School of Medicine and Health Sciences Poster Presentations

Title

Developmental changes in cardiac electrophysiology and calcium handling – implications for pediatric research

Document Type

Poster

Abstract Category

Cardiology/Cardiovascular Research

Keywords

cardiac electrophysiology, pediatric research

Publication Date

Spring 5-1-2019

Abstract

Background: Cardiac electrical conduction is the driving force behind the heart's ability to pump and facilitate adequate perfusion to vital organs. Despite intracellular differences in neonatal, pediatric and adult hearts - our current understanding of excitation-contraction coupling is largely limited to adults. To guide pediatric cardiac research, a more thorough understanding of age-dependent differences in cardiac physiology is needed. Objective: This study aimed to clarify normal pediatric cardiac physiology by monitoring developmental transformations in electrical activity, calcium handling, and cardiac gene expression. Methods/Design: Hearts from Sprague-Dawley rats (age day 1- adult) were excised and the aorta was cannulated. The hearts were transferred to a temperature-controlled constant pressure Langendorff- perfusion system and perfused with oxygenated Krebs-Henseleit buffer, supplemented with 10 µM blebbistatin to reduce motion artifact. The heart was stained with calcium (50 µg Rhod2-AM) and voltage (62 µg RH237) sensitive dyes and illuminated by a 530nm LED spotlight. Fluorescence signals were acquired using a sCMOS camera (Andor, Zyla 4.2 Plus; >500fps). Electrocardiograms were monitored and recorded throughout the duration of the study. In a subset of studies, RNA isolation was performed to measure age-dependent differences in gene expression. Results/Discussion: Compared with adults, isolated neonatal rat hearts displayed a significantly longer action potential duration (APD80: adult= 61.28ms, neonatal=109.4ms n= 9-34, P<0.05), which is likely attributed to delayed K+ channel expression. Calcium handling was also significantly slower in the neonatal heart (Cad80: Adults: 126.8ms, neonatal=170.1 n=12-30, P<0.05). This difference is likely due to improved calcium handling in the adult heart, which was facilitated by an increased SERCA2a (+175% Adult vs postnatal day 0-3), RYR2 (+39% Adult vs postnatal day 0-3), and CASQ2 (+61% Adult vs postnatal day 0-3) expression. Clarification of postnatal cardiac maturation can facilitate future pharmacological and toxicological studies. Acknowledgements: This work was supported by the National Institute of Health (R00ES023477, R01HL139472), Children's Research Institute and Children's National Heart Institute.

Open Access

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Presented at Research Days 2019.

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Developmental changes in cardiac electrophysiology and calcium handling – implications for pediatric research

Background: Cardiac electrical conduction is the driving force behind the heart's ability to pump and facilitate adequate perfusion to vital organs. Despite intracellular differences in neonatal, pediatric and adult hearts - our current understanding of excitation-contraction coupling is largely limited to adults. To guide pediatric cardiac research, a more thorough understanding of age-dependent differences in cardiac physiology is needed. Objective: This study aimed to clarify normal pediatric cardiac physiology by monitoring developmental transformations in electrical activity, calcium handling, and cardiac gene expression. Methods/Design: Hearts from Sprague-Dawley rats (age day 1- adult) were excised and the aorta was cannulated. The hearts were transferred to a temperature-controlled constant pressure Langendorff- perfusion system and perfused with oxygenated Krebs-Henseleit buffer, supplemented with 10 µM blebbistatin to reduce motion artifact. The heart was stained with calcium (50 µg Rhod2-AM) and voltage (62 µg RH237) sensitive dyes and illuminated by a 530nm LED spotlight. Fluorescence signals were acquired using a sCMOS camera (Andor, Zyla 4.2 Plus; >500fps). Electrocardiograms were monitored and recorded throughout the duration of the study. In a subset of studies, RNA isolation was performed to measure age-dependent differences in gene expression. Results/Discussion: Compared with adults, isolated neonatal rat hearts displayed a significantly longer action potential duration (APD80: adult= 61.28ms, neonatal=109.4ms n= 9-34, P<0.05), which is likely attributed to delayed K+ channel expression. Calcium handling was also significantly slower in the neonatal heart (Cad80: Adults: 126.8ms, neonatal=170.1 n=12-30, P<0.05). This difference is likely due to improved calcium handling in the adult heart, which was facilitated by an increased SERCA2a (+175% Adult vs postnatal day 0-3), RYR2 (+39% Adult vs postnatal day 0-3), and CASQ2 (+61% Adult vs postnatal day 0-3) expression. Clarification of postnatal cardiac maturation can facilitate future pharmacological and toxicological studies. Acknowledgements: This work was supported by the National Institute of Health (R00ES023477, R01HL139472), Children's Research Institute and Children's National Heart Institute.