Mitotic structure of aortic intimal cells induced by mechanical injury in swine.

Repair processes of the aortic wall have been studied electron microscopically after removal of the endothelium by an inflated balloon procedure in the thoracic aortae of swine. Initial responses after injury included a thrombotic reaction, the appearance of intimal cells over the denuded surface, and increased mitotic activity of medial cells adjacent to the dead cells by day 3. Cells which engaged in intimal thickening were classified as modified smooth muscle cells throughout the course of this investigation. Mitosis of intimal cells, which was initially observed at day 3, substantially increased at day 7 and decreased by day 14. Mitotic intimal cells contained the same cytoplasmic organelles as interphase modified smooth muscle cells. A detailed description of the paired cisternae as an ultrastructural feature of cell division of modified smooth muscle cells was provided. The paired cisternae were initially observed among the remnants of the nuclear envelope in late prophase; they remained at the periphery of the mitotic apparatus in meta- and anaphase, and finally attached themselves to the nuclear envelope of the daughter cells in late telophase.