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potentials, lower cell capacitance and less hERG currents and I
Electrophysiological measurements of the EBd20 cardiomyocytes
represented the cell properties before their incorporation into
biowires, whereas EBd44 cardiomyocytes were cultured for peri-
ods slightly longer than the biowire culture time, allowing assess-
ment of the independent effect of culture time on maturation
We acknowledge that biowire maturation is clearly incomplete,
as evidenced by the relatively low membrane conductance.
Nevertheless, it is intriguing to speculate that the combination
of low membrane conductance with V
an ‘intermediate’ phenotype as cardiomyocytes undergo matura-
tion from the embryonic state.
Correlating the properties of hPSC-derived cardiomyocytes in
biowires with mouse or human development could help to gauge
maturation stage, but mouse and rat cardiomyocytes are physi-
ologically distinct, and age-defined healthy human heart samples
are scarce. Additionally, in vitro maturation might not be compat-
ible with embryo development.
The small size (radius of ~300 µm) of biowire upon gel com-
paction was selected to be close to the diffusional limitations
for oxygen supply to ensure that the biowires can be maintained
in culture without perfusion. Addition of vascular cells will be
imperative for improving survival and promoting integration
with the host tissue in future in vivo studies
. We generated a
unique platform that enables generation of human cardiac tissues
of graded levels of maturation that can be used to determine, in
future in vivo studies, the optimal maturation level that will result
in the highest ability of cells to survive and integrate in adult
hearts with the lowest side effects (such as arrhythmias).
Methods and any associated references are available in the online
version of the paper.
Note: Supplementary information is available in the online version of the paper.
We thank P. Lai, C. Laschinger, N. Dubois and B. Calvieri for technical assistance,
C.C. Chang and L. Fu for assistance with biowire setup figure preparation. Funded
by grants from Ontario Research Fund–Global Leadership Round 2 (ORF-GL2),
National Sciences and Engineering Research Council of Canada (NSERC) Strategic
Grant (STPGP 381002-09), Canadian Institutes of Health Research (CIHR)
Operating Grant (MOP-126027 and MOP-62954), NSERC-CIHR Collaborative Health
Research Grant (CHRPJ 385981-10), NSERC Discovery Grant (RGPIN 326982-10),
and NSERC Discovery Accelerator Supplement (RGPAS 396125-10) and National
Institutes of Health grant 2R01 HL076485.
S.S.N. developed biowire concept, designed and performed experiments, analyzed
data and prepared the manuscript. J.W.M. performed experiments and analyzed
data. J.L., R.A.-S. and P.H.B. performed patch clamping and microelectrode
recordings. Y.X. designed and validated initial device. B.Z. designed and fabricated
masters for device fabrication. J.J. and G.J.G. performed calcium transient
measurement and analysis. S.M. and K.N. performed optical mapping measurements
and analysis. M.G. and G.K. differentiated hESC-derived cardiomyocytes.
A.H. designed primers. N.T. developed initial collagen gel mixture. M.A.L. provided
training on hiPSC differentiation and cells. P.H.B. contributed to writing of the
manuscript. M.R. envisioned the biowire concept and electrical stimulation
protocol, supervised the work and wrote the manuscript.
COMPETING FINANCIAL INTERESTS
The authors declare competing financial interests: details are available in the
online version of the paper.
Reprints and permissions information is available online at http://www.nature.
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