Synthetic Strands of Neonatal Mouse Cardiac Myocytes

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Abstract
—The aim of the present study was to morphologically and electrically characterize synthetic strands of mouse ventricular myocytes. Linear strands of mouse ventricular myocytes with widths of 34.7±4.4 μm (W1), 57.9±2.5 μm (W2), and 86.4±3.6 μm (W3) and a length of 10 mm were produced on glass coverslips with a photolithographic technique. Action potentials (APs) were measured from individual cells within the strands with cell-attached microelectrodes. Impulse propagation and AP upstrokes were measured with multisite optical mapping (RH237). Immunostaining was performed to assess cell-cell connections and myofibril arrangement with polyclonal antisera against connexin43 and N-cadherins and monoclonal antibodies against cardiac myosin. Light microscopy and myosin staining showed dense growth of well-developed elongated myocytes with lengths of 34.2±4.2 μm (W1), 36.9±5.8 μm (W2), and 43.7±6.9 μm (W3), and length/width ratios of 3.9±0.2. Gap junctions were distributed around the cell borders (3 to 4 junctions/μm2 cell area). Each cell was connected by gap junctions to 6.5±1.1 neighboring cells. AP duration shortened with time in culture (action potential duration at 50% repolarization: day 4, 103±34 ms; day 8, 16±3 ms; Pmax. This technique will permit the study of propagation, AP, and structure-function relations at cellular resolution in genetically modified mice.