title: Global gene expression profile of normal and regenerating liver in young and old mice.
abstract: The ability of the liver to regenerate and adjust its size after two/third partial hepatectomy (PH) is impaired in old rodents and humans. Here, we investigated by microarray analysis the expression pattern of hepatic genes in young and old untreated mice and the differences in gene expression profile following PH. Of the 10,237 messenger RNAs that had detectable expression, only 108 displayed a greater than 2-fold modification in gene expression levels between the two groups. These genes were involved in inflammatory and immune response, xenobiotics, and lipid and glucose metabolism. To identify the genes responsible for the different regenerative response, 10-week and 18-month-old mice subjected to PH were sacrificed at different time intervals after surgery. The results showed that 2463 transcripts had significantly different expression post PH between the two groups. However, in spite of impaired liver regeneration in old mice, cell cycle genes were similarly modified in both groups, the only exception being cyclin D1 gene which was up-regulated soon after PH in young mice, but mostly down-regulated in aged animals. Surprisingly, while in young hepatectomized mice, Yap messenger RNA (mRNA) expression was not significantly enhanced and protein expression essentially reflected the progression into cell cycle, its mRNA and protein levels were robustly increased in the liver of aged animals. Furthermore, a significant change of the age-related expression of the size regulator Yes-associated protein (YAP) was observed. Unexpectedly, while in young hepatectomized mice, Yap mRNA expression was not significantly enhanced and protein expression essentially reflected the progression into cell cycle, its mRNA and protein levels were robustly increased in the liver of aged animals. Moreover, when PH was performed on mitogen-induced enlarged livers, the earlier restoration of the original liver mass compared to animals subjected to PH only led to YAP down-regulation concomitantly with cyclin D1 up-regulation. Our data suggest that YAP activation is a size-dependent homeostatic mechanism that does not necessarily reflect cell cycle progression.
authors.affiliation: Department of Biomedical Sciences, Unit of Oncology and Molecular Pathology, University of Cagliari, Via Porcell 4, Cagliari, Italy, mpibiri@hotmail.com.
authors.forename: Monica
authors.initials: M
authors.lastname: Pibiri
authors.forename: Pia
authors.initials: P
authors.lastname: Sulas
authors.forename: Vera Piera
authors.initials: VP
authors.lastname: Leoni
authors.forename: Andrea
authors.initials: A
authors.lastname: Perra
authors.forename: Marta Anna
authors.initials: MA
authors.lastname: Kowalik
authors.forename: Angela
authors.initials: A
authors.lastname: Cordella
authors.forename: Pasquale
authors.initials: P
authors.lastname: Saggese
authors.forename: Giovanni
authors.initials: G
authors.lastname: Nassa
authors.forename: Maria
authors.initials: M
authors.lastname: Ravo
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D000375:Aging / Q000235:genetics*; D000818:Animals; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics; D005260:Female; D020869:Gene Expression Profiling; D006498:Hepatectomy; D007124:Immunoenzyme Techniques; D008099:Liver / Q000601:surgery; D008115:Liver Regeneration / Q000235:genetics*; D051379:Mice; D046228:Microarray Analysis; D010750:Phosphoproteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D000091102:YAP-Signaling Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D000091102:YAP-Signaling Proteins; C486223:Yap1 protein, mouse