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 3

IR induces cardiomyocyte-autonomous CV increases in a dose-dependent fashion in hiPSC-CM models.

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IR induces cardiomyocyte-autonomous CV increases in a dose-dependent fas...
(A) Tissue culture images of sham-treated and irradiated hiPSC-CMs 3 weeks after IR. Scale bar: 30 μm. (B) CV measurements assessed by MEA over time, shown as the CV and percentage of change in CV from day 0. Boxes represent the 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 = 0.030, **Padj = 0.005, ****Padj < 0.0001). (C) Western blots probed for NaV1.5, Cx43, and Na/K ATPase (loading control) from membrane preparations from sham-treated versus 25 Gy irradiated hiPSC-CMs 21 days after treatment. (D and E) FC in quantified density of NaV1.5 (D) and Cx43 (E) (n = 5 cryovials; 2-tailed t test: *PNaV1.5 = 0.014, PCx43 = 0.16). (F) Representative tissue culture images of sham-treated and 5, 15, and 25 Gy irradiated μEHTs 14 days after treatment. Scale bar: 1 mm. (G) Representative activation maps from optocardiography of sham-treated and 5, 15, and 25 Gy irradiated μEHTs 14 days after treatment. Tissues were stimulated at 1 Hz from the left knob. (H) Quantified CV 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 (≥22 μEHTs per condition from 5 differentiations; 1-way ANOVA: P = 0.0006; Tukey’s post hoc test: **Padj,sham–25Gy = 0.002, **Padj,5Gy–25Gy = 0.001).