Effects of low-dose x-ray radiation at varying dose rates on human aortic smooth muscle in vitro.

Abstract

Radiation has a variety of uses in the medical field such as diagnostic imaging and cancer treatment. However, we still know very little about radiation's effect on cells in the body particularly at low doses such as those used in x-ray and CT imaging. Our group has designed studies to determine the effects of low doses of x-rays on vascular cells. We helped to design a novel x-ray fluorescent experimental setup to irradiate human aortic smooth muscle cells with dosing rates varying from at the lower end of the medical imaging range. This novel setup allows us to expose the cells inside a standard incubator with x-rays that have very precisely controlled energy, total dose, and dose rate. Three specific protocols were conducted in 24 hour intervals over several days, ultimately showing clear and statistically significant differences between dose rates even when the total dose was kept constant. As dose rate increased, the total number of cells and the number of cells in a constricted state increased, while no significant increase in cell death was observed. We have shown, for the first time, that x-rays, at doses similar to what is given to patients during standard x-ray imaging, can cause changes in vascular cells in culture. Furthermore, RT-PCR was conducted at 12 hour intervals, showing along with the assays that radiation quantitatively changes the amount of collagen in vascular cells, thus supporting our previous assays. Future experiments will include determining a specific relationship between and mechanisms behind varying dose rate and the number of cells, as well as determining whether changing other characteristics of radiation has an impact on the cells being irradiated.