The effect of 137Cs γ-rays on the differentiation of human peripheral blood mononuclear cells to osteoclast-like cells

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 was determined by ELISA. Results PBMCs were differentiated into OCLs by the treatments of RANKL and M-CSF. 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-5b, 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. Key words: Ionizing radiation; Human peripheral blood mononuclear cells; Osteoclastogenesis