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Nikki Posnack, PhD, Laboratory

Posnack 1

Our work is focused on investigating the influence of pharmacological and toxicological exposures on cardiovascular and autonomic function.

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About Our Lab

Our work is focused on investigating the influence of pharmacological and toxicological exposures on cardiovascular and autonomic function. This work is particularly relevant to neonates and young infants undergoing blood transfusions and/or complex reconstructive heart surgery for congenital heart disease.  Pediatric patients can be exposed to plastic chemical contaminants for several hours during circulatory support with the heart and lung machine that involves blood flow through multiple plastic components. Not uncommonly these babies are also placed on extracorporeal membrane oxygenation (ECMO), a longer term form of circulatory support where the child’s blood is circulated through plastic ECMO circuitry for days to weeks.  Any toxic effects of chemicals leaching from the various components of the cardiopulmonary bypass circuit or ECMO circuit are likely to have a magnified effect on the vulnerable physiology of the immature neonate or young infant. We also aim to identify safer biomaterials, chemicals, and/or surface coatings for transfusion devices, circuitry and blood banking. Results of these studies can provide the foundation for objective decision making regarding the use of chemical additives in medical device manufacturing by scientific, medical and regulatory communities. Results of the proposed studies can also incentivize and accelerate the development and clinical adoption of alternative biomaterials, additives and/or fabrication techniques to improve transfusion patient safety.

Pediatric Risk Assessment
Pediatric cardiac research can be stalled by a shortage of appropriate human cardiac models. Human cardiomyocytes have a defined life-span and do not readily replicate in culture. Moreover, immortalized human cardiomyocyte cell lines are non-contractile, and lack both myofibril organization and a physiologically-relevant action potential. Consequently, cardiovascular researchers often rely on animal models – despite known species differences in myocardial structure and phenotype. To circumvent these hurdles, our laboratory utilizes human embryonic stem cell (hESC) and human induced pluripotent stem cell (hiPSC) differentiated cardiomyocytes as a pediatric cardiac model. These cells exhibit a phenotype that closely resembles fetal and neonatal human cardiac cells. Our laboratory employs these human cardiac cell models to predict pharmacological, toxicological, and biocompatibility risk outcomes.

Pharmacological Agents and Cardioprotection
Congenital heart defects remain the most common type of birth defect, affecting nearly 1% of newborns in the United States each year. Of those patients, 25% of infants have a critical heart defect that requires surgical repair. Postoperative arrhythmias are a common occurrence in patients undergoing reconstructive heart surgery. Clinical studies have shown that magnesium (Mg2+) administration may decrease the incidence of post-operative arrhythmias in pediatric patients undergoing heart surgery. Our laboratory is investigating the cardioprotective effects of Mg2+ administration on excitation-contraction coupling, cardiac metabolism, and recovery from ischemia-reperfusion injury. Experimental procedures involve phenotypic measurements of whole heart tissue using a high-speed optical mapping system. Results of these studies can provide clinical guidance to optimize the administration of Mg2+ as a prophylactic.

Our Team

We have an incredibly talented group of scientists from uniquely different disciplines and backgrounds committed to the work and team.

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Fellowship Opportunities

Positions are limited to openings under the guidance of fellows within the laboratory.

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Our Research

Our laboratory utilizes several different models to investigate and observe the cardiovascular system.

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Nikki Posnack, PhD

• Assistant Professor, Children’s National Heart Institute, Sheikh Zayed Institute for Pediatric Surgical Innovation: Children’s National Health System
• Department of Pediatrics, Department of Pharmacology and Physiology: George Washington University, School of Medicine and Health Sciences

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