Inhibiting Smooth Muscle Cell Proliferation via Immobilization of Heparin/Fibronectin Complexes on Titanium Surfaces

The aim of this study was to investigate the inhibitory effect of heparin/fibronectin （Hep/Fn） complexes on neointimal hyperplasia following endovascular intervention. Hep/Fn complexes were immobilized onto titanium （Ti） surfaces, with subsequent X-ray photoelectron spectroscopy （XPS）, Toluidine Blue 0 （TBO） and immunohistochemistry methods were used to characterize surface properties. Smooth muscle cell （SMC） cultures were used to evaluate the effect of Hep/Fn complexes on SMC proliferation. Results showed that Hep/Fn complexes successfully immobilized onto Ti surfaces and resulted in an inhibition of SMC proliferation. This study suggests that Hep/Fn surface-immobilized biomaterials develop as a new generation of biomaterials to prevent neointimal hyperplasia, particularly for use in cardiovascular implants.

Inhibition of vascular smooth muscle cell proliferation by in troduction of retinoblastoma gene via a recombinant adenovirus vector

This study was supported in part by grant from National Natural Science Foundation of China (No. 39570775). Objective To investigate the vascular smooth muscle cell (SMC) growth suppression by recombinant adenovirus vector expressing a retinoblastoma (Rb) protein and to explore a gene therapy approach for vascular proliferative disorders including atherosclerosis and artery restenosis. Methods A replication deficient adenovirus vector encoding a wild type Rb and AdCMVRb, was constructed and transfected into cultured rabbit aortic SMC. The efficiency of gene transfection and expression was detected by immunochemical staining and polymerase chain reaction. The role of Rb in regulating vascular SMC proliferation was observed by cell counting, thymidine incorporation, and flow cytometry. Results Wild type Rb gene transfected effectively into the cultured SMC with AdCMVRb can suppress growth factor stimulated cell proliferation through regulation of DNA synthesis and cell cycle progression. Conclusion The results demonstrate the potential of adenovirus mediated Rb gene therapy for atherosclerosis and artery restenosis after balloon angioplasty.

Glycosylation-independent binding to extracellular domains 11-13 of mannose-6-phosphate/insulin-like growth factor-2 receptor mediates the effects of soluble CREG on the phenotypic proliferation of vascular smooth muscle cells

Background The present study aimed to investigate the detailed mode and specific sites for their binding as well as the functional relevance of this binding in the phenotypic proliferation of vascular smooth muscle cells(SMCs). Methods CREG knocked-down SMCs were employed to evaluate the biological activity of wtCREG and mCREG.Expressions of SMC differentiation markers SM myosin heavy chain(SM-MHC),SM-actin,heavy caldesmon and myocardin were determined by Western blotting using specific antibodies. Cellular growth of SMCs was assessed by bromide dewuridine (BrdU) incorporation and cell cycle analysis on fluorescence-activated cell sorting(FACS).A solid-phase binding assay was used to study the binding of CREG to extracellular domains of M6P/IGF2R.The cellular co-localization of the two recombinant CREGs with M6P/IGF2R was detected on SMC surface by immunoprecipitation and immunofluorescence analysis.Results The molecular weight of wtCREG was around 30 kD while that of the mCREG was～25 kD.Treatment of wtCREG with PNGase F reduced its molecular weight from～30 kD to～25 kD,whereas PNGase F treatment had no effect on the molecular weight of mCREG.Both wtCREG and mCREG proteins enhanced SMC differentiation,inhibited BrdU incorporation,and arrested cell cycle progression when added to the culture medium.In CREG knocked-down SMCs,the amount of CREG detected by immunoblotting in M6P/IGF2R immunoprecipitates was significantly reduced when compared to normal cells.Both recombinant CREGs co-immunoprecipitated with M6P/IGF2R, although slightly reduced amount of the mutant CREG was detected in M6P/IGF2R immunoprecipitates.Immunostaining revealed that His-tagged CREGs co-localized with IGF2R on the cell surface in a glycosylation-independent manner.In vitro binding assay showed that CREGs bound to M6P/ IGF2R extracellular domains 7-10 and 11-13 in a glycosylation -dependent and -independent manner,respectively.Further blocking experiments using soluble M6P/IGF2R fragments and M6P/IGF2R neutralizing antibody indicated that the biological activities of recombinant CREGs in SMC growth and the up-regulation of SMC differentiation markers were all abolished by treatment with the M6P/IGF2R neutralizing antibody. However,although the growth inhibitory effect of wtCREG was nearly abolished by D7-10 or D11-13,the effect of mCREG was only reversed by Dll-13,indicating that the binding to domains 11-13 is required for CREG to modulate the proliferation of SMCs.Conclusions These data suggest that solubleCREG proteins can exert their biological function via binding to the extracellular domains 7-10 and 11-13 of cell surface M6P/IGF2R in both a glycosylation-dependent and -independent manner.

STUDY ON THE INHIBITORY EFFECT OF ANTISENSE ET_AR OLIGODEOXYNUCLEOTIDES ON THE PROLIFERATION OF VASCULAR SMOOTH CELLS

Objective To study the inhibitory effect of antisense endothelin receptor A (ET-AR) on the proliferation of the vascular smooth muscle cells. Methods The sense, antisense and mismatched ODNs for ET-AR were designed and synthetized. The study was carried out using MTT method and binding assays. Results ET-AR-ODNs could move successfully across VSMC membranes. Photo-absorption in the MTT test was reduced significantly (P<0.05) in the antisense group at 5μmol/L; the reduction of CPM also occurred in the 125 I-ET-1 specific binding assay; and the sense and mismatched ODNs groups did not show this reduction. Conclusion Our study suggested that the antisense oligomers inhibited the proliferation of VSMCs by hindering the translation of target mRNA and by reducing the production of related protein.

Influence of Stent Implantation on the Expression of PCNA and Apoptosis in Injured Vascular Smooth Muscle Cells

Objectives To evaluate the impact of stent implantation on proliferation and apop-tosis in injured media vascular smooth muscle cells (VSMC) and to explore the mechanism of restenosis after stent implantation. Methods Fifty male New Zealand rabbits were randomized into two groups, including balloon group and stent group. Control group was set up. The samples were harvested on 3, 7, 14, 28, 56 days after operation and the following investigation was carried out: (1) Assessing the expression of proliferating cell nuclear antigen (PCNA) of media VSMC by the method of immunohistochemistry; (2) Analyzing apoptosis of media VSMC by DNA agarose gel electrophoresis and TUNEL technique. Results The expression of PCNA and apoptosis in stent and balloon groups were markedly increased compared with control groups. (1) Stent group induced significant increased expression of PCNA in the media VSMC compared with balloon group on 3 to 28 days. On day 7, the positive rates of PCNA were 24. 36±0. 55 % vs 18. 74±1. 09 % ( P < 0. 01 ); (2) From 3 to 28 days, stent group appeared obvious DNA ladder, while balloon group only had little trace ; (3) TUNEL method showed that stent group induced much more significant apoptosis than that of balloon group on 3 to 28 days. The highest rate of apoptosis appeared on day 7: 12. 42 ±1.13% vs 5. 54±0.53% (P<0. 01); (4) By calculating the ratio of the positive rate of PCNA to apoptosis, it showed that on 3 to 28 days, the ratio of balloon group was higher than that of stent group. There was obvious difference between two groups. Conclusions Stent group induces augmented proliferation and much more significant apoptosis of media VSMC than that of balloon group. It makes the ratio of proliferation to apotosis reduced and the severity of restenosis relieved after stent implantation.

Rutaecarpine Inhibits Angiotensin Ⅱ-Induced Proliferation in Rat Vascular Smooth Muscle Cells

Objective： To evaluate the effects and possible mechanisms of rutaecarpine on angiotensin Ⅱ （Ang Ⅱ ）-induced proliferation in cultured rat vascular smooth muscle cells （VSMCs）. Methods： VSMCs were isolated from Male Sprague-Dawley rat aorta, and cultured by enzymic dispersion method. Experiments were performed with cells from passages 3-8. The cultured VSMCs were randomly divided into control, model （Ang Ⅱ 0.1 μ moVL）, and rutaecarpine （0.3-3.0μmol/L） groups. VMSC proliferation was induced by Ang Ⅱ, and was evaluated by the 3-（4, 5-dimethylthiazol-2-yl）-2, 5-diphenyltetrazolium bromide assay and cell counting. To examine the mechanisms involved in anti-proliferative effects of rutaecarpine, nitric oxide （NO） levels and NO synthetase （NOS） activity were determined. Expressions of VSMC proliferation-related genes including endothelial nitric oxide synthase （eNOS）, and c-myc hypertension related gene-1 （HRG-1） were determined by real-time reverse chain reaction （RT-PCR）. Results： Rutaecarpine （0.3-3.0μmol/l_） inhibited Ang R-induced VSMC proliferation and the best effects were achieved at 3.0 μmol/L. The Ang Ⅱ-induced decreases in cellular NO contents and NOS activities were antagonized by rutaecarpine （P〈0.05）. Ang Ⅱ administration suppressed the expressions of eNOS and HRG-1, while increased c-myc expression （P〈0.05）. All these effects were attenuated by 3.0μmol/L rutaecarpine （P〈0.05）. Conclusion： Rutaecarpine is effective against Ang Ⅱ-induced rat VSMC proliferation, and this effect is due, at least in part, to NO production and the modulation of VMSC proliferation-related gene expressions.

Kawasaki Disease on PDGF Expression and VSMC Proliferation

The effect of serum of patients with Kawasaki disease (KD) on expression of platelet-derived growth factor (PDGF) B chain protein in vascular en-dothelial cells (VEC) was studied by immunocytochemical method. Meanwhile, the effects of the endothelial cell conditioned media (ECM) on expression of PDGF receptor mRNA in vascular smooth muscle cells (VSMC) and on cell cycle of VSMC were investigated by the methods of nucleic acid hybridization and flow cytometry (FCM). The results showed that the serum of patients with KD induced the expression of PDGF-B chain protein significantly. ECM significantly promoted the expression of PDGF receptor mRNA and induced the proliferation of VSMC. These data suggest that the activation of PDGF-PDGF receptor may play a role in the pathogenesis of coronary complication of KD.

Focal adhesion kinase antisense oligodeoxynucleotides inhibit human pulmonary artery smooth muscle cells proliferation and promote human pulmonary artery smooth muscle cells apoptosis

Background Pulmonary artery smooth muscle cell (PASMC) proliferation plays an important role in pulmonary vessel structural remodelling At present, the mechanisms related to proliferation of PASMCs are not clear Focal adhesion kinase (FAK) is a widely expressed nonreceptor protein tyrosine kinase Recent research indicates that FAK is implicated in signalling pathways which regulate cytoskeletal organization, adhesion, migration, survival and proliferation of cells Furthermore, there are no reports about the role of FAK in human pulmonary artery smooth muscle cells (HPASMCs) We investigated whether FAK takes part in the intracellular signalling pathway involved in HPASMCs proliferation and apoptosis, by using antisense oligodeoxynucleotides (ODNs) to selectively suppress the expression of FAK protein Methods Cultured HPASMCs stimulated by fibronectin (40 μg/ml) were passively transfected with ODNs, sense FAK, mismatch sense and antisense FAK respectively Expression of FAK, Jun NH2 terminal kinase (JNK), cyclin dependent kinase 2 (CDK 2) and caspase 3 proteins were detected by immunoprecipitation and Western blots Cell cycle and cell apoptosis were analysed by flow cytometry In addition, cytoplasmic FAK expression was detected by immunocytochemical staining Results When compared with mismatch sense group, the protein expressions of FAK, JNK and CDK 2 in HPASMCs decreased in antisense FAK ODNs group and increased in sense FAK ODNs group significantly Caspase 3 expression upregulated in HPASMCs when treated with antisense ODNs and downregulated when treated with sense ODNs When compared with mismatch sense ODNs group, the proportion of cells at G 1 phase decreased significantly in sense ODNs group, while the proportion of cells at S phase increased significantly In contrast, compared with mismatch sense ODNs group, the proportion of cells at G 1 phase was increased significantly in antisense FAK ODNs group The level of cell apoptosis in antisense FAK group was higher than in the mismatch sense group and the latter was higher than sense FAK group In addition, the sense FAK ODNs group was strongly stained by immunocytochemistry, whereas the antisense FAK ODNs group was weakly stained Conclusions The results suggest that FAK relates to the proliferation of HPASMCs Antisense FAK ODNs inhibit HPASMCs proliferation and facilitate their apoptosis It is possible that FAK via JNK, CDK 2 signalling pathways enhances HPASMCs proliferation and via caspase 3 inhibits HPASMCs apoptosis

Contribution of protein kinase C to passively sensitized human airway smooth muscle cells proliferation

Background Airway smooth muscle proliferation plays an important role in airway remodeling in asthma. But little is known about the intracellular signal pathway in the airway smooth muscle cell proliferation in asthma. The objective of this paper is to investigate the contribution of protein kinase C (PKC) and its alpha isoform to passively sensitized human airway smooth muscle cells (HASMCs) proliferation. Methods HASMCs in culture were passively sensitized with 10% serum from asthmatic patients,with non-asthmatic human serum treated HASMCs used as the control. The proliferation of HASMCs was examined by cell cycle analysis,3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazoliumbromide (MTT) colorimetric assay and proliferating cell nuclear antigen (PCNA) immunofluorescence staining. The effect of PKC agonist phorbol 12-myristate 13-acetate (PMA) and PKC inhibitor Ro-31-8220 on the proliferation of HASMCs exposed to human asthmatic serum and non-asthmatic control serum was also examined by the same methods. The protein and mRNA expression of PKC-α in passively sensitized HASMCs were detected by immunofluorescence staining and reverse transcription-polymerase chain reaction. Results The percentage of S phase,absorbance (value A) and the positive percentage of PCNA protein expression in HASMCs passively sensitized with asthmatic serum were (16.30±2.68)%,0.430±0.060 and (63.4±7.4)% respectively,which were significantly increased compared with HASMCs treated with control serum [(10.01±1.38)%,0.328±0.034 and (37.2±4.8)%,respectively] ( P <0.05). After HASMCs were passively sensitized with asthmatic serum,they were treated with PMA,the percentage of S phase,value A and the positive percentage of PCNA protein expression were (20.33±3.39)%,0.542±0.065 and (76.0±8.7)% respectively,which were significantly increased compared with asthmatic serum sensitized HASMCs without PMA( P <0.05). After HASMCs passively sensitized with asthmatic serum were treated with Ro-31-8220,the percentage of S phase,value A and the positive percentage of PCNA protein expression were (11.21±1.56)%,0.331±0.047 and (38.8±6.0)% respectively,which were significantly decreased compared with asthmatic serum sensitized HASMCs without Ro-31-8220 ( P <0.05). The relative ratio of value A of PKC-α mRNA and the positive percentage of PKC-α protein expression in passively sensitized HASMCs were 1.23±0.10 and (61.1±9.4)% respectively, which were significantly increased compared with HASMCs treated with control serum [1.05±0.09 and (34.9±6.7)%,respectively] ( P <0.05). Conclusions The proliferation of HASMCs passively sensitized with human asthmatic serum is increased. PKC and its alpha isoform may contribute to this proliferation.

Effect of Aloe Emodin on Proliferation of Vascular Smooth Muscle Cells after Arterial Injury

Objective: To study the effect of Aloe emodin (AE), an active ingredient of Rhubarb,on the kinetics of proliferation of smooth muscular cells (SMCs) cultured in vitro after rabbit iliac arterial injury. Methods: Forty-eight hours after de-endothelialization (balloon endothelial denudation), the iliac arteries of the Japanese white rabbits were isolated and the smooth muscle cells were cultured primarily.AE was added to culture medium containing 10% fetal calf serum (FCS ). The cultures were pulse-labeled with 3H-TdR and TdR uptake into VSMC were measured and the cell cycle of the cultures were analyzed by using flow cytometer. Results: Compared with control, when the concentration gradient ranged from 10 - 1 to 10-5 g/L, the amount (cpm,count per minute) of 3H-TdR uptake into SMCs has significant differences (P < 0. 05 )and 10 -1 and 10 -2 g/L AE showed strong inhibitory effects on TdR uptake into VSMC and the percentage of inhibition [% inhibition =(cpm without AE-cpm with AE)/cpm without AE] was more than 90%. AE displayed concentration dependent inhibitory effects. The percentage of cells in G0/G1 phase was increased, but the percentage of cells in S phase was decreased in AE group, the transition of SMC cycle phase from G0 to S was blocked.Conclusion: AE is a strong inhibitor to the proliferation of SMCs and the pharmacological action of AE may reduce SMC proliferation in vivo and decrease intimal hyperplasia of restenosis.Original article on CJIM(Chin) 1998; 18(7): 420

EFFECTS OF HYPOXIC ENDOTHELIAL CELL CONDITIONED MEDIUM ON PROLIFERATION AND COLLAGEN SYNTHESIS OF SMOOTH MUSCLE CELLS AND INHIBITORY EFFECTS OF RADIX SALVIAE MILTIORRHIZAE

The effects of hypoxic endothelial cell conditioned medium (HECCM) on proliferation and collagen synthesis of cultured porcine pulmonary arterial smooth muscle cells (PASMCs) were studied by 3H-thymidine (3H-TdR) and 3H-proline incorporations, image analysis for determination of DNA content and colorimetric assay using MTT, and the inhibitory effects of radix salviae miltiorrhizae (RSM) on them were also investigated. The results showed that HECCM could induce enhancement of the enzymatic activity of mitochondria, increase of the nucleic DNA content and increases of the 3H-TdR and 3H-proline incorporations in PASMCs. The 3H-proline incorporation in PASMCs cultured in HECCM was 1.83 times as much as that cultured in normoxic endothelial cell conditioned medium (NECCM). Compared with the control, Chinese herb medicine RSM could inhibit the proliferation of PASMCs cultured in HECCM and decrease the 3H-prolinc incorporation in PASMCs cultured in both HECCM and NECCM (P< 0.001). However, RSM had no ef fects on the nucleic DNA content and 3H-TdR incorporation into DNA of PASMCs cultured in NECCM. It suggests that hypoxia may stimulate the endothelia to synthesize and secrete some cytokines which can stimulate the proliferation and the synthesis of collagen of PASMCs and RSM can inhibit this process.

Effect of aloe-emodin on expression of proliferating cell nuclear antigen of vascular smooth muscle cells in culture after arterial injury

Objective To observe the effect of aloe-emodin on the expression of proliferating cell nuclear antigen (PCNA) in smooth muscle cells (SMCs) after arterial injury and study the molecular mechanism of inhibition of aloe-emodin on SMC proliferation.Methods Deendothelialization was performed at the abdominal aorta in Japanese white rabbits using a 3F Fogarty arterial embolectomy catheter. 48 hours later, the medium of abdominal aorta was isolated and primary SMCs culture was performed. Cells were synchronized to G0 by serum starvation, then aloe-emodin at a concentration of 20?μg/ml was added to the culture medium containing 10%［v/v］ fetal calf serum. Vehicle was also added to the medium as a control. After 18 hours, the expression of PCNA at the level of mRNA and protein were examined using techniques of RT/PCR, Western blotting and inmmunocytochemistry respectively. Results Compared with the control group, the expression of PCNA mRNA and protein was prominently decreased after addition of aloe-emodin. Conclusion The inhibition of aloe-emodin on SMCs proliferation may be caused by inhibiting the expression of the PCNA gene.

Interferon-γ inhibits in situ expression of PDGF-β mRNA by smooth muscle cells in injured rabbit arteries after transluminal balloon angioplasty

Objective To elucidate the mechanism of interferon-gamma (IFN-γ) to inhibit the restenosis after successful percutaneous transluminal angioplasty (PTA).Methods A rabbit vascular restenotic model was constructed and the proliferation of intimal smooth muscle cells (SMCs) were observed by monitoring their expression of proliferating cell nuclear antigen (PCNA) and platelet-derived growth factor β chain mRNA (PDGF-β mRNA) at the indicated time points. Results IFN-γ could significantly inhibit the expression of PCNA by intimal SMCs one week after denudation, when counting 200 intimal cells for PCNA-positive reactions with an inhibitory rate of 88.50% (P<0.001). IFN-γ could downregulate in situ expression of PDGF-β mRNA by these cells as we calculated the average number of PDGF-β mRNA positive cells per square millimetre area at ×400 magnification with reduced rates of 86.85% in 1 week group (P<0.001), of 93.66% in 2 week group (P<0.001) and of 52.92% in 4 week group (0.02<P<0.05), respectively. Conclusions The local production of PDGF-β by vascular intimal SMCs via an autocrine mechanism may be responsible for continuous proliferation of these cells and the formation of neointima after injury. This could be inhibited by IFN-γ through downregulating the expression of PDGF-β mRNA. These results provide an in vivo basis for IFN-γ to be used clinically for the management of restenosis after percutaneous transluminal angioplasty.

Shexiang Baoxin Pill Regulates Intimal Hyperplasia,Migration,and Apoptosis after Platelet-Derived Growth Factor-BB-Stimulation of Vascular Smooth Muscle Cells via miR-451

Objective:To investigate the regulatory roles of Shexiang Baoxin Pill(SXBXW)in neointimal formation and vascular smooth muscle cells(VSMCs)invasion and apoptosis as well as the potential molecular mechanisms using cultured VSMCs model of vascular injury(platelet-derived growth factor(PDGF)-BBstimulated)in vitro.Methods:VSMCs were randomly assigned to 5 groups:blank,PDGF-BB(20 ng/mL+0.1%DMSO),SXBXW-L(PDGF-BB 20 ng/mL+SXBXW low dose 0.625 g/L),SXBXW-M(PDGF-BB 20 ng/mL+SXBXW medium dose 1.25 g/L)and SXBXW-H(PDGF-BB 20 ng/mL+SXBXW high dose 2.5 g/L)group.Cell proliferation was assessed using cell counting kit-8(CCK-8)assay and bromodeoxyuridine(BrdU)incorporation assay,the migration effects were detected by Transwell assay,cell apoptosis rate was measured by the Annexin V/propidium iodide(PI)apoptosis kit.The markers of contractile phenotype of VSMCs were detected with immunofluorescent staining.To validate the effects of miR-451 in regulating proliferation,migration and apoptosis treated with SXBXW,miR-451 overexpression experiments were performed,the VSMCs were exposed to PDGF-BB 20 ng/mL+0.1%DMSO and later divided into 4 groups:mimic-NC(multiplicity of infection,MOI=50),SXBXW(1.25 g/L)+mimic-NC,mimic-miR451(MOI=50),and SXBXW(1.25 g/L)+mimic-miR451,and alterations of proteins related to the miR-451 pathway were analyzed using Western blot.Results:PDGF-BB induced VSMCs injury causes acceleration of proliferation and migration.SXBXW inhibited phenotypic switching,proliferation and migration and promoted cell apoptosis in PDGF-BB-induced VSMCs.In addition,miR-451 was shown to be down-regulated in the VSMCs following PDGF-BB stimulation.SXBXW treatment enhanced the expression of miR-451 in PDGF-BB-induced VSMCs(P<0.05).Compared with SXBXW+mimic-NC and mimicmiR451 groups,the expression of tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta(Ywhaz)and p53 was further reduced in SXBXW+mimic-miR451 group,while activating transcription factor 2(ATF2)was increased in VSMCs(P<0.05).Conclusion:SXBXW regulated proliferation,migration and apoptosis via activation of miR-451 through ATF2,p53 and Ywhaz in PDGF-BB-stimulated VSMCs.

LOW-DOSE RADIOACTIVE ENDOVASCULAR STENTS PREVENT NEOINTIMAL HYPERPLASIA IN RABBITS RESTENOSIS MODEL

Objective To evaluate the effects of low-dose radioactive stents on the prevention of restenosis in rabbit model. Methods The stents were bombarded with suitable charged particles of adapted energy in the cyclotron to create a proper mixture of the radionuclides 59 Fe, 60 Co, 58 Co, 51 Cr, and 54 Mn. The radioactive stents were implanted in the iliac arteries of rabbits. The effects of radioactive stents on prevention of restenosis were assessed by angiography, histomorphometry and immunocytochemistry. Results All the iliac arteries that had been implanted with radioactive stents were patent on angiography and had no radiation complication during the 1～2 months of follow-up. There was a significant reduction in neointimal area (0.37±0.14mm 2 vs. 0.81±0.10mm 2, P<0.01), percent area stenosis (6.7±2.9% vs. 13.2±1.4%, P<0.01) and PCNA immunoreactive rate (2.00±1.58% vs. 10.88±6.98%, P<0.05) in the radioactive stent group compared with the control stent group. Conclusion Radioactive stents with an active of 0.91～1.65 μCi could inhibit SMC proliferation and neointimal hyperplasia in animal restenosis model. The low-dose radioactive stents are safe and feasible for prevention of restenosis.