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Articles by Edward R. O'Brien in JoVE
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A Novel Stretching plattform for applikasjoner i celler og vev mechanobiology
Dominique Tremblay1, Charles M. Cuerrier1,2, Lukasz Andrzejewski1, Edward R. O'Brien3, Andrew E. Pelling1,4,5
1Centre for Interdisciplinary NanoPhysics, Department of Physics, University of Ottawa, 2University of Ottawa Heart Institue, University of Ottawa, 3Libin Cardiovascular Institute of Alberta, University of Calgary, 4Department of Biology, University of Ottawa, 5Institute for Science, Society and Policy, University of Ottawa
Vi presenterer i denne artikkelen en ny strekking plattform som kan brukes til å undersøke enkelt celle responser på komplekse anisotrop biaksial mekanisk deformasjon og kvantifisere de mekaniske egenskapene til biologiske vev.
Other articles by Edward R. O'Brien on PubMed
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C-kit-immunopositive Vascular Progenitor Cells Populate Human Coronary In-stent Restenosis but Not Primary Atherosclerotic Lesions
American Journal of Physiology. Heart and Circulatory Physiology.
Aug, 2004 |
Pubmed ID: 15277195 Progress in the treatment of human in-stent restenosis (ISR) is hampered by an imprecise understanding of the nature of the cells that occlude vascular stents. Recent studies suggest that circulating vascular progenitor cells may mediate vascular repair and lesion formation. Moreover, functional endothelial progenitor cells appear to play a protective role in attenuating vascular lesion formation. Hence, we sought to answer two important questions: 1). Are primitive cells found in ISR lesions? 2). Is the abundance of cultured angiogenic cells (CACs) in patients with ISR different from that in patients with non-ISR lesions or normal controls? Human coronary atherectomy tissue from 13 ISR, 6 postangioplasty restenosis (RS), and 14 primary (PR) atherosclerotic lesions, as well as 15 postmortem coronary artery cross sections from young individuals without atherosclerosis, were studied. All 13 ISR and 4 of 6 RS tissue specimens contained cells that immunolabeled for the primitive cell marker c-kit and smooth muscle alpha-actin, whereas the intima and media of PR lesions and normal arteries were devoid of c-kit-immunopositive cells. The abundance of peripheral blood mononuclear cell-derived CACs was assessed in 10 patients with ISR, 6 patients with angiographically verified patent stents, and 6 individuals with no clinical evidence of coronary artery disease. CACs were less abundant in ISR patients than in non-ISR controls (13.9 +/- 3.1 vs. 22.3 +/- 6.7 cells/high-power field, P < 0.05), and both of these groups had fewer CACs than non-coronary artery disease patients (37.6 +/- 3.8, P < 0.05). These findings suggest a unique pathogenesis for ISR and RS lesions that involves c-kit-immunopositive smooth muscle cells. Moreover, the paucity of CACs in patients with ISR may contribute to the pathogenesis of ISR, perhaps because of attenuated reendothelialization.
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Antagonism of the Alpha4 Integrin Subunit Attenuates the Acute Inflammatory Response to Stent Implantation Yet is Insufficient to Prevent Late Intimal Formation
Journal of Leukocyte Biology.
Jun, 2004 |
Pubmed ID: 15020653 Mononuclear leukocytes infiltrate the artery wall via integrin-mediated mechanisms and play an integral role in intimal formation after stenting. We sought to determine if acute antagonism of the alpha4 subunit of very late antigen-4 is sufficient for the late attenuation of stent intimal area (IA). Twenty-four hypercholesterolemic rabbits underwent iliac artery balloon injury, followed 2 weeks later by stent implantation, and the animals were randomized to receive an anti-alpha4 antibody (HP1/2) or a nonspecific isotypic control immunoglobulin (1E6) intravenously 1 h before stenting. Compared with controls, HP1/2-treated rabbits showed 50%, 51%, and 44% reductions in the percentage on intimal cells that were macrophages on days 3, 7, and 28 after stenting and a 59% reduction in intimal proliferation on day 3. Although stent IA was reduced by 63% and 48% in the antibody-treated group compared with the control group on days 3 and 7, this difference was not present on day 28. These data highlight the need for sustained, anti-inflammatory therapies for the prevention of stent intimal formation.
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17beta-estradiol Downregulates Tissue Angiotensin-converting Enzyme and ANG II Type 1 Receptor in Female Rats
American Journal of Physiology. Regulatory, Integrative and Comparative Physiology.
Mar, 2005 |
Pubmed ID: 15550614 Estrogens have been implicated in both worsening and protecting from cardiovascular disease. The effects of 17beta-estradiol (E2) on the cardiovascular system may be mediated, at least in part, by its modulation of local tissue renin-angiotensin systems (RAS). We assessed two critical components, angiotensin-converting enzyme (ACE) and ANG II type 1 receptor (AT(1)R), in the heart, lung, abdominal aorta, adrenal, kidney, and brain in four groups of female Wistar rats (n = 5-6/group): 1) sham ovariectomized, 2) ovariectomized (OVX) treated with subcutaneous vehicle, 3) OVX treated with 25 mug/day (regular) E2 subcutaneously, and 4) OVX treated with 250 mug/day (high) subcutaneous E2 for 2 or 5 wk. After 2 wk, plasma ACE activity was not altered by OVX, but it was 34-38% lower in OVX + regular E2 and OVX + high E2 rats compared with sham OVX rats, and these decreases were no longer present after 5 wk. After 5 wk, OVX alone increased ACE activity and binding densities, and AT(1)R binding densities by 15-100% in right ventricle, left ventricle (LV), kidney, lung, abdominal aorta, adrenal and several cardiovascular regulatory nuclei in the brain. These effects were, for the most part, prevented by regular E2 replacement and were reversed to decreases by high E2 treatment. This regulation of tissue ACE and AT(1)R is significant as the activity of these tissue RAS contributes to the pathogenesis and/or progression of hypertension, atherosclerosis, and LV remodeling after myocardial infarction.
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Comparison of Processing and Sectioning Methodologies for Arteries Containing Metallic Stents
The Journal of Histochemistry and Cytochemistry : Official Journal of the Histochemistry Society.
Jun, 2006 |
Pubmed ID: 16714423 The histological study of arteries with implanted metallic scaffolding devices, known as stents, remains a technical challenge. Given that the arterial response to stent implantation can sometimes lead to adverse outcomes, including the re-accumulation of tissue mass within the stent (or in-stent restenosis), overcoming these technical challenges is a priority for the advancement of research and development in this important clinical field. Essentially, the task is to section the stent-tissue interface with the least amount of disruption of tissue and cellular morphology. Although many methacrylate resin methodologies are successfully applied toward the study of endovascular stents by a variety of research laboratories, the exact formulations, as well as subsequent processing and sectioning methodology, remain largely coveted. In this paper, we describe in detail a methyl methacrylate resin-embedding methodology that can successfully be applied to tungsten carbide blade, as well as saw and grinding sectioning methods and transmission electron microscopy. In addition, we present a comparison of the two sectioning methodologies in terms of their effectiveness with regard to morphological, histochemical, and immunohistochemical analyses. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.
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Regulation of Components of the Brain and Cardiac Renin-angiotensin Systems by 17beta-estradiol After Myocardial Infarction in Female Rats
American Journal of Physiology. Regulatory, Integrative and Comparative Physiology.
Jul, 2006 |
Pubmed ID: 16455770 The present study tested the hypothesis that 17beta-estradiol (E2) inhibits increases in angiotensin-converting enzyme (ACE) and ANG II type 1 receptor (AT1R) in the brain and heart after myocardial infarction (MI) and, thereby, inhibits development of left ventricular (LV) dysfunction after MI. Age-matched female Wistar rats were treated as follows: 1) no surgery (ovary intact), 2) ovariectomy + subcutaneous vehicle treatment (OVX + Veh), or 3) OVX + subcutaneous administration of a high dose of E2 (OVX + high-E2). After 2 wk, rats were randomly assigned to coronary artery ligation (MI) and sham operation groups and studied after 3 wk. E2 status did not affect LV function in sham rats. At 2-3 wk after MI, impairment of LV function was similar across MI groups, as measured by echocardiography and direct LV catheterization. LV ACE mRNA abundance and activity were increased severalfold in all MI groups compared with respective sham animals and to similar levels across MI groups. In most brain nuclei, ACE and AT1R densities increased after MI. Unexpectedly, compared with the respective sham groups the relative increase was clearest (20-40%) in OVX + high-E2 MI rats, somewhat less (10-15%) in ovary-intact MI rats, and least (< 10-15%) in OVX + Veh MI rats. However, because in the sham group brain ACE and AT1R densities increased in the OVX + Veh rats and decreased in the OVX + high-E2 rats compared with the ovary-intact rats, actual ACE and AT1R densities in most brain nuclei were modestly higher (< 20%) in OVX + Veh MI rats than in the other two MI groups. Thus E2 does not inhibit upregulation of ACE in the LV after MI and amplifies the percent increases in ACE and AT1R densities in brain nuclei after MI, despite E2-induced downregulation in sham rats. Consistent with these minor variations in the tissue renin-angiotensin system, during the initial post-MI phase, E2 appears not to enhance or hinder the development of LV dysfunction.
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NM23-H2, an Estrogen Receptor Beta-associated Protein, Shows Diminished Expression with Progression of Atherosclerosis
American Journal of Physiology. Regulatory, Integrative and Comparative Physiology.
Feb, 2007 |
Pubmed ID: 17272673 While estrogen receptor (ER) profile plays an important role in response to estrogens, receptor coregulators act as critical determinants of signaling. Although the clinical effects of ovarian hormones on various normal and pathological processes are an active area of research, the exact signaling effects on, for example, the vessel wall, are incompletely understood. Hence, we sought to discover proteins that associate with ERbeta, the isoform that shows upregulated mRNA expression after arterial injury. Using a yeast two-hybrid screen we identified NM23-H2, a multifaceted metastasis suppressor candidate protein, as an ERbeta-associated protein. Although NM23-H2 was immunodetected in arteries from young subjects (27 +/- 6 yr, 14 men and 6 women) with benign intimal hyperplasia, expression was diminished in fatty streaks/atheromas and altogether absent in advanced atherosclerotic lesions. Both nm23-H2 mRNA and protein were expressed by vascular cells in vitro. Treatment with 17beta-estradiol and an ERbeta-selective agonist, diarylpropionitrile, increased protein expression of NM23-H2; an effect that was not seen with an ERalpha-selective agonist, propylpyrazole-triol. Estrogen also prompted nuclear localization of NM23-H2 protein in human coronary smooth muscle cells (SMCs). An in vitro mimic of inflammation decreased the expression of NM23-H2 in SMCs, which was restored on addition of estrogen and dependent on the estrogen receptor. In summary, we report the novel association of NM23-H2 with ERbeta and show for the first time its expression in vascular cells and demonstrate regulation of its expression and localization by estrogen. In that the abundance of NM23-H2 diminishes with both the advancement of atherosclerosis and inflammation, this ERbeta-associated protein may play an important role in mediating the vasculoprotective effects of estrogens.
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Extracellular HSP27 Acts As a Signaling Molecule to Activate NF-κB in Macrophages
Cell Stress & Chaperones.
Jan, 2013 |
Pubmed ID: 22851137 Heat shock protein 27 (HSP27) shows attenuated expression in human coronary arteries as the extent of atherosclerosis progresses. In mice, overexpression of HSP27 reduces atherogenesis, yet the precise mechanism(s) are incompletely understood. Inflammation plays a central role in atherogenesis, and of particular interest is the balance of pro- and anti-inflammatory factors produced by macrophages. As nuclear factor-kappa B (NF-κB) is a key immune signaling modulator in atherogenesis, and macrophages are known to secrete HSP27, we sought to determine if recombinant HSP27 (rHSP27) alters NF-κB signaling in macrophages. Treatment of THP-1 macrophages with rHSP27 resulted in the degradation of an inhibitor of NF-κB, IκBα, nuclear translocation of the NF-κB p65 subunit, and increased NF-κB transcriptional activity. Treatment of THP-1 macrophages with rHSP27 yielded increased expression of a variety of genes, including the pro-inflammatory factors, IL-1β, and TNF-α. However, rHSP27 also increased the expression of the anti-inflammatory factors IL-10 and GM-CSF both at the mRNA and protein levels. Our study suggests that in macrophages, activation of NF-κB signaling by rHSP27 is associated with upregulated expression and secretion of key pro- and anti-inflammatory cytokines. Moreover, we surmise that it is the balance in expression of these mediators and antagonists of inflammation, and hence atherogenesis, that yields a favorable net effect of HSP27 on the vessel wall.
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Glycogen Synthase Kinase-3β Inhibition Augments Diabetic Endothelial Progenitor Cell Abundance and Functionality Via Cathepsin B: a Novel Therapeutic Opportunity for Arterial Repair
Diabetes.
Apr, 2014 |
Pubmed ID: 24296714 Progenitor cell therapy is hindered in patients with diabetes mellitus (DM) due to cellular senescence. Glycogen synthase kinase-3β (GSK3β) activity is increased in DM, potentially exacerbating impaired cell-based therapies. Thus, we aimed to determine if and how GSK3β inhibitors (GSKi) can improve therapeutic efficacy of endothelial progenitor cells (EPC) from patients with DM. Patients with DM had fewer EPCs and increased rates of apoptosis. DM EPCs also exhibited higher levels of GSK3β activity resulting in increased levels of phosphorylated β-catenin. Proteomic profiling of DM EPCs treated with GSKi identified 37 nonredundant, differentially regulated proteins. Cathepsin B (cathB) was subsequently confirmed to be differentially regulated and showed 40% less baseline activity in DM EPCs, an effect reversed by GSKi treatment. Finally, in vivo efficacy of cell-based therapy was assessed in a xenotransplant femoral wire injury mouse model. Administration of DM EPCs reduced the intima-to-media ratio, an effect that was further augmented when DM EPCs were pretreated with GSKi yet absent when cathB was antagonized. In DM, increased basal GSK3β activity contributes to accelerated EPC cellular senescence, an effect reversed by small molecule antagonism of GSK3β, which enhanced cell-based therapy after vascular injury.
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The Evolution of Coronary Stents: a Brief Review
The Canadian Journal of Cardiology.
Jan, 2014 |
Pubmed ID: 24286961 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.
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