The effects of low-dose radiation on neointimal hyperplasia.

Purpose: We sought to determine whether low-dose radiation can inhibit neointimal hyperplasia immediately after balloon injury to the common carotid artery and to assess the extent of endothelial regeneration after treatment.
Methods: Sprague-Dawley rats were subjected to balloon injury to the common carotid artery. Immediately after injury rats were treated with a single dose of iridium 192 radiation at 5 gy, 10 gy, and 15 gy or received no radiation (control). Three weeks after injury and treatment, vessels were harvested and compartment areas were measured on fixed specimens. Scanning and transmission electron microscopy, along with Evans blue dye uptake into injured vessels, was used to assess the effect radiation had on endothelial regeneration.
Results: Rats receiving radiation at all three doses demonstrated no intimal thickening when compared with rats that were not treated (at 5 Gy 0.01 +/- 0.01 mm2; at 10 Gy 0.02 +/- 0.01 mm2; at 15 Gy 0.05 +/- 0.02 mm2; with balloon injury/no radiation 0.12 +/- 0.02 mm2; p < 0.01). In addition, the groups that were irradiated had no medial thickening when compared with control rats (at 5 Gy 0.22 +/- 0.02 mm2; at 10 Gy 0.21 +/- 0.02 mm2; at 15 Gy 0.22 +/- 0.07 mm2; with balloon injury/no radiation 0.37 +/- 0.03 mm2; p < 0.01). Endothelial regeneration, evaluated by transmission and scanning electron micrographs along with uptake of Evans blue dye, was significantly greater in animals that received radiation compared with controls.
Conclusions: Low-dose radiation prevents the occurrence of neointimal hyperplasia after balloon injury and may have a future role in vascular grafting.