Hepatocyte senescence induced by radiation and partial hepatectomy in rat liver.
OBJECTIVE
Exposure to radiation primes the liver for extensive replacement of the resident parenchymal cells by transplanted hepatocytes. The mechanisms underlying this repopulation remain to be clarified. In these studies, we examined the possible occurrence of cell senescence in vivo following radiation-associated preconditioning of the host liver.


METHODS
Fischer 344 rats underwent external-beam, computed-tomography-based partial liver irradiation. A single dose of 25 Gy was delivered to the right liver lobes (40% of liver mass). An additional group of animals received a 1/3 partial hepatectomy (removal of the left anterior lobe) four days after irradiation. Non-irradiated groups served as controls. All rats were sacrificed four weeks after the initial treatment.


RESULTS
The irradiated livers displayed several markers of cell senescence, including expression of senescence-associated-β-galactosidase (SA-β-gal), increase in cell size, and up-regulation of cyclin-dependent kinase inhibitors (CDK-I) p16 and p21. Furthermore, quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) analysis revealed activation of the senescence-associated secretory phenotype (SASP), including the cytokines interleukin 6 (IL6) and 1α (IL1α). The senescence-related changes were more prominent in rats undergoing partial hepatectomy (PH) following irradiation (IR).


CONCLUSIONS
We conclude that priming with radiation for liver repopulation results in the induction of cell senescence and the up-regulation of a senescence-associated secretory phenotype. The latter can contribute to the extensive growth of transplanted cells in this system.
Department of Biomedical Sciences, University of Cagliari , Italy.
Maria Paola
MP
Serra
Fabio
F
Marongiu
Marcella
M
Sini
Michela
M
Marongiu
Antonella
A
Contini
Hendrik
H
Wolff
Margret
M
Rave-Frank
Petra
P
Krause
Ezio
E
Laconi
Sarah
S
Koenig
D000818:Animals; D049109:Cell Proliferation / Q000528:radiation effects; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology* / Q000528:radiation effects*; D006498:Hepatectomy; D022781:Hepatocytes / Q000502:physiology* / Q000528:radiation effects*; D008099:Liver / Q000502:physiology* / Q000528:radiation effects / Q000601:surgery; D008297:Male; D011829:Radiation Dosage; D051381:Rats; D011916:Rats, Inbred F344; D014916:Whole-Body Irradiation
Cell senescence; hepatocyte transplantation; liver repopulation; radiation; regenerative medicine