Facilitated maturation of Ca2+ handling properties of human embryonic stem cell-derived cardiomyocytes by calsequestrin expression

doi:10.1152/ajpcell.00060.2009

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Facilitated maturation of Ca²⁺ handling properties of human embryonic stem cell-derived cardiomyocytes by calsequestrin expression

Jing Liu,¹^,2^,3 Deborah K. Lieu,¹^,2^,3 Chung Wah Siu,¹^,2^,4^,5 Ji-Dong Fu,¹^,2^,3 Hung-Fat Tse,⁴^,5 and Ronald A. Li¹^,2^,3^,4^,5

¹Stem Cell Program and ²Department of Cell Biology and Human Anatomy, University of California Davis, Davis, California; ³Institute of Pediatric Regenerative Medicine, Shriners Hospital for Children of North America, Sacramento, California; ⁴Stem Cell and Regenerative Medicine Program, Heart, Brain, Hormone and Healthy Aging Research Center, and ⁵Cardiology Division, Department of Medicine, The University of Hong Kong, Hong Kong

Submitted 3 February 2009 ; accepted in final form 3 April 2009

Cardiomyocytes (CMs) are nonregenerative. Self-renewable pluripotenthuman embryonic stem cells (hESCs) can differentiate into CMsfor cell-based therapies. We recently reported that Ca²⁺ handling,crucial to excitation-contraction coupling of hESC-derived CMs(hESC-CMs), is functional but immature. Such immature propertiesas smaller cytosolic Ca²⁺ transient amplitudes, slower kinetics,and reduced Ca²⁺ content of sarcoplasmic reticulum (SR) canbe attributed to the differential developmental expression profilesof specific Ca²⁺ handling and regulatory proteins in hESC-CMsand their adult counterparts. In particular, calsequestrin (CSQ),the most abundant, high-capacity but low-affinity, Ca²⁺-bindingprotein in the SR that is anchored to the ryanodine receptor,is robustly expressed in adult CMs but completely absent inhESC-CMs. Here we hypothesized that gene transfer of CSQ inhESC-CMs suffices to induce functional improvement of SR. Transductionof hESC-CMs by the recombinant adenovirus Ad-CMV-CSQ-IRES-GFP(Ad-CSQ) significantly increased the transient amplitude, upstrokevelocity, and transient decay compared with the control Ad-CMV-GFP(Ad-GFP) and Ad-CMV-CSQ ${Delta}$ -IRES-GFP (Ad-CSQ ${Delta}$ , which mediated theexpression of a nonfunctional, truncated version of CSQ) groups.Ad-CSQ increased the SR Ca²⁺ content but did not alter L-typeCa²⁺ current. Pharmacologically, untransduced wild-type, Ad-GFP-,Ad-CSQ ${Delta}$ -, and Ad-CSQ-transduced hESC-CMs behaved similarly. Whereasryanodine significantly reduced the Ca²⁺ transient amplitudeand slowed the upstroke, thapsigargin slowed the decay. Neithertriadin nor junctin was affected. We conclude that CSQ expressionin hESC-CMs facilitates Ca²⁺ handling maturation. Our resultsshed insights into the suitability of hESC-CMs for therapiesand as certain heart disease models for drug screening.

calcium transients; ryanodine receptor; adenovirus

Address for reprint requests and other correspondence: R. Li, Univ. of California, Davis, Rm. 650, Shriners Hospital, 2425 Stockton Blvd., Sacramento, CA 95817 (ronaldli{at}ucdavis.edu)