Absence of transverse tubules contributes to non-uniform Ca(2+) wavefronts in mouse and human embryonic stem cell-derived cardiomyocytes

Stem Cells Dev. 2009 Dec;18(10):1493-500. doi: 10.1089/scd.2009.0052.


Mouse (m) and human embryonic stem cell-derived cardiomyocytes (hESC-CMs) are known to exhibit immature Ca(2+) dynamics such as small whole-cell peak amplitude and slower kinetics relative to those of adult. In this study, we examined the maturity and efficiency of Ca(2+)-induced Ca(2+) release in m and hESC-CMs, the presence of transverse (t) tubules and its effects on the regional Ca(2+) dynamics. In m and hESC-CMs, fluorescent staining and atomic force microscopy (AFM) were used to detect the presence of t-tubules, caveolin-3, amphiphysin-2 and colocalization of dihydropyridine receptors (DHPRs) and ryanodine receptors (RyRs). To avoid ambiguities, regional electrically-stimulated Ca(2+) dynamics of single ESC-CMs, rather than spontaneously beating clusters, were measured using confocal microscopy. m and hESC-CMs showed absence of dyads, with neither t-tubules nor colocalization of DHPRs and RyRs. Caveolin-3 and amphiphysin-2, crucial for the biogenesis of t-tubules with robust expression in adult CMs, were also absent. Single m and hESC-CMs displayed non-uniform Ca(2+) dynamics across the cell that is typical of CMs deficient of t-tubules. Local Ca(2+) transients exhibited greater peak amplitude at the peripheral than at the central region for m (3.50 +/- 0.42 vs. 3.05 +/- 0.38) and hESC-CMs (2.96 +/- 0.25 vs. 2.72 +/- 0.25). Kinetically, both the rates of rise to peak amplitude and transient decay were faster for the peripheral relative to the central region. Immature m and hESC-CMs display unsynchronized Ca(2+) transients due to the absence of t-tubules and gene products crucial for their biogenesis. Our results provide insights for driving the maturation of ESC-CMs.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium Channels, L-Type / metabolism
  • Calcium Signaling*
  • Caveolin 3 / metabolism
  • Electric Stimulation
  • Embryonic Stem Cells / cytology*
  • Embryonic Stem Cells / metabolism*
  • Humans
  • Mice
  • Myocytes, Cardiac / cytology*
  • Myocytes, Cardiac / metabolism*
  • Nerve Tissue Proteins / metabolism
  • Protein Transport
  • Ryanodine Receptor Calcium Release Channel / metabolism


  • Calcium Channels, L-Type
  • Caveolin 3
  • Nerve Tissue Proteins
  • Ryanodine Receptor Calcium Release Channel
  • amphiphysin