title: Dose-dependent onset of regenerative program in neutron irradiated mouse skin.
abstract: BACKGROUND
  Tissue response to irradiation is not easily recapitulated by cell culture studies. The objective of this investigation was to characterize, the transcriptional response and the onset of regenerative processes in mouse skin irradiated with different doses of fast neutrons.
  
  
  RESULTS
  To monitor general response to irradiation and individual animal to animal variation, we performed gene and protein expression analysis with both pooled and individual mouse samples. A high-throughput gene expression analysis, by DNA oligonucleotide microarray was done with three months old C57Bl/6 mice irradiated with 0.2 and 1 Gy of mono-energetic 14 MeV neutron compared to sham irradiated controls. The results on 440 irradiation modulated genes, partially validated by quantitative real time RT-PCR, showed a dose-dependent up-regulation of a sub-class of keratin and keratin associated proteins, and members of the S100 family of Ca(2+)-binding proteins. Immunohistochemistry confirmed mRNA expression data enabled mapping of protein expression. Interestingly, proteins up-regulated in thickening epidermis: keratin 6 and S100A8 showed the most significant up-regulation and the least mouse-to-mouse variation following 0.2 Gy irradiation, in a concerted effort toward skin tissue regeneration. Conversely, mice irradiated at 1 Gy showed most evidence of apoptosis (Caspase-3 and TUNEL staining) and most 8-oxo-G accumulation at 24 h post-irradiation. Moreover, no cell proliferation accompanied 1 Gy exposure as shown by Ki67 immunohistochemistry.
  
  
  CONCLUSIONS
  The dose-dependent differential gene expression at the tissue level following in vivo exposure to neutron radiation is reminiscent of the onset of re-epithelialization and wound healing and depends on the proportion of cells carrying multiple chromosomal lesions in the entire tissue. Thus, this study presents in vivo evidence of a skin regenerative program exerted independently from DNA repair-associated pathways.
authors.affiliation: ENEA, Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile Roma, Italy.
authors.forename: Emiliano
authors.initials: E
authors.lastname: Fratini
authors.forename: Valerio
authors.initials: V
authors.lastname: Licursi
authors.forename: Mara
authors.initials: M
authors.lastname: Artibani
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Kobos
authors.forename: Paolo
authors.initials: P
authors.lastname: Colautti
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Negri
authors.forename: Roberto
authors.initials: R
authors.lastname: Amendola
mesh_terms: D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D004307:Dose-Response Relationship, Radiation; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D009502:Neutrons; D020411:Oligonucleotide Array Sequence Analysis; D011829:Radiation Dosage; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012867:Skin / Q000528:radiation effects*
chemical_list: D017931:DNA Primers