title: Multiple facets of the DNA damage response contribute to the radioresistance of mouse mesenchymal stromal cell lines.
abstract: The regeneration of the hematopoietic system following total body irradiation is supported by host-derived mesenchymal stromal cells (MSCs) within the bone marrow. The mechanisms used by MSCs to survive radiation doses that are lethal to the hematopoietic system are poorly understood. The DNA damage response (DDR) represents a cohort of signaling pathways that enable cells to execute biological responses to genotoxic stress. Here, we examine the role of the DDR in mediating the resistance of MSCs to ionizing radiation (IR) treatment using two authentic clonal mouse MSC lines, MS5 and ST2, and primary bulk mouse MSCs. We show that multiple DDR mechanisms contribute to the radio-resistance of MSCs: robust DDR activation via rapid γ-H2AX formation, activation of effective S and G(2)/M DNA damage checkpoints, and efficient repair of IR-induced DNA double-strand breaks. We show that MSCs are intrinsically programmed to maximize survival following IR treatment by expressing high levels of key DDR proteins including ATM, Chk2, and DNA Ligase IV; high levels of the anti-apoptotic, Bcl-2 and Bcl-(XL); and low levels of the pro-apoptotic, Bim and Puma. As a result, we demonstrate that irradiated mouse MSCs withstand IR-induced genotoxic stress, continue to proliferate, and retain their capacity to differentiate long-term along mesenchymal-derived lineages. We have shown, for the first time, that the DDR plays key roles in mediating the radioresistance of mouse MSCs which may have important implications for the study and application of MSCs in allogeneic bone marrow transplantation, graft-versus-host disease, and cancer treatment.
authors.affiliation: Physiology Department, Regenerative Medicine Institute, National Centre of Biomedical Engineering Science and School of Medicine, Nursing and Health Sciences, National University of Ireland, Galway, Galway, Ireland.
authors.forename: Tara
authors.initials: T
authors.lastname: Sugrue
authors.forename: James A L
authors.initials: JA
authors.lastname: Brown
authors.forename: Noel F
authors.initials: NF
authors.lastname: Lowndes
authors.forename: Rhodri
authors.initials: R
authors.lastname: Ceredig
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D015496:CD4-Positive T-Lymphocytes / Q000528:radiation effects; D018414:CD8-Positive T-Lymphocytes / Q000528:radiation effects; D059447:Cell Cycle Checkpoints; D018797:Cell Cycle Proteins / Q000096:biosynthesis; D002454:Cell Differentiation / Q000528:radiation effects; D002460:Cell Line; D049109:Cell Proliferation / Q000528:radiation effects; D064447:Checkpoint Kinase 2; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D004249:DNA Damage / Q000528:radiation effects*; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000096:biosynthesis; D004260:DNA Repair / Q000528:radiation effects*; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D006657:Histones / Q000096:biosynthesis / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000528:radiation effects*; D051379:Mice; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D011836:Radiation Tolerance / Q000502:physiology*; D011839:Radiation, Ionizing; D015398:Signal Transduction; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis; D051020:bcl-X Protein / Q000096:biosynthesis
chemical_list: C494812:Bcl2l1 protein, mouse; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D006657:Histones; D019253:Proto-Oncogene Proteins c-bcl-2; D025521:Tumor Suppressor Proteins; D051020:bcl-X Protein; C475961:gamma-H2AX protein, mouse; D064447:Checkpoint Kinase 2; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; C578633:Chek2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D011088:DNA Ligases; D000072481:DNA Ligase ATP