Publications by authors named "Jesper Hjortnaes"

30 Publications

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Controlled delivery of gold nanoparticle-coupled miRNA therapeutics an injectable self-healing hydrogel.

Nanoscale 2021 Nov 24. Epub 2021 Nov 24.

David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 500 Main Street, Cambridge 02142, MA, USA.

Differential expression of microRNAs (miRNAs) plays a role in many diseases, including cancer and cardiovascular diseases. Potentially, miRNAs could be targeted with miRNA-therapeutics. Sustained delivery of these therapeutics remains challenging. This study couples miR-mimics to PEG-peptide gold nanoparticles (AuNP) and loads these AuNP-miRNAs in an injectable, shear thinning, self-assembling polymer nanoparticle (PNP) hydrogel drug delivery platform to improve delivery. Spherical AuNPs coated with fluorescently labelled miR-214 are loaded into an HPMC-PEG-b-PLA PNP hydrogel. Release of AuNP/miRNAs is quantified, AuNP-miR-214 functionality is shown in HEK293 cells, and AuNP-miRNAs are tracked in a 3D bioprinted human model of calcific aortic valve disease (CAVD). Lastly, biodistribution of PNP-AuNP-miR-67 is assessed after subcutaneous injection in C57BL/6 mice. AuNP-miRNA release from the PNP hydrogel demonstrates a linear pattern over 5 days up to 20%. AuNP-miR-214 transfection in HEK293 results in 33% decrease of Luciferase reporter activity. In the CAVD model, AuNP-miR-214 are tracked into the cytoplasm of human aortic valve interstitial cells. Lastly, 11 days after subcutaneous injection, AuNP-miR-67 predominantly clears the liver and kidneys, and fluorescence levels are again comparable to control animals. Thus, the PNP-AuNP-miRNA drug delivery platform provides linear release of functional miRNAs and has potential for applications.
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http://dx.doi.org/10.1039/d1nr04973aDOI Listing
November 2021

Radiation Induces Valvular Interstitial Cell Calcific Response in an Model of Calcific Aortic Valve Disease.

Front Cardiovasc Med 2021 30;8:687885. Epub 2021 Aug 30.

Department of Biomedical Engineering, Soft Tissue Engineering and Mechanobiology (STEM), Eindhoven University of Technology, Eindhoven, Netherlands.

Mediastinal ionizing radiotherapy is associated with an increased risk of valvular disease, which demonstrates pathological hallmarks similar to calcific aortic valve disease (CAVD). Despite advances in radiotherapy techniques, the prevalence of comorbidities such as radiation-associated valvular disease is still increasing due to improved survival of patients receiving radiotherapy. However, the mechanisms of radiation-associated valvular disease are largely unknown. CAVD is considered to be an actively regulated disease process, mainly controlled by valvular interstitial cells (VICs). We hypothesize that radiation exposure catalyzes the calcific response of VICs and, therefore, contributes to the development of radiation-associated valvular disease. To delineate the relationship between radiation and VIC behavior (morphology, calcification, and matrix turnover), two different models were established: (1) VICs were cultured two-dimensional (2D) on coverslips in control medium (CM) or osteogenic medium (OM) and irradiated with 0, 2, 4, 8, or 16 Gray (Gy); and (2) three-dimensional (3D) hydrogel system was designed, loaded with VICs and exposed to 0, 4, or 16 Gy of radiation. In both models, a dose-dependent decrease in cell viability and proliferation was observed in CM and OM. Radiation exposure caused myofibroblast-like morphological changes and differentiation of VICs, as characterized by decreased αSMA expression. Calcification, as defined by increased alkaline phosphatase activity, was mostly present in the 2D irradiated VICs exposed to 4 Gy, while after exposure to higher doses VICs acquired a unique giant fibroblast-like cell morphology. Finally, matrix turnover was significantly affected by radiation exposure in the 3D irradiated VICs, as shown by decreased collagen staining and increased MMP-2 and MMP-9 activity. The presented work demonstrates that radiation exposure enhances the calcific response in VICs, a hallmark of CAVD. In addition, high radiation exposure induces differentiation of VICs into a terminally differentiated giant-cell fibroblast. Further studies are essential to elucidate the underlying mechanisms of these radiation-induced valvular changes.
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http://dx.doi.org/10.3389/fcvm.2021.687885DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8435633PMC
August 2021

Superimposed Tissue Formation in Human Aortic Valve Disease: Differences between Regurgitant and Stenotic Valves.

J Cardiovasc Dev Dis 2021 Jul 8;8(7). Epub 2021 Jul 8.

Department of Cardiology, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands.

The formation of superimposed tissue (SIT), a layer on top of the original valve leaflet, has been described in patients with mitral regurgitation as a major contributor to valve thickening and possibly as a result of increased mechanical stresses. However, little is known whether SIT formation also occurs in aortic valve disease. We therefore performed histological analyses to assess SIT formation in aortic valve leaflets ( = 31) from patients with aortic stenosis ( = 17) or aortic regurgitation due to aortic dilatation ( = 14). SIT was observed in both stenotic and regurgitant aortic valves, both on the ventricular and aortic sides, but with significant differences in distribution and composition. Regurgitant aortic valves showed more SIT formation in the free edge, leading to a thicker leaflet at that level, while stenotic aortic valves showed relatively more SIT formation on the aortic side of the body part of the leaflet. SIT appeared to be a highly active area, as determined by large populations of myofibroblasts, with varied extracellular matrix composition (higher collagen content in stenotic valves). Further, the identification of the SIT revealed the presence of foldings of the free edge in the diseased aortic valves. Insights into SIT regulation may further help in understanding the pathophysiology of aortic valve disease and potentially lead to the development of new therapeutic treatments.
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http://dx.doi.org/10.3390/jcdd8070079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8306480PMC
July 2021

Editorial: Heart Valve Tissue Engineering: Are We Ready for Clinical Translation?

Front Cardiovasc Med 2021 13;8:658719. Epub 2021 May 13.

Department of Biomedical Engineering and Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, Netherlands.

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http://dx.doi.org/10.3389/fcvm.2021.658719DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8155343PMC
May 2021

Myocardial Disease and Long-Distance Space Travel: Solving the Radiation Problem.

Front Cardiovasc Med 2021 12;8:631985. Epub 2021 Feb 12.

Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, Netherlands.

Radiation-induced cardiovascular disease is a well-known complication of radiation exposure. Over the last few years, planning for deep space missions has increased interest in the effects of space radiation on the cardiovascular system, as an increasing number of astronauts will be exposed to space radiation for longer periods of time. Research has shown that exposure to different types of particles found in space radiation can lead to the development of diverse cardiovascular disease via fibrotic myocardial remodeling, accelerated atherosclerosis and microvascular damage. Several underlying mechanisms for radiation-induced cardiovascular disease have been identified, but many aspects of the pathophysiology remain unclear. Existing pharmacological compounds have been evaluated to protect the cardiovascular system from space radiation-induced damage, but currently no radioprotective compounds have been approved. This review critically analyzes the effects of space radiation on the cardiovascular system, the underlying mechanisms and potential countermeasures to space radiation-induced cardiovascular disease.
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http://dx.doi.org/10.3389/fcvm.2021.631985DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7906998PMC
February 2021

Massive expansion and cryopreservation of functional human induced pluripotent stem cell-derived cardiomyocytes.

STAR Protoc 2021 Mar 9;2(1):100334. Epub 2021 Feb 9.

Utrecht Regenerative Medicine Center, Circulatory Health Laboratory, University Utrecht, Department of Cardiology, University Medical Center Utrecht, 3508 GA Utrecht, the Netherlands.

Since the discovery of human induced pluripotent stem cells (hiPSCs), numerous strategies have been established to efficiently derive cardiomyocytes from hiPSCs (hiPSC-CMs). Here, we describe a cost-effective strategy for the subsequent massive expansion (>250-fold) of high-purity hiPSC-CMs relying on two aspects: removal of cell-cell contacts and small-molecule inhibition with CHIR99021. The protocol maintains CM functionality, allows cryopreservation, and the cells can be used in downstream assays such as disease modeling, drug and toxicity screening, and cell therapy. For complete details on the use and execution of this protocol, please refer to Buikema (2020).
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http://dx.doi.org/10.1016/j.xpro.2021.100334DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7881265PMC
March 2021

Advanced Modeling to Study the Paradox of Mechanically Induced Cardiac Fibrosis.

Tissue Eng Part C Methods 2021 02;27(2):100-114

Division of Heart and Lungs, Department of Cardiothoracic Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.

In heart failure, cardiac fibrosis is the result of an adverse remodeling process. Collagen is continuously synthesized in the myocardium in an ongoing attempt of the heart to repair itself. The resulting collagen depositions act counterproductively, causing diastolic dysfunction and disturbing electrical conduction. Efforts to treat cardiac fibrosis specifically have not been successful and the molecular etiology is only partially understood. The differentiation of quiescent cardiac fibroblasts to extracellular matrix-depositing myofibroblasts is a hallmark of cardiac fibrosis and a key aspect of the adverse remodeling process. This conversion is induced by a complex interplay of biochemical signals and mechanical stimuli. Tissue-engineered 3D models to study cardiac fibroblast behavior indicate that cyclic strain can activate a myofibroblast phenotype. This raises the question how fibroblast quiescence is maintained in the healthy myocardium, despite continuous stimulation of ultimately profibrotic mechanotransductive pathways. In this review, we will discuss the convergence of biochemical and mechanical differentiation signals of myofibroblasts, and hypothesize how these affect this paradoxical quiescence. Impact statement Mechanotransduction pathways of cardiac fibroblasts seem to ultimately be profibrotic in nature, but in healthy human myocardium, cardiac fibroblasts remain quiescent, despite continuous mechanical stimulation. We propose three hypotheses that could explain this paradoxical state of affairs. Furthermore, we provide suggestions for future research, which should lead to a better understanding of fibroblast quiescence and activation, and ultimately to new strategies for the prevention and treatment of cardiac fibrosis and heart failure.
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http://dx.doi.org/10.1089/ten.TEC.2020.0298DOI Listing
February 2021

Integrative Multi-Omics Analysis in Calcific Aortic Valve Disease Reveals a Link to the Formation of Amyloid-Like Deposits.

Cells 2020 09 24;9(10). Epub 2020 Sep 24.

Department of Internal Medicine I-Cardiology, Medical Faculty, RWTH Aachen University, 52074 Aachen, Germany.

Calcific aortic valve disease (CAVD) is the most prevalent valvular heart disease in the developed world, yet no pharmacological therapy exists. Here, we hypothesize that the integration of multiple omic data represents an approach towards unveiling novel molecular networks in CAVD. Databases were searched for CAVD omic studies. Differentially expressed molecules from calcified and control samples were retrieved, identifying 32 micro RNAs (miRNA), 596 mRNAs and 80 proteins. Over-representation pathway analysis revealed platelet degranulation and complement/coagulation cascade as dysregulated pathways. Multi-omics integration of overlapping proteome/transcriptome molecules, with the miRNAs, identified a CAVD protein-protein interaction network containing seven seed genes (apolipoprotein A1 (APOA1), hemoglobin subunit β (HBB), transferrin (TF), α-2-macroglobulin (A2M), transforming growth factor β-induced protein (TGFBI), serpin family A member 1 (SERPINA1), lipopolysaccharide binding protein (LBP), inter-α-trypsin inhibitor heavy chain 3 (ITIH3) and immunoglobulin κ constant (IGKC)), four input miRNAs (miR-335-5p, miR-3663-3p, miR-21-5p, miR-93-5p) and two connector genes (amyloid beta precursor protein (APP) and transthyretin (TTR)). In a metabolite-gene-disease network, Alzheimer's disease exhibited the highest degree of betweenness. To further strengthen the associations based on the multi-omics approach, we validated the presence of APP and TTR in calcified valves from CAVD patients by immunohistochemistry. Our study suggests a novel molecular CAVD network potentially linked to the formation of amyloid-like structures. Further investigations on the associated mechanisms and therapeutic potential of targeting amyloid-like deposits in CAVD may offer significant health benefits.
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http://dx.doi.org/10.3390/cells9102164DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7600313PMC
September 2020

The relation between systemic inflammation and incident cancer in patients with stable cardiovascular disease: a cohort study.

Eur Heart J 2019 12;40(48):3901-3909

Department of Vascular Medicine, UMCU, 3584 CX Utrecht, the Netherlands.

Aims: Low-grade inflammation, measured by elevated plasma concentrations of high-sensitive C-reactive protein (CRP), is a risk factor for cardiovascular disease (CVD). There is evidence that low-grade inflammation is also related to a higher risk of cancer. The present prospective cohort study evaluates the relation between low-grade systemic inflammation and risk of cancer in patients with stable CVD.

Methods And Results: In total, 7178 patients with stable CVD and plasma CRP levels ≤10 mg/L were included. Data were linked to the Dutch national cancer registry. Cox regression models were fitted to study the relation between CRP and incident CVD and cancer. After a median follow-up time of 8.3 years (interquartile range 4.6-12.3) 1072 incident cancer diagnoses were observed. C-reactive protein concentration was related to total cancer [hazard ratio (HR) 1.35; 95% confidence interval (CI) 1.10-1.65] comparing last quintile to first quintile of CRP. Especially lung cancer, independent of histopathological subtype, was related to CRP (HR 3.39; 95% CI 2.02-5.69 comparing last to first quintile of CRP). Incidence of epithelial neoplasms and especially squamous cell neoplasms were related to CRP concentration, irrespective of anatomical location. Sensitivity analyses after excluding patients with a cancer diagnosis within 1, 2, and 5 years of follow-up showed similar results. No effect modification was observed by smoking status or time since smoking cessation (P-values for interaction > 0.05).

Conclusion: Chronic systemic low-grade inflammation, measured by CRP levels ≤10 mg/L, is a risk factor for incident cancer, markedly lung cancer, in patients with stable CVD. The relation between inflammation and incident cancer is seen in former and current smokers and is uncertain in never smokers.
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http://dx.doi.org/10.1093/eurheartj/ehz587DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6925382PMC
December 2019

Anti-fibrotic Effects of Cardiac Progenitor Cells in a 3D-Model of Human Cardiac Fibrosis.

Front Cardiovasc Med 2019 26;6:52. Epub 2019 Apr 26.

Division Heart, and Lungs, Department of Cardiothoracic Surgery, University Medical Center Utrecht, Utrecht, Netherlands.

Cardiac fibroblasts play a key role in chronic heart failure. The conversion from cardiac fibroblast to myofibroblast as a result of cardiac injury, will lead to excessive matrix deposition and a perpetuation of pro-fibrotic signaling. Cardiac cell therapy for chronic heart failure may be able to target fibroblast behavior in a paracrine fashion. However, no reliable human fibrotic tissue model exists to evaluate this potential effect of cardiac cell therapy. Using a gelatin methacryloyl hydrogel and human fetal cardiac fibroblasts (hfCF), we created a 3D model of human cardiac fibrosis. This model was used to study the possibility to modulate cellular fibrotic responses. Our approach demonstrated paracrine inhibitory effects of cardiac progenitor cells (CPC) on both cardiac fibroblast activation and collagen synthesis and revealed that continuous cross-talk between hfCF and CPC seems to be indispensable for the observed anti-fibrotic effect.
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http://dx.doi.org/10.3389/fcvm.2019.00052DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6497755PMC
April 2019

Lipoprotein(a) and Oxidized Phospholipids Promote Valve Calcification in Patients With Aortic Stenosis.

J Am Coll Cardiol 2019 05;73(17):2150-2162

British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, United Kingdom. Electronic address:

Background: Lipoprotein(a) [Lp(a)], a major carrier of oxidized phospholipids (OxPL), is associated with an increased incidence of aortic stenosis (AS). However, it remains unclear whether elevated Lp(a) and OxPL drive disease progression and are therefore targets for therapeutic intervention.

Objectives: This study investigated whether Lp(a) and OxPL on apolipoprotein B-100 (OxPL-apoB) levels are associated with disease activity, disease progression, and clinical events in AS patients, along with the mechanisms underlying any associations.

Methods: This study combined 2 prospective cohorts and measured Lp(a) and OxPL-apoB levels in patients with AS (V >2.0 m/s), who underwent baseline F-sodium fluoride (F-NaF) positron emission tomography (PET), repeat computed tomography calcium scoring, and repeat echocardiography. In vitro studies investigated the effects of Lp(a) and OxPL on valvular interstitial cells.

Results: Overall, 145 patients were studied (68% men; age 70.3 ± 9.9 years). On baseline positron emission tomography, patients in the top Lp(a) tertile had increased valve calcification activity compared with those in lower tertiles (n = 79; F-NaF tissue-to-background ratio of the most diseased segment: 2.16 vs. 1.97; p = 0.043). During follow-up, patients in the top Lp(a) tertile had increased progression of valvular computed tomography calcium score (n = 51; 309 AU/year [interquartile range: 142 to 483 AU/year] vs. 93 AU/year [interquartile range: 56 to 296 AU/year; p = 0.015), faster hemodynamic progression on echocardiography (n = 129; 0.23 ± 0.20 m/s/year vs. 0.14 ± 0.20 m/s/year] p = 0.019), and increased risk for aortic valve replacement and death (n = 145; hazard ratio: 1.87; 95% CI: 1.13 to 3.08; p = 0.014), compared with lower tertiles. Similar results were noted with OxPL-apoB. In vitro, Lp(a) induced osteogenic differentiation of valvular interstitial cells, mediated by OxPL and inhibited with the E06 monoclonal antibody against OxPL.

Conclusions: In patients with AS, Lp(a) and OxPL drive valve calcification and disease progression. These findings suggest lowering Lp(a) or inactivating OxPL may slow AS progression and provide a rationale for clinical trials to test this hypothesis.
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http://dx.doi.org/10.1016/j.jacc.2019.01.070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6494952PMC
May 2019

Identification of thoracic injuries by emergency medical services providers among trauma patients.

Injury 2019 May 6;50(5):1036-1041. Epub 2018 Dec 6.

Department of Traumatology, University Medical Centre Utrecht, Utrecht, the Netherlands; Department of Surgery, Diakonessenhuis Utrecht/Zeist/Doorn, Utrecht, the Netherlands. Electronic address:

Introduction: Severe thoracic injuries are time sensitive and adequate triage to a facility with a high-level of trauma care is crucial. The emergency medical services (EMS) providers are required to identify patients with a severe thoracic injury to transport the patient to the right hospital. However, identifying these patients on-scene is difficult. The accuracy of prehospital assessment of potential thoracic injury by EMS providers of the ground ambulances is unknown. Therefore, the aim of this study is to evaluate the diagnostic accuracy of the assessment of the EMS provider in the identification of a thoracic injury and determine predictors of a severe thoracic injury.

Methods: In this multicentre cohort study, all trauma patients aged 16 and over, transported with a ground erence standard. Prehospital variables were analysed using logistic regression to explore prehospital ambulance to a trauma centre, were evaluated. The diagnostic value of EMS provider judgment was determined using the Abbreviated Injury Scale (AIS) of ≥ 1 in the thoracic region as ref predictors of a severe thoracic injury (AIS ≥ 3).

Results: In total 2766 patients were included, of whom 465 (16.8%) sustained a thoracic injury and 210 (7.6%) a severe thoracic injury. The EMS providers' judgment had a sensitivity of 54.8% and a specificity of 92.6% for the identification of a thoracic injury. Significant independent prehospital predictors were: age, oxygen saturation, Glasgow Coma Scale, fall > 2 m, and suspicion of inhalation trauma or a thoracic injury by the EMS provider.

Conclusion: EMS providers could identify little over half of the patients with a thoracic injury. A supplementary triage protocol to identify patients with a thoracic injury could improve prehospital triage of these patients. In this supplementary protocol, age, vital signs, and mechanism criteria could be included.
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http://dx.doi.org/10.1016/j.injury.2018.12.003DOI Listing
May 2019

Engineering a 3D-Bioprinted Model of Human Heart Valve Disease Using Nanoindentation-Based Biomechanics.

Nanomaterials (Basel) 2018 May 3;8(5). Epub 2018 May 3.

Center for Interdisciplinary Cardiovascular Sciences, Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.

In calcific aortic valve disease (CAVD), microcalcifications originating from nanoscale calcifying vesicles disrupt the aortic valve (AV) leaflets, which consist of three (biomechanically) distinct layers: the fibrosa, spongiosa, and ventricularis. CAVD has no pharmacotherapy and lacks in vitro models as a result of complex valvular biomechanical features surrounding resident mechanosensitive valvular interstitial cells (VICs). We measured layer-specific mechanical properties of the human AV and engineered a three-dimensional (3D)-bioprinted CAVD model that recapitulates leaflet layer biomechanics for the first time. Human AV leaflet layers were separated by microdissection, and nanoindentation determined layer-specific Young’s moduli. Methacrylated gelatin (GelMA)/methacrylated hyaluronic acid (HAMA) hydrogels were tuned to duplicate layer-specific mechanical characteristics, followed by 3D-printing with encapsulated human VICs. Hydrogels were exposed to osteogenic media (OM) to induce microcalcification, and VIC pathogenesis was assessed by near infrared or immunofluorescence microscopy. Median Young’s moduli of the AV layers were 37.1, 15.4, and 26.9 kPa (fibrosa/spongiosa/ventricularis, respectively). The fibrosa and spongiosa Young’s moduli matched the 3D 5% GelMa/1% HAMA UV-crosslinked hydrogels. OM stimulation of VIC-laden bioprinted hydrogels induced microcalcification without apoptosis. We report the first layer-specific measurements of human AV moduli and a novel 3D-bioprinted CAVD model that potentiates microcalcification by mimicking the native AV mechanical environment. This work sheds light on valvular mechanobiology and could facilitate high-throughput drug-screening in CAVD.
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http://dx.doi.org/10.3390/nano8050296DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5977310PMC
May 2018

Oxygen-Generating Photo-Cross-Linkable Hydrogels Support Cardiac Progenitor Cell Survival by Reducing Hypoxia-Induced Necrosis.

ACS Biomater Sci Eng 2017 Sep 20;3(9):1964-1971. Epub 2016 Jun 20.

Biomaterials Innovation Research Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Cambridge, Massachusetts 02139, United States.

Oxygen is essential to cell survival and tissue function. Not surprisingly, ischemia resulting from myocardial infarction induces cell death and tissue necrosis. Attempts to regenerate myocardial tissue with cell based therapies exacerbate the hypoxic stress by further increasing the metabolic burden. In consequence, implanted tissue engineered cardiac tissues suffer from hypoxia-induced cell death. Here, we report on the generation of oxygen-generating hydrogels composed of calcium peroxide (CPO) laden gelatin methacryloyl (GelMA). CPO-GelMA hydrogels released significant amounts of oxygen for over a period of 5 days under hypoxic conditions (1% O). The released oxygen proved sufficient to relieve the metabolic stress of cardiac side population cells that were encapsulated within CPO-GelMA hydrogels. In particular, incorporation of CPO in GelMA hydrogels strongly enhanced cell viability as compared to GelMA-only hydrogels. Importantly, CPO-based oxygen generation reduced cell death by limiting hypoxia-induced necrosis. The current study demonstrates that CPO based oxygen-generating hydrogels could be used to transiently provide oxygen to cardiac cells under ischemic conditions. Therefore, oxygen generating materials such as CPO-GelMA can improve cell-based therapies aimed at treatment or regeneration of infarcted myocardial tissue.
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http://dx.doi.org/10.1021/acsbiomaterials.6b00109DOI Listing
September 2017

Engineered 3D Cardiac Fibrotic Tissue to Study Fibrotic Remodeling.

Adv Healthc Mater 2017 Jun 12;6(11). Epub 2017 May 12.

Biomaterials Innovation Research Center, Division of Engineering in Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 65 Landsdowne Street, Cambridge, MA, 02139, USA.

Activation of cardiac fibroblasts into myofibroblasts is considered to play an essential role in cardiac remodeling and fibrosis. A limiting factor in studying this process is the spontaneous activation of cardiac fibroblasts when cultured on two-dimensional (2D) culture plates. In this study, a simplified three-dimensional (3D) hydrogel platform of contractile cardiac tissue, stimulated by transforming growth factor-β1 (TGF-β1), is presented to recapitulate a fibrogenic microenvironment. It is hypothesized that the quiescent state of cardiac fibroblasts can be maintained by mimicking the mechanical stiffness of native heart tissue. To test this hypothesis, a 3D cell culture model consisting of cardiomyocytes and cardiac fibroblasts encapsulated within a mechanically engineered gelatin methacryloyl hydrogel, is developed. The study shows that cardiac fibroblasts maintain their quiescent phenotype in mechanically tuned hydrogels. Additionally, treatment with a beta-adrenergic agonist increases beating frequency, demonstrating physiologic-like behavior of the heart constructs. Subsequently, quiescent cardiac fibroblasts within the constructs are activated by the exogenous addition of TGF-β1. The expression of fibrotic protein markers (and the functional changes in mechanical stiffness) in the fibrotic-like tissues are analyzed to validate the model. Overall, this 3D engineered culture model of contractile cardiac tissue enables controlled activation of cardiac fibroblasts, demonstrating the usability of this platform to study fibrotic remodeling.
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http://dx.doi.org/10.1002/adhm.201601434DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5545804PMC
June 2017

Modeling the Human Scarred Heart In Vitro: Toward New Tissue Engineered Models.

Adv Healthc Mater 2017 Feb 1;6(3). Epub 2016 Dec 1.

Department of Cardiology, University Medical Center Utrecht, 3584CX, Utrecht, The Netherlands.

Cardiac remodeling is critical for effective tissue healing, however, excessive production and deposition of extracellular matrix components contribute to scarring and failing of the heart. Despite the fact that novel therapies have emerged, there are still no lifelong solutions for this problem. An urgent need exists to improve the understanding of adverse cardiac remodeling in order to develop new therapeutic interventions that will prevent, reverse, or regenerate the fibrotic changes in the failing heart. With recent advances in both disease biology and cardiac tissue engineering, the translation of fundamental laboratory research toward the treatment of chronic heart failure patients becomes a more realistic option. Here, the current understanding of cardiac fibrosis and the great potential of tissue engineering are presented. Approaches using hydrogel-based tissue engineered heart constructs are discussed to contemplate key challenges for modeling tissue engineered cardiac fibrosis and to provide a future outlook for preclinical and clinical applications.
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http://dx.doi.org/10.1002/adhm.201600571DOI Listing
February 2017

Simulation of early calcific aortic valve disease in a 3D platform: A role for myofibroblast differentiation.

J Mol Cell Cardiol 2016 05 17;94:13-20. Epub 2016 Mar 17.

Center of Excellence in Vascular Biology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA; Center for Interdisciplinary Cardiovascular Sciences, Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA. Electronic address:

Purpose: Calcific aortic valve disease (CAVD) is the most prevalent valve disease in the Western world. Recent difficulty in translating experimental results on statins to beneficial clinical effects warrants the need for understanding the role of valvular interstitial cells (VICs) in CAVD. In two-dimensional culture conditions, VICs undergo spontaneous activation similar to pathological differentiation, which intrinsically limits the use of in vitro models to study CAVD. Here, we hypothesized that a three-dimensional (3D) culture system based on naturally derived extracellular matrix polymers, mimicking the microenvironment of native valve tissue, could serve as a physiologically relevant platform to study the osteogenic differentiation of VICs.

Principal Results: Aortic VICs loaded into 3D hydrogel constructs maintained a quiescent phenotype, similar to healthy human valves. In contrast, osteogenic environment induced an initial myofibroblast differentiation (hallmarked by increased alpha smooth muscle actin [α-SMA] expression), followed by an osteoblastic differentiation, characterized by elevated Runx2 expression, and subsequent calcific nodule formation recapitulating CAVD conditions. Silencing of α-SMA under osteogenic conditions diminished VIC osteoblast-like differentiation and calcification, indicating that a VIC myofibroblast-like phenotype may precede osteogenic differentiation in CAVD.

Major Conclusions: Using a 3D hydrogel model, we simulated events that occur during early CAVD in vivo and provided a platform to investigate mechanisms of CAVD. Differentiation of valvular interstitial cells to myofibroblasts was a key mechanistic step in the process of early mineralization. This novel approach can provide important insight into valve pathobiology and serve as a promising tool for drug screening.
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http://dx.doi.org/10.1016/j.yjmcc.2016.03.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4906202PMC
May 2016

Myocardial Infarction Alters Adaptation of the Tethered Mitral Valve.

J Am Coll Cardiol 2016 Jan;67(3):275-87

Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; Leducq Transatlantic Mitral Network, Fondation Leducq, Paris, France; Departments of Cardiology and Cardiovascular Surgery, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, University Paris Descartes, INSERM Unit 633, Paris, France. Electronic address:

Background: In patients with myocardial infarction (MI), leaflet tethering by displaced papillary muscles induces mitral regurgitation (MR), which doubles mortality. Mitral valves (MVs) are larger in such patients but fibrosis sets in counterproductively. The investigators previously reported that experimental tethering alone increases mitral valve area in association with endothelial-to-mesenchymal transition.

Objectives: The aim of this study was to explore the clinically relevant situation of tethering and MI, testing the hypothesis that ischemic milieu modifies mitral valve adaptation.

Methods: Twenty-three adult sheep were examined. Under cardiopulmonary bypass, the papillary muscle tips in 6 sheep were retracted apically to replicate tethering, short of producing MR (tethered alone). Papillary muscle retraction was combined with apical MI created by coronary ligation in another 6 sheep (tethered plus MI), and left ventricular remodeling was limited by external constraint in 5 additional sheep (left ventricular constraint). Six sham-operated sheep were control subjects. Diastolic mitral valve surface area was quantified by 3-dimensional echocardiography at baseline and after 58 ± 5 days, followed by histopathology and flow cytometry of excised leaflets.

Results: Tethered plus MI leaflets were markedly thicker than tethered-alone valves and sham control subjects. Leaflet area also increased significantly. Endothelial-to-mesenchymal transition, detected as α-smooth muscle actin-positive endothelial cells, significantly exceeded that in tethered-alone and control valves. Transforming growth factor-β, matrix metalloproteinase expression, and cellular proliferation were markedly increased. Uniquely, tethering plus MI showed endothelial activation with vascular adhesion molecule expression, neovascularization, and cells positive for CD45, considered a hematopoietic cell marker. Tethered plus MI findings were comparable with external ventricular constraint.

Conclusions: MI altered leaflet adaptation, including a profibrotic increase in valvular cell activation, CD45-positive cells, and matrix turnover. Understanding cellular and molecular mechanisms underlying leaflet adaptation and fibrosis could yield new therapeutic opportunities for reducing ischemic MR.
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http://dx.doi.org/10.1016/j.jacc.2015.10.092DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5099077PMC
January 2016

Comparative Histopathological Analysis of Mitral Valves in Barlow Disease and Fibroelastic Deficiency.

Semin Thorac Cardiovasc Surg 2016 Winter;28(4):757-767. Epub 2016 Sep 5.

Department of Medicine, Center of Excellence in Vascular Biology, Brigham and Women׳s Hospital, Harvard Medical School, Boston, Massachusetts; Center for Interdisciplinary Cardiovascular Sciences, Brigham and Women׳s Hospital, Harvard Medical School, Boston, Massachusetts. Electronic address:

Whether Barlow disease (BD) and fibroelastic deficiency (FED), the main causes of mitral valve prolapse (MVP), should be considered 2 distinct diseases remains unknown. Mitral valves from patients who required surgery for severe mitral regurgitation due to degenerative nonsyndromic MVP were analyzed. Intraoperative diagnosis of BD or FED was based on leaflet redundancy and thickness, number of segments involved, and annular dimension. The removed medial scallop of the posterior leaflet and attached chordae were used for histopathological and immunohistological assessment. Histologically, compared to normal controls (n = 3), BD (n = 14), and FED (n = 9) leaflets demonstrated an altered architecture and increased thickness. Leaflet thickness was greater and chordae thickness lower in BD than FED (P < 0.0001). In BD, increased thickness was owing to spongiosa expansion (proteoglycan accumulation) and intimal thickening on fibrosa and atrialis; in FED, local thickening was predominant on the fibrosa side, with accumulation of proteoglycan-like material around the chordae. Collagen accumulation was observed in FED leaflets and chords and decreased in BD. Fragmented elastin fibers were present in BD and FED; elastin decreased in BD but increased in FED leaflets and around chordae. Activated myofibroblasts accumulate in both diseased leaflets and chords, but more abundantly in FED chordae (P < 0.0001), independently of age, suggesting a role of these cells in chordal rupture. There were more CD34-positive cells in BD leaflets and in FED chordae (P < 0.01). In BD leaflets (but not chordae) proliferative Ki67-positive cells were more abundant (P < 0.01) and matrix metalloproteinase 2 levels were increased (P < 0.01) indicating tissue remodeling. Upregulation of transforming growth factor beta and pERK signaling pathways was evident in both diseases but more prominent in FED leaflets (continued on next page)(P < 0.001), with pERK upregulation in FED chordae (P < 0.0001). Most cellular and signaling markers were negligible in control valves. Quantitative immunohistopathological analyses demonstrated distinct changes between BD and FED valves: predominant matrix degradation in BD and increased profibrotic signaling pathways in FED, indicating that BD and FED are 2 different entities. These results may pave the way for genetic studies of MVP and development of preventive drug therapies.
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http://dx.doi.org/10.1053/j.semtcvs.2016.08.015DOI Listing
July 2017

Valvular interstitial cells suppress calcification of valvular endothelial cells.

Atherosclerosis 2015 Sep 17;242(1):251-260. Epub 2015 Jul 17.

Center of Excellence in Vascular Biology, Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston.

Background: Calcific aortic valve disease (CAVD) is the most common heart valve disease in the Western world. We previously proposed that valvular endothelial cells (VECs) replenish injured adult valve leaflets via endothelial-to-mesenchymal transformation (EndMT); however, whether EndMT contributes to valvular calcification is unknown. We hypothesized that aortic VECs undergo osteogenic differentiation via an EndMT process that can be inhibited by valvular interstitial cells (VICs).

Approach And Results: VEC clones underwent TGF-β1-mediated EndMT, shown by significantly increased mRNA expression of the EndMT markers α-SMA (5.3 ± 1.2), MMP-2 (13.5 ± 0.6) and Slug (12 ± 2.1) (p < 0.05), (compared to unstimulated controls). To study the effects of VIC on VEC EndMT, clonal populations of VICs were derived from the same valve leaflets, placed in co-culture with VECs, and grown in control/TGF-β1 supplemented media. In the presence of VICs, EndMT was inhibited, shown by decreased mRNA expression of α-SMA (0.1 ± 0.5), MMP-2 (0.1 ± 0.1), and Slug (0.2 ± 0.2) (p < 0.05). When cultured in osteogenic media, VECs demonstrated osteogenic changes confirmed by increase in mRNA expression of osteocalcin (8.6 ± 1.3), osteopontin (3.7 ± 0.3), and Runx2 (5.5 ± 1.5). The VIC presence inhibited VEC osteogenesis, demonstrated by decreased expression of osteocalcin (0.4 ± 0.1) and osteopontin (0.2 ± 0.1) (p < 0.05). Time course analysis suggested that EndMT precedes osteogenesis, shown by an initial increase of α-SMA and MMP-2 (day 7), followed by an increase of osteopontin and osteocalcin (day 14).

Conclusions: The data indicate that EndMT may precede VEC osteogenesis. This study shows that VICs inhibit VEC EndMT and osteogenesis, indicating the importance of VEC-VIC interactions in valve homeostasis.
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http://dx.doi.org/10.1016/j.atherosclerosis.2015.07.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4546848PMC
September 2015

Mortality after cardiac surgery in patients with liver cirrhosis classified by the Child-Pugh score.

Interact Cardiovasc Thorac Surg 2015 Apr 22;20(4):520-30. Epub 2015 Jan 22.

Department of Cardiothoracic Surgery, University Medical Centre Utrecht, Utrecht, Netherlands.

Liver cirrhosis is a known risk factor for postoperative mortality in patients undergoing cardiac surgery. Clinical assessment of liver cirrhosis using the widely accepted Child-Pugh (CP) score is thus vital for evaluation of surgical options and perioperative care. However, detailed mortality rates as a consequence of liver cirrhosis are unclear. This review aimed to stratify the risk of short-term (<30 days) and overall (up to 10 years) mortality after cardiac surgery in patients with liver cirrhosis, classified by the CP score. Thus, PubMed, Embase, CINAHL and the Cochrane Library were systematically reviewed by two independent investigators for studies published up to February 2014, in which mortality in cirrhotic patients, classified by the CP classification, undergoing cardiac surgery was evaluated postoperatively. A total of 993 articles were identified. After critical appraisal of 21 articles, 19 were selected for final analysis. Weighted short-term mortality of cirrhotic patients undergoing cardiac surgery was 19.3% [95% confidence interval (CI): 16.4-22.5%]. Across the different CP groups, short-term mortality appeared to be 9.0% (95% CI: 6.6-12.2%), 37.7% (95% CI: 30.8-44.3%) and 52.0% (95% CI: 33.5-70.0%) in Groups A, B and C, respectively. Weighted overall mortality within 1 year was 42.0% (95% CI: 36.0-48.3%) in all cirrhotic patients. Subdivided in groups, overall mortality within that 1 year was 27.2% (95% CI: 20.9-34.7%), 66.2% (95% CI: 54.3-76.3%) and 78.9% (95% CI: 56.1-92.1%) in Groups A, B and C, respectively. In conclusion, short-term mortality is considerably increased in patients with liver cirrhosis CP class B and C. Overall mortality is significantly high in all classes of liver cirrhosis.
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http://dx.doi.org/10.1093/icvts/ivu438DOI Listing
April 2015

Directing valvular interstitial cell myofibroblast-like differentiation in a hybrid hydrogel platform.

Adv Healthc Mater 2015 Jan 24;4(1):121-30. Epub 2014 Jun 24.

Biomaterials Innovation Research Center, Division of Biomedical Engineering, Department of MedicineBrigham and Women's Hospital, Harvard Medical School, Boston, MA, USA; Center of Excellence in Vascular Biology, Department of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA; Department of Cardiothoracic Surgery, University Medical Center Utrecht, Utrecht, The Netherlands.

Three dimensional (3D) hydrogel platforms are powerful tools, providing controllable, physiologically relevant microenvironments that could aid in understanding how various environmental factors direct valvular interstitial cell (VIC) phenotype. Continuous activation of VICs and their transformation from quiescent fibroblast to activated myofibroblast phenotype is considered to be an initiating event in the onset of valve disease. However, the relative contribution VIC phenotypes is poorly understood since most 2D culture systems lead to spontaneous VIC myofibroblastic activation. Here, a hydrogel platform composed of photocrosslinkable versions of native valvular extracellular matrix components-methacrylated hyaluronic acid (HAMA) and methacrylated gelatin (GelMA)-is proposed as a 3D culture system to study VIC phenotypic changes. These results show that VIC myofibroblast-like differentiation occurs spontaneously in mechanically soft GelMA hydrogels. Conversely, differentiation of VICs encapsulated in HAMA-GelMA hybrid hydrogels, does not occur spontaneously and requires exogenous delivery of TGFβ1, indicating that hybrid hydrogels can be used to study cytokine-dependent transition of VICs. This study demonstrates that a hybrid hydrogel platform can be used to maintain a quiescent VIC phenotype and study the effect of environmental cues on VIC activation, which will aid in understanding pathobiology of valvular disease.
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http://dx.doi.org/10.1002/adhm.201400029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4276556PMC
January 2015

Tri-layered elastomeric scaffolds for engineering heart valve leaflets.

Biomaterials 2014 Sep 16;35(27):7774-85. Epub 2014 Jun 16.

Biomaterials Innovation Research Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, 65 Landsdowne Street, Cambridge, MA 02139, USA; Wyss Institute for Biologically Inspired Engineering, Harvard University, 3 Blackfan Circle, Boston, MA 02115, USA; Department of Physics, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21569, Saudi Arabia. Electronic address:

Tissue engineered heart valves (TEHVs) that can grow and remodel have the potential to serve as permanent replacements of the current non-viable prosthetic valves particularly for pediatric patients. A major challenge in designing functional TEHVs is to mimic both structural and anisotropic mechanical characteristics of the native valve leaflets. To establish a more biomimetic model of TEHV, we fabricated tri-layered scaffolds by combining electrospinning and microfabrication techniques. These constructs were fabricated by assembling microfabricated poly(glycerol sebacate) (PGS) and fibrous PGS/poly(caprolactone) (PCL) electrospun sheets to develop elastic scaffolds with tunable anisotropic mechanical properties similar to the mechanical characteristics of the native heart valves. The engineered scaffolds supported the growth of valvular interstitial cells (VICs) and mesenchymal stem cells (MSCs) within the 3D structure and promoted the deposition of heart valve extracellular matrix (ECM). MSCs were also organized and aligned along the anisotropic axes of the engineered tri-layered scaffolds. In addition, the fabricated constructs opened and closed properly in an ex vivo model of porcine heart valve leaflet tissue replacement. The engineered tri-layered scaffolds have the potential for successful translation towards TEHV replacements.
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http://dx.doi.org/10.1016/j.biomaterials.2014.04.039DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4114056PMC
September 2014

Hydrogel bioprinted microchannel networks for vascularization of tissue engineering constructs.

Lab Chip 2014 Jul 23;14(13):2202-11. Epub 2014 May 23.

Biomaterials Research Unit, Faculty of Dentistry, University of Sydney, Sydney, NSW 2010, Australia.

Vascularization remains a critical challenge in tissue engineering. The development of vascular networks within densely populated and metabolically functional tissues facilitate transport of nutrients and removal of waste products, thus preserving cellular viability over a long period of time. Despite tremendous progress in fabricating complex tissue constructs in the past few years, approaches for controlled vascularization within hydrogel based engineered tissue constructs have remained limited. Here, we report a three dimensional (3D) micromolding technique utilizing bioprinted agarose template fibers to fabricate microchannel networks with various architectural features within photocrosslinkable hydrogel constructs. Using the proposed approach, we were able to successfully embed functional and perfusable microchannels inside methacrylated gelatin (GelMA), star poly(ethylene glycol-co-lactide) acrylate (SPELA), poly(ethylene glycol) dimethacrylate (PEGDMA) and poly(ethylene glycol) diacrylate (PEGDA) hydrogels at different concentrations. In particular, GelMA hydrogels were used as a model to demonstrate the functionality of the fabricated vascular networks in improving mass transport, cellular viability and differentiation within the cell-laden tissue constructs. In addition, successful formation of endothelial monolayers within the fabricated channels was confirmed. Overall, our proposed strategy represents an effective technique for vascularization of hydrogel constructs with useful applications in tissue engineering and organs on a chip.
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http://dx.doi.org/10.1039/c4lc00030gDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4201051PMC
July 2014

Visualizing novel concepts of cardiovascular calcification.

Trends Cardiovasc Med 2013 Apr 3;23(3):71-9. Epub 2013 Jan 3.

Cardiovascular Medicine, Brigham & Women's Hospital, Harvard Medical School, 77 Avenue Louis Pasteur, NRB741J, Boston, MA 02115, USA.

Cardiovascular calcification is currently viewed as an active disease process similar to embryonic bone formation. Cardiovascular calcification mainly affects the aortic valve and arteries and is associated with increased mortality risk. Aortic valve and arterial calcification share similar risk factors, including age, gender, diabetes, chronic renal disease, and smoking. However, the exact cellular and molecular mechanism of cardiovascular calcification is unknown. Late-stage cardiovascular calcification can be visualized with conventional imaging modalities such as echocardiography and computed tomography. However, these modalities are limited in their ability to detect the development of early calcification and the progression of calcification until advanced tissue mineralization is apparent. Due to the subsequent late diagnosis of cardiovascular calcification, treatment is usually comprised of invasive interventions such as surgery. The need to understand the process of calcification is therefore warranted and requires new imaging modalities which are able to visualize early cardiovascular calcification. This review focuses on the use of new imaging techniques to visualize novel concepts of cardiovascular calcification.
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http://dx.doi.org/10.1016/j.tcm.2012.09.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3626075PMC
April 2013

Surgical treatment of residual systolic anterior motion after otherwise successful percutaneous transluminal septal myocardial ablation: a case report.

J Thorac Cardiovasc Surg 2012 Aug 11;144(2):506-8. Epub 2012 Jan 11.

Division of Heart and Lungs, Department of Cardiothoracic Surgery, University Medical Center Utrecht, Utrecht, The Netherlands.

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http://dx.doi.org/10.1016/j.jtcvs.2011.11.020DOI Listing
August 2012

Arterial and aortic valve calcification inversely correlates with osteoporotic bone remodelling: a role for inflammation.

Eur Heart J 2010 Aug 2;31(16):1975-84. Epub 2010 Jul 2.

Center for Molecular Imaging Research, Massachusetts General Hospital, Boston, MA, USA.

Aims: Westernized countries face a growing burden of cardiovascular calcification and osteoporosis. Despite its vast clinical significance, the precise nature of this reciprocal relationship remains obscure. We hypothesize that cardiovascular calcification progresses with inflammation and inversely correlates with bone tissue mineral density (TMD).

Methods And Results: Arterial, valvular, and bone metabolism were visualized using near-infrared fluorescence (NIRF) molecular imaging agents, targeting macrophages and osteogenesis. We detected significant arterial and aortic valve calcification in apoE(-/-) mice with or without chronic renal disease (CRD, 30 weeks old; n = 28), correlating with the severity of atherosclerosis. We demonstrated decreases in osteogenic activity in the femurs of apoE(-/-) mice when compared with WT mice, which was further reduced with CRD. Three-dimensional micro-computed tomography imaging of the cortical and cancellous regions of femurs quantified structural remodelling and reductions in TMD in apoE(-/-) and CRD apoE(-/-) mice. We established significant correlations between arterial and valvular calcification and loss of TMD (R(2) = 0.67 and 0.71, respectively). Finally, we performed macrophage-targeted molecular imaging to explore a link between inflammation and osteoporosis in vivo. Although macrophage burden, visualized as uptake of NIRF-conjugated iron nanoparticles, was directly related to the degree of arterial and valvular inflammation and calcification, the same method inversely correlated inflammation with TMD (R(2) = 0.73; 0.83; 0.75, respectively).

Conclusion: This study provides direct in vivo evidence that in arteries and aortic valves, macrophage burden and calcification associate with each other, whereas inflammation inversely correlates with bone mineralization. Thus, understanding inflammatory signalling mechanisms may offer insight into selective abrogation of divergent calcific phenomena.
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http://dx.doi.org/10.1093/eurheartj/ehq237DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2921509PMC
August 2010

Intravital molecular imaging of small-diameter tissue-engineered vascular grafts in mice: a feasibility study.

Tissue Eng Part C Methods 2010 Aug;16(4):597-607

Center for Molecular Imaging Research , Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.

Objectives: Creating functional small-diameter tissue-engineered blood vessels has not been successful to date. Moreover, the processes underlying the in vivo remodeling of these grafts and the fate of cells seeded onto scaffolds remain unclear. Here we addressed these unmet scientific needs by using intravital molecular imaging to monitor the development of tissue-engineered vascular grafts (TEVG) implanted in mouse carotid artery.

Methods And Results: Green fluorescent protein-labeled human bone marrow-derived mesenchymal stem cells and cord blood-derived endothelial progenitor cells were seeded on polyglycolic acid-poly-L-lactic acid scaffolds to construct small-caliber TEVG that were subsequently implanted in the carotid artery position of nude mice (n = 9). Mice were injected with near-infrared agents and imaged using intravital fluorescence microscope at 0, 7, and 35 days to validate in vivo the TEVG remodeling capability (Prosense680; VisEn, Woburn, MA) and patency (Angiosense750; VisEn). Imaging coregistered strong proteolytic activity and blood flow through anastomoses at both 7 and 35 days postimplantation. In addition, image analyses showed green fluorescent protein signal produced from mesenchymal stem cell up to 35 days postimplantation. Comprehensive correlative histopathological analyses corroborated intravital imaging findings.

Conclusions: Multispectral imaging offers simultaneous characterization of in vivo remodeling enzyme activity, functionality, and cell fate of viable small-caliber TEVG.
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http://dx.doi.org/10.1089/ten.TEC.2009.0466DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7875113PMC
August 2010

Translating autologous heart valve tissue engineering from bench to bed.

Tissue Eng Part B Rev 2009 Sep;15(3):307-17

Division of Heart & Lungs, Department of Clinical and Experimental Cardio-Thoracic Surgery, University Medical Center Utrecht, Utrecht, The Netherlands.

Tissue engineering is currently being actively investigated to ascertain if it can offer an alternative to prosthetic aortic heart valves that may overcome the current limitations of prosthetic aortic heart valves while at the same time conferring the advantages of a living autologous structure, such as biocompatibility, the capacity to grow, repair, and remodel. In vitro studies have shown tissue-engineered heart valves to have adequate structural and functional properties, indicating a promising future for heart valve tissue engineering. However, criteria are required to be able to evaluate autologous heart valves and to deem them satisfactory for clinical use. Preclinical animal studies are needed, as a precursor to long-term in vivo follow-up studies, to establish such criteria. The first challenge is to find appropriate techniques to evaluate the functionality of tissue-engineered heart valves in vivo without having to kill the animal. As such, the development of such noninvasive techniques that are able to assess the functionality of tissue-engineered heart valves is the next step in translational research. This review discusses methods of evaluating the functionality of autologous heart valves when translating from in vitro to in vivo studies and determines potential assessment criteria imperative to achieve clinical applicability of tissue-engineered heart valves in aortic valve replacement.
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http://dx.doi.org/10.1089/ten.TEB.2008.0565DOI Listing
September 2009

Serum uric acid levels and risk for vascular diseases in patients with metabolic syndrome.

J Rheumatol 2007 Sep 1;34(9):1882-7. Epub 2007 Aug 1.

Department of Internal Medicine, Vascular Medicine Section, University Medical Centre, Utrecht, The Netherlands.

Objective: Gout and increased serum uric acid (SUA) levels are often seen in patients with components of the metabolic syndrome. Increased SUA levels are associated with increased vascular risk, as is the metabolic syndrome. We investigated the association between SUA levels and the metabolic syndrome in a population of patients with manifest vascular disease to determine whether SUA levels convey an independent risk for vascular disease in patients with the metabolic syndrome.

Methods: A nested case-cohort study of 431 patients with 220 cases with a new vascular event during followup, originating from the Second Manifestations of Arterial Disease (SMART) study. All patients had manifest vascular diseases, consisting of cerebral, coronary, or peripheral artery disease or abdominal aortic aneurysm. The relationship of SUA with the metabolic syndrome was analyzed with linear regression and adjusted for age, sex, creatinine clearance, and alcohol and diuretic use. The relationship of SUA levels with new vascular disease was investigated with Cox regression and adjusted for age and sex.

Results: The metabolic syndrome was present in 50% of patients. SUA levels were higher in 214 patients with the metabolic syndrome than in 217 patients without (0.36 +/- 0.08 mmol/l vs 0.32 +/- 0.09 mmol/l). SUA concentrations increased with the number of components of the metabolic syndrome (0.30 mmol/l to 0.38 mmol/l) adjusted for age, sex, creatinine clearance, and alcohol and diuretic use. Increased SUA concentrations were independently associated with risk for vascular events in patients without the metabolic syndrome (age and sex adjusted hazard ratio 2.4, 95% CI 1.0-5.5), in contrast to patients with the metabolic syndrome (adjusted hazard ratio 1.9, 95% CI 1.0-3.9).

Conclusion: Elevated SUA levels are strongly associated with the metabolic syndrome, yet are not an independent risk factor for vascular disease in patients with the metabolic syndrome. In patients without the metabolic syndrome, elevated SUA levels are associated with increased risk for vascular disease.
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September 2007
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