Studies On The Biological Effects Of Low Dose Radiation In The Bone Marrow Mesenchymal Stem Cell And Their Mechanisms

The biological responses of organisms to low dose ionizing radiation are different from high dose ionizing radiation. These mechanistic studies are focus on hormesis,adaptive responses, bystander effects, genomic instability and so on, and the first and second are researched in depth. Low-dose ionizing radiation induced hormesis has been extensively observed in different biological systems including reproduction, immune and hematopioetic system. Mammalian cells exposed to low dose ionizing radiation show a significantly enhanced tolerance to a subsequent exposure to high dose radiation. The cell proliferation and adaptive response have been reported in many normal celllines. However, only a few studies available for the effects of LDR on MSCs, but these previous studies were mainly performed in vivo. The molecular mechanisms that underlie these effects to LDR are not fully understood..In the present study, the bone marrow mesenchymal stem cells were isolated from rat bone marrow and culture expanded to billions of cells. The cells can greatly proliferate in vitro and maintain special phenotypic and can differentiate into adipocytes,chondrocytes and osteocytes.We demonstrate that low dose ionizing radiation stimulates proliferation of the bone marrow mesenchymal stem cell. The result demonstrated that activation of both MAPK/ERK and PI3K/AKT pathway may induce proliferation of bone marrow Mesenchymal Stem Cells exposed to low dose ionizing radiation. The adaptive responses also exist in BMMSC. the study suggests that an adaptive response can be induced by exposure to 75 mGy in bone marrow mesenchymal stem cells. ATM, a key DNA-damage response protein,play an essential role in the process. Coactivation of the p-ATM. H2AX is required for the prosurvival effect exhibited against the DNA damage and cytotoxic effects of the subsequent high dose radiation.