Children's National Health System Posters
Document Type
Poster
Status
Graduate Student - Masters
Abstract Category
Cardiology/Cardiovascular Research
Keywords
Whole Heart, EKG, Neonatal, Electrical Activity
Publication Date
Spring 2018
Abstract
Background:
Cardiovascular physiology studies have been largely limited to adult models; yet, significant developmental differences exist between the immature and adult heart. The field of pediatric research has largely been limited to immortalized cardiomyocyte cell lines, which lack physiologically relevant action potentials, and primary neonatal myocytes that have a limited life span and lack physiologically relevant automaticity. As a result, our understanding of developmental changes in ion channel expression, t-tubule development, and excitation-contraction coupling have been deduced from 2D simplified cell models. To fully understand cardiac development from neonate to adult, a physiologically-relevant 3D whole heart model is needed to monitor dynamic changes in electrical activity and excitation-contraction coupling.
Objective:
This study aimed to establish a pediatric research model to monitor developmental changes in electrical activity and excitation-contraction coupling, using both imaging tools and electrocardiograms.
Methods/Design:
Sprague-Dawley rat hearts (3 days – adult) were excised, the aorta was cannulated, and then the heart was transferred to a temperature-controlled constant pressure Langendorff-perfusion system. The perfusate was supplemented with 10 mM blebbistatin to reduce motion artifacts by mechanically uncoupling electrical and mechanical activity. Calcium (50 mg Rhod2-AM) and voltage (62 mg RH237) sensitive dyes were used to stain the heart, signals were acquired using a sCMOS camera (Andor, Zyla 4.2 Plus; >500fps). Electrocardiograms were monitored continuously (lead II configuration) and analyzed using ecgAUTO.
Results/Discussion:
Initial results showed that compared to adult cohorts, neonatal rats displayed a longer action potential duration (APD80: adult= 85.9ms, neonatal=95.5ms, p=0.026), and a steeper Tau Fall (adults: 33.8ms, neonatal 69.9ms, p=.012) which are likely associated with delayed Ito expression. Calcium handling was also slower in the neonatal hearts (Cad80: Adults: 128.9ms, neonatal=138.8, p=.004), likely due to immature calcium handling and less robust calcium-induced calcium release. The developing excitation-contraction coupling machinery will be further probed using pharmacological tools to elucidate underlying mechanisms; and the newly developed pediatric model will be used for toxicological screening.
Acknowledgements:
The authors gratefully acknowledge Daniel McInerney for technical assistance. This work was supported by the National Institutes of Health (R00ES023477, R01HL139472), Children’s Research Institute and Children’s National Heart Institute.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Open Access
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Included in
Comparing Cardiac Dynamics between Neonatal and Adult Rats
Background:
Cardiovascular physiology studies have been largely limited to adult models; yet, significant developmental differences exist between the immature and adult heart. The field of pediatric research has largely been limited to immortalized cardiomyocyte cell lines, which lack physiologically relevant action potentials, and primary neonatal myocytes that have a limited life span and lack physiologically relevant automaticity. As a result, our understanding of developmental changes in ion channel expression, t-tubule development, and excitation-contraction coupling have been deduced from 2D simplified cell models. To fully understand cardiac development from neonate to adult, a physiologically-relevant 3D whole heart model is needed to monitor dynamic changes in electrical activity and excitation-contraction coupling.
Objective:
This study aimed to establish a pediatric research model to monitor developmental changes in electrical activity and excitation-contraction coupling, using both imaging tools and electrocardiograms.
Methods/Design:
Sprague-Dawley rat hearts (3 days – adult) were excised, the aorta was cannulated, and then the heart was transferred to a temperature-controlled constant pressure Langendorff-perfusion system. The perfusate was supplemented with 10 mM blebbistatin to reduce motion artifacts by mechanically uncoupling electrical and mechanical activity. Calcium (50 mg Rhod2-AM) and voltage (62 mg RH237) sensitive dyes were used to stain the heart, signals were acquired using a sCMOS camera (Andor, Zyla 4.2 Plus; >500fps). Electrocardiograms were monitored continuously (lead II configuration) and analyzed using ecgAUTO.
Results/Discussion:
Initial results showed that compared to adult cohorts, neonatal rats displayed a longer action potential duration (APD80: adult= 85.9ms, neonatal=95.5ms, p=0.026), and a steeper Tau Fall (adults: 33.8ms, neonatal 69.9ms, p=.012) which are likely associated with delayed Ito expression. Calcium handling was also slower in the neonatal hearts (Cad80: Adults: 128.9ms, neonatal=138.8, p=.004), likely due to immature calcium handling and less robust calcium-induced calcium release. The developing excitation-contraction coupling machinery will be further probed using pharmacological tools to elucidate underlying mechanisms; and the newly developed pediatric model will be used for toxicological screening.
Acknowledgements:
The authors gratefully acknowledge Daniel McInerney for technical assistance. This work was supported by the National Institutes of Health (R00ES023477, R01HL139472), Children’s Research Institute and Children’s National Heart Institute.
Comments
Presented at GW Annual Research Days 2018.