Intramural delivery of agent via a novel drug-delivery sleeve. Histological and functional evaluation

Rho-kinase inhibitor suppressed restenosis in porcine coronary balloon angioplasty

BACKGROUND

Constrictive remodeling is thought to be more important than neointimal formation in coronary restenosis after balloon angioplasty. The inhibition of Rho-kinase prevents neointimal proliferation, but now this inhibition that affects constrictive remodeling remains unknown. To explore this issue further, we investigated whether a specific Rho-kinase inhibitor, Y-27632, could suppress restenosis after coronary balloon angioplasty in a porcine model.

METHODS

Balloon angioplasty with local administration of Y-27632 (Y group) or vehicle (C group) was performed at 2 and 3 weeks after overstretch injury in a porcine coronary artery. Quantitative coronary angiography (QCA) and quantitative coronary ultrasound (QCU) were performed to assess the coronary lesion segment. A morphometrical analysis was performed in a histological study. Proliferative cells and p27(Kip1)-positive cells were evaluated in the arterial wall using immunohistochemistry.

RESULTS

QCA and QCU demonstrated that the minimal lumen diameter and minimal lumen area were greater, and % stenosis was less in the Y group than in the C group. The QCU analysis also revealed a significant inhibition in the increase of the intimal area and a prevention of constrictive remodeling by Y-27632. In the histological study, the intimal, adventitial and collagen areas were significantly smaller in the Y group than in the C group. The Y group also exhibited significantly less proliferative activity and a significantly higher percentage of cells expressing p27(Kip1) in the arterial wall.

CONCLUSION

Local delivery of Y-27632 suppressed constrictive remodeling as well as neointimal formation after coronary balloon angioplasty in pigs.

Effects of altering infusion parameters on intimal hyperplasia following local catheter-based delivery into the rabbit iliac artery

BACKGROUND

Efficient local gene or drug therapy requires optimized application modalities to avoid vessel damage, which might lead to increased neointimal hyperplasia. Aim of the study was to evaluate different application parameters for local delivery using the channeled balloon catheter in order to minimize vessel trauma induced by local application.

METHODS AND RESULTS

Sixty cholesterol fed rabbits were randomly enrolled into twelve groups of different local application parameters: group I, application pressure 2atm/application volume 1ml physiologic saline; group II, 2atm/2ml; group III, 2atm/5ml; group IV, 4atm/1ml; group V, 4atm/2ml; group VI, 4atm/5ml. The other six groups received Ringer's solution instead of saline. Administration of the solution was randomly performed in one iliac artery using the channeled balloon catheter with simultaneous balloon angioplasty (8atm). The contralateral iliac artery served as a control and was treated with balloon angioplasty only. Four weeks after local therapy, calibrated angiography was performed; the animals were sacrificed, vessel segments were excised and quantitative morphometric measurements were obtained. In none of the animals acute complications, e.g. dissection, thrombosis or perforation of the vessel, was noted. Up to an application pressure of 4atm and an application volume of 5ml, no significant neointima formation was seen compared to arteries which underwent angioplasty only. Additionally, no significant differences between saline and Ringer's solution were detected. In a multivariate analysis, neither application pressure nor volume were found to have a statistically significant influence on the amount of neointimal hyperplasia.

CONCLUSIONS

Local application of "drugs" using the channeled balloon catheter is safe and feasible without significant induction of neointimal hyperplasia compared to angioplasty, if an application volume of 5ml and a pressure of 4atm is not exceeded.

Imaging of vascular gene therapy

Gene therapy is an exciting frontier in medicine today. Many genes have been shown to be useful for treatment of various vascular diseases, including chronic cardiac and limb ischemia syndromes, vasculoproliferative disorder, hypercholesterolemia, atherosclerosis, thrombosis, and hypertension. Precise delivery of genes into target vessels, efficient transfer of genes into vascular cells of the target, and prompt assessment of gene expression over time are three challenging tasks for successful vascular gene therapy. Thus, in vivo imaging methods that can be used to monitor gene delivery and localize gene expression are needed. Modern imaging techniques provide an opportunity to monitor and direct vascular gene therapy. Radiologists play a key role not only in developing and mastering endovascular genetic interventions but also in assessing the success of vascular gene therapy and directing further refinement of vascular gene therapy technology. This article provides an overview of the current status of imaging of vascular gene therapy.

Local gene delivery to the vessel wall

This review will provide an overview of delivery strategies that are being evaluated for vascular gene therapy. We will limit our discussion to those studies that have been demonstrated, utilizing in vivo model systems, to limit post-interventional restenosis. We also discuss the efficacy of the vectors and methods currently being used to transfer genetic material to the vessel wall. The efficiency of these techniques is a critical issue for the successful application of gene therapy.

Local delivery of 17-beta-estradiol decreases neointimal hyperplasia after coronary angioplasty in a porcine model

BACKGROUND

Neointimal hyperplasia is an important mechanism of restenosis after percutaneous transluminal coronary angioplasty (PTCA). Systemically administered estrogen is known to inhibit neointimal formation after arterial injury.

OBJECTIVES

We sought to assess the efficacy of locally delivered 17-beta-estradiol (BE) in inhibiting neointimal hyperplasia after PTCA.

METHODS

Eighteen juvenile farm pigs were studied. Coronary angioplasty was performed in all three coronary arteries of each animal. After PTCA, each coronary artery in each pig was randomized to receive either local delivery of 600 microg BE, vehicle alone or PTCA only. Twelve animals were euthanized at 28 days for morphometric analysis, and four animals were euthanized at seven days for immunohistochemical analysis of vascular smooth muscle cell (SMC) proliferative activity. Two animals died a few days after PTCA and were excluded.

RESULTS

On morphometric study, the arterial segments treated with BE demonstrated significantly less neointimal proliferation. Arteries treated with BE had reductions in several indexes of restenosis compared with arteries treated with vehicle alone or PTCA only: neointimal area (0.4+/-0.09 mm2 for BE vs. 1.14+/-0.33 mm2 for vehicle alone vs. 0.88+/-0.2 mm2 for PTCA only, p<0.05), percent neointima (12.16+/-2.57% vs. 25.46+/-4.73% vs. 23.02+/-3.97%, p<0.025), neointima/media area (0.59+/-0.14 vs. 1.75+/-0.41 vs. 1.67+/-0.43, p<0.01) and restenotic index (1.3+/-0.14 vs. 2.42+/-0.22 vs. 2.4+/-0.23, p<0.005). Immunohistochemistry showed decreased SMC proliferative activity in BE-treated arteries compared with the other two treatment groups (p<0.05).

CONCLUSIONS

Local delivery of BE significantly decreases neointimal hyperplasia after PTCA in pigs, probably by the inhibition of SMC proliferation.

Heparin infusion prior to stenting (HIPS) trial: final results of a prospective, randomized, controlled trial evaluating the effects of local vascular delivery on intimal hyperplasia

BACKGROUND

Local delivery of pharmacologic agents or genes at the site of angioplasty is a promising approach to reduce restenosis. However, there are unresolved questions concerning the safety and feasibility of local vascular delivery in clinical practice as well as the efficacy of delivered drug. To this end, the safety, feasibility, and efficacy of local delivery of heparin were evaluated in the Heparin Infusion Prior to Stenting (HIPS) trial.

METHODS AND RESULTS

A total of 179 patients were enrolled in this multicenter, randomized, prospective, core laboratory-evaluated trial. Patients were randomly assigned to 5000 U heparin either administered to the coronary artery lumen or infused into the arterial wall immediately after angioplasty and before stent placement. End points included procedural events and clinical, angiographic, and intravascular ultrasound events at 6 months. Patient groups were evenly matched. There was no difference in the incidence of arterial injury, defined as an increase in arterial dissection, acute closure, or decrease in Thrombolysis In Myocardial Infarction grade blood flow in the group receiving local delivery. At follow-up there was no difference in the major adverse event rate between intraluminal (22.7%) and local groups (24.7%). There was no difference between intraluminal and local therapy in the angiographic in-stent restenosis rate (12.5%, 12.7%) or the in-stent volumetric analysis by intravascular ultrasound (IVUS) (37.19 +/- 20. 86 mm(3) vs 43.79 +/- 25.52 mm(3)).

CONCLUSIONS

Local delivery of 5000 U heparin into the arterial wall before stent implantation is safe and feasible. There was not a favorable effect of locally delivered heparin on clinical, angiographic, or IVUS end points of restenosis. The use of IVUS to measure volume of intimal hyperplasia in a multicenter, core laboratory-controlled trial is feasible.

Local delivery of heparin post-PTCA: a multicenter randomized pilot study

Bailout stenting for major dissection and threatened closure has high rates of ischemic complications. We performed a randomized trial of local heparin delivery using the infusion sleeve before bailout stenting for suboptimal angioplasty results. In phase I, 20 patients were randomized to local delivery with either 40- or 100-psi infusion pressure. In phase II, 37 patients were randomized to local delivery at 100 psi or standard therapy. Local delivery succeeded in all but one patient; overall there was no significant worsening of intimal dissection. One patient treated with 100-psi drug infusion suffered a perforation after stent placement. There were no significant differences in the composite endpoint of death, MI, CABG, urgent repeat angioplasty, and stent thrombosis at 30 days (21% vs. 0%; P = 0.18). At 6 months, the rates of myocardial infarction in phase II were 27% with local delivery vs. 10% with standard treatment (P = 0.4). Local heparin delivery in dissected vessels may be associated with increased complications and should be approached with caution.

Intraarterial protein delivery via intimally-adherent bilayer hydrogels

Arterial structure plays an important role in drug delivery from intraarterial depots. The internal elastic lamina forms a major diffusive resistance to the transport of macromolecular drugs from intimally-adherent hydrogel depots to the arterial media. The objectives of this study were to develop an approach by which to form a bilayer hydrogel depot with a higher permeability intimally-adherent layer, containing the drug, and a lower permeability luminal layer, and to evaluate ex vivo whether this luminal layer could enhance the delivery of a protein to the arterial media. Sequential interfacial photopolymerization of polyethyleneglycol diacrylate precursors (molecular weight 4000 for the luminal layer, 10,000 for the intimal layer) with eosin Y and triethanolamine as an initiation system was employed to form these bilayer hydrogels. Horseradish peroxidase was used as a model protein, and delivery to the arterial media was measured in rat carotid arteries ex vivo. The lower permeability luminal layer served to enhance delivery of the model protein into the arterial media for delivery periods at least up to 72 h. Thus, it was possible to compensate for the diffusional resistance of the internal elastic lamina on the one side of the hydrogel depot with a second diffusional resistance on the other side of the hydrogel.

Analysis of adenoviral transport mechanisms in the vessel wall and optimization of gene transfer using local delivery catheters

Local delivery devices have been used for adenovirus-mediated gene transfer to the arterial wall for the potential treatment of vascular proliferative diseases. However, low levels of adenoviral gene expression in vascular smooth muscle cells may pose a serious limitation to the success of these procedures in the clinic. In this study, we examined the mechanisms controlling adenoviral transport to the vessel wall, using both hydrogel-coated and infusion-based local delivery catheters, with the goal of enhancing in vivo gene transfer under clinically relevant delivery conditions. The following delivery parameters were tested in vivo: applied transmural pressure, viral solution volume and concentration, and delivery time. We found that viral particles are transported into the vessel wall in a manner consistent with diffusion rather than pressure-driven convection. Consistent with diffusion, viral concentration was shown to be the key variable for viral transport in the vessel wall and thus gene expression in vascular smooth muscle cells. A transduction level of 17.8+/-3.2% was achieved by delivering a low volume of concentrated adenoviral beta-galactosidase solution through an infusion balloon catheter at low pressure without an adverse effect on medial cellularity. Under these conditions, effective gene transfer was accomplished within a clinically relevant time frame of 2 min, indicating that longer delivery times may not be necessary to achieve efficient gene transfer.

Effects of local heparin administration on coronary thrombin activity during percutaneous transluminal coronary angioplasty

Simultaneously obtained blood samples from the coronary sinus and systemic arterial circulation were analyzed for antithrombin III (ATIII) activity and fibrinopeptide A (FpA) concentration in nine patients undergoing elective PTCA in order to determine the effects of locally delivered heparin. Samples were obtained at the following designated times: prior to the administration of systemic heparin (period I); 5 min following a loading dose of systemic heparin (period II); 5 min following the final balloon inflation but prior to local delivery (period III); and 5 min following the administration of 4,000 units of unfractionated heparin using a local delivery catheter system (period IV). We found consistent increases in both systemic arterial (P = 0.006) and coronary sinus (P = 0.0002) ATIII activity with systemic heparinization designed to prolong the activated clotting time to 300 sec. However, local delivery of heparin further increased coronary sinus ATIII activity (P = 0.003, period III vs. period IV). FpA concentration decreased in both systemic arterial (P < 0.0001) and coronary sinus (P < 0. 0001) samples following systemic heparinization. Moreover, local delivery of heparin further decreased coronary sinus FpA concentration (P = 0.04). Thus, on a background of intense anticoagulation during PTCA, the local delivery of 4,000 units of unfractionated heparin confers incremental antithrombotic activity. Cathet. Cardiovasc. Intervent. 48:84-88, 1999.

Local intramural heparin delivery during primary angioplasty for acute myocardial infarction: results of the Local PAMI Pilot Study

The feasibility and safety of local heparin delivery during acute infarct angioplasty was evaluated in a prospective, multicenter, 120-patient series. Angioplasty was performed using standard techniques, after which heparin (4,000 U) was delivered locally; 25% of patients received stents. Procedural success was reported in 98% of patients; 6.7% of patients suffered death, reinfarction, recurrent ischemia, or stroke during the index hospitalization. The 6-month target vessel revascularization rate was 12.5%. Local heparin therapy with provisional stenting in acute myocardial infarction patients is safe, feasible, associated with a low rate of infarct artery revascularization at 6 months, and may potentially eliminate the need for systemic heparin following the procedure.

Local gene delivery within the media of rabbit iliac arteries by using the infiltrator intramural delivery device

Percutaneous transluminal angioplasty continues to be limited by restenosis. Prevention of restenosis is now focusing on local delivery of therapeutic agents, such as proliferation-inhibiting genes, directly to the site of arterial injury. We evaluated use of the Infiltrator catheter (IVT, San Diego, CA. U.S.A.) for gene delivery within the arterial media. The goals of our study were to evaluate the histologic effects of the injection and the suitability of the Infiltrator catheter for local delivery of viral therapy. We injected the femoral arteries of 21 New Zealand White rabbits. Six animals were used for an evaluation of the intramural distribution of dextran/rhodamine injected via the Infiltrator catheter. In seven animals, injection site histology and in vitro vasoreactivity were studied after an injection of saline. In the remaining eight animals, a replication-deficient adenovirus encoding for the firefly luciferase gene (Ad RSVLuc) was injected, and luciferase activity was quantified 3 and 8 days later. After injection via the Infiltrator catheter, the fluorescent tracer was distributed throughout the entire circumference and width of the arteries. Histologic examination showed minimal damage with partial endothelial abrasion and disruption of the internal elastic lamina confined to the penetration sites. In vitro endothelium-dependent vasodilation was present at a reduced level after injection via the Infiltrator (maximal endothelium-dependent acetylcholine-induced relaxation, 51.5 +/- 7.4% vs. 23.8 +/- 14.6%; p < 0.05). Significant luciferase expression was found in all the arteries, with a significant increase from day 3 to day 8 (5,392.5 +/- 2,300 vs. 2,012 +/- 471 cpm/mg; p < 0.05). These data obtained in a rabbit iliac artery model show that the Infiltrator catheter is an efficient and safe local intramural delivery device that provides significant transgene expression in the arterial wall without causing significant structural damage.

Local drug delivery: impact of pressure, substance characteristics, and stenting on drug transfer into the arterial wall

Injection parameters for local drug delivery are frequently determined by studies with marker substances. However, the pharmacologic properties of the actual drug may influence delivery efficiency and lead to different results. Aim of this study was to assess the delivery capacities of two device-drug combinations in order to verify this approach for further in vivo studies. Tritiated (3H) preparations (5 ml) of the hydrophylic low-molecular-weight heparin reviparin and the lipophilic taxane paclitaxel were injected into the left anterior descending artery of freshly explanted porcine hearts with the Infusasleeve II catheter system. A balloon support pressure of 6 atm and infusion pressures of 40, 60, 80, or 100 psi were used. In three additional groups, reviparin was injected following stent implantation and paclitaxel was injected prior to or following stent implantation. Arteries along with surrounding myocardium were harvested. The artery was carefully dissected, and artery and myocardium were separately homogenized, and activity was measured. Of the totally delivered activity, 0.09%+/-0.03% (40 psi) to 0.17%+/-0.13% (100 psi) of reviparin and 2.03%+/-0.67% (60 psi) to 2.68%+/-1.57% (100 psi) of paclitaxel were found in the vessel wall. The results for different injection pressures were not significantly different for either drug. The percentage activity delivered to the vessel wall was substantially larger in the paclitaxel group as compared to reviparin delivery (P < 0.01 at 60, 80, and 100 psi). The mean concentration of reviparin in the artery was 20 to 33 times higher than in the myocardium. For paclitaxel the factors were 110 to 243. Stent implantation prior to or following local delivery did not result in a different delivery efficiency. The results demonstrate that the characteristics of the delivered drug contribute largely to the delivery efficiency. Using identical injection parameters, drug concentrations in the arterial wall were significantly higher for the lipophilic paclitaxel as compared to the hydrophilic reviparin. Stenting of the artery did not influence delivery efficiency.

Mural delivery of iloprost with use of hydrogel-coated balloon catheters suppresses local platelet aggregation

PURPOSE

To develop reproducible and quantifiable methods for mural delivery of iloprost, a potent agent against platelet aggregation, with use of hydrogel-coated angioplasty balloons, and to determine the in vivo effect of direct iloprost delivery on platelet aggregation at the angioplasty site.

MATERIALS AND METHODS

Drug loading of tritiated iloprost from an immersion solution onto hydrogel-coated balloons was evaluated as a function of balloon size (3 mm x 2 cm, 6 mm x 2 cm, 8 mm x 3 cm; n = 4 each), drug concentration (0.0715 mg/mL, 0.1072 mg/mL, 0.1430 mg/mL; n = 3 each), and duration of immersion (40 seconds, 60 seconds, 120 seconds; n = 3 each). In another set of experiments, optimal drying methods were tested to minimize drug loss within a protective delivery sheath (n = 3 each). Ex vivo angioplasty was performed on excised swine arteries to estimate how much of the drug present on the balloon could be delivered to the wall (n = 3 iliac segments). Finally, in vivo angioplasty was performed in three Yorkshire pigs (n = 6 iloprost-treated and 6 control arteries) and indium-111-labeled platelet aggregation was measured at these sites, which were harvested 1 hour after the procedure.

RESULTS

In the initial set of experiments, the authors found that the volume of drug loaded is determined by the wet-volume of the hydrogel coating, that the majority of volume loading occurs within the first 2 minutes, and that the volume uptake is independent of the drug concentration. The optimal drying method resulting in the least loss of iloprost within the sheath (only 4%) was prolonged drying (5 hours) under ambient conditions. Ex vivo angioplasty experiments showed that approximately 33% of the drug present on the balloon can be delivered to the wall. Finally, in vivo experiments showed that platelet aggregation is significantly suppressed at treated sites (by approximately 33% compared to control sites; P = .03) by minuscule mural doses of iloprost (roughly estimated at under 1 microg).

CONCLUSION

Quantifiable and reproducible methods for loading iloprost onto hydrogel-coated angioplasty balloons were developed. The best of these methods was able to deliver enough iloprost into the wall to significantly reduce local platelet aggregation.

Local heparin delivery prior to coronary stent implantation: acute and six-month clinical and angiographic results

Stents increase smooth muscle cell proliferation, which may also lead to in-stent restenosis. A local delivery strategy provides higher drug concentration at the angioplasty site and may limit the proliferative response following stenting. Local heparin delivery was attempted in 35 patients following balloon angioplasty using an "over-the-balloon" style catheter (infusion sleeve). The infusion sleeve was successfully tracked and heparin was delivered in 33 (94%) patients. Heparin (1,000 IU/ml) was delivered under low (45 psi, 2 ml, n = 4), intermediate (75 psi, 4 ml, n = 11), and high (100 psi, 4 ml, n = 18) proximal infusion pressures. Stent placement was successful in all cases. Acute and in-hospital complications were a severe arterial spasm after heparin delivery, a non Q-wave myocardial infarction, and two vascular complications. Ten dissections were observed after PTCA and prior to heparin delivery. Of these dissections, 7 remained unchanged, 2 worsened, and 1 improved with local delivery. When heparin was delivered in the absence of dissection, no new dissections were observed. Of the 33 patients who received heparin, 30 (91%) had no symptoms and a negative exercise test at clinical follow-up. QCA analysis of 6-month follow-up angiograms, performed in 32 of 33 (97%) patients, demonstrated an acute gain of 1.98 +/- 0.67 mm, a late loss of 0.94 +/- 0.78 mm, a net gain of 1.04 +/- 0.78 mm, and a loss index of 0.48 +/- 0.32. Restenosis (> or = 50% stenosis) was observed in 4 of 32 (12%) patients. Local delivery of heparin via the infusion sleeve following PTCA and prior to stent deployment is feasible with an acceptable safety profile and a low clinical and angiographic restenosis rate at 6 months.

Quantitative evaluation of local drug delivery using the InfusaSleeve catheter

BACKGROUND

Restenosis is the most common long-term complication after angioplasty. Local delivery of pharmacologic agents at the site of angioplasty holds promise as a means of achieving higher concentrations of drug in the arterial wall than can be obtained by systemic infusion. In this study, a novel local drug delivery catheter system, the InfusaSleeve catheter, was evaluated in a porcine coronary balloon injury model. The purpose of the study was to evaluate the efficacy of solute transfer to the arterial wall and the influence of varying supporting angioplasty balloon pressure.

METHODS AND RESULTS

Ten pigs (total of 22 arterial segments) underwent overstretch balloon injury (artery/balloon ratio 1:1.29) with a standard angioplasty balloon. In 7 animals (16 arterial segments) horseradish peroxidase (HRP; 10 mg/ml) was administered locally after injury, by tracking the local infusion catheter as a sheath over the angioplasty balloon to the intended site of arterial drug delivery. Supporting angioplasty balloons were inflated to one of the three different pressures. In 3 pigs HRP (10 mg/ml) was administered intravenously. No significant arterial injury caused by the local delivery device was evident on histological examination (disruption of the internal lamina elastica, arterial media, or thrombosis). Radial concentrations of the HRP reaction product in the first 150 microns of the arterial wall were quantified against known standards by measurement of light transmission through tissue sections. Mean HRP concentrations were not significantly different from those obtained by intravenous infusion using a supporting pressure of 1 atm or a supporting pressure of 3 atm of the underlying angioplasty balloon. However, a supporting pressure of 6 atm resulted in a 6-fold greater mean HRP concentration in the arterial wall than that which could be achieved by systemic administration of an equal volume of tracer (P < 0.001).

CONCLUSION

Thus solute can be delivered throughout the coronary media by the InfusaSleeve, with the magnitude of wall uptake related to support pressure. Local delivery at 6 atm support pressure produced substantially greater uptake than did systemic delivery.

Inhibitory effects of bromocriptine on vascular smooth muscle cell proliferation

Bromocriptine (BC), an ergot alkaloid with wide therapeutic use in humans, has been shown to inhibit proliferation of several abnormally hyperproliferative cells in vivo and in vitro. In the present study, direct effects of BC on mitogen-stimulated proliferation of rat vascular smooth muscle cells (VSMC) (A7r5 cells) and human aortic smooth muscle cells (HAOSMC) were examined in vitro. Twenty-four hour proliferative responses of quiescent A7r5 cells and HAOSMC to a variety of mitogens in the presence or absence of BC were determined by quantifying the incorporation of 3H-thymidine into DNA. BC at 1 microM inhibited the responses of A7r5 cells to various concentrations of fetal calf serum (FCS) by 50-70% without affecting the ED50 of FCS (2%). BC dose dependently inhibited the proliferation of A7r5 cells and HAOSMC stimulated by 2% FCS, with 52% inhibition at 1 and 0.1 microM, respectively. BC at 1 microM also completely inhibited the maximal mitogenic responses of A7r5 cells to prolactin, platelet-derived growth factor, insulin-like growth factor, and phorbol mysterate acetate (PMA), and BC at 1 microM completely inhibited the mitogenic response of HAOSMC to PMA. BC is a dopamine D2 agonist, a noradrenergic alpha 2 agonist, and an .alpha 1 antagonist, but the inhibitory effects of BC on A7r5 cell proliferation could not be mimicked by the specific D2 agonists, LY162502 and LY171555; the alpha 2 agonist, clonidine; or the alpha 1 antagonist, WB-4101. Neither dopamine nor the D2 agonist, LY162502, could inhibit HAOSMC proliferation induced by FCS. The PMA-induced stimulation of protein kinase C (PKC), a positive regulator of mitogenesis, could be completely blocked in A7r5 cells and HAOSMC by 1 and 0.1 microM BC, respectively. However, FPCS (2%)-induced activation of PKC in A7r5 cells and HAOSMC could only be blocked by 61 and 19% by BC (1 microM for A7r5 cells and 0.1 microM for HAOSMC), respectively. Given the existing evidence that BC reduces the severity of several other pathological conditions, such as insulin resistance, inflammation, and hyperlipidemia, which potentiate vascular disease, the current findings further suggest that BC use in the treatment of atherosclerosis and/or restenosis deserves further investigation.

Efficacy of low-molecular-weight heparin delivery with the Dispatch catheter following balloon angioplasty in the rabbit iliac artery

Local drug delivery can be achieved with active injection systems or passive contact of a compound with the arterial wall. The Dispatch catheter allows for passive diffusion of drugs from drug compartments while preserving blood flow through the central conduit. The aim of this study was to investigate whether a reduction in neointima formation can be achieved by local delivery of a limited amount of a highly concentrated solution of the low-molecular-weight heparin Reviparin. In 16 New Zealand white rabbits, successful balloon dilatation was performed in both iliac arteries, followed by local delivery of 4 ml Reviparin (1,000 IU/ml). The arteries were harvested at 7, 28, or 56 d following the procedure. The intimal cell layers increased substantially between 7 and 28 d following balloon dilatation with or without local drug delivery. The medial cell layers showed only a little increase. Proliferation of smooth muscle cells reached an early peak after 7 d, with a significantly higher proliferation index following local delivery. The maximum amount of macrophages in the intima and media was detected after 28 d. The lumen area decreased with time and was 0.6 +/- 0.7 mm2 in the local delivery group at 56 d compared with 0.5 +/- 0.5 mm2 in the control group. In conclusion, local delivery of Reviparin with the Dispatch catheter is safe and feasible. However, the infusion of highly concentrated low-molecular-weight heparin over a short period of time did not result in a reduction of neointima formation and restenosis following balloon dilatation in the rabbit iliac artery.

Site-specific intravascular administration of drugs: history of a method applicable in humans

Demonstration and quantification of site-specific intracoronary administration of pharmacological compounds has been limited thus far to animal experimental models. Recently, a method applicable in humans has been developed. The aim of this study is to give an overview on the available methods to visualize and quantify intravascularly administered "labeled" drugs in animals and to describe the historical development of a method now applied in the clinical arena. The potential of this approach is briefly summarized.

Depolymerized holothurian glycosaminoglycan (DHG) prevents neointimal formation in balloon-injured rat carotid artery

The in vivo activity of depolymerized holothurian glycosaminoglycan (DHG), a newly developed polysaccharide anticoagulant, on neointimal formation induced by a balloon catheter in the left common carotid artery of rats was investigated. In every Sprague-Dawley rat weighing approximately 400 g, a Forgaty 2Fr balloon catheter was inserted from the left femoral artery to the left common carotid artery, and was passed through three times in order to denude the endothelium of the artery. These rats were divided into four groups by the following treatment protocols; DHG was given to rats by daily subcutaneous injection into their abdomens at a dose of 3 mg/kg or 10 mg/kg (D3 or D10 group). For controls, 250 microl saline was injected daily (C group). Furthermore, 1 mg/kg of unfractionated heparin was also injected daily as a comparison to DHG (H group). Each treatment was performed in six rats, and the injections were continued for two weeks after the catheterization. The area ratio of thickened intima/media (I/M ratio) treated with DHG decreased in a dose-dependent manner compared to the control. In addition, the ratio in the D10 group was significantly lower than in the control (P < 0.01). However, the ratio in the H group did not decrease. By anti-a smooth muscle actin antibody staining the intimal thickening layers were seen to be completely occupied by proliferated smooth muscle cells, and their amount in these layers was attenuated by the DHG treatment. This indicated that DHG has an inhibitory effect on intimal thickening induced by balloon catheterization, and that this might be due to the inactivation of aberrant smooth muscle cells by this agent.