Behavior and differentiation studies of hASCs and rBMSCs by the γ-ray irradiation

Recently, in tissue engineering, ionizing radiation has been used as stimulation. Especially, several studies showed that low-dose ionizing radiation induced the stimulation of cell proliferation. Also, it is reported that single low dose γ-irradiation for whole-body or lymphoid-organ significantly improved the spontaneous recovery. The purpose of this study is to investigate behavior and differentiation of human adipose tissue-derived stem cells (hASCs) and rabbit bone marrow stromal cells (rBMSCs) after low dose and high dose of γ-irradiation. Cells were irradiated with γ-rays of 1, 10, 100 mGy and 1 Gy. In addition, we investigated the effects on the osteogenic differentiation of γ-irradiation. PLLA scaffolds with 90% porosity and 300-500 μm pore size were fabricated and cells were seeded onto the scaffolds. After that, cell-scaffold construct were irradiated with 1 mGy and implanted subcutaneously in nude mice for up to 10 weeks. Specimens were harvested after 10 weeks and analyzed. In the results, p-H2AX/DAPI ratio increased with time while the p-H2X expression was not found all time point in control (no irradiation) group. But, in the group radiated with low γ-ray (1 mGy), the p-H2X expression almost did not appear similar with non-radiated group. However, in the osteogenic differentiation tests, the control group and the irradiated group revealed no significant difference. In conclusion, low dose γ-irradiation could be used as stimulation for tissue engineering using specific stem cells and consequently, this system will be useful for combination technology of radiation and cell therapy. However, further studies are needed for examining the general mechanism of the effects on the low dose irradiation for stem cells.