Media Area Ratio Research Articles

Effect of F11 Receptor/Junctional Adhesion Molecule-A–derived Peptide on Neointimal Hyperplasia in a Murine Model

PurposeTo determine whether inhibition of the F11 receptor/JAM-A (F11R) using F11R-specific antagonist peptide 4D results in inhibition of smooth muscle cell (SMC) proliferation and migration in vivo, known as neointimal hyperplasia (NIH), using a mouse focal carotid artery stenosis model (FCASM). Materials and MethodsThe mouse FCASM was chosen to test the hypothesis because the dominant cell type at the site of stenosis is SMC, similar to that in vascular access stenosis. Fourteen C57BL/6 mice underwent left carotid artery (LCA) partial ligation to induce stenosis, followed by daily injection of peptide 4D in 7 mice and saline in the remaining 7 mice, and these mice were observed for 21 days and then euthanized. Bilateral carotid arteries were excised for histologic analysis of the intima and media areas. ResultsThe mean intimal area was significantly larger in control mice compared with peptide 4D–treated mice (0.031 mm2 [SD ± 0.024] vs 0.0082 mm2 [SD ± 0.0103]; P = .011). The mean intima-to-intima + media area ratio was significantly larger in control mice compared with peptide 4D–treated mice (0.27 [SD ± 0.13] vs 0.089 [SD ± 0.081]; P = .0079). NIH was not observed in the right carotid arteries in both groups. ConclusionsPeptide 4D, an F11R antagonist, significantly inhibited NIH in C57BL/6 mice in a FCASM.

Exosomes of Endothelial Progenitor Cells Inhibit Neointima Formation After Carotid Artery Injury

BackgroundExosomes released from endothelial progenitor cells (EPCs) play a protective role in various disease models. Both endothelial cell (EC) damage and smooth muscle cell (SMC) proliferation are involved in the pathological process of restenosis after angioplasty and stenting. Few studies have focused on the therapeutic role of exosomes in EC damage and SMC proliferation. In this study, we sought to investigate the effect of exosomes released by human fetal aorta-derived EPCs on the rat carotid artery balloon injury model in vivo. We also sought to determine the effect of exosomes on both ECs and SMCs in vitro. MethodsExosomes (Exo group) or saline (Con group) were injected in rat carotid balloon injury model animals. The rats were sacrificed after 2, 4, 14, and 28 d, and injured carotid specimens were collected for Evans blue staining, hematoxylin-eosin staining, and immunohistochemistry. ResultsWhen the Con group and the Exo group were compared, the reendothelialized areas were not significantly different after 2 or 4 d, as shown by Evans blue staining. The hematoxylin-eosin results showed that the intimal to medial area ratio was slightly but not significantly higher in the Exo group after 2 and 4 d. The immunohistochemistry results showed that the proliferation of SMCs was slightly higher in the Exo group after 2 and 4 d, but the difference was not significant. The reendothelialization area of the Con group was significantly smaller than that of the Exo group at day 14. Both the intimal to medial area ratio and SMC proliferation in the Exo group were significantly smaller than those of the Con group at 14 or 28 d. In the in vitro study, exosome treatment significantly enhanced the proliferation and migration of both ECs and SMCs. ConclusionsExosomes derived from EPCs could inhibit neointimal hyperplasia after carotid artery injury in rats. The protective effect of exosomes may manifest through the promotion of EC repair rather than direct suppression of proliferation and migration of smooth muscles cells.

GW24-e3510 Mechanism of inhibitory effects of C-phycocyanin on over proliferation of vascular smooth muscle cells and luminal stenosis

ObjectivesTo investigate the effects and mechanism of C-phycocyanin (C-PC) from Spirulina Platensis on over proliferation of vascular smooth muscle cells (VSMCs), and endometrial hyperplasia and luminal stenosis after vascular damage.MethodsThe...

EFFECT OF DELETION OF CARTILAGE OLIGOMERIC MATRIX PROTEIN (COMP) ON COLLAGEN METABOLISM IN MURINE BRACHIOCEPHALIC ARTERY ATHEROSCLEROTIC LESIONS

Cartilage oligomeric matrix protein (COMP) is commonly found in bone and cartilage, but has also been detected in the extracellular matrix of atherosclerotic plaques. COMP is thought to act as...

Foxc2 overexpression enhances benefit of endothelial progenitor cells for inhibiting neointimal formation by promoting CXCR4-dependent homing

Endothelial progenitor cells (EPCs) are capable of enhancing re-endothelialization and attenuating neointimal formation. However, inefficient homing limits the therapeutic efficacy of EPCs transplantation. CXCR4 plays a critical role in regulating EPCs homing. Here, we studied the effect of Foxc2 overexpression on CXCR4 expression and the homing capacity of EPCs as well as the EPCs-mediated therapeutic benefit after artery injury. Bone marrow-derived EPCs were transfected with Foxc2 expression vector (Foxc2-EPCs) or empty control vector (Ctrl-EPCs) and examined 48 hours later. CXCR4 expression of EPCs was detected by flow cytometry and quantitative reverse transcriptase-polymerase chain reaction. The migration of EPCs toward SDF-1α was evaluated in a transwell migration assay, and the adhesion to fibronectin was determined using a static adhesion assay. For in vivo studies, EPCs were injected intravenously into the mice subjected to carotid injury. At 3 days after green fluorescent protein (GFP)/EPCs delivery, the recruited cells to the injury sites were detected by fluorescent microscopy. Re-endothelialization and neointimal formation were, respectively, assessed by Evans blue dye at 7 days and by the morphometric analysis for neointima and media area ratio (N/M) at 28 days after EPCs transfusion. Foxc2 overexpression significantly increased the surface expression of CXCR4 on EPCs (about 1.9-fold of Ctrl-EPCs, P < .05). Foxc2-EPCs showed an increased migration toward SDF-1α (P < .05); Foxc2 overexpression increased also the adhesion capacity of EPCs (P < .05). In vivo, the number of recruited GFP cells was significantly higher in the mice transfused with Foxc2-GFP/EPCs compared with Ctrl-GFP/EPCs (about 2-fold of Ctrl-GFP/EPCs). The degree of re-endothelialization was higher in mice transfused with Foxc2-EPCs compared with Ctrl-EPCs (90.3% ± 1.6% vs 57.2% ± 1.3%; P < .05). Foxc2-EPCs delivery resulted in a greater inhibition of neointimal hyperplasia than Ctrl-EPCs administration (N/M: 0.38 ± 0.03 vs 0.67 ± 0.05, P < .05). Preincubation with CXCR4-Ab, AMD3100, or LY294002 significantly attenuated the enhanced in vitro and in vivo effects of Foxc2-EPCs. Our findings indicate that Foxc2 overexpression increases CXCR4 expression of EPCs and efficiently enhances the homing potential of EPCs, thereby improving EPCs-mediated therapeutic benefit after endothelial injury. Foxc2 may be a novel molecular target for improving the therapeutic efficacy of EPCs transplantation.

VCAM-1 siRNA reduces neointimal formation after surgical mechanical injury of the rat carotid artery

Restenosis is one of several complications following carotid endarterectomy (CEA). The pathogenesis of restenosis may be related to postsurgery inflammation and leukocyte recruitment mediated by cellular adhesion molecules. In this study, we examine the role of vascular cell adhesion molecule-1 (VCAM-1) in carotid neointimal hyperplasia following carotid surgical mechanical de-endothelialization (CSMDE) in a rat model of CEA. The inhibition of siRNA on VCAM-1 protein expression was determined by using the methods of immunostaining and Western blot. Ultrasound imaging and morphometric analysis were applied to measure the degree of CSMDE-induced carotid artery neointimal hyperplasia of rats. We found that a lentivirus-based construct expressing a small interfering RNA (siRNA) against VCAM-1 could effectively (P < .05, n = 10 per group) reduce VCAM-1 protein expression in the carotid arteries of rats undergoing CSMDE (CSMDE+RNAi: 135.0 +/- 27.6%) when compared that of CSMDE with scrambled siRNA (CSMDE+CON: 182.7 +/- 36.4%). Doppler ultrasonography revealed that CSMDE+RNAi was accompanied by a significant reduction in the extent of stenosis demonstrated by increased blood velocity (665.85 +/- 48.37 mm/s) and linear diameter (0.59 +/- 0.77 mm) compared to CSMDE+CON (46.72 +/- 28.67 mm/s with undetectable linear diameter, P < .05, n = 10 per group). In addition, morphometric analysis of hematoxylin and eosin (HE)-stained sections indicated that the intima (innermost layer of media at lesion site)/media area ratio (I/M) was significantly increased (P < .05, n = 10 per group) both in the CSMDE (3.99 +/- 0.65) and CSMDE+CON (4.33 +/- 0.59) groups compared with the SHAM group (0.35 +/- 0.13). However, CSMDE+RNAi resulted in a significant (P < .05, n = 10 per group) decrease in the I/M ratio (1.79 +/- 0.43) compared to CSMDE+CON, whereas there were no significant differences in the total arterial area and medial areas among the groups. These results suggest that perivascular events mediated by VCAM-1 are likely to play an important role in the pathogenesis of carotid artery neointimal hyperplasia in rats after CSMDE.

Treatment of in‐stent restenosis with beraprost sodium: An experimental study of short‐ and intermediate‐term effects in dogs

1. The aim of the present study was to evaluate the inhibitory effects of the short-term administration of beraprost sodium, a stable prostaglandin I(2) analogue, on neointimal thickening after stenting. 2. To examine the immediate and short-term effects, Z-stents were placed in the iliac veins of 12 dogs, which were randomly assigned to either a beraprost-treated or control (saline) group. Beraprost (0.35 microg/kg per min) or saline (1.5 mL/min) was administered 30 min before stenting and was continued for 5 h thereafter. Platelet aggregation was measured before and after drug administration. At 3, 7 and 14 days after stenting, dogs were killed and immunohistochemical staining for proliferating cell nuclear antigen was used to quantify the proliferation of vascular smooth muscle cells (SMC). To evaluate intermediate-term effects, a Z-stent was placed in the right iliac vein in 10 dogs, followed by beraprost treatment. Three days later, a second Z-stent was placed contralaterally with saline infusion as a control. After 4 weeks, dogs were killed and neointimal thickness was measured under a light microscope to calculate the intima : media area ratio. 3. Platelet aggregation was more significantly suppressed in the beraprost-treated than in the control group (P = 0.01). In addition, SMC proliferation was significantly lower in the beraprost-treated group 7 and 14 days after stenting (P < 0.05). Over the intermediate term, the intima : media area ratio was significantly lower in the beraprost-treated vein compared with control (P < 0.05). 4. In conclusion, short-term beraprost treatment during stenting suppresses in situ platelet aggregation and SMC proliferation, thus reducing neointimal thickening.

Abstract 5541: Erythropoietin Receptor Signaling Exacerbates Neointimal Hyperplasia in the Rat Carotid Artery After Balloon Injury

Treatment with erythropoietin (EPO) was reported to accelerate reendothelialization, accompanying endothelial progenitor cell (EPC) induction, to result in suppression of neointimal hyperplasia in the carotid artery after balloon injury. We injured the right carotid artery of male SD rats (200 to 250 g) with an oversized balloon. Treatment with recombinant human EPO (1000 IU/kg/day) or asialoerythropoietin (AEPO, 1000 IU/kg/day), a nonerythrogenic derivative of EPO, was started at 1 week after injury when neointimal proliferates and continued for 3 days. The rats were examined 2 weeks after the surgery. The hemoglobin level was significantly increased in the EPO-treated rats but was unchanged in the saline control and AEPO-treated groups. FACS analysis revealed significantly increased circulating EPCs in the EPO-treated group but not in the AEPO-treated group. Reendothelialization was accelerated in both EPO- and AEPO-treated groups. However, the area of neointima was significantly greater in both treatment groups compared with the control group and accordingly the area of neointimal to medial area ratio (%) was significantly greater in the EPO- (150+/−26%) and AEPO-treated (157+/−15%) groups compared with the control group (132+/−7%). Alpha-smooth muscle actin-positive cell population was also greater in both treatment groups. The incidence of proliferating cells labeled with Ki-67 antigen was significantly greater not only in the endothelium but also in the neointima of the EPO- and AEPO-treated groups compared with the control group. In conclusion, EPO receptor signaling can proliferate not only endothelial cells but also intimal smooth muscle-like cells independently of EPC induction, which might have aggravated neointimal hyperplasia when EPO receptor was stimulated at the phase of intimal proliferation after injury. These findings caution an easy use of EPO in patients after vascular intervention.

Intimal thickness of the coronary arteries in low‐birthweight infants

Intimal thickening is considered to be an early manifestation of developing atherosclerosis in healthy young adults and children. Low birthweight correlates with increased incidence of cardiovascular diseases. To test the hypothesis that low birthweight is associated with relatively thickened intima at birth. The coronary arteries of 175 children were screened from serial cross-sections for maximal intimal thickening and measured morphometrically. The area of intima and media and the length of internal elastic lamina were measured. The intimal to medial area ratio and calculated thicknesses of intima were used in statistical comparisons. Only children who died within 30 d after birth (n=111) were included. There was a significant positive correlation between intimal thickness and birthweight in low-birthweight children (p<0.006). Neither the relative thickness of the intima nor the ratio of intimal to medial area increased with increasing growth restriction. The sum of the thicknesses of arterial media and intima had a significant positive correlation with birthweight in these infants. Intimal thickness present at birth in small-for-date children does not seem to be an aetiological factor for the increased risk of coronary heart disease later in life.

Effect of low molecular weight heparin on intimal hyperplasia.

Intimal hyperplasia is a significant cause of vascular graft failure. To investigate the potential uses of low molecular weight heparins (LMWHs) as prophylactic agents against graft thrombosis in humans, the anti-proliferative effects of a regimen of subcutaneous LMWH have been studied in an experimental model. Aortic intimal hyperplasia was created in 30 New Zealand White rabbits by endothelial denudation using an embolectomy balloon catheter technique. Three groups of ten animals were randomized to act as controls or to be treated with subcutaneous LMWH once or twice daily for 4 weeks. At 4 weeks all animals were killed and the aortas were harvested for analysis. The degree of intimal hyperplasia was measured using a computerized image analysis system and was expressed as an intimal:medial area ratio and also as percentage luminal reduction. A 60 per cent reduction in the degree of intimal hyperplasia was seen following treatment with LMWH. Heparin-treated animals had considerably less luminal reduction (daily LMWH 8 per cent and twice-daily LMWH 10 per cent) compared with untreated controls (26 per cent) (P less than 0.001). There was a similar difference seen in the intima:media area ratios, daily LMWH 0.38, and twice-daily LMWH 0.44, versus controls, 1.11 (P less than 0.001). In an experimental model, subcutaneous LMWH therapy effectively inhibits intimal hyperplasia.

Local delivery of E2F decoy oligodeoxynucleotides using ultrasound with microbubble agent (Optison) inhibits intimal hyperplasia after balloon injury in rat carotid artery model

Since restenosis after angioplasty still remains a major clinical problems, inhibition of neointimal formation is an important subject. In this study, we focused on the transcription factor, E2F, that plays a pivotal role in the transactivation of cell-cycle regulatory genes, and also we developed a newly delivery system of decoy oligodeoxynucleotides (ODN). We transfected E2F decoy ODN mixed with an echo-contrast microbubble agent (Optison) into rat carotid artery balloon-injured model by using therapeutic ultrasound (US) to inhibit neointimal formation. Two weeks after transfection, the intimal to medial area ratio in E2F decoy + Optison + US group was significantly decreased ( P<0.01). Inhibition of cell growth was also confirmed by PCNA staining. No apparent toxicity such as inflammation could be detected in blood vessels transfected with E2F decoy ODN with Optison and ultrasound. Overall, the present studies demonstrated a novel non-viral ODN transfer method into blood vessels. A novel therapeutic strategy using E2F decoy ODN with Optison using ultrasound may be useful to inhibit restenosis in clinical practice without a viral vector.

Relationship of collagen content, intimal thickening and angiotensin II level of iliac arteries after balloon injury in rabbits

OBJECTIVE: To investigate the relationship of collagen content intimal thickening and angiotensin II level of iliac arteries after balloon injury in rabbits. METHODS Fifty male New Zealand white rabbits were randomly devided into 6 groups: losartan groups, benazapril groups and control groups for 4 weeks or 8 weeks. Every rabbit underwent endothelial debridement of the right iliac artery. lorsartan (15 mg/kg/d) and benazapril (5 mg/kg/d) were orally administrated respectively in losartan groups and benazepril groups from 5 days before until 4 weeks or 8 weeks after balloon injury. RESULTS: Collagen content and intimal area of rabbit iliac arteries were increased after balloon injury. After intervention for 4 weeks with losartan and benazapril, collagen content was decreased in losartan and benazapril groups than in control group 23.58+/-6.16 % and 22.67+/-10.20 % compared with 35.20+/-7.25 % respectively, P<0.05. After intervention for 8 weeks, collagen content was significantly decreased (20.69+/-11.16)% and 25.41+/-11.00 % compared with 42.69+/-13.99 % respectively, P<0.05; Intimal area and intimal to medial area ratio were also decreased in losartan and benazapril groups than in control group; Lumen area was increased in losartan and benazapril groups than in control group(0.79+/-0.25)mm2 and (0.76+/-0.28)mm2 compared with (0.62+/-0.27)mm2 P<0.05; Tissue angiotensin II level was increased in losartan group (516.31+/-70.79)pg/mg.pro compared with (410.72+/-100.11)pg/mg.pro, P<0.05, and decreased in benazapril group than in control group (340.62+/-67.69)pg/mg.pro compared with (410.72+/-100.11)pg/mg.pro, P<0.05. There were close correlation between tissue angiotensin II level and intimal area, or between tissue angiotensin II level and intimal to medial area ratio, or and collagen content in benazapril group, respectively, P<0.05. Conclusion (1) Collagen protein is a dynamic participant in vascular injury. (2) Tissue renin angiotensin system may play an important role in collagen accumulation, intimal thickening and vascular injury after angioplasty. (3) Losartan and benazapril reduce vascular collagen content and inhibit intimal thickening after balloon injury.

Local Delivery of a Hydrophobic Heparin Reduces Neointimal Hyperplasia After Balloon Injury in Rat Carotid but not Pig Coronary Arteries

Intimal hyperplasia following percutaneous interventional vascular procedures is a major cause of restenosis. Although heparin inhibits intimal hyperplasia, it has not proven clinically useful in part due to an inadequate duration of intramural drug residence. This study was designed to evaluate the efficacy of local delivery of hydrophobic heparin (PTIR-RS-1), exhibiting increased intramural binding, on neointimal hyperplasia after angioplasty injury. PTIR-RS-1 was delivered locally into rat carotid arteries at three doses: 0.1 mM (440 IU), 0.3 mM (1320 IU), or 1.0 mM (4400 IU). Animals were killed at 14 days. In the pig, the doses tested were the low dose in the rat and a high dose 1 log higher. Animals were killed 28 days later. Morphometric analysis was performed to evaluate the intima: media ratio in rats and the normalized neointimal area in pigs. In rats a significant reduction in neointimal to medial area ratio from 0.73 +/- 0.15 for control vs 0.80 +/- 0.27 for sodium heparin (P = NS) and 0.15 +/- 0.07 for the 0.1 mM PTIR-RS-1 dose (P < 0.008). In pigs, PTIR-RS-1 the high dose reduced the normalized neointimal area by 16%, a difference that was not statistically significant. Increased hydrophobicity of heparin reduced neointimal area following balloon overstretch injury in the rat carotid but not the pig coronary artery model. This study attests to the importance of performing studies evaluating the pharmacologic effect of local delivery of a medication in at least two animal models of restenosis.

Substantial inhibition of neo-intimal response to balloon injury in the rat carotid artery using a combination of antibodies to platelet-derived growth factor-BB and basic fibroblast growth factor

Thirty percent of patients undergoing percutaneous transluminal coronary angioplasty develop recurrent disease within a year. This is usually due to the rapid accumulation of intimal smooth muscle cells and extracellular matrix, which causes luminal narrowing, and is probably orchestrated by several mitogenic and chemotactic factors, of which platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF) appear to be particularly important. We have investigated the effects of administering a combination of neutralizing antibodies directed against PDGF-BB and bFGF on neo-intima development following balloon catheter injury in the rat carotid artery. Purified sheep anti-PDGF-BB and anti-bFGF immunoglobulins (IgGs) were administered singly and in combination prior to mechanical injury and daily until sacrifice, 8 days later. Plasma titres of exogenous anti-PDGF-BB and anti-bFGF were maintained at levels 10–20-fold higher than those required to neutralise the mitogenic and chemotactic effects of 20 ng/ml of PDGF-BB, or 10 ng/ml bFGF in vitro. Used singly, anti-PDGF IgG treatment was associated with a 47% reduction in intimal thickness and a 59% reduction in intimal:medial area ratio; anti-bFGF IgG administration caused a 53% reduction in intimal thickness, and a 50% reduction in intimal:medial area ratio. Treatment with a combination of these antibodies resulted in a 83.8% reduction in intimal thickness ( P<0.05), and a 91% reduction in intimal:medial area ratio ( P<0.01). The latter treatment was also associated with a significantly higher intimal cell density (14.2±1.6×10 3 nuclei/mm 2) compared to animals receiving non-immune IgG (7.8±0.8×10 3 nuclei/mm 2; P<0.025), although intimal and medial cell proliferation indices were not significantly different between the groups ( P>0.05). Our results suggest that in this particular model, PDGF-BB and bFGF are the major factors controlling neointimal hyperplasia, and that these growth factors are operating principally via an effect on smooth muscle cell migration and extracellular matrix protein accumulation.

Endothelial cell seeding fails to attenuate intimal thickening in balloon-injured rabbit arteries

Restenosis of arteries or bypass grafts after vascular reconstruction is a common clinical entity that significantly limits long-term patency. This process, termed intimal hyperplasia (IH), is characterized by smooth muscle cell proliferation in the intima and subsequent accumulation of intercellular matrix. This study was designed to test the hypothesis that endothelial cell (EC) seeding of acutely injured arteries accelerates reendothelialization of the flow surface and limits the development of IH. ECs were harvested from jugular veins of New Zealand white rabbits (n = 13) and were amplified in tissue culture. Each animal subsequently underwent bilateral balloon catheter injury of the iliofemoral arteries; one side was immediately seeded with cultured autologous ECs at supraconfluent density, whereas the contralateral vessel served as a nonseeded control. Animals were killed 33 +/- 5 days after balloon injury. Intimal thickening was quantitated on histologic sections of vessels (three sections per vessel, total of 60 sections) and percent endothelialization was assessed by SEM; measurements were obtained by use of computer-aided morphometry performed by a blinded observer. Data were analyzed by use of a paired t test for comparison between seeded and control vessels. Seeded vessels exhibited a greater degree of reendothelialization (93.9% +/- 7.6% of the surface) than their unseeded counterparts (65.1% +/- 22.5%, p < 0.01). Intimal cross-sectional area and the ratio of intimal area to medial area were not significantly different between seeded and control vessels (intima: 0.32 +/- 0.19 vs 0.37 +/- 0.11 mm2, p = 0.28; intimal area to medial area ratio: 0.84 +/- 0.35 vs 1.02 +/- 0.2, p = 0.24). We conclude that seeding with autologous venous ECs accelerated restoration of the endothelial monolayer but failed to attenuate IH in balloon-injured rabbit arteries. Further studies are necessary to determine the functional properties of seeded endothelium and to examine the effect of EC seeding on intimal thickening in other clinically relevant models.

Late effects of locally delivered mitomycin C on formation of neointima and on vasomotor response to acetylcholine

Balloon angioplasty damages endothelial cells and stimulates smooth muscle cell proliferation. The effects of local cytotoxic drug therapy on formation of neointima and late endothelial function are not known. This study was designed to determine whether direct infusion of mitomycin C via a microporous balloon catheter could significantly reduce formation of neointima after angioplasty. Furthermore, we investigated whether endothelial cell function is normal 7 weeks after the initial microporous angioplasty procedure. In 34 New Zealand white rabbits, bilateral external iliac arteries underwent balloon angioplasty, followed by either high-dose (0.66 mg/kg) or low-dose (0.025 mg/kg) mitomycin C in one iliac artery and saline infusion in the contralateral artery, and a control group was given saline in both vessels. Formation of neointima was measured in the iliac arteries after 7 weeks by morphometry. Before sacrifice of 17 'angioplasty' rabbits and three undamaged rabbits, graded doses of acetylcholine and isosorbide dinitrate were infused in the distal aorta, and the iliac artery diameter was measured by computerized quantitative angiography. No significant differences in the absolute area of the intima or the intima: media ratio were demonstrated between control arteries and arteries that were directly infused with either high-dose or low-dose mitomycin. However, within the high-dose group, the mitomycin-treated vessel had a significantly lesser extent of formation of intimal hyperplasia (0.17 +/- 0.03 versus 0.27 +/- 0.03 mm2, P < 0.03) and lower intima: media area ratio (0.60 +/- 0.31 versus 1.09 +/- 0.42, P < 0.03) than the contralateral saline-treated vessel. Significant increases in mean luminal iliac artery diameter [0.18 mm (10.5%) at 1 min and 0.23 mm (13%) at 3 min, P < 0.05)] from baseline values following acetylcholine were observed in previously damaged iliac arteries. This vasodilatory response was not different from that in undamaged arteries. Local delivery of mitomycin C had no favorable effect on the inhibition of intimal hyperplasia compared with control saline-treated arteries. Normal endothelial function, determined on the basis of dilatory response to acetylcholine, can be demonstrated 7 weeks after balloon angioplasty injury.

The effect of low molecular weight heparin on intimal hyperplasia in vein grafts

Intimal hyperplasia due to smooth muscle cell proliferation is a well recognised cause of vascular graft failure. In experimental studies heparin and its low molecular weight derivatives can inhibit this proliferative response. This study examines the effect of subcutaneous low molecular weight heparin (LMWH) therapy on intimal hyperplasia in a model of arterial vein grafting. Twenty-four New Zealand White rabbits underwent interposition vein grafting of the carotid artery. Animals were randomly assigned to a control or treated group. Treated animals received 60 anti Xa units/kg of subcutaneous LMWH daily for 1 month. Animals were then sacrificed, graft patency assessed and the vessels then harvested for analysis of intimal hyperplasia. Intimal hyperplasia in carotid arteries and vein grafts was measured using a computerised image analysis system and was expressed as an intimal:medial area ratio. A statistically significant reduction in the degree of intimal hyperplasia seen in the arterial component of the distal anastomoses of carotid vein grafts was achieved using subcutaneous LMWH [Control 0.44 (0.37-0.55): LMWH 0.27 (0-0.37) p < 0.05]. There was no difference in the degree of intimal hyperplasia seen in the vein grafts themselves. [Control 0.21 (0-0.54): LMWH 0.23 (0-0.72)]. This study suggests that subcutaneous LMWH can inhibit the development of intimal hyperplasia in arteries undergoing vascular grafting but does not influence intimal hyperplasia within vein grafts. This has important implications for the further evaluation of antithrombotic agents following vascular surgery.

Use of histomorphometry in the assessment of fatal vertebral artery dissection.

To assess morphometrically the structural changes, which occur with ageing, along the length of the vertebral artery. A series of 36 vessels were removed at necropsy from subjects aged between 9 months and 86 years. Image analysis was used to measure the medial width, the circumference, the intimal: medial area ratio and the adventitial: medial area ratio along each artery. The artery from a case of fatal vertebral artery dissection, which occurred after a game of cricket and then chiropractic neck manipulation, was also examined in the same manner. The proteoglycan accumulation in the media was quantified using an eyepiece graticule. The vertebral arteries were, on average, larger around the origin of the vessel from the subclavian artery, and the adventitia were relatively thicker at this point, and also after piercing the dura mater. The media were much thinner within the intracranial segment and pronounced intimal thickening occurred with increasing age. The dissected artery showed undoubtable pre-existent structural abnormalities, in the form of massive proteoglycan accumulation, which predisposes an artery to dissection. These data should help pathologists faced with the task of assessing the underlying structural integrity of the vessel wall in cases of vertebral artery injury.

Effect of endothelin-1 infusion on the development of intimal hyperplasia after balloon catheter injury.

Previous studies have shown endothelin-1 (ET-1) to be mitogenic for smooth-muscle cells. We explored in vivo the ability of high ET-1 levels to worsen angioplasty restenosis. Left carotid artery balloon endothelial denudation was performed on 14 rats. ET-1 was delivered via osmotic pump at a rate of 5 pmol/kg/min. Intimal development and plasma ET-1 levels were assessed at 2 weeks. Blood pressure and heart rate were measured throughout the study. For analysis, the animals were divided into three groups based on ET-1 levels at harvest: control, 4.3 +/- 0.5 pmol/ml (n = 6); low ET-1, 5.2 +/- 0.9 pmol/ml (n = 4); and high ET-1, 23.1 +/- 5.9 pmol/ml (n = 4). Although ET-1 infusion caused blood pressure elevation in both ET-1 groups, this was more marked and prolonged in the group with a high ET-1 level at study conclusion. Evaluation of the intimal:medial area ratio showed a marked increase in intimal thickness in the high ET-1 group versus control (1.13 +/- 0.23 versus 0.35 +/- 0.11; p < 0.05). We conclude that ET-1 infusion in responsive animals can cause worsening of the intimal hyperplastic response after mechanical injury. Further study is required to elucidate whether this is entirely caused by a direct effect of ET-1 on smooth-muscle cell mitogenesis or is also by the hemodynamic effects of ET-1-induced hypertension, or an effect of another mediator released in response to the ET-1 (e.g., angiotensin II).