Stent thrombosis in real-world patients: a comparison of drug-eluting with bare metal stents

BackgroundAlthough the introduction of drugeluting stents (DES) has been associated with an impressive reduction in target vessel revascularisation, there has been concern about the safety profile. The aim of this study was to determine the incidence of stent thrombosis in real-world patients and evaluate the contribution of drug-eluting stents. Methods A prospective observational cohort study was conducted at a high-volume centre in Utrecht, the Netherlands. All patients who underwent a percutaneous coronary intervention (PCI) between 1 January and 31 December 2005 were evaluated. The patients were pretreated with aspirin and clopidogrel, which was continued for six months in bare metal stents (BMS) and 12 months in DES. ResultsIn 2005, 1309 patients underwent a percutaneous coronary intervention procedure with stent implantation. After a median follow-up of nine months, 1.8% (n=23) of the patients had suffered from stent thrombosis. Two cases could be attributed to incorrect use of antiplatelet agents. In 8/23 cases, a technical reason was found such as an unrecognised dissection or stent underexpansion. The timing of stent thrombosis was acute in 1/23 patients, subacute in 20/23 patients and late in 2/23 patients. In both cases of late stent thrombosis, a BMS had been used. There were no differences in stent thrombosis rates between DES and BMS (1.4 vs. 1.9%, ns.). This is remarkable since DES were used in more complex and longer lesions. ConclusionThe use of DES in routine daily practice does not appear to be associated with a higher rate of stent thrombosis than BMS. (Neth Heart J 2007;15:382-6).     

Biomechanical regulation of hedgehog signaling in vascular smooth muscle cells in vitro and in vivo

Hedgehog (Hh) signaling has recently been shown to be both responsive to mechanical loading in vitro and to control vascular development in vivo. We investigated the role of cyclic strain and pulsatile flow in modulating Hh signaling and growth of adult rat vascular smooth muscle cells (SMC) in culture. Exposure of SMC to defined equibiaxial cyclic strain (0% and 10% stretch, 60 cycles/min, for 24 h) significantly decreased sonic hedgehog (Shh) and patched 1 (Ptc1) expression while concurrently inhibiting Gli₂-dependent promoter activity and mRNA expression, respectively. Cyclic strain significantly decreased SMC proliferation (cell counts and proliferating cell nuclear antigen expression) concomitant with a marked increase in SMC apoptosis (fluorescence-activated cell sorter analysis, acridine orange staining of apoptotic nuclei and Bax/Bcl-x_L ratio). These strain-induced changes in proliferation and apoptosis were significantly attenuated following addition of either recombinant Shh (3.5 µg/ml) or overexpression of the Notch 3 intracellular domain (Notch IC). Further studies using a perfused transcapillary culture system demonstrated a significant decrease in Hh signaling in SMC following exposure of cells to increased pulsatile flow concomitant with a decrease in proliferation and an increase in apoptosis. Finally, the pulsatile flow-induced decreases in Hh signaling were validated in vivo following flow-induced rat carotid arterial remodeling after 28 days. These data suggest that Hh expression is diminished by biomechanical stimulation in vitro and in vivo and thus may play a fundamental role in arterial remodeling and atherogenesis in vivo. cyclic strain; apoptosis; proliferation     

Fluvastatin in the therapy of acute coronary syndrome: Rationale and design of a multicenter, randomized, double-blind, placebo-controlled trial (The FACS Trial)[ISRCTN81331696]

Background

Stent length serves as a predictor of restenosis in use of bare metal stents (BMS). This has been demonstrated in a feasibility study that used a single short BMS implant (<9 mm) in a high proportion of lesions; the study observed a low rate of restenosis.

Methods

We performed a pilot prospective study to investigate in a series of consecutive patients the immediate and long-term effects of implantation of either 1) a single short BMS for all lesions with low probability of restenosis or 2) a drug-eluting stent (DES) for all other lesions.

Results

The 200 patients studied had 236 coronary artery lesions that were treated with short BMS in 168/236 patients (71.2%) and with DES in 68/236 patients (28.8%). Angiographic success was achieved in 230/236 lesions (97.5%) and procedural success in 194/200 patients (97.0%). Restenosis occurred in 15/153 lesions (9.8%) after short BMS, in 3/62 lesions (4.8%) after DES, and in 18/215 of all lesions (8.4%) angiographically controlled after six to eight months. Target vessel revascularization was performed in 16/218 lesion (7.4%).

Conclusion

Most of the coronary artery lesions in this small group of consecutive patients were treated sufficiently with a single BMS implant. This differential approach of treating suitable lesions in medium- to large-sized vessels with a single short BMS device and treating all other lesions with a DES implant resulted in a low incidence of restenosis.     

药物涂层支架与金属裸支架治疗ST段抬高型心肌梗死的临床价值比较

目的：评价药物涂层支架（DES）与金属裸支架（BMS）在急性心肌梗死患者中应用的安全性和有效性。方法：选择2003年1月-2010年12月,在我院确诊的急性sT段抬高型心肌梗死（STEMI）167例患者,其中使用BMS65例,DES102例。对比分析两组患者住院期间和出院后1年内的主要心血管或脑血管事件（MAACE）的发生情况及支架内血栓形成的发生率。结果：至随访结束,BMS组有1例患者猝死,5例出现复发心绞痛。DES组有1例突发急性左心衰后死亡,1例复发心绞痛和1例发生亚急性支架内血栓。结论：DES应用于STEMI具有较好的安全性,其术后MAACE发生率较BMS低。     

Combining short stent implantation and drug-eluting stenting for routine use yields a low restenosis rate

Background

Stent length serves as a predictor of restenosis in use of bare metal stents (BMS). This has been demonstrated in a feasibility study that used a single short BMS implant (<9 mm) in a high proportion of lesions; the study observed a low rate of restenosis.

Methods

We performed a pilot prospective study to investigate in a series of consecutive patients the immediate and long-term effects of implantation of either 1) a single short BMS for all lesions with low probability of restenosis or 2) a drug-eluting stent (DES) for all other lesions.

Results

The 200 patients studied had 236 coronary artery lesions that were treated with short BMS in 168/236 patients (71.2%) and with DES in 68/236 patients (28.8%). Angiographic success was achieved in 230/236 lesions (97.5%) and procedural success in 194/200 patients (97.0%). Restenosis occurred in 15/153 lesions (9.8%) after short BMS, in 3/62 lesions (4.8%) after DES, and in 18/215 of all lesions (8.4%) angiographically controlled after six to eight months. Target vessel revascularization was performed in 16/218 lesion (7.4%).

Conclusion

Most of the coronary artery lesions in this small group of consecutive patients were treated sufficiently with a single BMS implant. This differential approach of treating suitable lesions in medium- to large-sized vessels with a single short BMS device and treating all other lesions with a DES implant resulted in a low incidence of restenosis.     

Use of a novel anti-proliferative compound coated on a biopolymer to mitigate platelet-derived growth factor-induced proliferation in human aortic smooth muscle cells: comparison with sirolimus

Drug eluting stents (DES) have become a common mode of treatment for stenosis in coronary arteries. However, currently, the use of sirolimus/paclitaxel-coated DES has come under scrutiny, because of their pro-thrombotic effects leading to potential adverse outcomes in the long run. We have previously documented that d-threo-1-phenyl-2-decanoylamino-3-morholino propanol (D-PDMP); an inhibitor of glucosylceramide synthase and lactosylceramide (LacCer) synthase markedly inhibited platelet-derived growth factor (PDGF)-induced cell proliferation. We have fabricated DES wherein, D-PDMP or sirolimus was coated on to a double layer of poly (lactic-co-glycolic acid) on a bare metal stent. The in vitro release of D-PDMP from biopolymer and its consequent effect on PDGF induced proliferation and apoptosis was assessed in human aortic smooth muscle cells (ASMC). D-PDMP was released from biopolymers in a dose-dependent fashion and was accompanied with a decrease in PDGF-induced cell proliferation, but not apoptosis. In contrast, sirolimus markedly increased apoptosis in these cells in addition to inhibiting proliferation. Our mechanistic studies revealed that D-PDMP, but not sirolimus decreased the cellular level of glucosyl and lactosylceramide that accompanied inhibition of PDGF-induced cell proliferation. Our short-term (14 days) in vivo studies in rabbits also attested to the safety and biocompatibility of the D-PDMP coated stents. Our data reveal the superiority of D-PDMP coated biopolymers over sirolimus coated biopolymers in mitigating ASMC proliferation. Such D-PDMP coated stents may be useful for localized delivery of drug to mitigate neo-vascular hyperplasia and other proliferative disorders. Yong-Dan Tang, Ambarish Pandey, Subbu S. Venkatraman, and Subroto Chatterjee contributed equally to this work.     

Utility of the modified ATP III defined metabolic syndrome and severe obesity as predictors of insulin resistance in overweight children and adolescents: a cross-sectional study

Background

Inhibition of vascular smooth muscle cell (vSMC) proliferation by oral anti-hyperglycemic agents may have a role to play in the amelioration of vascular disease in diabetes. Thiazolidinediones (TZDs) inhibit vSMC proliferation but it has been reported that they anomalously stimulate [³H]-thymidine incorporation. We investigated three TZDs, two biguanides and two sulfonylureas for their ability of inhibit vSMC proliferation. People with diabetes obviously have fluctuating blood glucose levels thus we determined the effect of media glucose concentration on the inhibitory activity of TZDs in a vSMC preparation that grew considerably more rapidly under high glucose conditions. We further explored the mechanisms by which TZDs increase [³H]-thymidine incorporation.

Methods

VSMC proliferation was investigated by [³H]-thymidine incorporation into DNA and cell counting. Activation and inhibition of thymidine kinase utilized short term [³H]-thymidine uptake. Cell cycle events were analyzed by FACS.

Results

VSMC cells grown for 3 days in DMEM with 5% fetal calf serum under low (5 mM glucose) and high (25 mM glucose) increased in number by 2.5 and 4.7 fold, respectively. Rosiglitazone and pioglitazone showed modest but statistically significantly greater inhibitory activity under high versus low glucose conditions (P < 0.05 and P < 0.001, respectively). We confirmed an earlier report that troglitazone (at low concentrations) causes enhanced incorporation of [³H]-thymidine into DNA but did not increase cell numbers. Troglitazone inhibited serum mediated thymidine kinase induction in a concentration dependent manner. FACS analysis showed that troglitazone and rosiglitazone but not pioglitazone placed a slightly higher percentage of cells in the S phase of a growing culture. Of the biguanides, metformin had no effect on proliferation assessed as [³H]-thymidine incorporation or cell numbers whereas phenformin was inhibitory in both assays albeit at high concentrations. The sulfonylureas chlorpropamide and gliclazide had no inhibitory effect on vSMC proliferation assessed by either [³H]-thymidine incorporation or cell numbers.

Conclusion

TZDs but not sulfonylureas nor biguanides (except phenformin at high concentrations) show favorable vascular actions assessed as inhibition of vSMC proliferation. The activity of rosiglitazone and pioglitazone is enhanced under high glucose conditions. These data provide further in vitro evidence for the potential efficacy of TZDs in preventing multiple cardiovascular diseases. However, the plethora of potentially beneficial actions of TZDs in cell and animal models have not been reflected in the results of major clinical trials and a greater understanding of these complex drugs is required to delineate their ultimate clinical utility in preventing macrovascular disease in diabetes.     

Role of PDGF-B and PDGFR-beta in recruitment of vascular smooth muscle cells and pericytes during embryonic blood vessel formation in the mouse.

Development of a vascular system involves the assembly of two principal cell types - endothelial cells and vascular smooth muscle cells/pericytes (vSMC/PC) - into many different types of blood vessels. Most, if not all, vessels begin as endothelial tubes that subsequently acquire a vSMC/PC coating. We have previously shown that PDGF-B is critically involved in the recruitment of pericytes to brain capillaries and to the kidney glomerular capillary tuft. Here, we used desmin and alpha-smooth muscle actin (ASMA) as markers to analyze vSMC/PC development in PDGF-B-/- and PDGFR-beta-/- embryos. Both mutants showed a site-specific reduction of desmin-positive pericytes and ASMA-positive vSMC. We found that endothelial expression of PDGF-B was restricted to immature capillary endothelial cells and to the endothelium of growing arteries. BrdU labeling showed that PDGFR-beta-positive vSMC/PC progenitors normally proliferate at sites of endothelial PDGF-B expression. In PDGF-B-/- embryos, limb arterial vSMC showed a reduced BrdU-labeling index. This suggests a role of PDGF-B in vSMC/PC cell proliferation during vascular growth. Two modes of vSMC recruitment to newly formed vessels have previously been suggested: (1) de novo formation of vSMC by induction of undifferentiated perivascular mesenchymal cells, and (2) co-migration of vSMC from a preexisting pool of vSMC. Our data support both modes of vSMC/PC development and lead to a model in which PDGFR-beta-positive vSMC/PC progenitors initially form around certain vessels by PDGF-B-independent induction. Subsequent angiogenic sprouting and vessel enlargement involves PDGF-B-dependent vSMC/PC progenitor co-migration and proliferation, and/or PDGF-B-independent new induction of vSMC/PC, depending on tissue context.     

Drug-eluting stents in patients with chronic kidney disease: a prospective registry study

Background

Chronic kidney disease (CKD) is strongly associated with adverse outcomes after percutaneous coronary intervention (PCI). There are limited data on the effectiveness of drug-eluting stents (DES) in patients with CKD.

Methodology/Principal Findings

Of 3,752 consecutive patients enrolled in the Guthrie PCI Registry between 2001 and 2006, 436 patients with CKD - defined as a creatinine clearance <60 mL/min - were included in this study. Patients who received DES were compared to those who received bare metal stents (BMS). Patients were followed for a mean duration of 3 years after the index PCI to determine the prognostic impact of stent type. Study end-points were all-cause death, myocardial infarction (MI), target vessel revascularization (TVR), stent thrombosis (ST) and the composite of major adverse cardiovascular events (MACE), defined as death, MI or TVR. Patients receiving DES in our study, by virtue of physician selection, had more stable coronary artery disease and had lower baseline risk of thrombotic or restenotic events. Kaplan-Meier estimates of proportions of patients reaching the end-points were significantly lower for DES vs. BMS for all-cause death (p = 0.0008), TVR (p = 0.029) and MACE (p = 0.0015), but not MI (p = 0.945) or ST (p = 0.88). Multivariable analysis with propensity adjustment demonstrated that DES implantation was an independent predictor of lower rates of all-cause death (hazard ratio [HR] 0.48, 95% confidence interval [CI] 0.25–0.92), TVR (HR 0.50, 95% CI 0.27–0.94) and MACE (HR 0.62, 95% CI 0.41–0.94).

Conclusions

In a contemporary PCI registry, selective use of DES in patients with CKD was safe and effective in the long term, with lower risk of all-cause death, TVR and MACE and similar risk of MI and ST as compared with BMS. The mortality benefit may be a result of selection bias and residual confounding, or represent a true finding; a hypothesis that warrants clarification by randomized clinical trials.     

Drug-Eluting versus Bare-Metal Stent for Treatment of Saphenous Vein Grafts: A Meta-Analysis

Background

Saphenous vein grafts develop an aggressive atherosclerotic process and the efficacy of drug eluting stents (DES) in treating saphenous vein graft (SVG) lesions has not been convincingly demonstrated. The aim of this study was to review and analyze the current literature for controlled studies comparing DES versus bare metal stents (BMS) for treatment of SVG stenoses.

Methodology/Principal Findings

We searched several scientific databases and conference proceedings up to March 15, 2010 for controlled studies comparing target vessel revascularization (TVR) between DES and BMS. Summary odds ratios (OR) for the primary endpoint TVR and secondary endpoints infarction, stent thrombosis and death were calculated using random-effect models. A total of 29 studies (3 randomized controlled trials RCT) involving 7549 (202 in RCT) patients were included. The need for target vessel revascularization in the DES group tended to be lower compared to BMS for the 3 RCT (OR 0.50 [0.24–1.00]; p = 0.051) and for observational studies (0.62 [0.49–0.79]; p<0.001). There was no significant difference in the risk for myocardial infarction in the RCT (OR 1.25 [0.22–6.99]; p = 0.250) but a lower risk for DES based on the observational studies 0.68 [0.49–0.95]; p = 0.023. The risk for stent thrombosis was found to be non-different in the RCT (OR 0.78 [0.03–21.73], p = 0.885) while it was in favor of DES in the observational studies (0.58 [0.38 – 0.84]; p<0.001). The mortality was not significantly different between DES and BMS in the RCT''s (OR 2.22 [0.17 – 29.50]; p = 0.546) while the observation studies showed a decreased mortality in the DES group (0.69 [0.55–0.85]; p<0.001).

Conclusion

DES may decrease TVR rate in treatment of SVG stenoses. No differences in reinfarction rate, stent thrombosis or mortality was found between the DES and BMS groups in the RCT''s while the observational data showed lower risk for myocardial infarction, stent thrombosis and death in the DES group. This may be a result of patient selection bias in the observational studies or represent a true finding that was not the detected in the RCT analysis due to limited statistical power.     

Lesion Length Impacts Long Term Outcomes of Drug-Eluting Stents and Bare Metal Stents Differently

Background

Long lesions have been associated with adverse outcomes in percutaneous coronary interventions with bare metal stents (BMS). However, the exact impact of lesion length on the short- and long-term outcomes of drug-eluting stent (DES) implantations is not as clear.

Methods and Results

This study compared the impact of lesion length on angiographic and clinical outcomes of BMS and DES in a single-center prospective registry. Lesion length was divided into tertiles. The primary endpoints were angiographically defined binary in-stent restenosis (ISR) rate and major adverse cardiac event (MACE). Of the 4,312 de novo lesions in 3,447 consecutive patients in the CAPTAIN registry, 2,791 lesions (of 2,246 patients) received BMS, and the remaining 1,521 lesions (of 1,201 patients) received DES. The mean follow-up duration was 4.5 years. The longer the lesion, the higher the ISR rate (14%, 18%, and 29%, p<0.001) and the lower the MACE-free survivals (p = 0.007) in the BMS group. However, lesion length showed no such correlation with ISR rates (4.7%, 3.3%, and 7.8%, p = 0.67) or MACE-free survivals (p = 0.19) in the DES group.

Conclusions

In our single-center prospective registry, lesion length defined in tertiles has no impact on the short-term (ISR) or long-term (MACE) outcomes of patients implanted with DES. In contrast, longer lesion correlates with higher ISR and MACE rates in BMS group.     

Stents Eluting 6-Mercaptopurine Reduce Neointima Formation and Inflammation while Enhancing Strut Coverage in Rabbits

Background

The introduction of drug-eluting stents (DES) has dramatically reduced restenosis rates compared with bare metal stents, but in-stent thrombosis remains a safety concern, necessitating prolonged dual anti-platelet therapy. The drug 6-Mercaptopurine (6-MP) has been shown to have beneficial effects in a cell-specific fashion on smooth muscle cells (SMC), endothelial cells and macrophages. We generated and analyzed a novel bioresorbable polymer coated DES, releasing 6-MP into the vessel wall, to reduce restenosis by inhibiting SMC proliferation and decreasing inflammation, without negatively affecting endothelialization of the stent surface.

Methods

Stents spray-coated with a bioresorbable polymer containing 0, 30 or 300 μg 6-MP were implanted in the iliac arteries of 17 male New Zealand White rabbits. Animals were euthanized for stent harvest 1 week after implantation for evaluation of cellular stent coverage and after 4 weeks for morphometric analyses of the lesions.

Results

Four weeks after implantation, the high dose of 6-MP attenuated restenosis with 16% compared to controls. Reduced neointima formation could at least partly be explained by an almost 2-fold induction of the cell cycle inhibiting kinase p27^Kip1. Additionally, inflammation score, the quantification of RAM11-positive cells in the vessel wall, was significantly reduced in the high dose group with 23% compared to the control group. Evaluation with scanning electron microscopy showed 6-MP did not inhibit strut coverage 1 week after implantation.

Conclusion

We demonstrate that novel stents coated with a bioresorbable polymer coating eluting 6-MP inhibit restenosis and attenuate inflammation, while stimulating endothelial coverage. The 6-MP-eluting stents demonstrate that inhibition of restenosis without leaving uncovered metal is feasible, bringing stents without risk of late thrombosis one step closer to the patient.     

Late stent thrombosis, endothelialisation and drug-eluting stents

Drug-eluting stents (DES) significantly reduce the risk of restenosis after percutaneous coronary revascularisation, but an increased risk of late stent thrombosis (LST) has been put forward as a major safety concern. Meta-analysis of clinical trials, however, does not support this caveat. Even so, many interventional cardiologists think that LST is associated with DES and related to delayed endothelialisation. This hypothesis is based on autopsy studies and clinical intracoronary angioscopy. In autopsy studies, differences between endothelialisation of DES and baremetal stents (BMS) have been reported. Most preclinical studies, however, have failed to show any significant differences in endothelialisation between DES and BMS. Our own studies, using the porcine coronary artery model, also suggest that DES show no differences in re-endothelialisation. However, DES do delay vascular healing and induce endothelial dysfunction. This paper will review clinical and animal studies which consider re-endothelialisation and LST. (Neth Heart J 2009;17:177–81.)     

Treatment variation in stent choice in patients with stable or unstable coronary artery disease

Aim

Variations in treatment are the result of differences in demographic and clinical factors (e.g. anatomy), but physician and hospital factors may also contribute to treatment variation. The choice of treatment is considered important since it could lead to differences in long-term outcomes. This study explores the associations with stent choice: i.e. drug-eluting stent (DES) versus bare-metal stents (BMS) for Dutch patients diagnosed with stable or unstable coronary artery disease (CAD).

Methods & results

Associations with treatment decisions were based on a prospective cohort of 692 patients with stable or unstable CAD. Of those patients, 442 patients were treated with BMS or DES. Multiple logistic regression analyses were performed to identify variables associated with stent choice. Bivariate analyses showed that NYHA class, number of diseased vessels, previous percutaneous coronary intervention, smoking, diabetes, and the treating hospital were associated with stent type. After correcting for other associations the treating hospital remained significantly associated with stent type in the stable CAD population.

Conclusions

This study showed that several factors were associated with stent choice. While patients generally appear to receive the most optimal stent given their clinical characteristics, stent choice seems partially determined by the treating hospital, which may lead to differences in long-term outcomes.

     

中性粒细胞／淋巴细胞比值与药物支架内再狭窄关系

目的：探讨经皮冠状动脉支架植入术前中性粒细胞／淋巴细胞比值（Neutrophil-to-LymphocyteRatio,NLR）与患者药物支架（DrugElutingStent,DES）植入后发生支架内再狭窄（In—StentRestenosis,ISR）的关系。方法：回顾性分析2012年01月至2012年10月间有DES植入史并再次入院接受冠脉造影的92例患者（平均年龄65．22±9．73岁）的血液学检查、既往冠脉造影结果及再次冠脉造影结果。根据DES植入前的NLR的四分位点将所有入选患者分为3组：最低三分位组（n=31,0．91-1．83）,中间三分位（n=30,1．87—2．63）,最高三分位（n=31,2．66—4．67）,比较3组间ISR发生率有无差异。结果：再狭窄发生在最低NLR三分位的有3例（9．68％）,发生在中间NLR三分位组的有2例（6．67％）,而有4例（12．90％）发生在NLR最高三分位组（P=0．714）,3组之间的差异无统计学意义。结论：因稳定或不稳定型心绞痛而植入药物支架的患者,其术前NLR同支架术后ISR的发生无明显相关性。NLR不能作为DES植入后发生再狭窄的预测指标。     

Coronary stent healing, endothelialisation and the role of co-medication

Since the second half of 2006 percutaneous coronary revascularisation using drug-eluting stents (DES) has come under the scrutiny of the general cardiology community. The initial favourable reports and publications on the merits of DES suddenly changed due to more or less qualified new data on complications such as late stent thrombosis. It seems that the commotion about late stent thrombosis has been over-emphasised, considering the publications that followed from the randomised controlled trials published together in one issue of the New England Journal of Medicine earlier this year.1 The main message from these publications was that indeed late stent thrombosis occurred, but also in the bare metal stent (BMS) groups. However, the debate was further fuelled by data showing that in pathological specimens from autopsy studies more fibrinoid and less endothelialisation could be demonstrated in DES.     

Nanoporous CREG-Eluting Stent Attenuates In-Stent Neointimal Formation in Porcine Coronary Arteries

Background

The goal of this study was to evaluate the efficacy of a nanoporous CREG-eluting stent (CREGES) in inhibiting neointimal formation in a porcine coronary model.

Methods

In vitro proliferation assays were performed using isolated human endothelial and smooth muscle cells to investigate the cell-specific pharmacokinetic effects of CREG and sirolimus. We implanted CREGES, control sirolimus-eluting stents (SES) or bare metal stents (BMS) into pig coronary arteries. Histology and immunohistochemistry were performed to assess the efficacy of CREGES in inhibiting neointimal formation.

Results

CREG and sirolimus inhibited in vitro vascular smooth muscle cell proliferation to a similar degree. Interestingly, human endothelial cell proliferation was only significantly inhibited by sirolimus and was increased by CREG. CREGES attenuated neointimal formation after 4 weeks in porcine coronary model compared with BMS. No differences were found in the injury and inflammation scores among the groups. Scanning electron microscopy and CD31 staining by immunohistochemistry demonstrated an accelerated reendothelialization in the CREGES group compared with the SES or BMS control groups.

Conclusions

The current study suggests that CREGES reduces neointimal formation, promotes reendothelialization in porcine coronary stent model.     

Mechanical strain increases PDGF-B and PDGF beta receptor expression in vascular smooth muscle cells

Cyclic mechanical strain causes proliferation of vascular smooth muscle cells, mediated in part by platelet-derived growth factor (PDGF). We examined the effect of cyclic strain on expression of PDGF-B and the PDGF beta receptor. Neonatal rat vascular smooth muscle cells were exposed to 1 hertz cyclic strain on silicone elastomer plates. PDGF-B mRNA increased after 6 h of strain. In cells transfected with a PDGF-B promoter chloramphenicol acetyl transferase construct (psisCAT 6A), activity increased by 12-fold following 12 h of strain. Two neutralizing antibodies to the PDGF beta receptor both reduced strain-induced [(3)H]thymidine incorporation by 50%. Expression of the PDGF beta receptor protein increased 1.8-fold following 24 h of strain. During strain, PDGF beta receptor expression was not significantly altered by neutralizing antibodies to PDGF-B. Thus, both PDGF-B and the PDGF beta receptor are induced by cyclic mechanical strain and both contribute to cell proliferation in response to strain.     

Effects of cyclic stretch on proliferation of mesenchymal stem cells and their differentiation to smooth muscle cells

Bone marrow mesenchymal stem cells (MSCs) are capable of differentiating into a variety of cell types such as vascular smooth muscle cells (SMCs). In this study, we investigated influence of cyclic stretch on proliferation of hMSCs for different loading conditions, alignment of actin filaments, and consequent differentiation to SMCs. Isolated cells from bone marrow were exposed to cyclic stretch utilizing a customized device. Cell proliferation was examined by MTT assay, alignment of actin fibers by a designed image processing code, and cell differentiation by fluorescence staining. Results indicated promoted proliferation of hMSCs by cyclic strain, enhanced by elevated strain amplitude and number of cycles. Such loading regulated smooth muscle α-actin, and reoriented actin fibers. Cyclic stretch led to differentiation of hMSCs to SMCs without addition of growth factor. It was concluded that applying appropriate loading treatment on hMSCs could enhance proliferation capability, and produce functional SMCs for engineered tissues.     

Endothelial heparan sulfate is necessary but not sufficient for control of vascular smooth muscle cell growth

The state of the endothelial cell (EC) determines the nature of its control of vascular smooth muscle cell (vSMC) biology. Conditioned medium from postconfluent ECs inhibits vSMC proliferation, whereas subconfluent conditioned medium from the same ECs has a stimulatory effect. We and others have identified confluent endothelial cells' production of heparan sulfate proteoglycans (HSPG) as critical to vSMC growth control. The question that arises is whether the stimulation that is observed with subconfluent cells is from (1) aberrant HSPG production, (2) elaboration of noninhibitory species of HSPG, or (3) production of other factors, such as mitogens, which counteract the inhibitory HSPG to stimulate vSMCs. We studied the relative effects of conditioned medium produced by both subconfluent and postconfluent EC cultures on vSMC growth. Conditioned medium was fractionated into nonproteoglycan (non-PG) and proteoglycan (PG) components by anion-exchange chromatography. The PG fractionation profile and the antiproliferative activity of the HSPGs isolated from both subconfluent and postconfluent EC-conditioned media were similar. However, the HSPG fraction alone could not approach the inhibitory potential of unfractionated conditioned medium from postconfluent EC cultures. Non-PG proteins produced by the endothelial cultures had no effect on vSMC growth on their own. Yet, when they were mixed together with HSPG fractions, from either subconfluent or postconfluent EC cultures, the full growth effects were returned. Non-PG protein fractions from postconfluent cultures with HSPG fractions gave maximal inhibition of vSMC growth, whereas non-PG protein fractions from subconfluent EC cultures with HSPG fractions produced the maximal stimulation. Thus, whereas the net stimulatory or inhibitory effect on vSMC growth of EC-conditioned medium is density dependent, this effect does not result from a difference in the antiproliferative heparan sulfate component but rather from non-PG proteins that interact with the heparan sulfates.