Development of smooth muscle cells in tissue culture.

Abstract

The development in vitro of smooth muscle cells from enzymically dispersed embryo chicken gizzard is reported. Forty per cent of muscle cells from the 10 day old embryo chicken gizzard were polyhedral in shape when first in culture. These became ribbon spindle in shape by day 3. The remaining 60% of muscle cells were spindle shaped when first in culture and became ribbon shaped by day 3. Spindle shaped cells contracted spontaneously and sometimes re aggregated into small clumps. After 6 days in culture all muscle cells became progressively ribbon shaped and more elongated, developing tapered ends by 14 days. Smooth muscle cells from the 8, 12, 17 and 19 day old embryo chicken gizzard developing in culture followed a similar sequence of changes in shape, except that the cells from the different aged chicks entered at different stages (i.e. 8 day old polyhedral; 12 day old -40% ribbon spindle, 60% ribbon; 17 day old ribbon and 19 day old ribbon with tapered ends). Ultrastructurally, after 3 days in culture, cells from the 10 day old embryo chicken gizzard resembled those of the 10 day old embryo chicken gizzard in vivo, with bundles of thin myofilaments (4-8 nm in diameter) and associated dark bodies. A few plasmalemmal vesicles and dense areas along the plasma membrane were noted in muscle cells after 6 days in vitro, as well as an increase both in the number of '10 nm filaments' and thin myofilaments. By 11 days, thick myofilaments (12-18 nm in diameter) were noted in some cells and there was an increase in basal lamina and plasmalemmal vesicles. After 14 days in vitro muscle cells contained most of the features of those of the adult gizzard. The results are compared with and discussed in relation to the normal development of the chicken gizzard.