Dietary Nitrate Metabolism in Porcine Ocular Tissues Determined Using 15N-Labeled Sodium Nitrate Supplementation

Nitrate (NO3-) obtained from the diet is converted to nitrite (NO2-) and subsequently to nitric oxide (NO) within the body. Previously, we showed that porcine eye components contain substantial amounts of nitrate and nitrite that are similar to those in blood. Notably, cornea and sclera exhibited the capability to reduce nitrate to nitrite. To gain deeper insights into nitrate metabolism in porcine eyes, our current study involved feeding pigs either NaCl or Na15NO3 and assessing the levels of total and 15N-labeled NO3-/NO2- in various ocular tissues. Three hours after Na15NO3 ingestion, a marked increase in 15NO3- and 15NO2- was observed in all parts of the eye; in particular, the aqueous and vitreous humor showed a high 15NO3- enrichment (77.5 and 74.5%, respectively), similar to that of plasma (77.1%) and showed an even higher 15NO2- enrichment (39.9 and 35.3%, respectively) than that of plasma (19.8%). The total amounts of NO3- and NO2- exhibited patterns consistent with those observed in 15N analysis. Next, to investigate whether nitrate or nitrite accumulate proportionally after multiple nitrate treatments, we measured nitrate and nitrite contents after supplementing pigs with Na15NO3 for five consecutive days. In both 15N-labeled and total nitrate and nitrite analysis, we did not observe further accumulation of these ions after multiple treatments, compared to a single treatment. These findings suggest that dietary nitrate supplementation exerts a significant influence on nitrate and nitrite levels and potentially NO levels in the eye and opens up the possibility for the therapeutic use of dietary nitrate/nitrite to enhance or restore NO levels in ocular tissues.

Intervention with selution SLR™ Agent Balloon for Endovascular Latent Limus therapy for failing AV Fistulas (ISABELLA) Trial: Protocol for a pilot clinical study and pre-clinical results

BACKGROUND

The aim of this pilot clinical study is to evaluate the safety and efficacy of the Selution Sustained Limus Release (SLR)™ sirolimus-coated balloon (M.A. MedAlliance SA, Nyon, Switzerland) for improving the patency of failing arterio-venous fistulas (AVF) in hemodialysis patients. We also present herein a pre-clinical pharmacokinetic and safety evaluation of Selution™ to justify its first use in hemodialysis patients for endovascular access salvage.

METHODS AND RESULTS

This is an investigator-initiated prospective single-center, non-blinded single-arm trial. Forty patients with clinically significant de novo or recurrent stenoses in a mature AVF circuit will be recruited. All stenotic lesions will be prepared with high pressure non-compliant conventional balloon angioplasty (CBA) prior to deployment of the Sustained-Release Selution™ sirolimus drug-eluting balloon. The primary efficacy endpoint is 6-month target lesion primary patency and the primary safety endpoint is freedom from localized or systemic serious adverse events through 30 days. Secondary endpoints of interest include technical and clinical success rates and circuit access patency at 3 and 6 months. Follow-up will occur for 2 years for those patients whose AVFs remain patent. Pharmacokinetic and histological animal safety studies performed with the Selution™ coating formulation showed prolonged arterial tissue retention of sirolimus with therapeutic levels up to 60 days and non-toxic and rapidly declining blood levels. Histological results in animal models demonstrated safety, freedom from intraluminal thrombus, reduction in restenosis by sirolimus elution compared to CBA, and no evidence of embolic phenomena indicative of adverse particulate effects.

DISCUSSION

Long release sirolimus coated balloons may serve as a promising novel alternative therapy to paclitaxel-based technology for treating conduit stenosis secondary to neointimal hyperplasia. Pre-clinical pharmacokinetic and histological animal data are encouraging and provide suggestion of safety and efficacy in this setting. This single-center trial will provide a first step toward demonstration of efficacy and safety of this device for treatment of stenotic fistulas.

Optical coherence tomography assessment of acute thrombogenicity at bifurcation sites using different stenting techniques: A porcine arteriovenous shunt study

OBJECTIVES

We aimed to compare bare-metal stents (BMS), durable-polymer everolimus-eluting stents (DP-EES), and abluminal biodegradable-polymer sirolimus-eluting stents (ABP-SES) in the bifurcation model setup.

BACKGROUND

The mechanism of thrombogenicity, which differs among second-generation stents implanted using double-kissing (DK) crush or culotte stenting techniques, remains unclear. We have shown previously that setting up a porcine arteriovenous shunt model is feasible and useful to assess thrombogenicity at vessel bifurcation points.

METHODS

Six porcine shunt models were prepared for the comparison between DK crush and culotte stenting techniques using BMS, DP-EES, and ABP-SES. Intracoronary imaging with high-resolution optical coherence tomography (OCT) was performed to evaluate the thrombogenicity in different stent types in the bifurcation stenting model and was evaluated by a core lab.

RESULTS

Culotte stenting demonstrated more thrombogenicity at the proximal main branch (MB) with DP-EES, side branch (SB) with BMS, and the bifurcation site irrespective of the stent type, while DK crush technique exhibited thrombogenicity only at SB with BMS and ABP-SES. OCT analysis revealed malapposition of DP-EES in the proximal MB with culotte stenting. Stent expansion was generally larger in ABP-SES than BMS and DP-EES.

CONCLUSIONS

The study provides hypothesis-generating findings in distinct thrombogenicity of bifurcation stenting with DP- or ABP-coated drug-eluting stents.

Potential roles of nitrate and nitrite in nitric oxide metabolism in the eye

Nitric oxide (NO) signaling has been studied in the eye, including in the pathophysiology of some eye diseases. While NO production by nitric oxide synthase (NOS) enzymes in the eye has been characterized, the more recently described pathways of NO generation by nitrate (NO₃^-) and nitrite (NO₂^-) ions reduction has received much less attention. To elucidate the potential roles of these pathways, we analyzed nitrate and nitrite levels in components of the eye and lacrimal glands, primarily in porcine samples. Nitrate and nitrite levels were higher in cornea than in other eye parts, while lens contained the least amounts. Lacrimal glands exhibited much higher levels of both ions compared to other organs, such as liver and skeletal muscle, and even to salivary glands which are known to concentrate these ions. Western blotting showed expression of sialin, a known nitrate transporter, in the lacrimal glands and other eye components, and also xanthine oxidoreductase, a nitrate and nitrite reductase, in cornea and sclera. Cornea and sclera homogenates possessed a measurable amount of nitrate reduction activity. These results suggest that nitrate ions are concentrated in the lacrimal glands by sialin and can be secreted into eye components via tears and then reduced to nitrite and NO, thereby being an important source of NO in the eye.

Aortic valve ChromaFlo®: a feasibility study of aortic regurgitation and effective annular aortic area assessment in a porcine model

Aortic valve annular complex was rediscovered after the introduction of transcatheter aortic valve replacement; and imaging has been crucial in determining the annular geometry. Although the procedure has evolved, complications related to the annular mechanical response following valve implantation, such as aortic insufficiency, still occur in practice. We documented the feasibility of invasive assessment of aortic valve annular complex and the detection of induced aortic insufficiency via intravascular ultrasound with ChromaFlo® technology in a porcine model.

Effects of exogenous peripheral-blood-derived endothelial progenitor cells or unfractionated bone-marrow-derived cells on neointimal formation and inflammation in cholesterol-fed, balloon-denuded, and radiated iliac arteries of inbred rabbits

BACKGROUND

Injection of bone marrow cells (BMC) and endothelial progenitor cells (EPC) or application of stem-cell-mobilizing factors has been associated both with reduction or exacerbation of atherosclerosis and with unstable plaque phenotype. The discrepancies may reflect the cell type, dosing, duration, and route of administration of cells in these studies. The aim of this study was to determine the effects of peripheral-blood-derived endothelial progenitor cells (PBEPC) or unfractionated BMC obtained from inbred siblings on neointimal formation and inflammation in cholesterol-fed, balloon-denuded, and radiated rabbit iliac arteries.

METHODS

Rabbits were fed a 1.0% cholesterol diet for 14 days, followed by endothelial denudation in both iliac arteries, and continued on a 0.15% cholesterol diet. On day 42, denuded areas were radiated, and animals were randomized. The first group received PBEPC (n=5), the second group received BMC (n=4), and the third group received heparinized (20 IU) saline (Control; n=3). PBEPC were characterized by flow cytometry. Cells (5x10(6)) or saline was administered twice through the ear vein: the first time at 1 h after radiation and the second time at 2 weeks after radiation. Four weeks after radiation, the animals were sacrificed, and arterial segments were processed for morphometry.

RESULTS

Administration of BMC or PBEPC from inbred siblings had no adverse effect. Lumen area (0.93+/-0.53 mm(2)), neointimal area (0.65+/-0.29 mm(2)), percent stenosis (44+/-21), and macrophage score (0.6+/-0.3) in controls were similar to those in cell-treated groups.

CONCLUSION

This study demonstrates that, in the current animal model, either PBEPC or BMC failed to affect neointimal formation or inflammation.

Optical coherence tomography and intravascular ultrasound imaging of bioabsorbable magnesium stent degradation in porcine coronary arteries

BACKGROUND

Absorbable metallic stents (AMS) composed of magnesium alloy were designed to complete degradation within 90-120 days. Among the potential advantages of these stents, when compared to conventional stents, are the elimination of late stent thrombosis, chronic inflammation, and artifacts during noninvasive imaging.

METHODS

Magnesium-based AMS were deployed in juvenile domestic pig coronary arteries. Angiography, optical coherence tomography (OCT), and intravascular ultrasound (IVUS) were performed before and after implant and then at 28 days and 3 months following stenting. The animals were sacrificed at 28 days or 3 months following stent implantation. Stented vessels were harvested and analyzed by histomorphometry.

RESULTS

Over time, OCT, IVUS, and histologic images revealed a progressive degradation of the stents. Mean stent strut width in the OCT images after implantation was 0.24+/-0.032 mm, then decreased to 0.12+/-0.007 mm (P<.0001) at 28 days and to 0.151+/-0.032 mm at 3 months (P<.0001 vs. implant, P=.078 vs. 28 days).

CONCLUSION

Magnesium-based AMS degrade over a 3-month time period in a porcine model. Its structure is not apparent by angiography but is well-visualized by OCT and IVUS. OCT allowed quantitative assessment of stent degradation.

Short-term effects of biocorrodible iron stents in porcine coronary arteries

BACKGROUND

Biocorrodible iron stents carry the potential to overcome limitations, such as chronic inflammation and premature recoil, posed by biodegradable polymer and magnesium alloy stents. This study aimed to test the safety and efficacy of biocorrodible iron stents in porcine coronary arteries.

METHODS

Iron stents and cobalt chromium stents were randomly deployed in the coronary arteries of juvenile domestic pigs. Animals were sacrificed at 28 days, and the vessels were fixed and processed for histochemistry.

RESULTS

At 28 days, iron stents started to show signs of degradation without evidence of stent particle embolization or thrombosis without traces of excess inflammation, or fibrin deposition. At 28 days, the surface of the iron stent struts was black to brown and the vascular wall adjacent to the iron stent had a brownish tinge. There were no statistically significant differences in any of the measured parameters between segments implanted with iron and cobalt chromium stents. There were also no adverse effects in the persistent areas.

CONCLUSION

The current study demonstrates that stents made of biocorrodible iron are safe. In some of the measured parameters, such as intimal thickness, intimal area, and percentage occlusion, there was a trend in favor of the iron stents.

Efficacy and safety of absorbable metallic stents with adjunct intracoronary beta radiation in porcine coronary arteries

BACKGROUND

Absorbable metallic stents (AMS) utilizing Mg alloy carry advantages over permanent metallic stents because of their potential to eliminate stent thrombosis, chronic inflammation, or artifacts with noninvasive imaging. These stents, however, are associated with a modest degree of late recoil and intimal hyperplasia. The aim of the study was to test whether adjunct vascular brachytherapy (VBT) compared to AMS alone can overcome these limitations.

METHODS

Juvenile domestic pig coronary arteries underwent implantation of either AMS (n = 11) with prior adjunct VBT utilizing Sr/Y-90 beta source seeds, with a dose of 24 Gy at 2 mm from the source, or AMS alone (n = 11). At 28 days following intravascular ultrasound, vessels were harvested and analyzed by histomorphometry.

RESULTS

Intravascular ultrasound analysis indicated that at follow-up, though statistically not significant, lumen and stent areas in the segments deployed with AMS following radiation were larger than those deployed with AMS alone (3.94 +/- 1.38 and 3.53 +/- 1.75 vs. 2.99 +/- 1.05 and 3.58 +/- 1.48). Extrastent plaque and intrastent plaque areas in the same segments were smaller (2.76 +/- 0.82 and 0.24 +/- 0.47 vs. 3.25 +/- 1.94 and 0.58 +/- 0.81). Morphometric data indicate that vessels in the VBT + AMS group showed characteristics of delayed healing and re-endothelialization. Neointimal area was significantly lower in the VBT + AMS group (0.49 +/- 0.34) compared to AMS (1.3 +/- 0.62, P = 0.001). Lumen area of the VBT + AMS was larger when compared with AMS alone (2.49 +/- 0.82 vs. 1.75 +/- 0.51, P = 0.02).

CONCLUSION

VBT as an adjunct to AMS further reduces the intimal hyperplasia and improves the lumen area when compared to AMS alone but does not have any impact on late recoil.

Bone marrow-derived stem cell interactions with adult cardiomyocytes and skeletal myoblasts in vitro

BACKGROUND AND OBJECTIVES

Secreted growth factors and cell-to-cell contact are both required to elicit cellular functions. We tested the hypothesis that bone-marrow-derived growth factors, together with cell-to-cell contact between bone-marrow-derived stem cells and cardiomyocytes or myoblasts, promote the proliferation of cardiomyocytes and myoblasts.

METHODS

Human cardiomyocytes or skeletal myoblasts were cultured for 4 days in the presence of low and high concentrations of bone-marrow-derived mononuclear cell conditioned medium (MNC-CM) or marrow stromal cell conditioned medium (MSC-CM). The concentrations of vascular endothelial growth factor (VEGF), monocyte chemoattractant protein-1 (MCP-1), hepatocyte growth factor (HGF), and insulin-like growth factor-1 in their respective conditioned media were assayed by enzyme-linked immunosorbent assay. Stem cells were mixed with cardiomyocytes or skeletal myoblasts at a 1:1 ratio and cultured for 7 days to assess the proliferation of these cells. In parallel experiments, equal numbers of various cell types were cultured alone.

RESULTS

The concentrations of VEGF, MCP-1, and HGF increased in MNC-CM and MSC-CM. MNC-CM showed no effect on cardiomyocyte proliferation. A low concentration of MSC-CM increased cardiomyocyte proliferation by 60% (P<.05). Low concentrations of MNC-CM or MSC-CM showed a trend toward an increased proliferation of myoblasts. A high concentration of either conditioned medium showed a toxic effect. In contact coculture, the proliferation of cardiomyocytes and MNC showed no synergistic effect; instead, there was some evidence of inhibition. The proliferation of cardiomyocytes and stromal cells showed an additive effect. Myoblasts in contact coculture with MNC or MSC showed no synergistic effect.

CONCLUSION

These in vitro results suggest that paracrine effects may be the mechanism by which stromal cells become beneficial in cardiac therapy. MNC do not induce the proliferation of cardiomyocytes. Stem-cell-secreted growth factors induce the proliferation of myoblasts, which is not influenced by cell-to-cell contact.

Peroxisome Proliferator-Activated Receptor γ Ligand Pioglitazone Alters Neointimal Composition in a Balloon-Denuded and Radiated Hypercholesterolemic Rabbit

Peroxisome proliferator-activated receptor (PPAR)-gamma activation suppresses inflammatory response, monocyte recruitment, and vascular cell proliferation. Because inflammation, deregulated growth, and migration of monocytes and vascular smooth muscle cells (VSMC) play important roles in the development of neointima, we tested the effect of pioglitazone, a high-affinity ligand, for PPAR-gamma on neointima formation in the iliac arteries of a balloon-denuded and radiated hypercholesterolemic rabbit. Rabbits were fed a 1.0% cholesterol diet for 7 days followed by denudation of endothelial layer and continued on a 0.15% cholesterol diet. On day 32, animals were divided into 2 groups. One group received a 0.15% cholesterol diet (n = 7) and the other group received a 0.15% cholesterol diet supplemented with 400 mg of pioglitazone per kilogram. On day 35, the balloon-denuded area was radiated. Four weeks after radiation, animals were sacrificed and arterial segments were processed for morphometry and immunohistochemistry. Data analysis showed that the pioglitazone group had smaller neointima (0.85 +/- 0.36 vs. 1.41 +/- 0.56, P < 0.05), with more cells positive for VSMC (23.07 +/- 6.16 vs. 18.33 +/- 5.19, P = 0.04), less for monocytes (16.01 +/- 5.33 vs. 21.29 +/- 4.33, P < 0.05), and fewer cells expressing metalloproteinase (MMP)-1 and MMP-9 (3.69 +/- 0.47 vs. 4.82 +/- 0.93, P < 0.05 and 3.24 +/- 0.71 vs. 4.29 +/- 0.74, P < 0.05, respectively). Pioglitazone reduced neointimal area and modified its composition in a balloon-denuded and radiated hypercholesterolemic rabbit model.

Optimal dosing and duration of oral everolimus to inhibit in-stent neointimal growth in rabbit iliac arteries

BACKGROUND

Everolimus is an orally active derivative of sirolimus. Oral administration of rapamycin is efficacious in the reduction of neointima formation and clinical restenosis; however, its optimal dose and duration have not been determined.

METHODS

New Zealand White rabbits were divided into three groups. The first (low-dose) group received 1.5 mg/kg everolimus 1 day before stenting, followed by 0.75 mg/kg/day everolimus for 28 days. The second (high-dose) group received 6 mg/kg everolimus 1 day before, on the day of, and on the day after stenting, followed by 2 mg/kg/day for 4 days. The third (placebo) group received a matching volume of vehicle similar to that of Group 2. Twenty-eight days after stenting, animals were euthanized and morphometry was performed.

RESULTS

In the high-dose group, circulating everolimus levels corresponded with administrated dose levels; by Day 12, no circulating everolimus could be detected. In the low-dose everolimus group, levels remained constant up to 28 days. When compared with placebo, low-dose everolimus was associated with a significant reduction in medial thickness (32%), neointimal area (60%), and percent stent stenosis (33%); however, high-dose everolimus had no significant effect.

CONCLUSIONS

In conclusion, oral everolimus suppresses in-stent neointimal growth in rabbit iliac arteries. Four weeks of low-dose everolimus is more effective than 7 days of high-dose everolimus.

Safety and efficacy of bioabsorbable magnesium alloy stents in porcine coronary arteries

OBJECTIVE

We aimed to determine the safety and efficacy of biobasorbable magnesium alloy stents in porcine coronary arteries. Bioabsorbable magnesium stents carry the potential to overcome the limitations posed by permanent metallic stents such as chronic inflammation, late stent thrombosis, prolonged antiplatelet therapy, and artifacts when imaged by multislice-computed tomography or magnetic resonance imaging.

METHODS

Magnesium alloy stents or stainless steel stents were randomly deployed in coronary arteries of domestic or minipigs. Domestic pigs were sacrificed at 3 days (n = 2) or 28 days, and minipigs at 3 months.

RESULTS

At 3 days, magnesium alloy stents were intact, but started to show signs of degradation by 28 days. There was no evidence of stent particle embolization, thrombosis, excess inflammation, or fibrin deposition. At 28 days and 3 months, neointimal area was significantly less in magnesium alloy stent segments (2.44 +/- 0.88 mm(2) and 1.16 +/- 0.19 mm(2)) as compared with the stainless steel stent segments (5.03 +/- 1.5 mm(2) and 1.72 +/- 0.68 mm(2), P < 0.001 and 0.02). Quantitative coronary analysis indicates that percentage area stenosis and percentage diameter stenosis in magnesium alloy stent segments improved significantly at 3 months as compared to 28 days. Despite decreased neointimal hyperplasia, lumen area of the magnesium alloy stented vessels did not improve significantly.

CONCLUSION

Magnesium alloy stents are safe and are associated with less neointima formation; however, reduced neointima did not result in larger lumen.

Effect of Antioxidants on Atherosclerotic Plaque Formation in Balloon-Denuded and Irradiated Hypercholesterolemic Rabbits

The oxidative modification of low-density lipoprotein (LDL) hypothesis implies that antioxidants should be effective in suppressing atherosclerosis. This study is designed to test the potential of antioxidants to inhibit atherosclerotic plaque progression in balloon-denuded and irradiated hypercholesterolemic rabbits. Rabbits were fed with a 1% cholesterol diet supplemented with or without a mixture of antioxidants (vitamin E, vitamin C, selenium, zinc, copper, manganese, N-acetylcysteine, glutamine). At 7 days both iliac arteries were balloon denuded, and 4 weeks later, 1 iliac artery underwent endovascular irradiation (n=12), while the contralateral was sham treated (n=12). Four weeks after irradiation, animals were euthanized, and arteries were fixed and processed for histo- or immunohistochemistry for determining the plaque area, macrophage count, and oxidized LDL-positive areas. Plasma antioxidant levels were significantly higher in the animals fed with antioxidant diet. Plasma (thiobarbituric acid-reactive substances) and arterial tissue oxidized LDL (immunoreactive to specific oxidized LDL antibody) levels were significantly higher in the irradiated as compared with nonirradiated animals (0.69+/-0.09 and 31.05+/-4.21 versus 0.24+/-0.04 and 18.42+/-4.62, P<0.001 and 0.05), and antioxidants partially lowered the oxidized LDL levels (0.35+/-0.14 and 25.41+/-4.82, P<0.001 and 0.01). Plaque area in the irradiated animals was 175% greater than in nonirradiated animals (P<0.05). Antioxidant supplementation resulted in a 50% decrease in plaque area of both control and irradiated animals. Antioxidants reduced both the cholesterol-induced and radiation-enhanced circulating and tissue oxidized LDL levels, resulting in reduced plaque.

Novel site-specific systemic delivery of Rapamycin with perfluorobutane gas microbubble carrier reduced neointimal formation in a porcine coronary restenosis model

Earlier studies demonstrated that perfluorobutane gas microbubble carrier (PGMC) adheres to injured arteries and enhances the drug uptake specifically into the cells of the denuded vessel segment. The purpose of this study was to investigate the effect of PGMC-based systemic delivery of Rapamycin on expression of p27 in vascular tissue and restenosis in porcine coronary arteries after stent implantation. Eight pigs underwent coronary stent implantation (three stents per animal). Five pigs were treated with i.v. injection of PGMC with 2 mg of Rapamycin and three animals served as control. Four hours postprocedure, three pigs were sacrificed and stented segments were analyzed by high-performance liquid chromatography (HPLC) and Western blot. In chronic experiments, five pigs (15 stent sites) were sacrificed at 28 days following intervention and vessels were perfusion-fixed. HPLC of the treated arteries demonstrated high drug concentration in the vessel tissue, and Western blot analysis showed elevated expression of p27 at 4 hr postprocedure. Histomorphometry revealed significantly reduced (by 40%) neointimal formation in the PGMC/Rapamycin group compared with controls (1.84 +/- 0.84 vs. 4.77 +/- 1.71 mm2, respectively; P < 0.001). In the porcine coronary model, site-specific systemic delivery of Rapamycin utilizing PGMC resulted in overexpression of p27 and a significant reduction of neointimal formation within the stented segments.

Systemic targeted delivery of antisense with perflourobutane gas microbubble carrier reduced neointimal formation in the porcine coronary restenosis model

HYPOTHESIS

The antisense phosphorodiamidate morpholino oligomer (PMO), AVI-4126, has been effective in reducing neointimal formation in animal models following delivery by pluronic gels, local delivery catheters and coated stents. Greater flexibility of repeated-dosage regimens and reduced procedure complexity may be provided by systemic injection of AVI-4126 bound to perfluorobutane gas microbubble carriers. The purpose of this study was to investigate the effects of perfluorocarbon gas microbubble carrier (PGMC)-based systemic delivery of AVI-4126 on expression of the c-myc in vascular tissue and restenosis after stent implantation.

METHODS

Seven pigs underwent stent implantation (3 stents/animal). Five pigs received IV injection of PGMC and 2 mg of AVI-4126 (AVI BioPharma). Two served as control. Four hours postprocedure, 3 pigs were sacrificed and stented segments analyzed by high-performance liquid chromatography (HPLC) and Western blot. In chronic experiments, 4 pigs (12 stent sites) were sacrificed at 28 days.

RESULTS

HPLC analysis of plasma samples of treated animals showed minimal presence of AVI-4126. HPLC of the treated arteries demonstrated easily detected concentrations of AVI-4126. Western blot analysis of the stented vessels demonstrated modest inhibition of c-myc. Morphometry showed that the neointimal area was significantly reduced in the AVI-4126/PGMC group compared with control (2.63+/-1.99 vs. 4.77+/-.1.71 mm2, respectively, P<.05).

CONCLUSION

In the porcine coronary stent model, systemic targeted delivery of AVI-4126 using PGMC carrier significantly inhibited neointimal formation.

Effects of contrast media on porcine bone marrow-derived mononuclear cells and calf myoblast viability and secretion of VEGF and MCP-1

We investigated the effect of contrast media on bone marrow-derived cell viability, growth factor secretion, and myoblast viability. Bone marrow was exposed to contrast media, mononuclear cells were isolated, viability was assessed by Trypan blue exclusion or cultured for 4 weeks, and conditioned medium was assayed for vascular endothelial growth factor (VEGF) and monocyte chemoattractant protein-1 (MCP-1). Skeletal myoblasts viability was assessed after exposing them to contrast media. In separate experiments, bone marrow or bone marrow-derived mononuclear cells were exposed to contrast media, cultured for 40 hr, then assessed for viability. None of the contrast media tested had any effect on bone marrow-derived cell viability. Hypaque or Hexabrix increased myoblasts viability by 8-10%. VEGF and MCP-1 concentrations in the conditioned medium increased in a time-related manner. These findings support the concept that for cell therapy, bone marrow cells or myoblasts may be mixed with contrast media and injected into ischemic myocardium without compromise in viability or function.

Transepicardial autologous bone marrow-derived mononuclear cell therapy in a porcine model of chronically infarcted myocardium

OBJECTIVE

Cell therapy is becoming a viable strategy to improve revascularization and myocardial function after myocardial injury. We evaluated the effect of bone marrow-derived mononuclear cell (BMMNC) transplantation on collateral vessel development and myocardial function in a porcine model of chronically infarcted heart.

METHODS

Myocardial infarction was produced in 13 domestic swine. At 4 weeks, animals were randomized to receive transepicardial injections of autologous BMMNCs (approximately 24x10(6) cells, n=8) or phosphate buffered saline (PBS; control, n=5) into infarcted and border regions. Collateral growth, angiogenesis, and infarct size were assessed by angiography, immunohistochemistry, and histomorphometry.

RESULTS

Regional contractility was assessed by transepicardial echocardiography at baseline and 4 weeks following treatment. Angiography revealed a trend toward increased collateral growth in the BMMNC group. Wall motion score index (myocardial function) was similar in both groups at baseline (1.63+/-0.16 vs. 1.25+/-0.25, P=.21) and at 4 weeks (1.83+/-0.22 vs. 1.63+/-0.38, P=.62). alpha-Actin-positive smooth muscle cells (SMCs) and Factor VIII positive endothelial cells were significantly greater in the BMMNC-injected animals (314.8+/-37.4/0.1 vs. 167.1+/-11.9/0.1 mm(2) in controls, P=.02, and 363.3+/-28.2 cells/0.1 mm(2) vs. 254.4+/-28.1 cells/0.1 mm(2) in controls, P=.03, respectively). The number of blood vessels >50 mum in diameter was significantly increased in the BMMNC group (317.9+/-54.9 vs. 149.1+/-6.1, P<.05). The size of the infarct area was smaller in the BMMNC-transplanted group than in the controls (P=.015).

CONCLUSION

BMMNC transplantation appears to improve angiogenesis and reduce infarct size yet results in no improvement in left ventricular function in a chronically infarcted heart.

Effect of ionizing radiation on the stability and performance of the TAXUS Express2 paclitaxel-eluting stent

BACKGROUND

The advent of drug-eluting stents has provided the interventional cardiologist an effective new tool in treating coronary restenosis. There remains, however, a small group of patients that still require intervention following drug-eluting stent therapy. Currently, intravascular brachytherapy (IVBT) is approved for use in the treatment of in-stent restenosis (ISR). This study investigated the effect of gamma and beta radiation doses typically used in IVBT on the performance of the TAXUS Express(2) paclitaxel-eluting stent.

METHODS AND RESULTS

It was determined that there were no statistically significant changes to in vitro paclitaxel release from stent exposed to radiation compared to controls subjected to the same conditions except for the radiation exposure. The molecular weight of the Translute polymer carrier matrix and the level of paclitaxel degradants were not changed following exposure to radiation doses up to twice what is typically used in IVBT. Beta and gamma radiation doses typically used in IVBT had no significant effect on the Translute polymer carrier, paclitaxel degradation, or paclitaxel release in this in vitro model.

CONCLUSION

The data are encouraging and support further evaluation of the use of IVBT in the treatment of ISR in the presence of drug-eluting stents.

Comparison of effectiveness and safety of three different antithrombotic regimens (bivalirudin, eptifibatide, and heparin) in preventing myocardial ischemia during percutaneous coronary intervention

The aim of this retrospective, observational analysis was to compare the efficacy and safety of 3 antithrombotic regimens: bivalirudin, eptifibatide plus heparin, and heparin alone, with emphasis on preventing interventional procedural creatinine kinase-MB fraction (CK-MB) release, and consequently, myocardial necrosis.

Radiation-Induced Atherosclerotic Plaque Progression in a Hypercholesterolemic Rabbit

PURPOSE

Human observations provide rich soil for making hypotheses, but good animal models are essential for understanding the disease and to test treatment modalities. Currently, there is no standard animal model of vulnerable plaque; therefore, the purpose of this study is to develop a pathophysiologically relevant vulnerable plaque model.

METHODS

New Zealand White rabbits were fed with 1% hypercholesterolemic (HC) diet for 7 days, followed by balloon denudation of both the iliac arteries, and continued on 1% HC diet. Four weeks later, in 12 rabbits one of the iliac arteries was radiated (192-Ir, 15 Gy), and in five rabbits both the iliac arteries were sham treated. Following that, rabbits were fed with 0.15% HC diet. Four weeks later, arteries were processed for histomorphometry or immunohistochemistry.

RESULTS

Serum cholesterol levels were similar in all the groups. In radiated arteries, plaque area was significantly larger (32% larger then in sham). Macrophage-positive area in radiated arteries was 2.4 times greater than the macrophage-positive area in the nonradiated arteries. The area positive for macrophages is also positive for metalloproteinases (MMP)-1. The extent of alpha-actin positive area was significantly less (2.3-fold) in radiated arteries.

CONCLUSION

The atherosclerotic plaque developed in the current model is predominantly composed of macrophages expressing metalloproteinases with few smooth muscle cells (SMC)--a characteristic of vulnerable plaque. The animal model presented in this study can elucidate at least part of the mechanism of plaque vulnerability and could be used to test treatment modalities to test plaque stability.

Oral rapamycin inhibits growth of atherosclerotic plaque in apoE knock-out mice

INTRODUCTION

Inflammatory and immunological responses of vascular cells are known to play significant roles in atherosclerotic plaque development. Rapamycin with antiinflammatory, immunosuppressive and antiproliferative properties has been shown to reduce neointima formation when coated on stents. This study is designed to test the potential of oral rapamycin to inhibit atherosclerotic plaque development.

METHODS

Eight-week-old apoE knock-out mice were fed with 0.25% cholesterol supplemented diet (control diet), control diet containing 50 microg/kg rapamycin (low-dose rapamycin) or 100 microg/kg rapamycin (high-dose rapamycin) for 4 or 8 weeks. Subsets of mice from each group (n=10) were weighed and euthanized. Whole blood rapamycin levels were determined using HPLC-MS/MS, and histological analyses of atherosclerotic lesions in the aortic root were performed.

RESULTS

Mice fed with high-dose rapamycin did not gain weight (18.5+/-1.5 vs. 20.6+/-0.9 g, P=.01). Blood levels of rapamycin 117+/-7 pg/ml were detected in the blood of mice fed with high-dose rapamycin for 8 weeks. The plaque area in mice fed with high dose oral rapamycin is significantly less as compared to control (0.168+/-0.008 vs. 0.326+/-0.013 mm2, P=.001 at 4 weeks; 0.234+/-0.013 vs. 0.447+/-0.011 mm2, P=.001 at 8 weeks). Lumen area was inversely proportional to the plaque area.

CONCLUSIONS

The results indicate that oral rapamycin is effective in attenuating the progression of atherosclerotic plaque in the mice.

Antioxidants attenuate atherosclerotic plaque development in a balloon-denuded and -radiated hypercholesterolemic rabbit

BACKGROUND

Oxidation of lipoproteins is considered to be a key contributor to atherogenesis. Antioxidants are potential antiatherogenic agents because they can inhibit lipoprotein oxidation. Radiation has been shown to increase oxidative stress leading to increased atherogenesis. This study is designed to test the potential of antioxidants to inhibit atherosclerotic plaque progression in balloon-denuded and -radiated rabbits.

METHODS AND RESULTS

Two groups of New Zealand white rabbits (n=36) were fed with 1% cholesterol diet (control diet) or with 1% cholesterol diet containing a mixture of various antioxidants for 1 week. Iliac arteries in all the animals were balloon denuded and continued to fed with 0.15% cholesterol diet or 0.15% cholesterol diet containing antioxidants (antioxidant diet). Four weeks after balloon denudation one iliac artery in 12 animals from each group was radiated and all the animals were continued to be fed with the same diet. Four weeks after radiation animals were sacrificed and morphometric analysis of iliac arteries (n=12) in nonradiated and radiated animals were performed. Plaque area (PA) in the rabbits that were fed with cholesterol diet is 0.2+/-0.12 mm2, and it is increased by 2.75-fold (P<.05) in the radiated arteries of animals fed with cholesterol diet. Plaque area in the animals fed with antioxidant diet is 50% less then the one in the animals fed with cholesterol diet. Similarly, plaque area in radiated arteries of the animals fed with antioxidant diet is 50% less then the animals fed with cholesterol diet.

CONCLUSION

Antioxidants significantly attenuate atherosclerotic plaque progression in balloon-injured and -radiated hypercholesterolemic rabbits.