- - - PhD, Ionizing and Non-ionizing Radiation Protection Research Center, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
- - - PhD, Ionizing and Non-ionizing Radiation Protection Research Center, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
- - - PhD, Shiraz Institute for Cancer Research, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
- - - PhD, Department of Medical Physics and Engineering, Shiraz University of Medical Science, Shiraz, Iran
- - - PhD, Shiraz Institute for Cancer Research, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran

Background: The effects of radiation on the cellular compartments of the tumor microenvironment (TME) might be essential in radiotherapy outcomes. Objective: We aimed to assess the effects of the different doses of gamma irradiation on viability, ABCA۱ and MMP-۹ expression in adipose-derived mesenchymal stem cells (ASCs) as a critical part of TME.Material and Methods: In this experimental study, ASCs were extracted from five healthy donors and irradiated with different doses of ۵, ۱۰ and ۳۰ Gy of gamma. Then, RNA was extracted from irradiated ASCs and cDNA was synthesized. The viability of ASCs was determined at ۲۴, ۴۸, ۷۲ and ۱۶۸ h after irradiation using trypan blue staining. The expression of ABCA۱ was checked by quantitative real-time (qRT)-PCR technique and the expression of MMP-۹ protein was evaluated by western-blot. Results: Based on our findings, ۱۰ Gy and ۳۰ Gy but not ۵ Gy of gamma irradiation significantly decreased the viability of ASCs after ۲۴, ۴۸, ۷۲ and ۱۶۸ h compared to the non-irradiated cells (p < ۰.۰۵). However, a dose of ۵ Gy increased ABCA۱ in ASCs significantly compared to ۱۰ Gy and ۳۰ Gy (P=۰.۰۱ and P=۰.۰۲, respectively). In addition, the analysis of western blot data showed that ۵ Gy of gamma irradiation significantly increased the expression of MMP-۹ in ASCs (P=۰.۰۱۹). Conclusion: It is concluded that various doses of gamma radiation elicit differential ASCs responses that may lead to different tumor cell reactions to the radiotherapy through bystander effects.

Radiation, cancer, stem cells, Tumor Microenvironment, Bystander Effects