Benjamin Hibbert

Modulation of Estrogen Signaling by the Novel Interaction of Heat Shock Protein 27, a Biomarker for Atherosclerosis, and Estrogen Receptor β: Mechanistic Insight Into the Vascular Effects of Estrogens

Objective—We sought to discover proteins that associate with estrogen receptor beta (ER&bgr;) and modulate estrogen signaling. Methods and Result—Using a yeast 2-hybrid screen, we identified heat shock protein 27 (HSP27) as an ER&bgr;-associated protein. HSP27 is a recently identified biomarker of atherosclerosis that is secreted at reduced levels from atherosclerotic compared with normal arteries. In vitro protein-binding assays confirmed the specific interaction of HSP27 with ER&bgr; and not ER&agr;. HSP27 expression was absent in coronary arteries with complex atherosclerotic lesions. Interestingly, HSP27 expression was also absent in 60% of coronary arteries from young males and females (27±6.5 years) with normal histology or nonobstructive fatty streaks/atheromas. Moreover, the absence of HSP27 in these normal or minimally diseased arteries coincided with the loss of ER&bgr; expression. Only 35% of arteries showed coexpression of HSP27 and ER&bgr;. Relative to controls, estradiol-mediated transcription was reduced 20% with overexpression of HSP27 and increased 44% when HSP27 protein levels were reduced with HSP27 siRNA. Conclusions—HSP27, an ER&bgr;-associated protein, shows attenuated expression with coronary atherosclerosis and modulates estrogen signaling.

The Evolution of Coronary Stents: A Brief Review

Percutaneous coronary intervention is the most prevalent method for coronary artery revascularization. Initial interventions using balloon angioplasty had limited efficacy because coronary dissections, arterial recoil, and neointimal formation led to high rates of abrupt vessel closure and clinical restenosis. With the introduction of coronary stents, vascular dissections were stabilized and arterial recoil was eliminated, but neointimal accumulation remained problematic, resulting in the development of in-stent restenosis (ISR) in 20%-30% of cases. Drug-eluting stents (DESs) were developed to release antiproliferative agents at the site of arterial injury to attenuate neointimal formation. Although DESs have incrementally improved outcomes after percutaneous coronary intervention, delayed re-endothelialization and stent thrombosis remain important challenges. Herein we review the pathophysiology of ISR, stent thrombosis, and briefly summarize the clinical evidence behind first- and second-generation DESs. Moreover, we discuss advancements in our understanding of the pathogenesis of ISR and potential novel therapeutic strategies to improve clinical outcomes.

Natural History and Management of Aortocoronary Saphenous Vein Graft Aneurysms A Systematic Review of Published Cases

Despite ongoing advances in percutaneous revascularization, coronary artery bypass grafting (CABG) continues to be performed in a large number of patients, with >400 000 operations reported in 2007 in the United States alone.1 Although arterial conduits are generally preferred, saphenous vein grafts (SVGs) continue to be used regularly. First described by Riahi and colleagues2 in 1975, aneurysmal dilatation of aortocoronary SVGs remains a rare yet widely reported phenomenon. Indeed, subsequent literature on the topic consists almost exclusively of case reports and small case series. Thus, the precise incidence of aortocoronary SVG aneurysms (SVGAs) remains difficult to ascertain, although in 1 case series, an incidence of 0.07% was estimated from a review of >5500 grafts at a single institution.3 However, this likely underestimates the true number because SVGAs often remain clinically silent and no guidelines exist to screen for their development. Given the infrequent identification of SVGAs, our current understanding of the epidemiology and pathogenesis of these aneurysms remains limited. Aneurysms are generally defined as a focal dilatation of vessels >1.5 times the proximal reference diameter; however, aneurysmal dilatation of aortocoronary SVGs has led to “giant” aneurysm formation, with reports of cases exceeding 10 cm.4–6 SVGAs are often incidentally identified on imaging, but cases of rupture,7 fistula formation with neighboring anatomy,8 and hemodynamic compromise resulting from compression of adjacent cardiac and vascular structures have been reported.9 To date, 2 reviews have been published that briefly summarize 108 cases of SVGAs.10,11 Traditionally, their management has been surgical—generally resection of the aneurysm with or without bypass of the affected territory. However, with refinement of percutaneous techniques, including the use of Amplatzer devices, covered stents, and arterial coiling, the management options …

Transradial Versus Transfemoral Artery Approach for Coronary Angiography and Percutaneous Coronary Intervention in the Extremely Obese

OBJECTIVES This study sought to evaluate the safety and efficacy of transradial versus transfemoral access for coronary angiography and percutaneous coronary intervention in patients with a body mass index ≥ 40 kg/m(2). BACKGROUND Coronary angiography is most commonly performed via femoral artery access; however, the optimal approach in extremely obese (EO) patients remains unclear. METHODS Between January 2007 and August 2010, a cohort of consecutive EO patients who underwent coronary angiography was identified in our centers registry of angiography and percutaneous coronary intervention procedures. Of 21,103 procedures, 564 (2.7%) were performed in unique EO patients: 203 (36%) via the transradial approach; and 361 (64%) via the transfemoral approach. RESULTS The primary outcome, a combined endpoint of major bleeding, access site complications, and nonaccess site complications, occurred in 7.5% of the transfemoral group and 2.0% of the transradial group (odds ratio [OR]: 0.30, 95% confidence interval [CI]: 0.10 to 0.88, p = 0.029), an endpoint driven by reductions in major bleeding (3.3% vs. 0.0%, OR: 0.12, 95% CI: 0 to 0.71, p = 0.015), as well as access site injuries (4.7% vs. 0.0%, OR: 0.08, 95% CI: 0 to 0.48, p = 0.002). There were no differences in nonaccess site complications (1.7% vs. 2.0%, OR: 1.50, 95% CI: 0.41 to 5.55), but transradial access procedures were associated with an increase in procedure time and patient radiation dose (p < 0.05). CONCLUSIONS Transfemoral access for coronary angiography and percutaneous coronary intervention was associated with more bleeding and access site complications when compared with a transradial approach. Important reductions in procedural associated morbidity may be possible with a transradial approach in EO patients.

Inhibition of endothelial progenitor cell glycogen synthase kinase-3β results in attenuated neointima formation and enhanced re-endothelialization after arterial injury

AIMS Endothelial progenitor cells (EPCs) are circulating pluripotent vascular cells capable of enhancing re-endothelialization and diminishing neointima formation following arterial injury. Glycogen synthase kinase (GSK)-3beta is a protein kinase that has been implicated in the regulation of progenitor cell biology. We hypothesized that EPC abundance and function could be enhanced with the use of an inhibitor of GSK-3beta (GSKi), thereby resulting in improved arterial repair. METHODS AND RESULTS Human EPCs were expanded ex vivo, treated with a specific GSKi, and then assessed for both yield and functional characteristics by in vitro assays for adherence, apoptosis, and survival. In vivo functionality of treated human EPCs was assessed in immune-tolerant mice subjected to femoral artery wire injury. Re-endothelialization was assessed at 72 h and neointima formation at 7 and 14 days following injury. GSKi treatment resulted in an improvement in the yield of EPCs and a reduction in apoptosis in cells derived from both healthy controls and patients with coronary artery disease. Treatment also increased vascular endothelial growth factor secretion, up-regulated expression of mRNA for the alpha-4 integrin subunit, and improved adhesion, an effect which could be abrogated with an alpha-4 integrin blocking antibody. EPCs without or with ex vivo GSKi treatment enhanced re-endothelialization 72 h following injury as well as reduced neointima formation at 7 days (e.g. endothelial coverage: 7.2 +/- 1.7% vs. 70.7 +/- 5.8% vs. 87.2 +/- 4.1%; intima to media ratios: 1.05 +/- 0.19 vs. 0.39 +/- 0.08 vs. 0.14 +/- 0.02; P < 0.05 for all comparisons), an effect that was persistent at 14 days. CONCLUSION GSKi improves the functional profile of EPCs and is associated with improved re-endothelialization and reduced neointima formation following injury.

Transcatheter aortic valve implantation in patients with bicuspid aortic valve: A patient level multi-center analysis

OBJECTIVE We sought to evaluate the safety and efficacy of transcatheter aortic valve implantation (TAVI) in patients with bicuspid aortic valve (BiAV). BACKGROUND BiAV remains a relative contraindication to TAVI resulting in exclusion from TAVI trials and thus limiting data on the clinical performance of transcatheter valves in these patients. METHODOLOGY We conducted an international patient level multicenter analysis on outcomes in patients with BiAV undergoing TAVI. The primary outcome of the study was the combined early safety endpoint--a composite of 30 day mortality, stroke, life-threatening bleeding, acute kidney injury, coronary artery obstruction, major vascular complication and valve related dysfunction. Secondary endpoints included the individual components of the primary endpoint as well as post-TAVI paravalvular leak (PVL), rehospitalization, new pacemaker insertion and device success rates at 30 days and 1 year. RESULTS A total of 108 patients with BiAV were identified in 21 centers in Canada, Spain, Italy, Poland and Singapore who underwent TAVI between January 2005 and March 2014. The composite primary outcome occurred in one quarter of patients (26.9%)--mainly driven by re-intervention for valve malposition (9.3%). The 30-day and 1 year mortality rates were 8.3% and 16.9% respectively with AR ≥ 3+ occurring in 9.6% of patients. Device success was achieved in 85.2% of cases with pacemaker insertion in 19.4%. While PVL was not associated with an increased risk of 30 day or 1 year mortality--Type I BiAV anatomy with left and right cusp fusion had significantly better outcomes than other valve variants. CONCLUSION In selected patients with BiAV and severe aortic stenosis, TAVI appears both safe and feasible with acceptable clinical outcomes. Clinical studies of TAVI in this patient population are warranted.

Pre-Procedural Atorvastatin Mobilizes Endothelial Progenitor Cells: Clues to the Salutary Effects of Statins on Healing of Stented Human Arteries

Objectives Recent clinical trials suggest an LDL-independent superiority of intensive statin therapy in reducing target vessel revascularization and peri-procedural myocardial infarctions in patients who undergo percutaneous coronary interventions (PCI). While animal studies demonstrate that statins mobilize endothelial progenitor cells (EPCs) which can enhance arterial repair and attenuate neointimal formation, the precise explanation for the clinical PCI benefits of high dose statin therapy remain elusive. Thus we serially assessed patients undergoing PCI to test the hypothesis that high dose Atorvastatin therapy initiated prior to PCI mobilizes EPCs that may be capable of enhancing arterial repair. Methods and Results Statin naïve male patients undergoing angiography for stent placement were randomized to standard therapy without Atorvastatin (n = 10) or treatment with Atorvastatin 80 mg (n = 10) beginning three days prior to stent implantation. EPCs were defined by flow cytometry (e.g., surface marker profile of CD45dim/34+/133+/117+). As well, we also enumerated cultured angiogenic cells (CACs) by standard in vitro culture assay. While EPC levels did not fluctuate over time for the patients free of Atorvastatin, there was a 3.5-fold increase in EPC levels with high dose Atorvastatin beginning within 3 days of the first dose (and immediately pre-PCI) which persisted at 4 and 24 hours post-PCI (p<0.05). There was a similar rise in CAC levels as assessed by in vitro culture. CACs cultured in the presence of Atorvastatin failed to show augmented survival or VEGF secretion but displayed a 2-fold increase in adhesion to stent struts (p<0.05). Conclusions High dose Atorvastatin therapy pre-PCI improves EPC number and CAC number and function in humans which may in part explain the benefit in clinical outcomes seen in patients undergoing coronary interventions.

Pathogenesis of Neointima Formation Following Vascular Injury

Revascularization remains the cornerstone of managing obstructive coronary artery disease. Although percutaneous coronary interventions involving the insertion of metal scaffolds, known as stents, has emerged as the preferred method of restoring vessel patency, as many as 30% of patients will experience a gradual re-narrowing of the lumen caused by neointima (NI) formation, resulting in a condition known as in-stent restenosis (ISR). ISR represents a significant limitation to percutaneous revascularization - however, abrogating NI formation following stent implantation has been hampered by an incomplete understanding of the pathogenesis of in-stent lesions. While numerous mechanisms have been proposed to explain the pathogenesis of ISR, data from human and animal models have yielded conflicting results. Herein, we review key studies of NI development following vascular injury with a focus on the origin of cells participating in NI formation.

Delayed re-endothelialization with rapamycin-coated stents is rescued by the addition of a glycogen synthase kinase-3β inhibitor

AIMS Drug-eluting stents (DESs) reduce neointima area and in-stent restenosis but delay re-endothelialization. Recently, we demonstrated that pharmacological expansion and functional enhancement of endothelial progenitor cells (EPCs) can be achieved by treatment with a glycogen synthase kinase-3beta inhibitor (GSKi)-even for feeble cells derived from coronary artery disease patients. GSKi treatment enhanced EPC adhesion via up-regulated expression of the alpha-4 integrin, ameliorated re-endothelialization, and reduced neointima formation in denuded murine arteries. Hence, we hypothesized that GSKi-coated stents (GSs) will enhance EPC adhesion and attenuate delayed vascular healing associated with rapamycin, a key DES agent. METHODS AND RESULTS In vitro human EPCs adhered to GS with affinities that were 2x, 14x, and 13x greater than vehicle (VSs)-, rapamycin (RSs)-, and rapamycin plus GSKi (RGSs)-coated stents, respectively. Stents were inserted in rabbit carotid arteries, and at 14 days, neointima area was 45 and 49% lower in GSs compared with bare metal stents (BMSs) and VSs. Moreover, RSs had a 47% larger neointima area than GSs, but RGSs reduced neointima area to a level comparable to GSs. Seven days after stenting, GSs displayed re-endothelialization that was 40, 33, and 42% greater than BMSs, VSs, and RSs, respectively. Moreover, RGSs had 41% more re-endothelialization than RSs. At 14 days, the 7-day re-endothelialization patterns persisted. CONCLUSION GSKi efficiently ameliorates the vascular response to stent implantation and has an important redeeming effect on the deleterious endothelial effects of rapamycin-coated stents.

Discovery of NM23-H2 as an estrogen receptor β-associated protein : Role in estrogen-induced gene transcription and cell migration

The regulation of the estrogenic responses may be influenced by the proteins that associate with estrogen receptors (ERs) rather than solely with the receptors themselves. ERbeta is expressed in blood vessels and may play an important role in vascular disease. We hypothesized that specific proteins interact with ERbeta to modulate its response to estrogens. By means of a yeast two hybrid screen, we discovered that NM23-H2, a multi-faceted protein associates specifically with ERbeta. NM23-H2 and ERbeta consistently co-localize in a variety of human tissues (e.g. breast tissue), whereas ERalpha and NM23-H2 did not co-localize. Estrogen response element-mediated transcription increased by 97% when NM23-H2 and ERbeta were over-expressed in MCF-7 cells (p< or =0.001). Moreover, there was a synergistic effect of NM23-H2 over-expression with estrogen treatment on the reduction of MCF-7 cell migration (p< or =0.001). These results suggest that NM23-H2 associates with ERbeta and is capable of modulating estrogen-induced gene transcription, as well as cell migration. Hence, NM23-H2 may play an important role in modulating the response to endogenous and exogenous estrogens, perhaps even within the context of vascular disease.