEVGs, and the benefits of the peritoneal pre-implantation step.

A Modified Technique for Arteriovenous Fistula Construction in Rabbits.

Juxta-anastomotic stenosis is a challenging problem that often causes non-maturation and decreases the patency of an arteriovenous fistula (AVF). Injury to the veins and arteries during the operation and hemodynamic changes can lead to intimal hyperplasia, leading to juxta-anastomotic stenosis. To reduce injury to the veins and arteries during the operation, this study proposes a new modified no-touch technique (MNTT) for AVF construction that can decrease the rate of juxta-anastomotic stenosis and improve the AVF patency. To unravel the hemodynamic changes and mechanisms of the MNTT, this study presented an AVF procedure using this technique. Although this procedure is technically challenging, 94.4% procedural success was achieved after adequate training. Ultimately, 13 out of 34 rabbits had a functional AVF 4 weeks after the surgery, leading to a 38.2% AVF patency rate. However, at 4 weeks, the survival rate was 86.1%. Ultrasonography showed active blood flow through AVF anastomosis. Furthermore, the spiral laminar flow was observed in the vein and artery near the anastomosis, suggesting that this technique may improve the hemodynamics of the AVF. On histological observation, significant venous intimal hyperplasia was observed at the AVF anastomosis, whereas no significant intimal hyperplasia was observed at the proximal external jugular vein (EJV) of the anastomosis. This technique will improve the understanding of the mechanisms underlying the use of MNTT for AVF construction and provide technical support for the further optimization of the surgical approach in AVF construction.

P3581Periinterventional cocoa flavanol supplementation prevents functional and structural damage to the arterial wall after transradial catheter intervention

Abstract Background The transradial approach is commonly preferred over the femoral approach for coronary angiography to reduce vascular complications like bleeding, aneurysm formation and all-cause mortality ensuring early ambulation after coronary procedures. However, there is growing evidence that damage to the radial artery endothelium elicits intimal hyperplasia, vascular remodeling and might ultimately lead to total vessel occlusion. Objective Our study aimed to investigate the effects of dietary flavanol intervention on (a) early endothelial functional recovery and (b) late structural changes i.e. intimal hyperplasia after mechanical vascular wall injury in the human forearm model during coronary angiography. Methods Radial artery flow-mediated vasodilation (RA-FMD), local stiffness (fractional diameter change, Fdc), intima-media thickness (IMT), luminal and external arterial diameter at the site of intervention and the contralateral control artery were measured in 38 male patients (19 flavanol intervention, 19 placebo control) undergoing transradial coronary angiography (TCA) at baseline, after 7 days of 450mg flavanol supplementation BID, directly after TCA and 6 months after TCA. Circulating levels of endothelial microparticle (EMP) subpopulations CD31+/41-, CD62e+and CD144+were analyzed simultaneously as a surrogate for endothelial functional integrity and activation. Results One week of flavanol supplementation, not placebo, significantly increased RA-FMD (8.88±2.03% vs. 11.17±2.89%, p<0.01 in flavanol and 8.64±1.87% vs. 8.32±1.63%, p=n.s. in placebo). RA-FMD significantly decreased in the intervention artery directly after TCA, which was partly mitigated by flavanol supplementation (delta to baseline: −2.61±0.82% in flavanol vs. −4.91±0.63% in placebo, p=0.034). TCA induced significant intimal hyperplasia in the radial artery (0.36±0.02mm vs. 0.44±0.04mm, p<0.01) in placebo, but not in the flavanol group (0.36±0.02mm vs. 0.37±0.02mm, p=n.s.) after 6 month. One week of flavanol supplementation increased Fdc (1.94±0.99 vs. 3.07±1.31, p<0.01). No changes occurred in the placebo group (1.99±1.29 vs. 1.96±1.17, p=n.s.). On the contralateral arm, the decrease in RA-FMD was blunted by flavanols (delta to baseline: +0.42±1.05% in flavanol vs. −0.61±1.55% in placebo) along with decreased circulating levels of EMPs. Conclusions TCA impairs endothelial function (RA-FMD), vascular physicomechanics (Fdc) and induces intimal hyperplasia (IMT). Periinterventional flavanol supplementation blunts the acute decreases in endothelial function and physicomechanics and prevents chronic negative vascular remodeling.

Distinct Vascular Remodeling Pattern of Adult Rats with Carotid-Jugular Shunt

Previous research has revealed that patent vein grafts lose their venous identity Eph-B4 but do not gain arterial identity ephrin-B2 during adaptation to the arterial circulation, and vascular identity marker, for example, the Eph-B4 signaling is a critical determinant of venous wall thickness of vein grafts. But what is the remodeling pattern, especially the remodeling pattern of vascular identity in the venous segment of arteriovenous shunt at a late stage postoperation has not been fully explored. This study was conducted to characterize the remodeling pattern of shear stress, vascular identity, structural composition and morphology, and transcriptional profiles in jugular segment of carotid-jugular (CJ) shunt and/or pulmonary artery (PA), which delivers an increased amount of mixed blood at a late stage postoperation in adult rats. CJ shunt was created in adult Wistar rats via end-to-end anastomosis of carotid artery (CA) and jugular vein (JV). At the time of 15weeks, after hemodynamics test, remodeled jugular segment of CJ shunt, PA, and sham-operated corresponding vessels were isolated. Reverse transcription polymerase chain reaction, microarray, western blot, immunohistochemistry experiments, and morphology analyses were performed. CJ shunt shear stresses have been patterned to some sort of balance with no significant difference in shear stress between carotid segment and jugular segment (P>0.05). Immunohistochemical analysis reveals that venous identity marker Eph-B4 is lost, but arterial identity markers ephrin-B2 and regulator of G-protein signaling 5 are gained in jugular segment of CJ shunt (P<0.01), and these 2 arterial identity markers further strengthened in PA (P<0.01) in shunted rats compared with controls. Jugular segment of CJ shunt undergoes significant intimal hyperplasia with strong expression of smooth muscle cell markers (P<0.05) and demonstrates a distinct transcriptional profiles which reveals that transcripts of 5 arterial markers are significantly upregulated (P<0.05 or<0.01) compared with sham-operated JV; among them, G-protein signaling 5 is exactly the gene with the largest fold change (10.14-fold) in all genes tested by microarray experiment. Venous identity is lost, but arterial identity is gained in jugular segment of CJ shunt and arterial identity further strengthened in PA in adult shunted rats during late adaptation.

Biomechanics and Mechanobiology of Saphenous Vein Grafts.

Within several weeks of use as coronary artery bypass grafts (CABG), saphenous veins (SV) exhibit significant intimal hyperplasia (IH). IH predisposes vessels to thrombosis and atherosclerosis, the two major modes of vein graft failure. The fact that SV do not develop significant IH in their native venous environment coupled with the rapidity with which they develop IH following grafting into the arterial circulation suggests that factors associated with the isolation and preparation of SV and/or differences between the venous and arterial environments contribute to disease progression. There is strong evidence suggesting that mechanical trauma associated with traditional techniques of SV preparation can significantly damage the vessel and might potentially reduce graft patency though modern surgical techniques reduces these injuries. In contrast, it seems possible that modern surgical technique, specifically endoscopic vein harvest, might introduce other mechanical trauma that could subtly injure the vein and perhaps contribute to the reduced patency observed in veins harvested using endoscopic techniques. Aspects of the arterial mechanical environment influence remodeling of SV grafted into the arterial circulation. Increased pressure likely leads to thickening of the medial wall but its role in IH is less clear. Changes in fluid flow, including increased average wall shear stress, may reduce IH while disturbed flow likely increase IH. Nonmechanical stimuli, such as exposure to arterial levels of oxygen, may also have a significant but not widely recognized role in IH. Several potentially promising approaches to alter the mechanical environment to improve graft patency are including extravascular supports or altered graft geometries are covered.

Perivascular sustained release of atorvastatin from a hydrogel-microparticle delivery system decreases intimal hyperplasia

Intimal hyperplasia (IH) is the major cause of grafted vessel occlusion and occurs frequently after bypass intervention. No pharmaceutical formulation is currently available to prevent this pathology. Local perivascular delivery of an appropriate active compound released in a time-dependent manner (from day one up to 4weeks) is necessary for an efficient single-administration preventive therapy. To this aim, we propose the combination of gel and microparticles delivery system containing atorvastatin (ATV). The incorporation of ATV in a cross-linked hyaluronic acid gel, provided in vitro a fast release over 3days, while ATV-loaded poly-lactic-co-glycolic acid (PLGA) microparticles dispersed in the gel gave a sustained release over 4weeks. In vivo, ATV formulations were applied perivascularly in mice undergoing carotid artery ligation. IH was significantly reduced (‐68%) in presence of ATV incorporated in hyaluronic acid gel and encapsulated in microparticles compared to control. No significant IH alteration was observed when ATV was incorporated only in the gel (fast release) or only in the microparticles (slow release) demonstrating that a biphasic release of ATV is essential to interfere with the development of IH.ATV was detected in adjacent tissues 28days after the intervention, showing the sustained presence of the drug in vivo. After four weeks ATV was not detected in remote tissues, except at a very low concentration (0.044ng/mg) in the liver, suggesting a very low risk of systemic toxicity of locally delivered ATV. Additionally, the ex vivo data showed that ATV in solution permeates through isolated human saphenous veins and thus is a good candidate for perivascular delivery.Our data demonstrate that a local biphasic ATV release on the mice ligated carotid efficiently prevents the development of IH without apparent toxicity.

REGRESSED CORONARY ANEURYSM AFTER KAWASAKI DISEASE: AN OPTICAL COHERENCE TOMOGRAPHY (OCT) STUDY FROM A SINGLE INSTITUTION

Coronary artery aneurysms (CAA) are a serious complication of Kawasaki disease (KD). CAA size regresses in nearly 50% of the cases on follow up. Nevertheless, patients with regressed CAA have an increased risk of ischemic heart disease, myocardial infarction and sudden cardiac death on long-term follow-up. Actual imaging techniques often describe these segments as normal, whereas studies have shown significant endothelial and smooth muscle dysfunction. Optical Coherence Tomography (OCT) is a high-resolution intracoronary imaging modality that characterizes coronary artery wall structure. KD patients scheduled for routine coronary angiography underwent OCT imaging between March 2013 and April 2015. The aim of the study was to compare microstructural coronary changes in coronary artery segments with no history of CAA to segments with regressed CAA, and segments with persistent CAA. OCT was performed on 27 patients at 12.4 ± 5.5 years, 9.3 ± 5.3 years following onset of KD. Overall, 22/27 (81.5%) had a history of CAA. Of those, 11/22 (50.0%) had regressed CAA at time of OCT. Data was analyzed according to echocardiographic and angiographic progress of CAA segments. All 19/19 (100.0%) persistent CAA segments and 20/23 (87.0%) regressed CAA segments had significant intimal hyperplasia, compared to 2/19 (10.5%) with no history of segmental CAA (P<0.001), amounting 475.0 ± 179.1 μm, 305.4 ± 164.2 μm and 79.6 ± 78.2 μm respectively (p<0.001). Also, partial disappearance of the media was found more frequently in segments with persistent CAA, 17/19 (89.5%), followed by segments with regressed CAA, 12/23 (52.2%), and those with no history of CAA, 1/19 (5.3%); p<0.001. Neovascularization was found more often in segments with persistent CAA, 8/19 (42.1%), compared to segments with regressed CAA, 3/23 (13.0%), and no history of CAA, 0/19; p=0.002. Calcifications were identified almost exclusively in patients with persistent CAA, 6/19 (31.6%), compared to 1/23 (4.3%) for segments with regressed CAA and 0/19 for segments with no history of CAA (p=0.004). Macrophage accumulation was identified more often in segments with persistent CAA compared to those with regressed CAA and no history of CAA, in 10/19 (52.6%), 3/23 (13.0%) and 3/19 (15.8%) respectively (p=0.007). Despite normal angiographic appearance, regressed CAA segments displayed significant intimal hyperplasia and disruption of the media, among other anomalies, similarly to segments with persistent CAA. These features represent an increased risk for adverse coronary events. The additional diagnostic value of OCT following KD may bring prognostic potential in future chronological series.View Large Image Figure ViewerDownload (PPT)

Abstract 163: Regressed Coronary Aneurysm after Kawasaki Disease: What are they hiding? An Optical Coherence Tomography (OCT) study

Background: Coronary artery aneurysms (CAA) are a serious complication of Kawasaki disease (KD). Regression of CAA occurs in 50% of the cases on follow up. Actual imaging techniques often described these segments as normal, whereas studies have shown significant endothelial and smooth muscle dysfunction. Method: KD patients scheduled for angiographic follow-up between June 2013 and August 2014 underwent OCT imaging. We compared coronary intimal changes in coronary artery segments with no history of CAA to segments with regressed CAA, and segments with persistent CAA. The intima was measured in sections adjacent to the CAA for the segments with persistent CAA, at the former CAA and adjacent sections for those who regressed, and at various corresponding sections for segments with no history of CAA. Results: OCT was performed on 18 patients at 12.4 ± 5.5 years. Overall 14/18 (77.7%) had a history of CAA. Of those, 7/14 (50.0%) had regressed CAA at time of OCT. Data was analyzed according to echocardiographic and angiographic progress of CAA segments. Accordingly, all 18/18 persistent CAA segments and 11/11 regressed CAA segments had significant intimal hyperplasia, compared to 1/13 with no history of segmental CAA (P&lt;0.001). The intensity of intimal hyperplasia is displayed in Table 1. Conclusion: Despite normal angiographic features, regressed CAA segments displayed significant intimal hyperplasia, similarly to those with persistent CAA. These features may present a risk of adverse coronary events.

Abstract 363: Prolonged Upregulation of Proinflammatory and Profibrotic Genes is Characteristic of Successful Arteriovenous Fistula Maturation

Objective: Understanding the molecular mechanisms of vascular remodeling is critical to improving outcomes following revascularization procedures. While extensive animal data exists, correlative data on the mechanisms and kinetics of vascular healing in humans are lacking. Creation of brachio-basilic arteriovenous fistulas (AVF), often completed in 2 stages, offers an opportunity to examine the same vessel at 2 distinct time points. We hypothesized that immune and developmental related pathways are involved in AVF maturation. Methods: Human basilic vein samples were obtained at the time of AVF creation as baseline. Second samples were taken at basilic vein transposition after exposure to arterial hemodynamic forces. These paired samples were analyzed for differential gene expression using whole genome microarray. Structural staining and confirmatory qPCR were performed in selected genes. Results: Paired vein samples were collected from 3 patients. All subjects had successful AVF maturation. An average of 3 months transpired between collection of the first and second samples. Overall, 700 genes were significantly down-regulated and 732 genes were significantly up-regulated. Gene ontogeny analysis revealed no difference in the genes regulating developmental re-activation pathways or angiogenesis. However, inflammatory and fibrosis genes were still significantly up-regulated 3 months following AVF creation (p &lt;&lt;.05). Structural stains confirmed an increase in lumen and total vessel area and deposition of elastin and collagen with significant intimal hyperplasia between baseline and 3 month samples. Additionally, qPCR showed a 9.7 fold increase in IL-6 and a 10.4 fold increase in e-selectin at 3 months. Conclusions: Inflammatory and fibrosis gene pathways remain activated in mature fistulas despite stabilization of geometric remodeling. Further study is warranted to characterize these pathways and determine their significance in AVF patency.

Acute reductions in mechanical wall strain precede the formation of intimal hyperplasia in a murine model of arterial occlusive disease

Intimal hyperplasia (IH) continues to plague the durability of vascular interventions. Employing a validated murine model, ultrasound biomicroscopy, and speckle-tracking algorithms, we tested the hypothesis that reduced cyclic arterial wall strain results in accentuated arterial wall IH. A 9-0 suture was tied around the left mouse (n= 10) common carotid artery and a 35-gauge (outer diameter= 0.14mm) blunt mandrel. We previously showed that mandrel removal results in a ∼78% reduction in diameter and ∼85% reduction in flow, with subsequent delayed induction of IH by day 28. Preoperative, postoperative day-4 (before measurable IH), and postoperative day-27 circumferential wall strains were measured in locations 1, 2, and 3mm proximal to the stenosis and in the same locations on the contralateral (nonstenosed) carotid. At postoperative day 28, arteries were perfusion fixed and arterial wall morphology was assessed microscopically in the same regions. Strains were the same in all locations preoperatively. Wall strain was decreased in all regions proximal to the stenosis by day 4 (0.26± 0.01 to 0.11± 0.02; P< .001), while strains remained unchanged for the contralateral artery (P= .45). No statistical regional differences in mean strain or IH were noted at any time point for the experimental or contralateral artery. Based on the median, regions were divided into those with low strain (≤0.1) and high strain (>0.1). Average preoperative strains in both groups were the same (0.27± 0.09 and 0.27± 0.08). All segments in the low-strain group (n= 13) demonstrated significant IH formation by day 28, while only 31% of the high strain group demonstrated any detectable IH at day 28. (Mean low-strain intimal thickness= 32± 20μm, high strain= 8.0± 16μm; P< .01). Changes in cross-sectional area at diastole drove the reduction in strain in the low-strain group, increasing significantly from preoperatively to day 4 (P= .04), while lumen cross-section at systole remained unchanged (P= .46). Cross-sectional area at diastole and systole in the high-strain group remained unchanged from preoperatively to day 4 (P= .67). Early reduction in arterial wall strain is associated with subsequent development of hemodynamically induced IH.

Abstract 270: Acute Reductions in Wall Strain Precede Formation of Intimal Hyperplasia

Intimal hyperplasia (IH) remains the major culprit in revascularization failures. We aimed to unravel relationships between acute changes in circumferential arterial wall strain and genesis of IH. Methods To induce IH, we employed a validated model using a 9-0 nylon suture tie around the distal mouse common carotid artery (n=10) and an external 35-gauge needle mandrel (OD=0.14mm), with subsequent removal of the mandrel to create a distal common carotid focal stenosis (~78% lumen diameter/~85% flow reduction). Wall strains were measured in three, 1 mm wide regions along the vessel proximal to the focal stenosis at pre-op day 1 and at post-op day 4 (before detectable IH) using Vevo 2100 ultrasonography with VevoVasc software. At post-op day 28, arteries were perfusion fixed and IH was assessed in the same regions as those where strain was analyzed. Strain and morphology were also assessed in the contralateral control artery. Results Decreased wall strain was noted in all regions proximal to the focal stenosis from 0.26 ± 0.01 to 0.11 ± 0.02 (p&lt;0.001) with no change in the control artery from pre-op to post-op day 4 (p=0.45). Based on a strain level histogram, vessels were divided into groups with strain ≤0.1 and &gt;0.1. All segments (n = 13) with wall strain ≤0.1 at post-op day 4 had significant IH at day 28. In regions with strains &gt;0.1 at day 4, only 30% had IH at day 28. The average pre-op strains were identical in &gt;0.1 and ≤0.1 strain groups (0.27 ± 0.09 and 0.27 ± 0.08). Mean intimal thickness in vessels with strain ≤0.1 was 32 ± 20 μm, significantly greater than 8.0 ± 16 μm in the group with strain &gt;0.1 (p&lt;0.01). To further understand the mechanisms underlying changes in strain, systolic and diastolic lumen areas were assessed. Although systolic lumen areas in both &gt;0.1 and ≤0.1 groups remained unchanged from pre-op to post-op day 4 (p=0.46), diastolic area was significantly increased in regions with post-op day 4 strain ≤0.1 (p=0.04) but remained unchanged in mice with post-op day 4 strain &gt;0.1 (p=0.67). Conclusions Acute reduction in wall strain precedes the formation of IH in this murine model and this change is primarily caused by an increase in diastolic lumen area. Manipulations of wall strain offer a strategy to prevent and attenuate occlusive IH lesions after revascularizations.

The role of short-term oxygen administration in the prevention of intimal hyperplasia

Intimal hyperplasia (IH) is the cause of most failed arteriovenous fistulas (AVFs), resulting in repeat procedures and leading to increased utilization of scarce health care resources. Our laboratory has previously demonstrated the role of supplemental oxygen in preventing IH and smooth muscle cell proliferation (SMCp) at an artery-to-graft anastomosis and at the deployment site of an intra-arterial stent. This study examines the effect of supplemental oxygen in preventing IH and SMCp in an AVF in a rabbit model. Ninety-six rabbits were randomized into four groups: group 1, control; group 2, no surgery with supplemental oxygen; group 3, AVF without supplemental oxygen; and group 4, AVF with supplemental oxygen. Rabbits receiving supplemental oxygen received 30% oxygen for up to 42 days. Specimens were collected in all groups at days 1, 3, 7, 21, 42, and 90. IH and SMCp were measured at the AVF site as well as in the artery and vein proximal and distal to the AVF. IH was first noted at day 7 and significantly increased through day 90 at all locations in the nonoxygen-supplemented groups. No significant IH was noted in the oxygen-supplemented group at any location or any time point. SMCp was noted at day 3 through day 21 in the nonoxygen-supplemented group, whereas almost no SMCp was noted in the oxygen-supplemented group at any location or time point. Without oxygen supplementation, SMCp begins at day 3 and is no longer noted at day 21 after creation of an AVF, whereas IH begins by day 7 and increases at least through day 90 after creation of an AVF. Forty-two days of 30% supplemental oxygen inhibits IH and SCMp after creation of an AVF. These data suggest a role for the short-term administration of low-dose O2 to prevent both IH and SMCp after creation of an AVF that may prolong patency and function.

Autologous Mesenchymal Stem Cells Prevent Transplant Arteriosclerosis by Enhancing Local Expression of Interleukin-10, Interferon-γ, and Indoleamine 2,3-dioxygenase

Transplant arteriosclerosis (TA) remains the major limitation of long-term graft survival in heart transplantation despite the advances in immunosuppressants. Mesenchymal stem cells (MSCs) have been demonstrated to suppress allogeneic immune responses by numerous in vitro studies. However, the immunomodulatory effects of MSCs in vivo are controversial and the underlying molecular mechanisms are not conclusive. In this study, we investigated the therapeutic potential of autologous bone marrow-derived MSCs on TA in a porcine model of femoral artery transplantation. MSCs or saline were injected into the soft tissue surrounding the arterial grafts immediately postanastomosis. Four weeks after transplantation, neointimal formation increased significantly in untreated allografts compared with the MSC-treated grafts as assessed by intravascular ultrasound (maximum luminal area stenosis: 40 ± 12% vs. 18 ± 6%, p < 0.001). Grafts harvested at 4 weeks showed dense perivascular lymphocyte infiltration accompanied by significant intimal hyperplasia in the untreated but not in the MSC-treated allografts. Serial angiographic examination showed that all of the untreated allografts became occluded at the 8th week whereas the majority of the MSC-treated grafts remained patent at the 12th week posttransplantation (n = 12 each group, p < 0.001). Quantitative PCR analysis revealed that Foxp3 expression was comparable between the untreated and the MSC-treated groups. However, expression of interleukin-10 (IL-10), interferon-γ (IFN-γ), and indoleamine 2,3-dioxygenase (IDO) was increased significantly in the MSC-treated allografts compared with that in the allograft controls (p = 0.021 for IL-10, p = 0.003 for IFN-γ, and p = 0.008 for IDO). In conclusion, local delivery of autologous MSCs alleviates TA by inducing allograft tolerance via enhanced expression of IL-10, IFN-γ, and IDO but not Foxp3-positive cells in the vessel wall. These results suggest that MSCs induce immune tolerance by activating the type 1 regulatory T-like cells.

Role of toll like receptor 4 in low shear stress-induced intimal hyperplasia

To determine the role of toll like receptor 4 (TLR4) in intimal hyperplasia induced by low shear stress (LSS). TLR4(-/-) mice and control mice C57BL/6J were used. Polyethylene cuff was placed on murine carotid to establishing a LSS model. Cultured vascular endothelial cells under LSS condition were used as an in vitro LSS cell model. Intimal hyperplasia was evaluated pathologically. TLR4 was tested by Western blot and the expression of IL-1β, IL-6 and TNF-α mRNA were detected using RT-PCR. Cell proliferation was determined by detecting DNA synthesis. LSS elicited significant carotid intimal hyperplasia in normal mice but a slight neointima formation in TLR4(-/-) mice (42.67 ± 16.46 vs 7.03 ± 2.95, P < 0.05). LSS upregulated the expression of TLR4 (2.30 ± 0.66 vs 0.16 ± 0.10, P < 0.05), as well as the mRNA of IL-1β (6.52 ± 3.15 vs 1.65 ± 0.45, P < 0.01), IL-6 (16.17 ± 7.49 vs 6.50 ± 1.84, P < 0.01) and TNF-α(9.98 ± 3.77 vs 2.72 ± 1.03, P < 0.01) in normal mice. However, only moderate increases in IL-6 and TNF-α mRNA were observed in TLR4(-/-) mice. LSS induced the proliferation in cultured endothelial cells. And it was further enhanced by TLR4 overexpression (177 ± 33 vs 83 ± 15, P < 0.05) but attenuated by TLR4 silencing (40 ± 8 vs 83 ± 15, P < 0.05). TLR4 plays an important role in LSS-induced intimal hyperplasia. It is likely that LSS induces the proliferation of endothelial cells through TLR4-mediated inflammatory reaction and ultimately promotes intimal hyperplasia.

アンジオテンシンII受容体拮抗薬(losartan)が有効と考えられた強皮症腎クリーゼの1例

A 67-year-old man with a one-and-a half-year history of Raynaud's phenomenon was admitted to our hospital for progressive dyspnea occurring over the previous two weeks. Physical examination revealed a blood pressure of 200/124 mmHg, and slightly tight and smooth skin of the fingers, hands and forearms. Laboratory evaluation included serum creatinine of 5.42 mg/dl, plasma renin activity > 20 ng/ml/hr, and antinuclear antibody with a titer of 1 : 1,280. Renal biopsy was performed and the histopathological findings showed that some glomeruli exhibited ischemic retraction with wrinkling of the basement membranes, and that one arteriole exhibited significant intimal hyperplasia with luminal stenosis. These findings were compatible with scleroderma renal crisis (SRC). On the 5th day, serum creatinine had risen to 9.16 mg/dl, and he required temporary hemodialysis therapy. After the administration of captopril was started, his blood pressure fell to 160/86 mmHg and serum creatinine was reduced to 5.12 mg/dl. On the 9th day, he exhibited skin eruptions, and captopril was discontinued accordingly and temocapril started. Because of continued eruptions, temocapril was replaced by losartan. His blood pressure was controlled easily and his serum creatinine level reduced steadily. One year after the start of losartan, serum creatinine was 2.25 mg/dl and blood pressure was 130/82 mmHg. SRC is a life-threatening manifestation of systemic sclerosis. In the late 1970s, angiotensin converting enzyme (ACE) inhibitor was introduced and has dramatically improved the outcome in SRC patients. As ACE inhibitors act mainly on hyperreninemic renal vasoconstrictive hypertension in SRC, we would expect losartan, a selective antagonist of angiotensin receptor subtype 1, to be interchangeable with ACE inhibitors in SRC. In 1997, Caskey and colleagues reported the failure of losartan to control hypertension in a patient of SRC, and the reason has remained unclear. We report here, a case of SRC whose blood pressure was controlled successfully and his renal failure reversed by the administration of losartan.

Mechanisms of In-Stent Restenosis After Drug-Eluting Stent Implantation

Background— We used intravascular ultrasound (IVUS) to (1) clarify the mechanisms of luminal loss after drug-eluting stent (DES) implantation and (2) classify morphological patterns of in-stent restenosis (ISR). Methods and Results— On the basis of IVUS-identified luminal narrowing (in-stent minimum lumen area &lt;4 mm 2 ), IVUS-defined ISR was classified as focal (luminal narrowing ≤10 mm in length), multifocal (≥1 focal lesions), and diffuse (luminal narrowing &gt;10 mm in length) with or without stent edge involvement. Significant intimal hyperplasia (IH) was defined as IH area &gt;50% of stent. Overall, 76 lesions had IVUS-defined ISR; 32 (42%) had stent underexpansion (minimal stent area &lt;5 mm 2 ); and 71 (93%) had IH area &gt;50% of stent. Total stent length negatively correlated with minimal stent area ( r =−0.613, P &lt;0.001) as well as with stent area at the minimum lumen site ( r =−0.436, P &lt;0.001) but not with minimum lumen area ( r =−0.084, P =0.472). Underexpansion was present at the minimum lumen site in 15 of 43 (35%) lesions with stent length &gt;28 mm, even though there was significant IH in 34 (79%) lesions; conversely, in 32 of 33 (97%) lesions with stent length ≤28 mm, the minimum lumen site was not associated with stent underexpansion but significant IH. IVUS-defined focal ISR was most common (47%). Compared with focal ISR, normalized vessel, stent, lumen, and plaque volumes were smaller in diffuse and multifocal than focal ISR, with no difference in IH extent. Conclusions— In most DES restenosis, IH was the dominant mechanism of ISR. Nevertheless, underexpansion associated with longer stent length remained an important preventable mechanism of ISR.

Significant intimal hyperplasia regression between 6 and 18 months following Genous™ endothelial progenitor cell capturing stent placement

Circulating endothelial progenitor cells (EPCs) play an important role in vessel wall homeostasis [1,2]. When attracted to a site of vessel wall injury, EPCs rapidly differentiate into a functional layer as part of the healing process. Accelerated re-endothelialisation after stent placement may change the physiology of neo-intimal hyperplasia and smooth muscle cell (SMC) proliferation that cause in-stent restenosis. The Bio-engineered Genous™ Endothelial Progenitor Cell Capturing Stent (OrbusNeich Medical Technologies Inc., FL, USA) (ECS) is coated with immobilized CD34+antibodies designed to capture circulating EPCs.

Accelerated intimal hyperplasia in aortocoronary internal mammary vein grafts in minipigs

BackgroundMore than 50% of aortocoronary saphenous vein grafts are occluded 10 years after surgery. Intimal hyperplasia is the initial critical step in the progression toward occlusion. Internal mammary veins, which are physiologically prone to less hydrostatic pressure, may undergo an accelerated progression to intimal hyperplasia and thus be suitable for investigation of the mechanisms of aortocoronary vein graft disease.MethodsSix minipigs underwent aortocoronary bypass grafting using standard cardiopulmonary bypass and cardioplegic arrest. Mammary vein were grafted in a reversed manner from ascending aorta to left anterior descending coronary artery (LAD). The proximal LAD was ligated, rendering the anterior left ventricle vein graft-dependent. Minipigs were killed after 4 weeks, and vein grafts were harvested. Histological and immunohistological investigation were performed with respect to morphometric analysis, endothelial damage/dysfunction (v-Willebrand-factor (vWF)), smooth muscle cells (α-smooth actin) and proliferation rate (proliferation marker Ki 67).ResultsMean intimal area of vein grafts was increased compared to ungrafted mammary veins. Intimal hyperplasia in vein grafts was characterized by massive accumulation of smooth muscle cells with a high proliferation rate and endothelial perturbation. Significant (p = 0.001) intimal hyperplasia of the grafted mammary vein compared to the ungrafted mammary vein was found. These changes were absent in ungrafted mammary veins.ConclusionThe present study demonstrates a pig model of aortocoronary vein graft intimal hyperplasia which is characterized by an accelerated progression within internal mammary veins. The model is suitable to investigate the pathophysiology of aortocoronary vein graft intimal hyperplasia as well as therapeutic approaches.

Histologic Damage of Lung Allografts According to Magnitude of Acute Rejection in the Re-isotransplant Model

Graft damage due to acute rejection has been reported as one of the risk factors in the chronic stage of cardiac and renal allografts. This study was designed to elucidate the histologic changes of grafts after ongoing acute allograft rejection was discontinued in models of lung re-isotransplantation. WKAH rat lungs were orthotopically transplanted into F344 recipients. Three days (3A group) and 5 days (5A group) after the first allotransplantation, the grafts were re-isotransplanted back into the WKAH rats (3RA and 5RA groups, respectively). Five days (5I group) after the first isotransplantation, the grafts were re-isotransplanted back into the WKAH rats (5RI group). The grafts were removed 30 and 60 days after re-isotransplantation and assessed histologically. Typical acute allograft rejection developed in the 3A and 5A groups, and the changes were reduced after re-isotransplantation, although they remained significantly greater in the 5RA group than in the 3RA and 5RI groups. For intimal hyperplasia, the graft score 60 days after re-isotransplantation in the 5RA group was significantly higher than in the 5RI and 3RA groups. The changes in airway inflammation were significantly greater in the 5RA group than in the 3RA and 5RI groups at 60 days. Peribronchiolar fibrosis was significantly more frequent in the 5RA and 3RA groups than in the 5RI group. Acute rejection and airway inflammation corresponded to the magnitude of rejection before retransplantation. Significant intimal hyperplasia developed in severe acute rejection, and peribronchiolar fibrosis occurred after the first acute rejection.

Effects of myocardial constraint on the passive mechanical behaviors of the coronary vessel wall

The large epicardial coronary arteries and veins span the surface of the heart and gradually penetrate into the myocardium. It has recently been shown that remodeling of the epicardial veins in response to pressure overload strongly depends on the degree of myocardial support. The nontethered regions of the vessel wall show significant intimal hyperplasia compared with the tethered regions. Our hypothesis is that such circumferentially nonuniform structural adaptation in the vessel wall is due to nonuniform wall stress and strain. Transmural stress and strain are significantly influenced by the support of the surrounding myocardial tissue, which significantly limits distension of the vessel. In this finite-element study, we modeled the nonuniform support by embedding the left anterior descending artery into the myocardium to different depths and analyzed deformation and strain in the vessel wall. Circumferential wall strain was much higher in the untethered than tethered region at physiological pressure. On the basis of the hypothesis that elevated wall strain is the stimulus for remodeling, the simulation results suggest that large epicardial coronary vessels have a greater tendency to become thicker in the absence of myocardial constraint. This study provides a mechanical basis for understanding the local growth and remodeling of vessels subjected to various degrees of surrounding tissue.