| Co-Investigator(Kenkyū-buntansha) |
HAYASHIZAKI Yoshihide RIKEN GENOME SCIENCE, INSTITUTE PROJECT LEADER, ゲノム科学総合研究センター, プロジェクトディレクター (70192705)
ISHIKAWA Takashi YOKOHAMA CITY UNIV., SCHOOL OF MEDCINE, ASSIST PROF., センター病院・総合外科, 講師 (80275049)
岡崎 康司 横浜市立大学, 医学部, 助教授 (80280733)
窪田 徹 横浜市立大学, 医学部, 助手 (10315773)
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| Budget Amount *help |
¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 2003: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 2002: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2001: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
Massive hepatectomy often induced lethal hepatic failure. The mechanism has been described using two theories : indirect injury caused by microcircular disturbance induces necrosis to hepatocytes, and direct injury caused by cytotoxic disturbance induces apoptosis to hepatocyte.
Exp.1
Excessive hepatectomy often causes fatal liver failure. We have reported that this is mainly mediated by apoptosis, characterized pathologically by TUNEL assay positive hepatocytes and a ladder pattern in DNA fragmentation assays. To investigate the mechanism, we used a cDNA microarray analysis to compare clearly differentiated rat partial hepatectomy (PHx) models (90%PHx, and 95%PHx). All 90%PHx rats survived, but the 95%PHx animals died of hepatic failure within 96 hours. The remnant liver was obtained at 4 time points (1,3,12, and 24 hrs after PHx). After RNA extraction, two samples were labeled with different fluorescent dyes and hybridized to the RIKEN set of 18,816 full-length enriched mouse cDNA arra
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ys. Scanning for fluorescent dye signals was performed, and many caspases were upregulated at 1 hr after PHx in the 95%PHx group. On the other hand, genes of Bcl-2, heat shock proteins and gluthatione-S-transferase were downregulated. We concluded that fatal hepatic after excessive hepatectomy was characterized by increased apoptosis and diminished liver regeneration.
Exp.2
Background/Aim : The liver has the capacity to regenerate after partial hepatectomy. In order to clarify the mechanism of liver regeneration, we observed the initial stage, especially the mechanism of gene expression during progress from G0 to S phase (0〜24 hrs), and attempted to identify the new gene controlling progress to the S phase.
Methods : We applied large-scale gene expression analysis with complementary DNA (cDNA) microarrays in mouse hepatectomy models to clarify the mechanism of liver regeneration after partial hepatectomy.
Results : As a result, 23 new immediate-early gene candidates such as IRAK-1 (interleukin-1 receptor associated kinase-1) and karyopherin alpha 1, which are involved in transportation within the nucleus, were discovered. Candidates for new genes concerned with the progress to the S phase were discovered : ID2 (inhibitor of DNA binding 2) and ID3 (inhibitor of DNA binding 3), both new liver regeneration factors that promoted progress to the S phase, and Gadd45 gamma (growth arrest and DNA-damage-inducible protein) as a factor inhibiting that process.
Conclusions : The above result not only suggests the importance of NF-κB in the initial stage of liver regeneration but also points to the orderly maintenance of the proliferation of the cells in liver regeneration. Less
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