Intramural methotrexate therapy for the prevention of neointimal thickening after balloon angioplasty

Prospects for site-specific delivery of pharmacologic and molecular therapies

The local delivery of therapeutic agents to the arterial wall represents a new strategy for the treatment of vascular diseases, including restenosis. Approaches for local, intravascular, site-specific delivery include 1) direct deposition of therapeutic agents into the vessel wall through an intravascular delivery system; 2) systemic administration of inactive agents followed by local activation; and 3) systemic administration of fusion toxins that have a specific affinity to proliferating smooth muscle cells at the angioplasty site. In addition to conventional drugs, new therapeutic agents based on molecular mechanisms, including recombinant genes and antisense oligonucleotides, are now under investigation. Although development of intravascular drug delivery devices, including those tailored to accommodate novel therapeutic agents, offers new treatment options for restenosis and other vascular diseases, certain issues that currently limit the safety and efficacy of these approaches remain to be addressed.

Local delivery of dexamethasone for prevention of neointimal proliferation in a rat model of balloon angioplasty

A periadventitial polymer system is an alternative local drug delivery technique to obtain and maintain high tissue levels of the drug at the site of vascular injury. To determine if local periadventitial delivery of dexamethasone decreases neointimal proliferation after balloon vascular injury, in three groups of Sprague-Dawley rats, 5% dexamethasone, 0.5% dexamethasone, and placebo silicone polymers were implanted around the left common carotid artery after balloon injury. In a fourth group, placebo polymers were implanted without balloon injury. Dexamethasone serum and tissue levels after polymer implantation were significantly higher in the 5% dexamethasone group compared with the 0.5% dexamethasone group. There was no neointima formation in any of the arterial segments covered with placebo polymers for 3 wk, but without balloon injury. In the arterial segments covered by the 5 and 0.5% dexamethasone polymers, there was a 76 and 75% reduction in intima/media ratios, respectively, compared with the placebo group (5% dexamethasone, 0.26 +/- 0.04; 0.5% dexamethasone, 0.27 +/- 0.03; placebo, 1.09 +/- 0.16, respectively; P < 0.0001). These results suggest that: (a) silicone polymers wrapped around the common carotid arteries for 3 wk did not, without balloon injury, stimulate neointimal proliferation in the rat model; (b) the activity of the drug-eluting polymer for suppressing intimal proliferation was chiefly, but not exclusively, site specific; and (c) transadventitial local delivery of dexamethasone at two different doses markedly inhibits neointimal proliferation after balloon vascular injury.

Local intramural drug delivery using an infusion balloon following angioplasty in normal and atherosclerotic vessels

Local intramural delivery of various pharmacologic agents following angioplasty has been proposed as a means of reducing restenosis. This study tested whether local intramural delivery of aqueous solutions using an infusion balloon could be accomplished safely in normal vessels and whether such infusion was safe following standard angioplasty in diseased vessels. Infusion of aqueous agents into normal canine arteries had no adverse effect. Infusion of several aqueous agents (< or = 4 cc at 4 atm) into diseased swine iliac arteries following balloon angioplasty did not worsen existing or create new dissections. Histologically, infusion treated vessels did not differ in either model from vessels treated with angioplasty alone. We conclude that local intramural drug infusion does not create new, or worsen existing, dissections produced during standard balloon angioplasty in diseased vessels.

Use of the porous balloon in porcine coronary arteries: rationale for low pressure and volume delivery

Using agents administered systemically, attempts to control the restenotic myoproliferative response associated with angioplasty have been unsuccessful. The porous balloon has the advantage of achieving high local concentrations by directly infusing agents into the arterial wall. The purpose of this study is to identify any acute and chronic morphological changes in swine coronary arteries infused with normal saline through the porous balloon at different driving pressures. In order to establish the safety of local arterial wall infusion through the porous balloon, swine underwent porous balloon infusion of 3, 6, or 10 ml of saline at 5 atmospheres, or infusion of 3 ml of normal saline delivered at either 2, 5, or 10 atmospheres of pressure into the normal left anterior descending and left circumflex arteries. To assess the histopathologic alterations induced by the porous balloon, sized 1.1 to 1 with respect to the artery, animals were sacrificed either immediately after porous balloon infusion or 14 ays later. Acute vessels were evaluated for the presence of medial injury, disruption and/or dissection, whereas chronic vessels underwent morphometric analysis measuring the residual luminal area (Lumen area/Intimal area+Lumen area) and the maximal intimal thickness. Adequate adventitial penetration was confirmed by infusing as little as 2-3 ml of methylene blue at 2 atmospheres of pressure. Infusion of 3 ml of normal saline at 2 atmospheres resulted in minor focal medial edema and disorganization, detected both acutely and 14 days after porous balloon infusion. At delivery pressures of 5 or 10 atmospheres, proportionally more acute injury was noted and measurable neointimal lesions were observed 2 weeks after infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of porous infusion balloon-delivered angiopeptin on myointimal hyperplasia after balloon injury in the rabbit

BACKGROUND

Angiopeptin, a synthetic somatostatin analogue, reduces myointimal hyperplasia after experimental balloon angioplasty when given subcutaneously. The feasibility and efficacy of a single dose of angiopeptin delivered locally via the Wolinsky porous balloon on myointimal hyperplasia were studied.

METHODS AND RESULTS

Three rabbits received 125I-angiopeptin in the mid abdominal aorta via the Wolinsky balloon at 5 atm for 1 minute after balloon injury. Thirty minutes later, autoradiography demonstrated radioactivity in the media and the adventitia. Forty rabbits were divided equally into one control group receiving saline and three angiopeptin groups receiving 1, 10, or 100 micrograms/mL of angiopeptin delivered locally at 5 atm for 1 minute via the Wolinsky balloon into the mid abdominal aorta after balloon injury of the entire abdominal aorta. On day 21, the abdominal aortas were fixed in situ and harvested. There was no statistical difference in the amount of myointimal hyperplasia in the locally treated aorta in the angiopeptin groups compared with the control group. However, in the lower abdominal aorta, where balloon injury without local delivery was performed, there was a significant reduction of myointimal hyperplasia in the highest-concentration angiopeptin group (P < .001 versus the control group). Electron microscopy showed that the control animals had a pseudointima of smooth muscle cells throughout the aorta, whereas in all the angiopeptin-treated animals, endothelial cells were present at both locations.

CONCLUSIONS

Angiopeptin can be delivered intramurally via the Wolinsky porous balloon and reduces myointimal hyperplasia only in the area distal to the local drug delivery site (downstream effect), possibly by healing the injured endothelium, by transport via the vasa vasora, and/or by systemic effect.