|
PresentationsComparative analysis of γH2AX and Rad51 protein foci changes during prolonged X-ray irradiation in proliferating vs quiescent human mesenchymal stromal cellsFederal biomedical agency of Russian Federation National research Center Federal Medico-Biophysical Center of Burnazyan Double strand breaks (DSBs) and their repair are one of the key events that determine cellular fate after irradiation. Even one DSB left unrepaired can lead to cell death . So this kind of damage is of critical importance for cell survival. There are two DSB repair pathways homologous recombination (HR) and non-homologus end joining (NHEJ) . HR is precise, but it takes a lot of time and what is more can happen only during certain phases of cell cycle (late S - G2) when another chromatid is present. The events of HR can be easily tracked by immunostaining of the cells for the central for this pathway Rad51 protein. NHEJ pathway is fast, error -prone and more common for mammalian cells. The number of DSBs can be easily examined by the immunostaining for the γH2AX protein foci. γH2AX is a specific form of H2AX histone, phosphorylated on its 139 Ser. This form arise within minutes after DSB occurrence. H2AX histone is phosphorylated within several megabase pairs around DSB by the family of PIKK kinases. The major kinase responsible for this process is the ATM (ataxia-telangiectasia mutated) kinase. One of the important factor that influence cell sensvity to irradiation and cellular consequences of it for each cell is its cell cycle phase. In this study we distinguished G0 cells from all others by using the Ki67 marker protein. Ki67 protein is a well-known cell proliferation marker. It is present in the nucleus of interphase and mitotic cells. G0 cells lack Ki67 protein inside them. Dose rate is a significant factor that influence cellular conseques of irradiation. Although for high doses of X-rays with high dose rate cellular effects are well understood, these effects are less clear for low doses of prolonged irradiation with a low dose rate. Multipotent mesenchymal stromal cells (MSCs) are well-characterized type of stem cells They have a fibroblast-like phenotype and are able to renew themselves. Surface markers of these cells resemble those of fibroblasts. MSCs are considered to be relatively radioresistant in comparison to radiosensitive hematopoietic stem cells. Their radioresistance is caused by the activity of DNA DSBs repair systems in MSCs. This mean that MSCs can survive irradiation lethal to hematopoietic cells and can, in some cases, undergo oncotransformation. In this work we show how DNA repair machinery of MSCs is activated during prolonged irradiation.
|
