Intimal Plaque Research Articles

Smooth Muscle Cell (SMC) phenotype in diffuse intimal thickening and atherosclerotic plaques of human aorta

Smooth Muscle Cell (SMC) phenotype in diffuse intimal thickening and atherosclerotic plaques of human aorta

Immunolocalization of BMP-6, a novel TGF-β-related cytokine, in normal and atherosclerotic smooth muscle cells

We have analyzed expression of a novel transforming growth factor type β (TGF-β)-related cytokine, bone morphogenetic protein-6 (BMP-6) in normal and atherosclerotic brain arteries. BMP-6 immunoreactivity was detected in smooth muscle cells of normal cerebral blood vessels. It is also expressed by smooth muscle cells of intimal plaques in atherosclerotically changed blood vessels. The BMPs regulate tissue modeling and remodeling and aberrant expression of BMPs might contribute to smooth muscle cell migration, proliferation, tissue reorganization and macrophage attraction, which are known mechanisms of atherosclerotic plaque formation.

812-3 Angiographic Evidence for Frequent “Silent” Plaque Disruption In Patients with Stable Angina

Histopathological studies of human coronary atheroma (post mortem and atherectomy) suggest that acute coronary syndrome (ACS) may be the extreme end of a spectrum of outcomes from intimal plaque disruption and that “silent” plaque disruption is much more common in the population than would be predicted from the incidence of ACS. It is generally held that angiographic complex coronary stenoses represent previous plaque disruption. We therefore assessed the incidence of angiographic complex plaques in 295 consecutive patients (pts) presenting with moderate to severe stable angina for single vessel PTCA. Two groups were compared: pts with a previous episode of ACS and pts without previous ACS. There were no clinical or biochemical differences between groups. Complex stenosis severity was (mean ± 1SD) 67 ± 8% in both groups using quantitative coronary angiography. Angiographic morphology Clinical features Smooth Complex n p Previous ACS 35 (38%) 56 (62%) 0.0001 No previous ACS 151 (74%) 53 (26%) There is a relatively high incidence (26%) of angiographically complex plaques in clinically stable patients with no previous clinical evidence of acute coronary syndrome. This indicates that clinically “silent” plaque disruption is common.

Chronic generalized obliterative arteriopathy in cattle: a sequel to sheep-associated malignant catarrhal fever.

Malignant catarrhal fever (MCF) in cattle is generally associated with a short clinical course and a high case fatality rate (90-95%). The lesions in cattle that survive acute MCF for a prolonged period or appear to recover have not been documented. In a naturally occurring outbreak of MCF in a herd of beef cattle in Wyoming, 7 of 84 yearling heifers (8.3% of replacement herd) and 2 of 230 cows (0.9% of cow herd) developed clinical signs of pyrexia, mucopurulent discharge, bilateral keratitis, and weight loss following contact with ewes that had lambed 34-62 days earlier. Six of 9 affected cattle were examined postmortem following clinical signs (CS) that developed 2-150 days earlier. Three cattle with CS for < or = 39 days had lesions of regional lymphadenopathy and widespread severe segmental lymphoid arteritis-phlebitis that were typical of acute MCF, and proliferative intimal lesions were present in a small proportion of arteries at days 20 and 39 of CS. By contrast, 3 cattle that survived to 90, 105, and 150 days after clinical onset had distinctive arterial lesions in multiple organs, characterized by proliferative concentric fibrointimal plaques, disrupted inner elastic lamina, focally atrophic tunica media, and vasculitis of variable severity. Immunohistochemical and ultrastructural examination of intimal plaques identified the predominant cellular component to be smooth muscle cells with a contractile phenotype. No viral structures were seen. Serologic studies, using a competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA) that detects antibody to an epitope broadly conserved among isolates of the MCF virus, found that 2 chronically affected cattle were serologically positive between days 42 and 100 of CS, with seroconversion in 1 animal between days 52 and 73 of CS. Seroprevalence was 7.9% in the 76 remaining healthy animals of the replacement heifer herd and 40% (75% in adult sheep and 4% in lambs) in the in-contact sheep flock 77 days after onset of CS in the index case. This episode suggests that, in addition to the common and well recognized acute form of MCF in cattle, this viral infection encompasses a disease spectrum that includes chronic disease and partial to "complete" clinical recovery, and in recovered animals chronic obliterative arteriopathy is the preeminent lesion.

Acute arterial thrombosis associated with total knee arthroplasty

Purpose: Acute arterial thrombosis associated with total knee arthroplasty (TKA) is a rare but limb-threatening complication. The purpose of this report was to determine the incidence and optimal management of these complications by reviewing our extensive orthopedic experience and the English-language literature.Methods: Between April 1989 and March 1994 seven (0.17%) patients had development of acute limb-threatening ischemia after 4097 TKAs that were performed at our hospital. Management of these complications included (1) emergency arteriography to define inflow and outflow arteries, (2) use of autologous vein from the contralateral leg when arterial bypasses were necessary (because TKAs are associated with a high incidence of deep vein thrombosis), and (3) early, aggressive revascularization that often required difficult distal bypasses to achieve limb salvage. Management of our cases are compared with treatment of 13 patients described in the literature.Results: Ten patients treated at other hospitals by arterial thrombectomy alone (six cases), sympathectomy alone (two cases), fasciotomy alone (one case) or delayed arterial bypass resulted in seven major amputations and one death. All seven of our patients and three patients treated elsewhere underwent emergency femorodistal bypasses (six tibial, three below-knee popliteal, one pedal). All 10 patients had limb salvage after long-term follow-up (average 18 months; range 1 to 58).Conclusion: Thrombectomy alone for acute arterial thrombosis associated with TKA generally is unsuccessful and associated with unacceptably high amputation rates. Dismal results without emergency bypass is due to underlying chronic occlusive atherosclerotic disease found in these patients and intimal plaque disruption that can occur with knee manipulation or tourniquet compression. Acute arterial occlusion after TKA is best managed by emergency arteriography and a femoroinfrageniculate bypass.

Quantitative morphologic study of intimal thickening at the human carotid bifurcation: II. The compensatory enlargement response and the role of the intima in tensile support

Arteries enlarge where intimal plaques form, tending to preserve lumen cross sectional area but causing an increase in mural tangential tension due to the increase in radius. To characterize the compensatory enlargement process at the carotid bifurcation and to evaluate the possible contribution of intima thickening to mural tensile support during the enlarging process, we assessed the relationships among intimal thickening, artery size and estimated tensile stress at 9 sequential axial levels in 42 human carotid bifurcations obtained during post-mortem examinations of 36 adults with no clinical or anatomical evidence of cerebrovascular disease. Right and left bifurcations were available for 6 patients. The arteries were fixed under conditions of controlled pressure distention and histologic sections were prepared at 0.5 cm axial intervals. We determined vessel radius ( r), intima thickness (IT), media thickness (MT), intima area (IA), lumen area (LuA) and the area encompassed by the internal elastic lamina (IELA), i.e. the lumen area if there were no intimal thickening. Although IT, IA and r were greatest in the proximal sinus region, there was a highly significant linear relationship between IA and IELA at each axial level; correlation coefficients ranged from 0.64 to 0.97 with P < 0.001 at each level. Stenosis (IA/IELA × 100) ranged from 10.8 ± 8.0% at the common carotid level immediately proximal to the bifurcation angle to 22.3 ± 17.9% at the level immediately distal to the angle, but LuA remained nearly constant at each level regardless of IA. When wall tensile stress (TS) was computed using only media thickness (MT), values ranged from 8.2 ± 2.5 to 17 ± 7.0 × 10 5 dyn/cm 2 (1 dyn = 10 −5 N) with the maximum occurring at the proximal sinus. When, however, total wall thickness (IT + MT) was used, TS was similar at all levels with a mean of 6.5 ± 2.5 × 10 5 dyn/cm 2, (range, 5.5 ± 1.8 to 7.3 ± 2.7 × 10 5 dyn/cm 2) with no significant differences among the 9 levels, including those with little or no intimal thickening. We conclude that during stages of minimal or moderate intimal thickening and plaque formation at the carotid bifurcation, artery size (IELA) at each level increases with IA, thereby preserving LuA. The sum of intima and media thickness corresponds to the increase in radius such that estimated tangential mural tensile stress remains normal at each level.

Differences in compensatory vessel enlargement, not intimal formation, account for restenosis after angioplasty in the hypercholesterolemic rabbit model.

In de novo human atherosclerosis, compensatory vessel enlargement limits the effect of intimal plaque formation on lumen narrowing. We hypothesized that arterial remodeling may also play an important role in determining the chronic lumen size after angioplasty and tested this hypothesis using the hypercholesterolemic rabbit iliac artery angioplasty model. Morphometric analysis of histological cross-sectional areas of vessels from animals killed immediately after angioplasty (acute group, n = 11) were compared with the same areas from animals killed 4 weeks after the procedure (chronic group, n = 37), when restenosis occurs in this model. The area circumscribed by the internal elastic lamina (IEL) increased by 20% from acute to 4 week follow-up after angioplasty (acute group, 2.36 +/- 0.45 mm2, chronic group, 2.84 +/- 0.89 mm2). Over the same time period, intimal area increased by 0.82 mm2. Despite this increase in intimal area, lumen area decreased by only 0.34 mm2 because of the compensatory enlargement of the IEL area. In the chronic group, polynomial regression analysis revealed a quadratic relation between intimal area and lumen area (R2 = .35, P < .001). A lumen area of 0.45 mm2 (the nadir of the quadratic relation) was used to divide the chronic group into two subgroups: restenotic (n = 21; lumen area, < 0.45 mm2) and nonrestenotic (n = 16; lumen area, > 0.45 mm2). By definition, there was a significant difference in lumen area between the two subgroups (0.15 +/- 0.15 mm2 for restenotic; 0.73 +/- 0.18 mm2 for nonrestenotic). Surprisingly, the intimal areas in the two subgroups were virtually identical (2.41 +/- 0.92 mm2 for restenotic, 2.49 +/- 0.69 mm2 for nonrestenotic, P = NS). The difference in the lumen area between restenotic and nonrestenotic vessels was a result of the significantly greater IEL area in the nonrestenotic subgroup (3.22 +/- 0.83 mm2 for nonrestenotic, 2.56 +/- 0.84 mm2 for restenotic, P < .05). In both restenotic and nonrestenotic vessels, the IEL area increased with increases in intimal area. In the restenotic arteries, the slope of this correlation was < 1, showing inadequate compensatory enlargement for the intimal plaque. In the nonrestenotic vessels, the slope was > 1, limiting the effect of intimal plaque on luminal narrowing. These data indicate that the iliac artery in an atherosclerotic rabbit model compensates for intimal formation after angioplasty by vessel enlargement. Furthermore, the degree of vessel enlargement is more important than intimal area in determining the chronic lumen size.

Static circumferential tangential modulus of human atherosclerotic tissue

The mechanical properties of atherosclerotic plaque may be of critical importance to the processes of plaque rupture, the most common antecedent of myocardial infarction. To investigate the effects of plaque structure and applied tensile stress on the static circumferential tangential modulus of atherosclerotic plaque, the stress-strain behavior of 26 human aortic intimal plaques was studied. Intimal plaques were collected during routine autopsies of 21 patients from the abdominal ( n = 19) and thoracic ( n = 2) aorta and were classified by histological analysis as cellular ( n = 12), hypocellular ( n = 9), and calcified ( n = 5). At a physiologic applied circumferential tensile stress of 25 kPa, the tangential moduli of cellular, hypocellular, and calcified specimens were 927 ± 468 kPa, 2312 ± 2180 kPa, and 1466 ± 1284 kPa, respectively. There was a nonsignificant difference in tangential modulus at 25 kPa stress between specimens classified as cellular and hypocellular ( p = 0.098), cellular and calcified ( p = 0.410), and hypocellular and calcified ( p = 0.380). This is in marked contrast to the previously measured radial compressive behavior of plaque tissue, which showed that cellular, hypocellular, and calcified plaques were significantly different in their modulus. In tension, all 26 plaques tested demonstrated a statistically significant increase in tangential modulus with increasing applied circumferential stress. We conclude that the static circumferential tangential modulus of atherosclerotic plaque, unlike its radial compressive modulus, is not significantly affected by the degree of cellularity and calcification determined by histological characterization. Cellular and hypocellular plaques exhibit strongly anisotropic and nonlinear properties in the physiologic range of loading, with circumferential tangential modulus about 20 times greater than previously reported measurements of radial compressive modulus.

Superiority of transesophageal echocardiography in detecting aortic arch atheromatous disease: Identification of patients at increased risk of stroke during cardiac surgery

It has been shown that transesophageal echocardiography (TEE) is useful in evaluating atheromatous disease of the aortic arch and that such disease is a risk factor for stroke in medical patients. Data obtained by traditional methods of evaluating the aortic arch prior to cardiac surgery, namely, chest x-ray (CXR) and cardiac catheterization (CATH), were compared with that detected by TEE. Images of the descending thoracic aorta and aortic arch seen on intraoperative TEE in 258 cardiac surgical patients were graded as I = normal, II = intimal thickening or plaques <5 mm thick (moderate disease), III = plaques ≥5 mm thick or with a mobile component (severe disease). The aortic knob seen on CXR in 209 of these patients was graded as normal, < 1 2 or ≥ 1 2 ring of calcification. Calcification in the aortic root (graded as 0, 1+, 2+) and irregularities in the aortic lumen seen at CATH in 33 patients were also examined. Data were analyzed with respect to age, gender, type of surgery, and stroke. Increasing age correlated strongly with increasing severity of aortic arch and descending thoracic aortic disease seen by TEE. Severe disease was not present in patients under age 50 but was present in about 20% of those over age 70. Atheromatous disease was found by TEE in 55% of patients with a normal CXR and 91% of those with heavily calcified aortic knobs. Ischemic strokes occurred in seven patients. Severe arch disease correlated significantly with stroke ( P < .01). Other variables did not correlate with stroke. TEE evaluation of the aorta is useful in older patients and those with radiographic evidence of aortic calcification to determine the presence of severe atheromatous disease of the aortic arch, a condition that may increase the risk of perioperative stroke. Identifying severe aortic arch disease has important clinical implications because surgical technique may be altered to avoid dislodging arch “debris.”

Early experience of directional coronary atherectomy: clinical results, complications and histopathological findings

Objective: To report the early experience, clinical results and histopathologic findings of Directional Coronary Atherectomy from a UK centre experienced in coronary angioplasty. Design: Prospective study of the first 45 Directional Coronary Atherectomy (DCA) procedures using the Simpson coronary atherectomy device. Results: Forty-five procedures were performed in 33 male and 5 female patients (mean age, 55.1 years). Directional Coronary Atherectomy was performed to 50 lesions (39 de novo, 11 restenosis; 44 left anterior descending, 3 right, 2 circumflex coronary arteries and 1 saphenous vein graft). Clinical and primary angiographic success was achieved in 43 of 45 cases (95.5%) and in 47 of 50 lesions (94%) after DCA alone. Before DCA the mean diameter stenosis was 88.7% (range, 50–100%) but following DCA (and percutaneous coronary angioplasty (PTCA) if necessary) the mean diameter stenosis was 3.5% (range, 0–15%; P < 0.001). Complications included occlusive dissection requiring coronary artery bypass surgery in two patients; abrupt closure of right coronary artery in one patient successfully reopened by PTCA and thrombolysis, complicated by excessive blood loss; reversible coronary artery spasm due to minor nose-cone trauma in four patients and temporary side branch loss in one patient. There were no coronary artery perforations, guide catheter complications, peripheral vascular trauma or deaths. On average 5.6 specimens (range, 1–18) were removed per case. Histology showed fibrous intimal plaque in 98%, media in 39% and adventitia in 7%. Neo-intimal hyperplasia was found in all restenosis lesions but also in 30% of de novo lesions. Conclusions: This small initial series indicates that directional coronary atherectomy is an effective and safe procedure for the treatment of obstructive coronary artery disease in carefully selected patients. With care, a high success rate can be achieved even during a learning phase. The technique is particularly effective for morphologically complex lesions that are unfavourable for PTCA. The procedure is unlike PTCA and requires additional training if pitfalls are to be avoided, high success rates achieved and complication rates kept low.

Response of Femoral Arteries of Cholesterol-Fed Rabbits to Balloon Angioplasty with or without Laser: Emphasis on the Distribution of Foam Cells

Very little is known about the structural composition of the restenotic plaque in evolution. The responses of atherosclerotic femoral arteries of rabbits to balloon angioplasty (BA), thallium/holmium/chromium: YAG infrared laser angioplasty (LA), combined LA and BA, or no angioplasty were compared by blinded quantitative histomorphometry and angiography. The endothelium was injured by nitrogen/air desiccation, and the animals were fed a 2% cholesterol diet for 1 month prior to the angioplasty procedure. Animals were sacrificed 2 hr or 28 days after angioplasty by pressure perfusion with 10% formaldehyde (100 mm Hg), and arterial segments (4-5 cm) were excised bilaterally. The frequency of thrombus was greatest in arteries with LA. Arteries with combined LA and BA had the greatest initial gain in luminal diameter by angiography, but they also had the greatest reduction in luminal diameter from 2 hr to 28 days and the greatest cross-sectional area narrowing by plaque at 28 days. The principal component of the intimal plaques in all groups was fibrous tissue (approximately 90%), with the remainder consisting primarily of "foam cells." By multiple regression analysis, the strongest predictors of cross-sectional area narrowing were contiguity of foam cells between the intima and media, depth of the tear, percentage of foam cells in the plaque, and the intervention of LA followed by BA. The principal predictors of foam cells in the plaque, irrespective of treatment, were also cross-sectional area narrowing, contiguity of foam cells between plaque and media, and the depth of tear. It is suggested that a large proportion of the foam cells of the intima may be derived from foam cells of the media and adventitia rather than from the lumen. These observations may be of particular importance regarding angioplasty in young people where foam cells occupy a significantly greater proportion of the atherosclerotic plaque.

Increased prevalence of aortic fatty streaks in cholesterol-fed rabbits administered intravenous cocaine: the role of vascular endothelium.

Several recent postmortem studies suggest an increased prevalence of atherosclerosis in young habitual cocaine abusers. However, little is known about the effects of cocaine abuse on the vascular endothelium and its relationship to atherosclerosis. Therefore, the consequence of chronic administration of intravenous cocaine on the induction of aortic sudanophilia was examined. Male New Zealand White rabbits were fed a 0.5% cholesterol diet for 10 wk. During this period, animals were randomized to receive either cocaine-hydrochloride (0.25 mg/kg) intravenously (n = 17) twice daily; or an equivalent volume of 0.9% physiologic saline, control group (n = 16). Mean values for total circulating leukocytes and platelets and total plasma cholesterol and triglycerides were similar in both groups throughout the protocol. At the completion of the study, aortic sudanophilia was measured and expressed as a percentage of regional involvement (R1 = proximal 4 cm, R2 = middle 6 cm, and R3 = distal 10 cm). Statistical significance among groups was achieved in the proximal thoracic aorta (p = 0.057). No significant differences in sudanophilia were noted in the middle and distal segments. When animals were placed in subgroups according to percent total plaque involvement, there was a significant increased distribution of rabbits with a greater extent of sudanophilia in the cocaine-treated group as compared with control (p = 0.01, chi-square analysis). Immunocytochemical studies using the macrophage-specific and muscle actin-specific monoclonal antibodies demonstrated that sudanophilic areas in both groups were predominantly composed of macrophage-derived foam cells. Evaluation of plaque morphology showed an increase in intimal plaque thickness and in the number of macrophages and smooth muscle cells in cocaine-treated animals; however, group differences were not statistically significant. Because no significant differences were found in the cellular composition of atherosclerotic plaques between groups, further studies were performed to assess the effects of cocaine on the permeability function of cultured endothelial cell monolayers as a possible mechanism of increased sudanophilia. Cocaine (100 microM)-treated endothelial cell monolayers demonstrated an increased permeability to horseradish peroxidase during all time intervals studied (0-6 hr). Permeability differences were statistically significant at 30 min and 1 hr (p = 0.003 and 0.02, respectively). Collectively, these observations suggest that administration of cocaine to cholesterol-fed rabbits increases the prevalence of aortic sudanophilia via at least one possible mechanism involving enhanced vascular permeability.

Carotid Plaque Associations Among Hypertensive Patients

To assess the relationship between cardiovascular risk factors and carotid plaque. Hypertensive patients were screened for randomization into the Multicenter Isradipine Diuretic Atherosclerosis Study, a trial intended to determine if blood pressure control by isradipine as compared with hydrochlorothiazide will blunt the progression of carotid plaque (intima plus media thickness, 1.3 to 3.5 mm) in patients with serum cholesterol levels of less than 6.85 mmol/L (265 mg/dL) without insulin-dependent diabetes mellitus or estrogen therapy. Demographics of those who underwent B-mode ultrasound evaluations at common, bifurcation, and internal carotid artery sites to detect plaque were assessed from a southern and a northern site. Participants were from ambulatory outpatient clinics associated with medical schools. The initial screening included 1823 hypertensive volunteer patients who were between 40 and 83 years of age who had a diastolic pressure of 90 to 114 mm Hg (or < 90 mm Hg with treatment). Complete data were collected on the variables of age, cholesterol, cigarette smoking, race, gender, and the presence of carotid plaque in 1126 patients. All variables were significantly associated with carotid plaque (intima plus media thickness, > or = 1.3 mm). The adjusted percentage with plaque was 66.4% +/- 3.4% for blacks and 70.1% +/- 2.3% for whites at the southern site and 42.7% +/- 4.5% for blacks and 61.3% +/- 3.2% for whites at the northern site. The rate of plaque was 75.8% among cigarette smokers, despite a mildly elevated cholesterol level. Although these 1126 cases do not constitute a random sample of patients, these data suggest that there may be regional differences in racial tendencies toward plaque among blacks.

Vascular injury and time course of smooth muscle cell proliferation after experimental holmium laser angioplasty.

In vitro experiments have shown that holmium laser energy can effectively ablate even calcified plaque in human arterial vessels. Because high-energy densities from holmium lasers can easily be transmitted through quartz fibers, this solid-state laser has been suggested as an alternative intraluminal treatment of atherosclerotic plaque. To develop an intimal plaque, 35 New Zealand White rabbits underwent electrical stimulation of their right carotid artery for 28 days. Subsequently, in 25 rabbits, holmium laser angioplasty (wavelength, 2.12 microns; pulse duration, 150 microseconds; energy density, 350 mJ/mm2) was performed. To study the morphological results, the vessels were excised after 7, 14, 28, and 42 days. Cross sections were analyzed in regard to laser-specific injury. Staining of alpha-actin was used to identify smooth muscle cells (SMCs). After bromodeoxyuridine labeling, the extent of proliferation (number of cells undergoing DNA synthesis) was determined by using a monoclonal antibody. Holmium laser ablation resulted in an initial decrease of the numbers of intimal cell layers in the early group (7 days after treatment: 5 +/- 1 cell layers with 76 +/- 39 microns; control: 13 +/- 3 cell layers with 144 +/- 44 microns). Quantification of SMCs undergoing DNA synthesis in the intima (control: 51 +/- 19 cells/mm2) showed a significant increase of labeled cells after 7 (216 +/- 74 cells/mm2, p = 0.003) and 14 days (281 +/- 139 cells/mm2, p = 0.011). Integrity of the internal elastic lamina was disrupted in all animals after intervention. Seven and 14 days after treatment, a considerable reduction of medial cell nuclei was found in 10 of 12 animals. SMC proliferation in the medial layer was increased within the first 2 weeks after laser ablation (168 +/- 113 cells/mm2; control: 8 +/- 4 cells/mm2; p = 0.023). Six weeks after holmium laser angioplasty, SMC proliferation had returned to control levels in the intima and remained increased in the medial layer. This proliferative response resulted in a significant increase of intimal thickening within 6 weeks after laser ablation (30 +/- 6 cell layers, 375 +/- 97 microns resp.; p = 0.001 each). Holmium laser treatment leads to considerable vessel wall injury and results in SMC proliferation in the intimal and medial layer with a maximum of proliferative activity within the first 2 weeks. Subsequently, this results in considerable intimal and medial hyperplasia within 6 weeks after treatment.

Inhibition of cellular proliferation after experimental balloon angioplasty by low-molecular-weight heparin.

The proliferative response induced by balloon angioplasty is known to be an important factor in the development of restenosis after successful coronary angioplasty. To study the effects of low-molecular-weight heparin (LMWH) on cellular proliferation after experimental balloon angioplasty, LMWH (3.9 kd, 400 anti-Xa units/kg/day) was given to 20 male New Zealand White rabbits. After an intimal fibromuscular plaque was induced by electrical stimulation in the right carotid artery, LMWH was applied during the 7 days after balloon dilatation. As the control group, 20 other rabbits underwent balloon angioplasty without application of LMWH. The vessels were excised 3, 7, 14, and 28 days after balloon treatment. During the final 18 hours before the rabbits were killed, bromodeoxyuridine was applied. Intimal wall thickness increased from 13 +/- 5 cell layers (preangioplasty control group) to 20 +/- 6 cell layers in the LMWH-treated group at 28 days (p less than 0.05). In contrast, histological examination of control animals 28 days after angioplasty revealed a significant increase to 35 +/- 15 cell layers (p less than 0.01). Immunohistological quantification showed a significant increase (p less than 0.001) of cells undergoing DNA synthesis at 3 (10.2 +/- 4.2%) and 7 (7.7 +/- 4.8%) days after balloon dilatation in control animals. In contrast, at 3 and 7 days after balloon treatment, the percentage of cells undergoing DNA synthesis in LMWH-treated rabbits was lower (3 days, 2.7 +/- 1.8%; 7 days, 1.9 +/- 0.3%) than the corresponding untreated controls but showed a significant increase (p less than 0.01) compared with the preangioplasty controls. The differences between the two groups were statistically significant, however (3 days, p less than 0.01; 7 days, p less than 0.05). As early as 14 days after angioplasty, the extent of cellular proliferation was normalized and was comparable to the preintervention levels in both groups. Our data indicate that the proliferative response after balloon angioplasty can be reduced in vivo by early treatment with LMWH and thus encourage further clinical investigations.

Hypercholesterolemia and atherosclerosis change vascular reactivity in rabbits by different mechanisms.

Vasomotor reactivity was assessed in vitro in arterial segments obtained from rabbits with different stages of atherosclerosis. Rabbits were fed a standard chow diet (controls) or a cholesterol-enriched diet to induce hypercholesterolemia and atherosclerosis. A third group received the hydroxymethylglutaryl coenzyme A reductase inhibitor, lovastatin, simultaneously with the cholesterol diet. Contractile responses of thoracic aortas to norepinephrine, serotonin, and potassium-rich solution, as well as endothelium-dependent dilations to acetylcholine, were compared after 2 and 4 months on the respective diet. Additionally, plasma cholesterol levels and the amount of plaques covering the intimal surface (as a percentage of the intimal surface) were determined; transmission electron microscopy of atherosclerotic arteries was also performed. After 2 months, the only difference was an enhancement of contractile responses to serotonin in the cholesterol-fed versus the control group. After 4 months on the diet, contractile responses to serotonin were further enhanced, and norepinephrine- and potassium-induced vasoconstrictions were now also significantly enhanced in cholesterol-fed animals versus controls. Endothelium-dependent vasodilations were simultaneously reduced in cholesterol-fed animals. These alterations were partly prevented in cholesterol-fed and lovastatin-treated animals. Suppression of nitric oxide synthesis in control aortas by NG-nitro-L-arginine did not reveal any significant increases in contractile responses. Contractile responses to serotonin were enhanced after 2 months on the diet but before the appearance of intimal plaques, whereas attenuation of endothelium-dependent dilations, as well as the further enhancement of contractile responses to serotonin and to other agonists, were closely correlated with the degree of intimal plaques after 4 months on the diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of cytokeratin 8 in human aortic smooth muscle cells

An immunofluorescence method was used to study the expression of cytokeratin 8 in human aortic smooth muscle cells (SMCs) during prenatal development and in atherosclerotic plaques. Aortic SMCs from a 10-wk-old fetus contained cytokeratin 8 in additional to vimentin and a small amount of desmin, whereas, in the cells from a 25-wk-old fetus, cytokeratin 8 was not detected. Cytokeratin 8 was found in the SMCs from intimal thickenings, fatty streaks, and atherosclerotic fibrous plaques. Clusters of cytokeratin 8-positive cells were more abundant in rather advanced lesions (fibrous plaques) that contained at least some amount of lipid. Expression of cytokeratin 8 in the cells of human atherosclerotic lesions probably reflects general rearrangement of gene expression in the intimal cells.

Expression of cytokeratin 8 in human aortic smooth muscle cells

An immunofluorescence method was used to study the expression of cytokeratin 8 in human aortic smooth muscle cells (SMCs) during prenatal development and in atherosclerotic plaques. Aortic SMCs from a 10-wk-old fetus contained cytokeratin 8 in additional to vimentin and a small amount of desmin, whereas, in the cells from a 25-wk-old fetus, cytokeratin 8 was not detected. Cytokeratin 8 was found in the SMCs from intimal thickenings, fatty streaks, and atherosclerotic fibrous plaques. Clusters of cytokeratin 8-positive cells were more abundant in rather advanced lesions (fibrous plaques) that contained at least some amount of lipid. Expression of cytokeratin 8 in the cells of human atherosclerotic lesions probably reflects general rearrangement of gene expression in the intimal cells. cytodifferentiation; fetal phenotype; lipid accumulation

Anatomic correlates of aortic pulse wave velocity and carotid artery elasticity during atherosclerosis progression and regression in monkeys.

We noninvasively measured changes in average aortic stiffness in 79 cynomolgus monkeys being fed cholesterol progression, regression, and control diets by measuring pulse wave velocity (PWV) in 260 experiments during a 30-month period. Every 6 months, a group of monkeys was studied with invasive aortic PWV techniques and with ultrasonically determined pressure-strain elastic modulus (Ep) of the carotid artery, and then the group was killed so that morphometric evaluation of atherosclerosis severity could be made. After 6 months of a cholesterol progression diet, PWV decreased slightly from 6.2 +/- 0.1 to 5.7 +/- 0.1 m/sec, followed by an approximate linear increase to 8.8 +/- 1.2 m/sec after 30 months on the diet. The corresponding ratio of intimal (plaque) area to medial area (IA/MA) measured on perfusion-fixed cross-sections of the abdominal and thoracic aortas increased from 0.16 +/- 0.07 at 6 months to 1.23 +/- 0.22 at 30 months. Monkeys in the regression groups were fed the cholesterol progression diet for 18 months, followed by a chow diet for 6 or 12 months. In the first 6 months of the cholesterol regression diet, PWV continued to increase from 7.0 +/- 0.2 to 8.1 +/- 0.4 m/sec, and IA/MA was 1.24 +/- 0.18. However, after 12 months of the cholesterol regression diet, PWV decreased to 6.8 +/- 0.4 m/sec, and IA/MA was 0.90 +/- 0.18. The variability of the data demonstrates that PWV is not a simple function of atherosclerosis severity, and the best simple correlation was r = 0.69 (r2 = 0.48) between PWV and intimal area. However, multiple regression analysis of aortic PWV, systolic (SP) and diastolic (DP) blood pressures, and total plasma cholesterol concentration (TPC), all of which can be measured with minimally invasive techniques, improved the prediction of the IA/MA ratio through the following equation: IA/MA = 0.127 PWV-0.039 DP+0.023SP+0.0003TPC-0.292 (r = 0.81, r2 = 0.66). These data suggest that arterial stiffness in combination with minimally invasive parameters can be used to predict the severity of diffuse asymptomatic atherosclerosis in monkeys. However, more widespread application of these data to humans is uncertain because of biological variability and differences between animal models and human subjects.

Reduction of endothelial microfilament bundles in the low-shear region of the canine aorta. Association with intimal plaque formation in hypercholesterolemia.

To interrelate in vivo wall shear stress, endothelial microfilament bundle formation, and atherosclerosis localization, we used a mild abdominal aortic stenosis in 11 beagles to produce a range of wall shear stresses above and below the constriction. Six of the beagles were fed standard animal chow supplemented with 5% cholesterol and 10% coconut oil. Wall shear stresses, endothelial microfilament bundles, and intimal plaque localization were assessed along the stenosed aorta. Shear stress was determined in vivo from the near-wall velocity profiles with a 20-MHz, 80-channel, multigate Doppler velocimeter. Content of the microfilament bundles was quantified by planimetry of transmission electron photomicrographs. After 6 weeks, mean shear stress was higher immediately upstream from the throat of the stenosis than at the proximal site (46.1 +/- 7.3 dynes/cm2 versus 24.0 +/- 6.2 dynes/mc2, p less than 0.001) and was significantly lower immediately distal to the stenosis than at the proximal site (9.4 +/- 0.3 dynes/cm2, p less than 0.01). The microfilament bundle content increased immediately upstream from the throat of the stenosis and decreased immediately distal to the stenosis compared with the proximal site in both normocholesterolemic and hypercholesterolemic fat-fed beagles. Intimal plaques formed exclusively immediately distal to the stenosis in the hypercholesterolemic beagles. These findings suggest that a low shear-stress environment attenuates endothelial microfilament bundle formation, thus leading to a predilection for the initiation of atherosclerosis in atherogenic conditions such as hypercholesterolemia.