Synthetic strands of neonatal mouse cardiac myocytes - Structural and electrophysiological properties

The aim of the present study was to morphologically and electrically charac terize synthetic strands of mouse ventricular myocytes, Linear strands of m ouse ventricular myocytes with widths of 34.7+/-4.4 mu m (W-1), 57.9+/-2.5 mu m (W-2), and 86.4+/-3.6 mu m (W-3) and a length of 10 mm were produced o n glass coverslips with a photolithographic technique. Action potentials (A Ps) were measured from individual cells within the strands with cell-attach ed 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 ag ainst connexin43 and N-cadherins and monoclonal antibodies against cardiac myosin. Light microscopy and myosin staining showed dense growth of well-de veloped elongated myocytes with lengths of 34.2+/-4.2 mu m (W-1), 36.9+/-5. 8 mu m (W-2), and 43.7+/-6.9 mu m (W-3), and length/width ratios of 3.9+/-0 .2. Gap junctions were distributed around the cell borders (3 to 4 junction s/mu m(2) cell area). Each cell was connected by gap junctions to 6.5+/-1.1 neighboring cells. AP duration shortened with time in culture (action pote ntial duration at 50% repolarization: day 4, 103+/-34 ms; day 8, 16+/-3 ms; P<0.01). Minimum diastolic potential and AP amplitude were 71+/-5 and 97.2 +/-7.6 mV, respectively. Conduction velocity and the maximum dV/dt of the A P upstroke were 43.9+/-13.6 cm/s and 196+/-67 V/s, respectively. Thus, neon atal ventricular mouse myocytes can be grown in continuous synthetic strand s. Gap junction distribution is similar to the neonatal pattern observed in the hearts of larger mammals. Conduction velocity is in the range observed in adult mice and in the higher range for mammalian species probably due t o the higher dV/dt(max). This technique will permit the study of propagatio n, AP, and structure-function relations at cellular resolution in genetical ly modified mice.