Patterned growth of neonatal rat heart cells in culture. Morphological and electrophysiological characterization.

A culture method was developed that permits patterning of the growth of ventricular myocytes of neonatal rats. Regions were created on the culture substrate that either prevented (photoresist coat) or supported (glass surface) attachment of cells. In this way the geometry of interconnecting growth channels could be specified. Single-layered myocyte strands of variable length and with widths of as little as 65 micron (three to four cells wide) were obtained. The shape and orientation of the individual myocytes were a function of growth-channel width: the narrower the channel, the more elongated the cells and the more likely was the long axis to be oriented along the channel axis. In channels with width of 100 micron or less, cells were aligned longitudinally and cross-striated as in vivo. A high degree of morphological cell differentiation required the presence of contractile activity. Maximal diastolic potential (-71 mV), action potential amplitude (93 mV), and maximal upstroke velocity (140 V/sec) did not change with increasing culture age. Mean longitudinal conduction velocity was 0.39 m/sec. No electrophysiological or morphological evidence of photoresist toxicity was seen, and the data indicate a high degree of cell differentiation in the patterned cell cultures. The method thus is suitable for the study of the relation between impulse propagation and structure at a cellular level in artificial networks of predefined shape.