Different responses by cultured aortic and venous smooth muscle cells to gamma radiation.

Background: Stenosis of hemodialysis arteriovenous grafts is usually focal and caused by the proliferation of vascular smooth muscle cells (SMCs). External radiation of the graft is a potential strategy to prevent stenosis; however, the relative responsiveness of arterial and venous SMCs to radiation is unknown.

Methods: Human aortic and saphenous vein SMCs were cultured in a medium containing growth factors and serum and treated with 0 to 50 Gy in a gamma irradiator. At 2 to 20 days post-irradiation, cell counting, methylthiazoletetrazolium dye reduction, [(3)H]-thymidine uptake, and bromodeoxyuridine (BrdU) incorporation assays were performed.

Results: All assays showed that 1 to 50 Gy inhibited the proliferation of both aortic and venous SMCs in a dose-dependent manner. Importantly, venous cells were less susceptible to radiation in all assays, compared to aortic cells. At day 10, 1 to 50 Gy of radiation inhibited the increase in the number of aortic cells by 24% to 66% and venous cells by 8% to 25% (P < 0.01) (aortic vs. venous). The differences between aortic and venous cells varied among different assays and were most pronounced in the BrdU assay.

Conclusion: Inasmuch as myointimal hyperplasia occurs at both arterial and venous anastomoses, future strategies using radiation to prevent hemodialysis vascular access stenosis should take these differences into consideration.