Stem Cell Research & Therapy (Sep 2020)

Optical mapping of human embryonic stem cell-derived cardiomyocyte graft electrical activity in injured hearts

  • Dominic Filice,
  • Wahiba Dhahri,
  • Joell L. Solan,
  • Paul D. Lampe,
  • Erin Steele,
  • Nikita Milani,
  • Benjamin Van Biber,
  • Wei-Zhong Zhu,
  • Tamilla Sadikov Valdman,
  • Rocco Romagnolo,
  • José David Otero-Cruz,
  • Kip D. Hauch,
  • Matthew W. Kay,
  • Narine Sarvazyan,
  • Michael A. Laflamme

DOI
https://doi.org/10.1186/s13287-020-01919-w
Journal volume & issue
Vol. 11, no. 1
pp. 1 – 18

Abstract

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Abstract Background Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) show tremendous promise for cardiac regeneration, but the successful development of hESC-CM-based therapies requires improved tools to investigate their electrical behavior in recipient hearts. While optical voltage mapping is a powerful technique for studying myocardial electrical activity ex vivo, we have previously shown that intra-cardiac hESC-CM grafts are not labeled by conventional voltage-sensitive fluorescent dyes. We hypothesized that the water-soluble voltage-sensitive dye di-2-ANEPEQ would label engrafted hESC-CMs and thereby facilitate characterization of graft electrical function and integration. Methods We developed and validated a novel optical voltage mapping strategy based on the simultaneous imaging of the calcium-sensitive fluorescent protein GCaMP3, a graft-autonomous reporter of graft activation, and optical action potentials (oAPs) derived from di-2-ANEPEQ, which labels both graft and host myocardium. Cardiomyocytes from three different GCaMP3+ hESC lines (H7, RUES2, or ESI-17) were transplanted into guinea pig models of subacute and chronic infarction, followed by optical mapping at 2 weeks post-transplantation. Results Use of a water-soluble voltage-sensitive dye revealed pro-arrhythmic properties of GCaMP3+ hESC-CM grafts from all three lines including slow conduction velocity, incomplete host-graft coupling, and spatially heterogeneous patterns of activation that varied beat-to-beat. GCaMP3+ hESC-CMs from the RUES2 and ESI-17 lines both showed prolonged oAP durations both in vitro and in vivo. Although hESC-CMs partially remuscularize the injured hearts, histological evaluation revealed immature graft structure and impaired gap junction expression at this early timepoint. Conclusion Simultaneous imaging of GCaMP3 and di-2-ANEPEQ allowed us to acquire the first unambiguously graft-derived oAPs from hESC-CM-engrafted hearts and yielded critical insights into their arrhythmogenic potential and line-to-line variation.

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