Cardiac radiotherapy–induced epigenetic memory underlies electrophysiologic and metabolic reprogramming
Samuel D. Jordan, Shuhua Fu, Abigail Fulkerson, Donghua Hu, Sherwin Ng, David M. Zhang, Sneha Manikandan, Jeffrey Szymanski, Nan Hu, Yuqian Xie, Anish Bedi, James Tabor, Lauren Boggs-Bailey, Lori Strong, Stephanie Hicks, Lavanya Aryan, Nishanth Gabriel, Geoffrey D. Hugo, Kuo-Chan Weng, Nathaniel Huebsch, Julie K. Schwarz, Bo Zhang, Stacey L. Rentschler
Samuel D. Jordan, Shuhua Fu, Abigail Fulkerson, Donghua Hu, Sherwin Ng, David M. Zhang, Sneha Manikandan, Jeffrey Szymanski, Nan Hu, Yuqian Xie, Anish Bedi, James Tabor, Lauren Boggs-Bailey, Lori Strong, Stephanie Hicks, Lavanya Aryan, Nishanth Gabriel, Geoffrey D. Hugo, Kuo-Chan Weng, Nathaniel Huebsch, Julie K. Schwarz, Bo Zhang, Stacey L. Rentschler
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Research Article Cardiology Cell biology

Cardiac radiotherapy–induced epigenetic memory underlies electrophysiologic and metabolic reprogramming

Abstract

Stereotactic arrhythmia radiotherapy (STAR) is emerging as a highly effective treatment for ventricular tachycardia (VT). Growing evidence indicates that STAR favorably reprograms the electrical substrate by speeding conduction and/or prolonging repolarization via modulation of ion channel expression, although the mechanisms by which single-fraction radiation mediates durable changes in gene expression are incompletely understood. Here, we identify dynamic changes in the cardiomyocyte epigenome and transcriptome after irradiation (IR) in vivo and in vitro, including durably increased expression and chromatin accessibility of Scn5a (encodes the α subunit of the sodium channel, NaV1.5), demonstrating a role for epigenetic memory in conduction velocity (CV) increases observed after STAR. Transcriptomic and epigenetic sequencing further identified dynamic changes in gene expression and regulatory regions involved in cellular repolarization, calcium handling, and metabolism after IR. These changes were mirrored by dose-dependent and cell-autonomous changes in repolarization, calcium flux, and mitochondrial respiration, highlighting important cellular processes that may mediate the therapeutic effects of STAR. Overall, we found that cardiomyocytes exposed to a single fraction of high-dose IR exhibited epigenetic reprogramming that mediated broad and dynamic physiologic responses.

Authors

Samuel D. Jordan, Shuhua Fu, Abigail Fulkerson, Donghua Hu, Sherwin Ng, David M. Zhang, Sneha Manikandan, Jeffrey Szymanski, Nan Hu, Yuqian Xie, Anish Bedi, James Tabor, Lauren Boggs-Bailey, Lori Strong, Stephanie Hicks, Lavanya Aryan, Nishanth Gabriel, Geoffrey D. Hugo, Kuo-Chan Weng, Nathaniel Huebsch, Julie K. Schwarz, Bo Zhang, Stacey L. Rentschler

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Figure 5

Epigenetic profiling reveals changes to repolarization and calcium handling after IR in hiPSC-CMs.

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Epigenetic profiling reveals changes to repolarization and calcium handl...
(A) Heatmap of transcripts and epigenetic changes for potassium channels involved in the cardiac action potential. (B) FPD measurements assessed by MEA over time shown as FPD and the percentage change in FPD from day 0. Boxes represent 25th_75th percentiles, and whiskers represent minimum-to-maximum values (nwells = 24 sham, 12 irradiated from 3 cryovials; 2-way ANOVA: Ptime, Ptreatment, and Pinteraction < 0.0001; Šídák’s post hoc test: ***Padj < 0.0005, ****Padj < 0.0001). (C) Quantified ERP from optocardiography in μEHTs 7 days after sham or 25 Gy IR, shown as the FC relative to the sham average by batch (≥25 μEHTs per condition from 3 differentiations; 2-tailed t test: ****P < 0.0001). (D) Quantified ERP from optocardiography in μEHTs 14 days after sham treatment or 5, 15, or 25 Gy IR, shown as the FC relative to the sham average by batch (≥27 μEHTs per condition from 5 independent differentiations; 1-way ANOVA: P = 0.76). (E) Heatmap of transcripts and epigenetic changes for calcium channels involved in cardiomyocyte excitation-contraction coupling. (F) Representative traces of relative GCaMP6 fluorescence intensity during 1 Hz pacing for tissues 2 weeks after sham treatment or 5, 15, or 25 Gy IR. (G–L) Quantification of calcium-handling parameters (CaAmp, calcium amplitude) (G); FC in the AUC (H); FC in dCa/dt (change in GCaMP fluorescence/time) (I); FC in Decay30 (J); FC in Decay50 (K); and FC in Decay75 (L) by GCaMP6 fluorescence in sham-treated versus 5, 15, and 25 Gy irradiated μEHTs 14 days after treatment, presented as the FC relative to the sham average by batch (≥23 μEHTs from 5 independent differentiations; 1-way ANOVA: PDecay75 = 0.0002, all others < 0.0001; Tukey’s post hoc test: *Padj ≤ 0.05, **Padj ≤ 0.01, ***Padj ≤ 0.001, ****Padj ≤ 0.0001).