Therapy For Restenosis Research Articles

Nano- and Biotechnological Approaches in Current and Future Generation of Cardiovascular Stents

Drug eluting stents (DESs) have considerably reduced the occurrence of restenosis followed by balloon angioplasty. But the recent concerns of late stent thrombosis have rekindled an interest in developing an improved stent. A multidisciplinary approach of nanotechnology and biotechnology is the next frontier for this. This presents a comprehensive overview of the evolving nanobiotechnological approaches for biomedical implants and articulates the potential of these technologies to design the next generation stent. A diverse range of nano-delivery systems are being used to transport drugs, genes and oligonucleotides from the stent surface to remodel the damaged local vascular biology. In addition, the review encompasses the upcoming technologies which include modulation of the stent surface nano-topography by regulating the nanocoatings, use of nanotubes to increase the biocompatibility and promote endothelial cell proliferation, inhibit smooth muscle cell growth, and deliver drugs. Keywords: Restenosis, stent thrombosis, stent base therapy, nano-biotechnology, polymeric nanoparticles, nano-topography, nanotubes, nanocoatings, Drug eluting stents (DESs), balloon angioplasty, bare metal stent (BMS), acute ST-segment, myocardial infarction, computational fluid dynamics (CFD), Biofunctionalized Stents, Antibody Coating, Gene Delivery, Bioresorbable Polymeric Stents, Non-Viral Liposomal Particles, Polymeric Nanoscaffolds, Nano-Carriers, Antisense Restenosis Therapy, Regulate Surface Roughness

Valproic acid inhibits proliferation of human coronary vascular cells (SI/MPL-ratio: 0.5): a novel candidate for systemic and local therapy of postinterventional restenosis

The branched-chain fatty acid, valproic acid (VPA), is the most commonly used anti-epileptic drug for treating generalized epilepsy. Recently antiproliferative effects of VPA have been described in human cancer cells, and phase I trials for the treatment of solid tumors have been initiated. In cardiologic patients, increased cell proliferation and migration from the media into the subendothelial space are the key events causing restenosis after coronary angioplasty and stenting. This study investigates the effect of VPA on proliferation and migration in human coronary vascular cells. The theoretical clinical relevance of the data is estimated with a SI/MPL-ratio, which is defined as the relationship between a significant effect in vitro (SI) and the maximal plasma level in vivo (MPL). Dilution of VPA: Aqua dest, MPL in vivo: 100 microg/ml. Cell culture: HUVEC, human umbilical endothelial cells; HCAEC, human coronary artery endothelial cells; HCMSMC, human coronary media smooth muscle cells. Proliferation assay: HUVEC, HCAEC, and HCMSMC were seeded as described. At day 1, after seeding the cell number was calculated in a cell counter. VPA was added in six different concentrations ranging between 50 and 300 microg/ml. At day 3, the medium and agent were renewed, and after another 2 days, the cell number was calculated in relation with the cell number at day 1. Cell toxicity: Cytotoxic effects of VPA were studied in concentrations ranging from 50 to 300 microg/ml. Migration assay: migration of HCMSMC after incubation with VPA in concentrations ranging from 50 to 300 microg/ml was studied for a period of 24 h. Proliferation assay: strong dose-dependent antiproliferative effects were detected after 5 days of incubation with all the three tested cell types. In HUVEC, significant antiproliferative effects were found with VPA in concentrations of 100 microg/ml (P<0.05, SI/MPL-ratio: 1.0) and more. In HCAEC and HCMSMC, significant antiproliferative effects were detected after incubation with VPA in the concentrations of 50 microg/ml (HCAEC: P<0.01, SI/MPL ratio: 0.5; HCMSMC: P<0.001, SI/MPL-ratio: 0.5). Migration assay: no effect on cell migration was detected after incubation of HCMSMC for a period of 48 h with VPA in concentrations ranging from 50 to 300 microg/ml. Cell toxicity: in HUVEC, HCAEC, and HCMSMC significant toxic effects were detected in all the VPA concentrations studied. Significant dose-dependent antiproliferative effects of VPA with SI/MPL ratios of 0.5 identify the drug as a promising candidate for both systemic and local therapy of postinterventional restenosis. The partial cytotoxic effects, however, may restrict the use of VPA to local high-dose devices such as drug eluting stents.

Acute Renal Artery Stent Thrombosis With a Solitary Functioning Kidney

A 55-year-old woman with a history of hypertension, bilateral renal artery disease with a left renal artery stent, and a chronically occluded right renal bypass graft presented with anuria and acute renal failure. Diagnostic studies showed high-grade renal artery in-stent stenosis with thrombotic occlusion of the main left renal artery distal to the stent. Catheter-directed thrombolysis and stent-in-stent placement within the left renal artery were successful at restoration of renal artery perfusion and function. Acute renal artery thromboembolic events are rare but can be devastating when these occur bilaterally or within a solitary functioning kidney. Timely diagnosis and therapy can often restore renal function and prevent dialysis dependence. The evolution of therapy for acute renal thromboembolism is discussed in this study. Recurrent stenosis within a stented renal artery is not uncommon and can be dependent on certain risk factors. Routine surveillance duplex ultrasound after endovascular therapy is essential for prevention of restenosis or thrombotic stent occlusion. The optimal therapy for in-stent restenosis is not defined; however, restenosis rates are lower with repeat stent-in-stent procedures as opposed to balloon angioplasty alone.

Physicochemical parameters affecting liposomal bisphosphonates bioactivity for restenosis therapy: Internalization, cell inhibition, activation of cytokines and complement, and mechanism of cell death

Partial inactivation and transient depletion of monocytes/macrophages by liposomal bisphosphonates (LIP-BPs) is widely experimented in various inflammatory disorders including restenosis. Previous studies on activation of cytokines by LIP-BPs are limited to certain cell lines. Moreover, the correlation between in vitro and in vivo studies and complement (C) activation has not been reported. We report here a comprehensive study on the bioactivity of LIP-BPs on various cells' internalization and proliferation, mechanism of cell death, cytokines ( in vitro and in vivo) and C activation (in the rat, rabbit and pig). The role of the following parameters has been determined i) drug type (clodronate/alendronate); ii) vesicles size (60–800 nm); iii) charge (neutral/negative/ positive); and iv) cell culture type (various cell lines and primary cultures). It was found that monocyte/macrophage inhibition and cytokine activation depend on the cell type, with a limited correlation to the bioactivity obtained in the rat and rabbit models of restenosis. Negatively charged liposomes (85 ± 20 nm) effectively depleted rabbit's monocytes (67% depletion), with a minor activation of cytokines and no C activation. It is concluded that cell culture studies are insufficient for assessing cytokine activation, and that by controlling LIP-BP properties (size, charge and drug type) optimal bioactivity could be achieved.

Abstract 5815: Therapeutic Targeting of the Calmodulin-Cyclin E Interaction in Vascular Smooth Muscle Cells

Background: Cell cycle regulation in vascular smooth muscle cells (VSMC) is a putative target in proliferative vascular diseases. Having shown that increases in intracellular [Ca 2+ ] are tightly coordinated and critical for VSMC proliferation, we also discovered that binding of Ca 2+ /calmodulin (CaM) to cyclin E/cdk2 is necessary for Ca 2+ -sensitive G 1 -to-S phase progression in VSMC. To test the importance of this, we developed a synthetic C aM- b inding sequence (CBS) that blocked CaM-cyclin E interactions, prevented activation of cdk2, and abrogated Ca 2+ -sensitive G1-to-S transitions in VSMC. Of note, binding of CaM to another target protein, calcineurin, was not altered by CBS. Objective: To evaluate the physiological relevance of targeting CaM-cyclin E interactions in human VSMC in vitro and in a mouse model of neointima formation in vivo. Methods &amp; Results: Human aortic SMC (HA-SMC) were treated with the CBS peptide conjugated to the viral TAT transduction domain to increase bioavailability. Peptide delivery of TAT-CBS was confirmed by immunochemistry. TAT-CBS caused a dose-dependent anti-proliferative effect in HA-SMC, as well as in human aortic endothelial cells and mouse embryonic fibroblasts (MEF) as measured by 3 H-thymidine incorporation. Importantly, these effects were lost in MEF from cyclin E1/E2 double knockout mice, further supporting target specificity for CaM/cyclin E. Moreover, TAT-CBS treatment was not cytotoxic, as it did not increase either LDH or caspase-3 release compared to controls. In vivo application of TAT-CBS in pluronic gel to the outside of injured mouse carotid arteries significantly decreased neointima formation and medial thickening without affecting re-endothelialization as compared to animals treated with vehicle-only or negative-control peptide. Summary: Inhibition of CaM binding to cyclin E/cdk2 with the TAT-CBS peptide significantly decreases HA-SMC proliferation in a dose-dependent manner in vitro. Moreover, application of TAT-CBS-containing gel to injured carotid arteries inhibits VSMC proliferation without affecting re-endothelialization. These data support TAT-CBS as a novel therapy for restenosis, and the general approach of targeting Ca 2+ -sensitive cell cycle control in VSMC.

Outcomes of Endoluminal Re-intervention for Recurrent Disease after Percutaneous Iliac Angioplasty and Stenting

Endovascular therapy for symptomatic atherosclerotic iliac artery stenosis is common but is associated with a significant restenosis rate. This study evaluates the outcomes of percutaneous therapy for symptomatic restenosis (>50% on angiography) after iliac intervention at a national academic medical center.

Mesenchymal Stem Cells: A Good Candidate for Restenosis Therapy?

Restenosis is a pathophysiological phenomenon that can occur in patients submitted to revascularization procedures (bypass, endarterectomy, angioplasty), possibly resulting in new narrowing of injured vessels. Vascular restenosis remains a pressing clinical problem, despite the therapeutic strategies and devices developed so far. Stem cells hold a great potential for the regeneration of damaged tissues in cardiovascular diseases. Recent studies clearly indicated that different stem cell populations contribute to vascular remodeling after injury. Nevertheless, the exact role of vascular cell precursors in restenosis pathophysiology is not yet well defined, as heterogeneous and contrasting data are currently available. Mesenchymal stromal/stem cells (MSCs) are non-hematopoietic multi-potent stem-like cells able of differentiating into both mesenchymal and non-mesenchymal lineages. MSCs offer a series of advantages: a) they can be isolated from a small aspirate of bone marrow; b) extensively proliferate in vitro while preserving a normal karyotype and telomerase activity on several passages; c) express low immunogenicity and hence their use should not require a pharmacological immunosuppression. MSCs have an intrinsic ability to differentiate into functional cell types able to repair the diseased or injured tissue in which they are localised. For this reason, MSCs are currently under scrutiny for treatment of different cardiovascular diseases. Nevertheless, it has not yet been clearly determined whether MSCs can substantially contribute to a positive resolution of restenosis after vascular injury. This review will provide information about the mechanisms at the basis of vascular restenosis and the current knowledge of the role, positive or negative, played by MSCs in restenosis progression as highlighted by recent experimental protocols.

Single and Double Emulsion Manufacturing Techniques of an Amphiphilic Drug in PLGA Nanoparticles: Formulations of Mithramycin and Bioactivity

Formulation of hydrophilic compounds in nanoparticles is problematic due to their escape to the external aqueous phase. The certain amphiphilic nature of mithramycin, utilized clinically in cancer, makes its incorporation into nanoparticles an interesting challenge, elucidating the formulation factors of amphiphilics in nanoparticles. We hypothesized that mithramycin nanoparticles could provide more effective therapy of restenosis due to its antiproliferating and potential monocyte inhibition properties. The nanoprecipitation technique (designed for lipophilic compounds) was found preferable, with better encapsulation efficiency, than the emulsification solvent diffusion (ESD) technique (79.3 +/- 3.1% and 40.8 +/- 1.1%, respectively). The double emulsion solvent diffusion (DESD) method, designed for hydrophilic compounds, yielded similar encapsulation efficiency (80%). Nanoparticles size was, 110 +/- 36, 130 +/- 30, and 160 +/- 31 nm, ESD, nanoprecipitation, and DESD techniques, respectively. Mithramycin solution and in nanoparticles significantly inhibited RAW264 macrophages and smooth muscle cells in a dose-dependent relationship, and reduced the number of circulating monocytes in rabbits. However, no inhibition of restenosis was obtained in the rat carotid model following i.v. administration of mithramycin nanoparticles. It can be concluded that PLGA-based polymeric nanoparticles of mithramycin can be formulated by techniques suitable for lipophilic/hydrophilic compounds. The ineffectiveness in the rat restenosis model is probably due to the short depletion period of circulating monocytes and lack of arterial targeting.

Outcomes of endoluminal reintervention for restenosis after percutaneous renal angioplasty and stenting

Endovascular therapy for symptomatic atherosclerotic renal artery stenosis (ARAS) is common but is associated with a significant restenosis rate. This study evaluates the outcomes of percutaneous endoluminal therapy for symptomatic restenosis (>50% on angiography) after renal intervention. We performed a retrospective analysis of records from patients who underwent endovascular intervention for ARAS and were followed by duplex ultrasound scan between January 1990 and January 2008. Clinical benefit defined as freedom from recurrent hypertension or renal-related morbidity (increase in persistent creatinine >20% of baseline, progression to hemodialysis, death from renal-related causes), anatomic patency, restenosis, and patient survival were measured. A total of 447 patients underwent 619 renal artery interventions. A total of 80 vessels restenosed with an actuarial restenosis rate of 19% at 5 years. Of these restenoses, 65 (81%) were associated with recurrent symptoms (recurrent hypertension 84%, or continuing deterioration in renal function 16%). Fifty-five (85%) underwent repeat angioplasty and 10 underwent bypass surgery. The remainder was observed. The 55 percutaneous interventions were performed in 51 patients (61% female, average age 62 years, range, 51-85). A total of 73% had metabolic syndrome, 58% had hyperlipidemia, and 51% were considered diabetic; all of them had primary stenting during their first procedure. There was a 4% technical failure rate in both groups. In the restenosis group, the presence of stent was associated with a 9% technical failure rate, while in the absence of a stent the technical failure rate was only 3% (P < .05). At 5 years, outcomes were equivalent between the primary and recurrent groups for survival (76 +/- 2% vs 75 +/- 8%, primary vs recurrent), cumulative patency (82 +/- 3% vs 70 +/- 10%), freedom from restenosis (81 +/- 3% vs 81 +/- 9%), and retained clinical benefit (44 +/- 4% vs 46 +/- 10%). By Cox proportional hazards and multivariate analysis, administration of statins were associated with freedom from restenosis in the recurrent lesions. Statins, contralateral kidney size (>9 cm) and a >/=20% improvement in baseline creatinine with 3 months were associated with freedom from recurrent symptoms. Restenosis after therapy in recurrent lesions was significantly correlated with recurrent symptoms (Spearman r = 0.4614, P < .0004). Percutaneous reintervention for renal artery restenosis is safe and effective with equivalent outcomes to primary intervention. The patients are more likely to present with recurrent hypertension and be younger and of female gender than patients presenting for primary intervention. Functional outcomes after reintervention are equivalent to primary intervention.

Predicting In Vivo Efficacy of Potential Restenosis Therapies by Cell Culture Studies: Species-Dependent Susceptibility of Vascular Smooth Muscle Cells

Although drug-eluting stents (DES) are successfully utilized for restenosis therapy, the development of local and systemic therapeutic means including nanoparticles (NP) continues. Lack of correlation between in vitro and in vivo studies is one of the major drawbacks in developing new drug delivery systems. The present study was designed to examine the applicability of the arterial explant outgrowth model, and of smooth muscle cells (SMC) cultures for prescreening of possible drugs. Elucidation of different species sensitivity (rat, rabbit, porcine and human) to diverse drugs (tyrphostins, heparin and bisphsophonates) and a delivery system (nanoparticles) could provide a valuable screening tool for further in vivo studies. The anticipated sensitivity ranking from the explant outgrowth model and SMC mitotic rates (porcine>rat>>rabbit>human) do not correlate with the observed relative sensitivity of those animals to antiproliferative therapy in restenosis models (rat≥rabbit>porcine>human). Similarly, the inhibitory profile of the various antirestenotic drugs in SMC cultures (rabbit>porcine>rat>>human) do not correlate with animal studies, the rabbit- and porcine-derived SMC being highly sensitive. The validity of in vitro culture studies for the screening of controlled release delivery systems such as nanoparticles is limited. It is suggested that prescreening studies of possible drug candidates for restenosis therapy should include both SMC cell cultures of rat and human, appropriately designed with a suitable serum.

Contemporary Treatment of In-Stent Restenosis and the Incidence of Recurrent In-Stent Restenosis in the Era of Drug-Eluting Stents

Optimal treatment of in-stent restenosis (ISR) remains uncertain in the era of drug-eluting stents (DES). This study aims to determine contemporary treatment of ISR and to assess recurrent ISR rates in the era of DES. We examined 60 patients presenting for treatment of ISR (one lesion per patient) who were enrolled in the Melbourne Interventional Group Registry (4% of total population of 1423 patients) between April 2004 and January 2005. Twelve-month follow-up is complete for all patients. The majority of ISR treated occurred in bare metal stents [BMS (n=52, 87%)] and had a focal (<10 mm) pattern of ISR (53%). In-stent restenosis of DES occurred in eight (13%) patients. The majority of ISR were treated with additional stenting with a preference for DES over BMS in almost all cases. At 12 months, one patient died of non-cardiac cause and four patients (7%) presented with recurrent ISR. The incidence of recurrent ISR in DES was 5% (n=3). No late thrombosis was reported despite only 50% of patients having >or=12 months of clopidogrel therapy. Our study suggests drug-eluting stents are safe, effective and the preferred therapy for in-stent restenosis. The incidence of recurrent drug-eluting stent restenosis at 12 months is low.

Drug-eluting stents beat other therapies for in-stent restenosis

Drug-eluting stents beat other therapies for in-stent restenosis

Gene therapy and stem cell therapy for cardiovascular diseases today: a model for translational research

Clinical trials looking at ways to promote myocardial regeneration have reported that the administered therapies have either neutral effects or modest benefits of questionable impact. These somewhat disappointing results should emphasize the need for translational research, with bidirectional feedback between the basic research laboratory and the clinical arena. Such a translational pathway is illustrated by the quest to find an effective therapy for restenosis, which culminated in the development of sirolimus. At this point a move away from the bedside and a return to the bench seems necessary to better understand the mechanisms of action of progenitor cells and stimulating factors. Without such basic knowledge research might be prematurely discouraged and the opportunity to fully understand the true potential of cardiovascular regenerative therapy might be missed.

A meta-analysis of randomized controlled trials of intracoronary gamma- and beta-radiation therapy for in-stent restenosis

We assessed the effectiveness of intracoronary brachytherapy and compared treatment effects for the two radiation sources as well as the performance of the procedure in saphenous vein grafts (SVG) and native coronary arteries. Five randomized controlled trials comparing intracoronary brachytherapy with placebo involving a total of 1310 patients were reviewed for a meta-analysis. Risk differences (RD) for major adverse cardiac events (MACE), target vessel revascularization, target lesion revascularization, and angiographic binary restenosis at 6-12 months were computed, and a meta-regression analysis of MACE was performed. For MACE, the RD was 0.19 (95% confidence interval [CI], 0.09%-0.29%; P value, 0.00); there was significant between-study variance of 0.2395. In univariate meta-regression analyses, diabetes was a significant factor for the between-study variance (P value, 0.000). In multivariate meta-regression analyses adjusted for diabetes and lesion length, neither gamma-radiation source nor SVG was a significant factor for the between-study variance (P value, 0.675 and 0.433, respectively); the adjusted between-study variance was 0.000. Intra-coronary brachytherapy is effective compared with placebo at mid-term follow up. Neither procedure in SVG (gamma radiation) nor difference in radiation source (beta or gamma) in native coronary arteries was a significant factor in brachytherapy effectiveness compared to placebo.

Comparison With Conventional Therapies of Repeated Sirolimus-Eluting Stent Implantation for the Treatment of Drug-Eluting Coronary Stent Restenosis

This study compared the safety and efficacy of repeat percutaneous coronary intervention (PCI) using sirolimus-eluting stents (SESs) with conventional therapies for restenosis after drug-eluting stent placement. Fifty-five consecutive patients with 58 restenotic lesions (31 treated with SESs and 27 treated with paclitaxel-eluting stents) underwent PCI using SESs (33 lesions) or conventional therapies comprising cutting balloon angioplasty alone (11 lesions) or intracoronary brachytherapy (14 lesions). Baseline characteristics were similar for the 2 groups, except for greater edge involvement (75.8% vs 36.0%, p = 0.002) and less stent expansion (0.74 +/- 0.17 vs 0.95 +/- 0.21, p = 0.006) in the SES group than in the conventional group. The SES group achieved a greater postprocedural luminal gain than the conventional group (1.98 +/- 0.50 vs 1.22 +/- 0.48 mm, p <0.001). Follow-up angiography showed that late luminal loss (0.27 +/- 0.56 vs 0.76 +/- 0.84 mm, p = 0.021) and recurrent angiographic restenosis rate (3.6% vs 35.0%, p = 0.006) were lower in the SES group than in the conventional group. The repeated target lesion revascularization-free survival rates at 1 year were 96.7 +/- 3.2% for the SES group and 91.7 +/- 5.6% for the conventional group (p = 0.399). In conclusion, use of SESs was associated with a lower recurrent restenosis rate compared with conventional therapies.

Clinical outcome of patients undergoing low aggressive angioplasty combined with brachytherapy and short-term dual antiplatelet therapy for in-stent restenosis

The impact of vessel injury on the outcome of patients undergoing percutaneous coronary intervention combined with brachytherapy for in-stent restenosis is under investigation. We report our clinical experience adopting a low aggressive balloon angioplasty technique, to limit vessel trauma, associated with brachytherapy and short-term dual antiplatelet therapy. Forty-nine consecutive patients, undergoing percutaneous coronary intervention with brachytherapy for symptomatic in-stent restenosis, were prospectively observed for a median time of 21 + or - 8 months. Clinical follow-up included anginal status, death, myocardial infarction and repeat revascularization; only patients with evidence of ischaemia repeated coronary angiography. Low aggressive angioplasty consisted in the use of a conventional balloon with a balloon to artery ratio < or = 1, avoiding high inflation pressures and the use of other devices. Dual antiplatelet therapy was continued for 3-6 months. Early angiographic result was good and the need for additional stent implantation was low (3.9%). At follow-up, we did not observe death, acute myocardial infarction or stent thrombosis, but 10 patients repeated coronary angiography for recurrence of ischaemia: disease progression was present in two cases (4.1%). Restenosis emerged in the remaining eight patients (16.3%): two cases showed restenosis within the target lesion segment, one case within the injured segment, one case within the radiated segment, and four cases at the edges. The consequent new revascularization was surgical in three patients and percutaneous in seven patients. Our data suggest that low aggressive angioplasty followed by brachytherapy and short-term dual antiplatelet therapy for in-stent restenosis is related to a good outcome, with a low restenosis rate and without stent thrombosis.

Predictors of Recurrent In‐Stent Restenosis after Beta‐Radiation: An Analysis from the START 40/20 Trial

The purpose of this study was to identify potential predictors, including clinical, procedural, angiographic, and intravascular ultrasound (IVUS) parameters, for recurrent in-stent restenosis (ISR) following beta-radiation 90Strontium/Yttrium (90Sr/Y) in a large multicenter trial. Although adjunct brachytherapy reduces recurrent ISR after primary catheter-based intervention, recurrence of stenosis after brachytherapy still occurs. We analyzed 185 IVUS cohort patients in the STent And Restenosis Therapy (START) 40/20 trial where a 40-mm, 90Sr/Y, radioactive source train was exclusively used for treatment of ISR to be treatable with a 20-mm balloon. Thirty-nine patients underwent target lesion revascularization. Preliminary univariate analysis showed that age, smoking, balloon/artery ratio, geographic miss, minimum lumen diameter, and diameter stenosis at baseline were associated with target lesion revascularization, while none of IVUS variables were (minimum lumen area, minimum stent area, or residual plaque burden). The multivariate logistic regression analysis showed that younger age, lower balloon/artery ratio, and presence of geographic miss were independent predictors of target lesion revascularization. Even with adjunct beta-radiation therapy, initial mechanical optimization, such as appropriate balloon sizing and positioning, may be critical for the prevention of recurrent ISR.

Stent-Based Delivery of Antisense Oligodeoxynucleotides Targeted to the PDGF A-Chain Decreases In-Stent Restenosis of the Coronary Artery

Although the use of drug-eluting stents (DESs) has been shown to limit neointima hyperplasia, currently available DESs may adversely affect reendothelialization, possibly precipitating cardiac events. We evaluated the effect of an antisense oligodeoxynucleotide (ODN) targeted to the platelet-derived growth factor (PDGF) A-chain on in-stent restenosis in pig coronary artery. A bare metal stent coated with phosphorothioate-linked antisense ODN or nonsense ODN, or a bare metal stent without ODN (control), was implanted in the mid segment of the left anterior descending artery (LAD). Twenty-eight days after implantation, angiography and intravascular ultrasound (IVUS) were performed, the LAD was removed, and stenosis was evaluated pathologically. Volumetric stenosis ratios were 64 +/- 11.9, 44 +/- 3.4, and 26 +/- 3.8% in coronary arteries implanted with control, nonsense ODN-coated, and antisense ODN-coated stents, respectively. In angioscopic findings, the lumen surface was smooth in the stented segments in all groups. Struts of antisense ODN-coated stents were observed embedded in the neointima, whereas embedding was not observed in nonsense ODN-coated stents or control stents, indicating a decrease in hyperplasia in response to antisense ODN treatment. Pathologic findings showed 77 +/- 5.8, 68 +/- 12.2, and 38 +/- 5.3% stenosis in coronary arteries implanted with control stents, nonsense ODN-coated stents, and antisense ODN-coated stents, respectively. A continuous lining of endothelial cells was observed along the lumen of coronary arteries implanted with antisense ODN-coated stents. Stent-based delivery of an antisense ODN targeted to the PDGF A-chain effectively inhibits neointima formation after stent implantation in pig coronary artery by suppressing VSMC hyperplasia and preserving endothelialization. Antisense-ODNs may provide a therapy for in-stent restenosis of the coronary artery.

Nanospheres of a Bisphosphonate Attenuate Intimal Hyperplasia

The present study explored a novel strategy for attenuation of restenosis after arterial injury by a bisphosphonate encapsulated in polymeric nanoparticles (NP) for transient selective depletion of macrophages. A bisphosphonate (BP), 2-(2-Aminopyrimidino) ethyldiene-1,1-bisphosphonic acid betaine (ISA), was successfully formulated in 400 nm sized polylactide/glycolide-based NP with high yield (69%) and entrapment efficiency (60% w/w). ISA NP, but not blank NP or free ISA, exhibited specific and significant cytotoxic effect on macrophages-like RAW 264 cells, in a dose-dependent manner, with no inhibitory effect on the growth of smooth muscle cells (SMCs). Fluorescent pyrene-labeled NP were shown to be taken up by RAW 264 cells, but not by SMCs. Intravenously (i.v.) administered ISA NP (15 mg/kg, single dose on day-1) resulted in a significant attenuation of neointima to media area ratio (N/M) by 40% and stenosis by 45% 14 days after rat carotid injury, in comparison to animals treated with free ISA, buffer or blank NP. However, the effect was not preserved 30 days post injury, and an insignificant reduction of neointimal formation was observed. Neointimal hyperplasia was also significantly suppressed after subcutaneous (SC) injection of ISA NP (15 mg/kg, single dose on day-1), reducing both N/M and stenosis. Intraperitoneal (i.p.) injection of silica, a known selective toxin for macrophages, (1000 mg/kg), also resulted in a significant inhibition of N/M and stenosis, which further reinforces the cause-effect relationship of macrophage-inactivation and the prevention of neointima formation. Biocompatible and biodegradable NP loaded with ISA characterized by high colloidal stability, reproducible activity, and high drug entrapment warrant further consideration for restenosis therapy, and may be useful in other disease processes involving monocytes/macrophages.

Intravascular Magnetic Resonance/Radiofrequency May Enhance Gene Therapy for Prevention of In-stent Neointimal Hyperplasia

We evaluated the potential of using intravascular magnetic resonance (MR)/radiofrequency (RF) to enhance vascular endothelial growth factor (VEGF) gene therapy of in-stent neointimal hyperplasia. By using a catheter-based approach, VEGF/lentivirus was locally transferred into 10 (five paired) bilateral femoral-iliac arteries of five hypercholesterolemic pigs, whereas the right arteries were heated up to approximately 41 degrees C by using an intravascular MR/RF system. Then, identical stents were placed immediately into the bilateral VEGF-targeted arteries to create in-stent neointimal hyperplasia. At day 60 after gene/stent interventions, the targeted arteries were harvested for histological correlation. X-Ray angiography-detectable in-stent stenoses were found in three of the arteries treated with VEGF genes only, whereas there were no in-stent stenoses in arteries treated by using MR/RF-heated VEGF genes. Correlative histological examination confirmed a 138% reduction in average thickness of neointimal hyperplasia in VEGF/RF-treated arteries compared with VEGF-only-treated arteries (P < .01). We report a potential method of using an intravascular MR/RF heating technique to enhance gene therapy of in-stent restenosis.