抄録
Purpose/Objective(s)
The radiosensitivity on neurons is believed to be difficult to be evaluated due to the complexity for culturing them alone. The growth cone collapse (GCC) assay has been reported as a useful means of quantifying the effects of various factors on cultured explants of nervous tissue. Therefore, we used the GCC assay to determine the radiosensitivity of neurons by estimating RBE of carbon-beams to X-ray on the cell neurons.
Materials/Methods
Dorsal root ganglia (DRG) and sympathetic ganglion chains (SYMP) were isolated from day-16 (mature) and day-8 (immature) chick embryos and cultured for 20 h. Thereafter, neurons were exposed to graded doses of X-rays, or high-LET 12C ions (18.3 MeV/amu, 108 keV/μm). Morphological, time- and dose-dependence changes of the neurons were examined quantitatively by GCC assay. Apoptosis induction was examined using TUNEL assay.
Results
Carbon-beams induced GCC and neurite destruction in a time and dose–dependent manner. Day-8 neurons were more radiosensitive than day-16 neurons (p=0.01). At 12 h post-irradiation, 20 Gy carbon-beams and 30 Gy X-ray induced about 65% and 25% apoptosis, respectively. The simple regression analysis revealed that the carbon-beams RBE at day-8 DRG and SYMP using the GCC data were 4.6 and 4.2, respectively. Whilst, at day-16 DRG and SYMP were 3.4 and 3.3, respectively. However, the RBE at day-8 DRG and SYMP for apoptosis induction was 4.1 and 3.7, respectively, whereas that at day-16 DRG and SYMP was 4.2 and 3.7 respectively.
Conclusions
The carbon-beams were 3.3-4.6-fold more effective than X-rays for GCC and apoptosis induction in both day-16 and day-8 neurons. Growth cone collapse assay is potentially beneficial in assessing the effect of irradiation on neuron cells
