Korean Circ J.  2008 Feb;38(2):80-86. 10.4070/kcj.2008.38.2.80.

Perivascular Delivery of Rapamycin in Pluronic Gel Inhibits Neointimal Hyperplasia in a Rat Carotid Artery Injury Model, and the Complementary Role of Carotid Arteriography

• Jung MJ
• Kwon JS
• Park NK
• Kim YK
• Shim TJ
• Jeong IH
• Bae JW
• Hwang KK
• Kim DW
• Cho MC

• KMID: 2225840
• DOI: http://doi.org/10.4070/kcj.2008.38.2.80

Abstract

BACKGROUND AND OBJECTIVES
Rapamycin has been shown to inhibit the vascular smooth muscle cell migration and proliferation that contributes to neointimal formation. We investigated whether the perivascular delivery of rapamycin in Pluronic gel could inhibit neointimal hyperplasia in a rat carotid artery model, and we tested the usefulness of carotid arteriography.
MATERIALS AND METHODS
To assess the kinetics of rapamycin's release from Pluronic gel, a [3H] thymidine incorporation assay was performed with using the media exposed to rapamycin in Pluronic gel for 10, 20, 60 and 120 min. We applied 100 microgram of rapamycin in Pluronic gel to the perivascular space of the carotid artery after the balloon injury (n=9), whereas only gel was applied in a control group (n=9). We performed the carotid arteriography and the morphometric analysis 14 days after injury.
RESULTS
The [3H] thymidine incorporation assay showed a reduction of uptake in a time-dependent manner (86%, 48%, 45% and 40% of the control, respectively, at 10, 20, 60 and 120 minutes). The inhibiting effect of rapamycin on neointimal hyperplasia was identified on the carotid arteriography (mean luminal diameter; 0.75+/-0.11 vs. 0.60+/-0.12 arbitrary units, respectively, p< 0.05) and on the morphometric analysis (neointima area: 0.09+/-0.03 vs. 0.17+/-0.06 mm(2), respectively, p< 0.05).
CONCLUSION
This study demonstrated that perivascular delivery of rapamycin in Pluronic gel inhibits neointimal hyperplasia in a rat carotid injury model. This animal model combined with arteriography can be used for developing new drugs to treat restenosis. In addition, this technique might be useful for vascular surgery such as coronary artery bypass grafting, arteriovenous fistula formation and peripheral vascular bypass graft insertion.

Keyword

Rapamycin; Drug delivery system; Angiography; Restenosis

MeSH Terms

Angiography
Animals
Arteriovenous Fistula
Carotid Arteries
Carotid Artery Injuries
Cell Movement
Coronary Artery Bypass
Drug Delivery Systems
Hyperplasia
Kinetics
Models, Animal
Muscle, Smooth, Vascular
Phenobarbital
Rats
Sirolimus
Thymidine
Transplants
Phenobarbital
Sirolimus
Thymidine

Figure

• 

  Fig. 1 Degraded gel containing rapamycin according to the incubation time. 500 µL of the Pluronic gel containing 500 µg of rapamycin in 5 mL of serum-free media were applied separately; each column was left in the water bath for 10, 30, 60 and 120 minutes, respectively. The Pluronic gel mass containing rapamycin was continually degraded in the water bath over time. A very small amount of gel was remained on the bottom of the column after 120 minutes of incubation.

• 

  Fig. 2 A representative carotid arteriographic finding at 14 days after injury. Diffuse and significant narrowing of the right carotid artery (double arrows) was observed in the control group (A). The rapamycin treated group (B) showed less narrowing of the lumen (double red arrows) compared to the untreated control group. A narrow injured segment (single yellow arrow) was seen beneath the clavicular line where the drug could not be applied.

• 

  Fig. 3 Representative cross sections (5 µm) of the rat carotid artery at 14 days after balloon injury were stained with hematoxylin-eosin. A: the control group showed a concentric pattern of diffuse neointimal formation. B: rapamycin inhibited the proliferation of vascular smooth muscle cells. Note the eccentric pattern of inhibition resulting from perivascular application of rapamycin in the Pluronic gel at the anterior part of the vessel wall across the posterior neck muscle, over roughly one third of the circumference (upper panels ×100, lower panels ×400).

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