Objective To study the effect of γ-rays irradiation on the differentiation potential of the human peripheral blood monocytes (PBMCs) into osteoclast-like cells (OCLs) in vitro.Methods PBMCs were isolated by density gradient centrifugation,treated by receptor activator of nuclear factor-κ B ligand (RANKL) and macrophage-colony stimulating factor (M-CSF) and exposed to 137Cs γ-rays with different radiation doses (0,0.75,2 Gy).After seven days of incubation,the cells were stained for tartrate resistant acid phosphatase (TRAP) and bone slices were stained by toluidine blue on the tenth day.Meanwhile,the characteristic osteoclast markers including Cathepsin K and integrin β3 were analyzed by real-time PCR.Tartrate resistant acid phosphatase 5b (TRAcP-5b) in the culture supernatant wasdetermined by ELISA.Results PBMCs were differentiated into OCLs by the treatments of RANKL and MCSF.The number of TRAP positive multinucleated OCLs was significantly higher in the dose of 0.75 Gy group than in control (0 Gy) group (t =3.451,P ＜ 0.05).Compared with the control group,the expression levels of Cathepsin K and integrin β3 and the concentration of TRAcP-5b were significantly elevated (t =2.343,2.728,3.631,P ＜ 0.05).However,in the 2 Gy group,there was a decrease in the number of osteoclasts,mRNA expression level of osteoclast characteristic markers and TRAcP-Sb,but no statistically significant differences compared with the control group.Conclusions Ionizing radiation may influence the osteoclastogenesis during the PBMCs differentiation to OCLs.At low dosage,ionizing radiation promotes osteoclastogenesis and enhances the resorptive activity of osteoclasts,but a decline of differentiation potential was observed at high dosage of radiation.

Objective To explore the feasibility of using glycophorin A somatic mutation in peripheral erythrocytes,in order to evaluate the cancer risk of occupational medical exposure to ionizing radiation.Methods Totally 336 medical radiation workers were recruited as three groups (general radiation group,computer tomography group,intervention and radiation treatment group) and 112 healthy adults were selected as control by using stratified random cluster sampling method,where 176 medicalradiation workers and 58 health controls had a MN-heterozygous type.The erythrocytes were fixed and bound with fluorescent-labeled monoclonal antibody,and the glycophorin A somatic mutation frequency was assayed by a modified BR6-1W1 method using a FACScan flow cytometer.The individual susceptibility to radiation was investigated using micronuclei test and 3-Aminobenzamide index test.Results The GPA somatic mutation frequency of medical-radiation workers was significantly higher than that of healthy control ( t =2.29 - 11.48,P ＜ 0.05 ).In particular,the NO GPA aberration frequency of interventional radiology workers was much higher than that of the general medical diagnostic workers (t =2.01,P ＜ 0.05).In addition,the NO GPA variant frequency changed significantly with the years of radiation service,cumulative doses,and 3AB index.However,the NN GPA variant frequency was only associated with the years of radiation service,and no significant correlations were found between NN GPA variant frequency and cumulative dose of radiation exposure or 3AB index. Conclusions GPA mutation frequency,especially NO GPA mutation frequency could be used as a sensitive biomarker to predict the DNA damage and individual susceptibility for the population exposed to professional low-dose ionizing radiation.