Chromosomal Radiosensitivity in Secondary-Progressive Multiple Sclerosis Patients

Purpose : To investigate chromosomal radiosensitivity of secondary progressive (SP) multiple sclerosis (MS) patients in comparison to a group of healthy individuals. Material and methods : Chromosomal radiosensitivity was assessed in vitro with the G2 assay and the G0-micronucleus (MN) assay. For the G2 assay phytohaemagglutinin (PHA) stimulated blood cultures were irradiated with a dose of 0.4 Gy 60 Co rays in the G2 phase of the cell cycle. For the MN assay unstimulated diluted blood samples were exposed to 3.5 Gy 60 Co rays delivered at a high dose-rate (HDR=1 Gy/min) or low dose-rate (LDR=4 mGy/min). Results : No significant differences in the number of chromatid breaks were observed between MS patients and healthy individuals. With the G0-MN assay a higher spontaneous MN yield was found in MS patients. At HDR irradiation no significant differences were shown, while at LDR irradiation, MS patients were found less sensitive than healthy controls. The dose-rate sparing index was higher for MS patients, pointing to a better repair capacity. Conclusions : MS patients are not characterised by an enhanced in vitro chromosomal radiosensitivity. The radioresistant response, which was only observed with the MN assay after LDR irradiation, may point to an adaptive response induced by in vivo oxidative stress in SPMS patients.