title: DNA double-strand break rejoining in complex normal tissues.
abstract: OBJECTIVE
  The clinical radiation responses of different organs vary widely and likely depend on the intrinsic radiosensitivities of their different cell populations. Double-strand breaks (DSBs) are the most deleterious form of DNA damage induced by ionizing radiation, and the cells' capacity to rejoin radiation-induced DSBs is known to affect their intrinsic radiosensitivity. To date, only little is known about the induction and processing of radiation-induced DSBs in complex normal tissues. Using an in vivo model with repair-proficient mice, the highly sensitive gammaH2AX immunofluorescence was established to investigate whether differences in DSB rejoining could account for the substantial differences in clinical radiosensitivity observed among normal tissues.
  
  
  METHODS
  After whole body irradiation of C57BL/6 mice (0.1, 0.5, 1.0, and 2.0 Gy), the formation and rejoining of DSBs was analyzed by enumerating gammaH2AX foci in various organs representative of both early-responding (small intestine) and late-responding (lung, brain, heart, kidney) tissues.
  
  
  RESULTS
  The linear dose correlation observed in all analyzed tissues indicated that gammaH2AX immunofluorescence allows for the accurate quantification of DSBs in complex organs. Strikingly, the various normal tissues exhibited identical kinetics for gammaH2AX foci loss, despite their clearly different clinical radiation responses.
  
  
  CONCLUSIONS
  The identical kinetics of DSB rejoining measured in different organs suggest that tissue-specific differences in radiation responses are independent of DSB rejoining. This finding emphasizes the fundamental role of DSB repair in maintaining genomic integrity, thereby contributing to cellular viability and functionality and, thus, tissue homeostasis.
authors.affiliation: Department of Radiation Oncology, Saarland University, Homburg/Saar, Saarland, Germany. claudia.ruebe@uks.eu
authors.forename: Claudia E
authors.initials: CE
authors.lastname: Rübe
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Dong
authors.forename: Martin
authors.initials: M
authors.lastname: Kühne
authors.forename: Andreas
authors.initials: A
authors.lastname: Fricke
authors.forename: Lars
authors.initials: L
authors.lastname: Kaestner
authors.forename: Peter
authors.initials: P
authors.lastname: Lipp
authors.forename: Christian
authors.initials: C
authors.lastname: Rübe
mesh_terms: D000818:Animals; D004247:DNA / Q000502:physiology* / Q000528:radiation effects*; D004249:DNA Damage / Q000502:physiology*; D004260:DNA Repair / Q000502:physiology* / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D051379:Mice; D008810:Mice, Inbred C57BL; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000502:physiology* / Q000528:radiation effects; D014916:Whole-Body Irradiation
chemical_list: D004247:DNA