Irradiated versus nonirradiated endothelial cells: Effect on proliferation of vascular smooth muscle cells

PURPOSE: Endovascular radiation therapy is a promising strategy for the prevention of restenosis. Radiation prevents proliferation of vascular smooth muscle cells, thereby reducing the incidence of restenosis, but may also affect the remaining endothelial cells. For this reason, a comparison was made between irradiated and nonirradiated endothelial cells and their effects on the proliferation of vascular smooth muscle cells in a coculture system was evaluated. MATERIALS AND METHODS: A coculture system was used, in which both endothelial cells and vascular smooth muscle cells were grown on opposite sides of a semipermeable membrane. After a period of growth arrest, the proliferation of vascular smooth muscle cells was measured during four subsequent days. RESULTS: The presence of endothelial cells stimulated the proliferation of vascular smooth muscle cells during the first days of analysis but had an inhibitory effect during the subsequent days (P < .5). gamma -irradiation of endothelial cells resulted in a complete blockage of the proliferation of these cells. However, irradiated endothelial cells affected the proliferation of: vascular smooth muscle tells in coculture in a fashion comparable to nonirradiated endothelial cells (P > .5). CONCLUSION: The results suggest that, in endovascular radiation therapy, irradiation of endothelial cells does not change their effects on the proliferative behavior of vascular smooth muscle cells.