Different radiosensitivity of smooth muscle cells and endothelial cells invitro as demonstrated by irradiation from a Re-188 filled balloon catheter

There is an increasing interest in irradiation to control restenosis after balloon angioplasty by an internal radioactive source. Differences in radio sensitivity of the predominant cells of the human coronary artery (i.e. end othelial cells (HCAEC), smooth muscle cells from the media (HCMSMC) and fro m plaque material (HCPSMC), are issues of controversal discussion. Therefor e, we investigated the graded inhibition of cells by irradiation from a bal loon catheter filled with a high-energy beta-emitter (Rhenium-188) in vitro . HCPSMC. HCMSMC and HCAEC were cultured and irradiated with increasing dos e from 7.5 to 37.5 Gy at a dose rate of 1.5 +/- 0.3 Gy/min. After irradiati on, bromodeoxyuridine (BrdU) was added and cells were fixed 18 h later. In a limited field opposite to the balloon, the number of BrdU-positive cells were analysed in comparison to non-irradiated controls. Significant inhibit ion was demonstrated in HCPSMC and HCMSMC at 7.5 Gy while HCAEC needed 22.5 Gy for similar effects. The antiproliferative effect was dose dependent in all cell strains. The effect of irradiation with 22.5 Gy on smooth muscle alpha-actin, vimentin, and alpha-tubulin of HCPSMC and HCMSMC and on von Wi llebrand factor (vWF), vimentin, and alpha-tubulin of HCAEC was investigate d by means of indirect immunofluorescence. Within 18 h after irradiation no effect on cytoskeletal components and vWF was documented. This in vitro st udy demonstrates that irradiation inhibits HCMSMC and HCPSMC at lower dose rates compared to HCAEC. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.