Local delivery of NO-donor molsidomine post-PTA improves haemodynamics, wall mechanics and histomorphometry in atherosclerotic porcine SFA

OBJECTIVES

we investigated the therapeutic effect of angioplasty with local drug delivery (LDD) of the wall-accumulating NO-donor molsidomine (M) in the superficial femoral arteries (SFA) of atherosclerotic swine.

MATERIALS AND METHODS

atherosclerotic Pietrin swines (n=14) underwent PTA-LDD-M (4 mg/2 ml) vs contralateral PTA-LDD-Placebo in the SFA using a channelled balloon angioplasty catheter. Invasive and colour Doppler energy (CDE) assessments of haemodynamics and wall mechanics were performed at 24 h (n=4) and 5 months (n=10). Immuno-histolabelling of cell proliferation and histomorphometry were serially performed in perfusion fixed SFA samples.

RESULTS

at 24 h, PCNA-positive nuclei revealed 33+/-14 and 12+/-3 proliferating cells/mm2 at placebo and molsidomine PTA-LDD sites, respectively (p<0.001). At 5 months, PTA-LDD-M vessels, compared with PTA-LDD-P, had increased compliance (66+/-9 vs 11+/-4 ml/mmHg) and lowered impedance (0.11+/-0.05 vs 0.45+/-0.14 mmHg/ml x min(-1)) (p<0.05). CDE revealed low, middle and high velocity peaks at 7.5, 20 and 35, and 8, 15 and 22 cm x s(-1) in systolic and diastolic flows, respectively; and PTA-LDD-M prevented emergence of restenosis-associated increases in low blood velocities (p<0.01). PTA-LDD-M inhibited restenotic intimal thickening and medial thinning which decreased mean lumenal diameter in placebo-treated (2.6+/-0.3) as compared to molsidomine-treated (3.4+/-0.3 mm) vessels (p<0.05).

CONCLUSIONS

in the atherosclerotic porcine SFA model, PTA-LDD with molsidomine consistently improved haemodynamic wall mechanics, lowered cell proliferation and prevented late lumen loss observed with PTA-LDD with placebo.

Neointimal thickening after stent delivery of paclitaxel: change in composition and arrest of growth over six months

OBJECTIVES

The purpose of this study was to determine long-term effects of stent-based paclitaxel delivery on amount, rate and composition of neointimal thickening after stent implantation.

BACKGROUND

Paclitaxel prevents vascular smooth muscle cell proliferation and migration in vitro and in vivo. These actions, coupled with low solubility, make it a viable candidate for modulating vascular responses to injury and prolonged effects after local delivery. We asked whether local delivery of paclitaxel for a period of weeks from a stent coated with a bioerodible polymer could produce a sustained reduction in neointimal hyperplasia for up to six months after stenting.

METHODS

Stainless steel stents were implanted in the iliac arteries of rabbits after endothelial denudation. Stents were uncoated or coated with a thin layer of poly(lactide-co-sigma-caprolactone) copolymer alone or containing paclitaxel, 200 microg.

RESULTS

Paclitaxel release in vitro followed first-order kinetics for two months. Tissue responses were examined 7, 28, 56 or 180 days after implantation. Paclitaxel reduced intimal and medial cell proliferation three-fold seven days after stenting and virtually eliminated later intimal thickening. Six months after stenting, long after drug release and polymer degradation were likely complete, neointimal area was two-fold lower in paclitaxel-releasing stents. Tissue responses in paclitaxel-treated vessels included incomplete healing, few smooth muscle cells, late persistence of macrophages and dense fibrin with little collagen.

CONCLUSIONS

Poly(lactide-co-sigma-caprolactone) copolymer-coated stents permit sustained paclitaxel delivery in a manner that virtually abolishes neointimal hyperplasia for months after stent implantation, long after likely completion of drug delivery and polymer degradation.

Inhibition of neointimal proliferation with low-dose irradiation from a beta-particle-emitting stent

BACKGROUND

Restenosis after successful percutaneous transluminal coronary angioplasty is the major factor limiting the long-term effectiveness of this procedure. Neointimal proliferation in response to arterial injury is an important contributor to restenosis. The use of radiation for the treatment of malignant and benign proliferative conditions has been well established. External beam irradiation and endovascular irradiation by use of an after-loading technique have been shown to inhibit neointimal proliferation in experimental models of restenosis. The objective of this study was to investigate whether low-dose irradiation from a beta-particle-emitting stent would inhibit neointimal proliferation after placement in porcine iliac arteries.

METHODS AND RESULTS

Fourteen titanium-mesh stents were implanted in the iliac arteries of nine NIH miniature swine. There were seven beta-particle-emitting radioisotope stents (32P, activity level 0.14 microCi) and seven control stents (31P, nonradioactive). Treatment effect was assessed by angiography and histomorphological examination of the stented iliac segments 28 days after implantation. There was a significant reduction in neointimal area (1.76 +/- 0.37 mm2 versus 2.81 +/- 1.22 mm2, P = .05) and percent area stenosis (24.6 +/- 2.9% versus 36.0 +/- 10.7%, P = .02) within the beta-particle-emitting stents compared with the control stents. Neointimal thickness, which was assessed at each wire site, was also significantly less within the treatment stents (0.26 +/- 0.04 mm versus 0.38 +/- 0.10 mm, P = .012). Scanning electron microscopy was performed on sections from four stents. This demonstrated endothelialization of both the treatment and control stents. There was no excess inflammatory reaction or fibrosis in the media, adventitia, or perivascular space of vessels treated with the beta-particle-emitting stent compared with control vessels. At 28 days, there was no difference in smooth muscle cell proliferation as measured by the proliferating cell nuclear antigen index.

CONCLUSIONS

A local, continuous source of low-dose endovascular irradiation via a beta-particle-emitting stent inhibits neointimal formation in porcine arteries. This low dose of local irradiation did not prevent endothelialization of the stents. This novel technique offers promise for the prevention of restenosis and warrants further investigation.