The objective of this study was to establish a three-dimensional (3-D) in vitro model system of cardiac muscle for electrophysiological studies. Primary neonatal rat ventricular cells containing lower or higher fractions of cardiac myocytes were cultured on polymeric scaffolds in bioreactors to form regular or enriched cardiac muscle constructs, respectively. After 1 wk, all constructs contained a peripheral tissue-like region (50–70 μm thick) in which differentiated cardiac myocytes were organized in multiple layers in a 3-D configuration. Indexes of cell size (protein/DNA) and metabolic activity (tetrazolium conversion/DNA) were similar for constructs and neonatal rat ventricles. Electrophysiological studies conducted using a linear array of extracellular electrodes showed that the peripheral region of constructs exhibited relatively homogeneous electrical properties and sustained macroscopically continuous impulse propagation on a centimeter-size scale. Electrophysiological properties of enriched constructs were superior to those of regular constructs but inferior to those of native ventricles. These results demonstrate that 3-D cardiac muscle constructs can be engineered with cardiac-specific structural and electrophysiological properties and used for in vitro impulse propagation studies.

  • myocyte
  • impulse propagation
  • electrophysiology
  • three-dimensional


  • Address for reprint requests and other correspondence: L. E. Freed, Massachusetts Institute of Technology, Div. of Health Science and Technology, MIT, Bldg. E25–342, Cambridge, MA 02139 (E-mail:lfreed{at}mit.edu).

  • We thank R. Langer for advice, R. Padera for help with animal surgery, H. Shing for carrying out the transmission electron microscopy, Y. Lee for help establishing the electrophysiological recording system, and J. Merok, H. Cho, and P. Gupta for help with biochemical assays.

  • This work was supported by National Aeronautics and Space Administration Grant NAG9-836.

  • The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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