Jabe Best

BS, Allegheny College, 2003

Faculty Trainer:
Timothy J. Kamp, MD, Ph.D., Associate Professor, Cardiovascular Medicine

Cellular and Molecular Arrhythmia Research Program; focus on regulation of cardiac L-type Ca²⁺ channel

Research Statement
Calcium influx through L-type Ca²⁺ channels plays a vital role in many aspects of cardiac physiology, regulating excitation-contraction coupling, contributing to the plateau phase of the action potential, serving as a second messenger in signaling cascades, and influencing gene transcription. Not surprisingly then, alterations in the function and density of L-type Ca²⁺ channels have been implicated in several diseases including atrial fibrillation, ischemic heart disease, heart failure, and long QT syndrome. The channels themselves are targets of multiple signaling pathways including the b-adrenergic system, as stimulation of b1 and b2 adrenergic receptors leads to increased calcium current through L-type channels (I_Ca,L). In failing myocardium, not only is the b–adrenergic regulation of I_Ca,L altered, but the number of channels at the membrane is drastically reduced. Despite this, relatively little is known about the trafficking and targeting of L-type Ca²⁺ channels and relevant signaling molecules in cardiomyocytes. Membrane trafficking of a growing number of ion channels has been shown to be under the regulation of small GTPases such as the Rab family of GTPases. Part of my research will use a variety of electrophysiological, biochemical, and optical techniques to study the role of small GTPases in proper membrane targeting of L-type Ca²⁺ channels.

An additional interest relates to previous work in our lab that has shown that a subpopulation of L-type Ca²⁺ channels exist in caveolae, flask-shaped invaginations of the plasma membrane enriched in caveolin, cholesterol, and sphingolipids that serve as localized signaling centers. Some studies in non-cardiac systems have suggested that caveolae are quite dynamic, with cycling of caveolar vesicles to and from the membrane. Using fluorescent imaging techniques, I hope to characterize the trafficking of caveolar vesicles in cardiac myocytes and explore the potential implications regarding L-type Ca²⁺ channel function and regulation.

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Nathan Evans

BA, Ripon College, Chemistry/Biology, 2000

Faculty Trainer:
Jeffery W. Walker, Ph.D., Professor, Physiology

Cardiovascular Signaling

Research Statement
In the cardiovascular system, endothelin-1 regulates critical physiological functions including heart contractility, growth and vascular constriction and dilation. It has also been suggested to play a role related to cardiac hypertrophy, remodeling and subsequent heart failure. Therefore, understanding the intricacies of endothelin signaling is critical to understanding the signaling pathways that lead to heart failure. Endothelins bind two distinct class A G-protein coupled receptor (GPCR) subtypes, the endothelin A and B receptors (ET_AR, ET_BR). Despite co-expression of the ET_AR and ET_BR in a variety of cells including cells in endothelial and cardiac tissue, little is known about their dimerization capabilities. Of particular interest is that dimerization may fundamentally alter receptor function as noted in subtypes of cardiac adrenergic receptors, as well as opioid receptors. The fact that many GPCRs have altered rates and pathways of internalization and cross-internalize upon ligand binding suggests a dramatic consequence for dimers. Therefore, my research is dedicated to understanding the interaction(s) between the endothelin receptors in order to provide valuable insight into receptor function.

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Elyssa Monzack

BS, Brown University, 2005

Faculty Trainer:
Kristyn S. Masters, Ph.D., Assistant Professor, Biomedical Engineering

Heart Valve Disease; Heart Valve Tissue Engineering

Research Statement
Calcification is the leading cause of native and bioprosthetic heart valve failure, and the number of people who need valve transplants is increasing every year. The mechanisms of calcific aortic stenosis are poorly understood, but statins (3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors), a drug class best known for its ability to block the enzyme in the liver that is responsible for the catalysis of cholesterol, may prove beneficial for the treatment of calcific aortic stenosis. Our lab has demonstrated that certain components of the extracellular matrix (ECM) and specific cytokines create a pro-calcific environment in cultures of valvular interstitial cells (VICs). By combining the power of statins, which may provide an anti-calcific environment, with pro-calcific culture conditions that mimic native valvular disease, I will be able to create 2-D and 3-D disease models. Through these models, I will investigate under-studied, intermediate stages of calcification, and consequently, at which stages the statins will be able to control or reverse disease progression. In order to fully understand the valvular effects of statins, I will be conducting an in vitro investigation of which concentration, timing, and treatment period for statin administration is most effective at preventing or ameliorating calcification in VICs, as well as the environments in which the statins are able to positively affect VIC calcification. My research should provide information that is clinically relevant in terms of its applications for drug treatment, and will also help to advance both biomaterials and basic science. Biomaterials and valve tissue engineering would benefit from the knowledge gained regarding the specific ECM and pharmaceutical environments leading to either healthy or diseased VICs, and basic science would gain an initial look into the mechanisms of the intermediate stages of aortic valve calcification.

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Karien J. Rodriguez

BS, Chemical Engineering, University of Puerto Rico-Mayaguez, 2004

Faculty Trainer:
Kristyn S. Masters, Ph.D., Assistant Professor, Biomedical Engineering

Biomaterials/Tissue Engineering

Research Statement
Much attention has been directed toward the development of tissue-engineered heart valves, which have the potential to circumvent serious problems associated with existing valve replacements. Biomimetic scaffolds are believed to offer the most promising environment for the creation of tissue engineered valves using valvular interstitial cells (VICs). Data recently generated in our lab demonstrate that the composition of the extracellular matrix (ECM) upon which VICs are cultured has a profound impact upon VIC phenotype and the formation of calcific nodules in VIC cultures. Thus, currently my goal is to investigate how native extracellular proteins and growth factors regulate VIC function, hence providing valuable information about not only the appropriateness of a biomimetic scaffold environment, but also valvular disease progression and treatment. The hypothesis driving this research is that the propensity of VICs to assume a diseased phenotype is dependent upon the composition of the surface that they are in; specifically, surfaces that incorporate certain ‘protective’ ECM components will enable appropriate function of VICs by shielding them against pathological outcomes such as calcification. In the immediate future I will be focusing my work in the elucidation of the mechanism(s) by which the 2-D ECM environment regulates VIC (dys)function. In the second phase of this project, I will identify the role of the major native ECM components in regulating valve (dys)function in a 3-D environment. The results of this investigation may have significant clinical implications, because it addresses two critical needs in clinical cardiovascular repair: (1) the need for functional, living valve replacements is addressed via the characterization of necessary components for the development of an appropriate biomimetic biomaterials for valve regeneration, and (2) the need to understand and treat valvular disease is addressed via exploration of the potential protective mechanism of native ECM components against induction of VIC dysfunction and calcification.

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Amanda Farley Vega

BS, Mount Union College, Chemistry/Biology 2003

Faculty Trainer:
Jonathan C. Makielski, MD, Professor, Medicine (Cardiovascular)

Cellular and Molecular Mechanisms of the Inward Rectifying Potassium Channel Kir2.1, Cardiac Arrhythmias

Research Statement
The inward rectifying potassium channel, Kir2.1, encoded by KCNJ2, predominantly carry the instantaneous inward rectifier current IK1 in the heart. IK1 is important for maintenance of resting membrane potential and regulation of terminal repolarization of the cardiac action potential. Dysfunction of IK1 and calcium homeostasis is known to play a role in arrhythmogenesis in heart failure and other cardiac arrhythmia syndromes. Specifically, mutations of Kir2.1 underlie cardiac arrhythmia of Andersen-Tawil syndrome, familial Atrial Fibrillation and Short QT syndrome SQT3. Recently a small number of Kir2.1 mutations have been identified from Catecholaminergic Polymorphic Ventricular Tachycardia, or CPVT, patients referred for genetic testing, including a novel mutation from our lab.

CPVT is characterized as an exercise/emotional stress induced cardiac arrhythmia in the absence of structural heart disease which can cause sudden death, notably in young and otherwise healthy individuals. Mutation in the calcium genes, cardiac ryanodine receptor, RyR2, and calsequestrin-2, CASQ2, disrupt regulation excitation contraction-coupling and calcium homeostasis, conditions exacerbated by catecholamine signaling during periods of exercise or emotional stress. Additionally these mutations account for only half of all CPVT cases. This suggests that CPVT may be a genetically heterogeneous disease. Due to the increased frequency of Kir2.1 mutations being discovered via genetic testing of CPVT patients, we are currently exploring Kir2.1 as a novel gene candidate for CPVT arrhythmia.

My research focuses on investigating the molecular and cellular mechanisms leading to a CPVT arrhythmogenesis of novel Kir2.1 mutation, V227F. My goal is to understand how exercise/emotional stress catecholamine signaling cascades disrupt Kir2.1 channel function and IK1 function using patch clamp technique in heterologous expression systems and ventricular myocytes. I hypothesize that IK1 dysfunction may also alter other cellular processes, specifically calcium homeostasis. Viral mediated expression of Kir2.1-V227F in ventricular myocytes will enable me to explore mutation effect on cellular mechanisms, including the cardiac action potential and calcium transients in the presence and absence of catecholamine signaling using current clamp technique and confocal microscopy.

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Claudia Korcarz

DVM, Universidad Nacional de Buenos Aires Veterinary School, Argentina, 1984

Faculty Trainer:
James H. Stein, MD, Medicine (Cardiovascular)

Cardiovascular Ultrasound

Research Statement
My area of interest in cardiovascular medicine is the use and clinical applications of non-invasive techniques to evaluate cardiovascular disease. I will be analyzing longitudinal data collected from the Bogalusa Heart study with specific interest in the relationships between cardiac remodeling and arterial compliance characteristics such as pulse wave velocity, wave reflections, regional distensibility and carotid intima-media thickness (CIMT). Further information regarding the influence of age, race, sex and cardiovascular risk factors could lead to more beneficial prevention strategies and treatment options in the future.

I will also focus on the use of ultrasound evaluation of CIMT as a screening tool for cardiovascular risk assessment in office practice settings. Until recently, extensive protocols and intense training regimens have relegated this screening tool to epidemiological studies or large academic centers. I will investigate the capability of non–sonographers to learn and successfully perform clinically validated CIMT screening examinations in conjunction with five collaborating institutions. Each organization will participate in the specific training and submit cases for evaluation. We hope to collect information that could help develop an enhanced standardized path of training for non-sonographers and primary care physicians.

A parallel project includes the measurements of regional arterial compliance, wave reflections, and pulse wave velocity in conduit and peripheral circulations in a subset of subjects from the Sleep Cohort Study. Combining these parameters with brachial artery reactivity testing and CIMT will help describe vascular changes in subjects with different degrees of sleep disordered breeding (SDB) when compared to matched controls. This study may provide more information about the physiological changes that occur in the vasculature of individuals with SDB and could provide a link between SDB, systemic hypertension and increased CV risk.

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Holly Norman

Ph.D., Uppsala University, Neuroscience, 2006
BS, College of William and Mary, Kinesiology, 2002

Faculty Trainer:
Richard L. Moss, Ph.D., Physiology

Heart failure/contractility

Research Statement
My current research focus is on the functional importance of varied myocardial performance throughout the heart muscle. Myosin heavy chain (MHC) and the phosphorylation of proteins, e.g. myosin binding protein C (MyBP-C) and myosin light chain 2 (regulatory light chain; RLC) are important for heart contraction, but are unevenly distributed throughout the heart. Recently it has been shown that mechanisms of stretch activation (Davis et al 2001) and wall motion are significantly affected by alterations in these proteins and phosphorylation state. The aim of this project is to determine the differential expression of these proteins and phosphorylation state in the myocardium and to evaluate how they impact the overall performance in the heart in various states, e.g. healthy, disease and b-adrenergic stimulation (increased contractility). The hypothesis is that alterations in these proteins and/or phosphorylation state will result in an altered distribution which will ultimately affect myocardial performance. The proposed experiments will assess the relative distribution of the above stated proteins and systematically evaluate their functional importance in myocardial performance in rodent heart in which myosin binding protein C is altered, i.e. ablated or mutated to either be constitutively unphosphorylated (ser→ala substitution) or constitutively mimic the charge (ser→asp substitution), under conditions of increased contractility. Results from this project should provide insight into the basis for normal cardiac pump function and for altered function in disease.

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Mauricio Velez

MD, Universidad del Norte, Columbia, 1999

Faculty Trainer:
Nancy K. Sweitzer, MD, Ph.D., Cardiovascular Medicine

Relationship of Insulin Resistance Genomics with Heart Failure Natural History and Clinical Outcomes

Research Statement
My current interest in cardiovascular research is to study the relationship between insulin resistance syndromes and heart failure. The medical literature offers a wealth of evidence that indicates that diabetes is a major risk factor for the development of heart failure in men and women in the United States, but in spite of a clear clinical association, a pathophysiologic link has not been elucidated. Many investigators in recent years have shed light on a number of metabolically active proteins whose function is impaired in insulin resistance syndromes. Their research has led to the discovery of several single-nucleotide polymorphisms (SNPs) in the genes coding for these proteins. Some of these SNPs are highly prevalent in individuals with a metabolic syndrome or diabetes type 2 phenotype. The proteins most prominently featured in the literature thus far are plasminogen activator inhibitor-1, adiponectin, and endothelial nitric oxide synthase. It is unknown if SNPs in the promoter and coding regions of these proteins are prevalent in patients with insulin resistance and heart failure, and whether their presence has any impact on clinical outcomes.

I intend to quantify the frequency of SNPs in the genes for plasminogen activator inhibitor-1, adiponectin, and endothelial nitric oxide synthase in a population of HF patients with insulin resistance phenotypes, and to study their relationship with clinical outcomes. Using the combined UW/Penn heart failure database as substrate, I will begin my research by studying the frequency of genetic polymorphisms associated with insulin resistance syndromes in a cohort of patients with HF with the metabolic syndrome or diabetes type 2, isolating highly prevalent SNPs. I have partnered with Dr. Orly Vardeny at the School of Pharmacy to utilize DNA extraction and pyrosequencing techniques for this project. I will focus on the prevalent SNPs and investigate their association with the rate of hospitalization for heart failure, incidence of major adverse cardiovascular events, and mortality in the study population. I will also assess whether these SNPs have a relationship with ventricular remodeling, renal dysfunction, arterial stiffness, and other physiologic parameters. I would welcome the opportunity to collaborate with other investigators with a basic science background on campus who have similar interests, to expand the scope of my project. This might include investigating the functional implications of identified SNPs, their impact on post-translational protein phenotypes or their effects on cardiovascular physiology.

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