The Effect of miR-155 on DNA Damage in Mesenchymal Stem Cells

Considering the crucial role of miR-155 in DNA repair regulation, the aim of this study was to evaluate the effect of miR-155 on the expression of DNA repair factors involved in single- and double-strand DNA breaks (SSBs and DSBs) and mismatch repair (MMR) in mesenchymal stem cells (MSCs). MSCs were isolated from the bone marrow of a healthy individual, and then confirmed by their adipogenic/osteogenic differentiation and flow cytometric analysis of surface markers of MSCs (CD105, CD90, and CD73). MSCs transfection by green fluorescent protein (GFP) plasmid bearing miR-155 was verified by fluorescent microscope, and was measured via analyzing the percentage of transfected cells compared to non-transfected by flow cytometry. The expression of miR-155 and mRNAs related to DNA repair response system, i.e. XRCC1, XRCC5, XRCC6, and RAD51, were assessed by real-time PCR. Overexpression of miR-155 in MSCs was significant compared to control (p = 0.034). Increase in the expression of DNA repair genes, including XRCC1, XRCC6, XRCC5, and RAD51 was not significant (p = 0.066, 0.108, 0.092, 0.631, and 0.262, respectively). In conclusion, although the expression of DNA repair genes by miR-155 overexpression was not significant, it has the potential to affect DNA repair genes expression.