Proliferative capability of hepatocytes and expression of G1-related cell cycle molecules in the development of liver cirrhosis in rats.
Liver cirrhosis is the end stage of various chronic liver diseases and its prognosis is very poor. One of the most important causes of liver cirrhosis appears to be impaired proliferative capability of hepatocytes caused by continuous hepatic damage. Cell cycle-related molecules have been shown to play essential roles in cell proliferation. Specifically, G1-related cell cycle molecules are important, because they are requisite for the entry into the cell cycle from the quiescent state. However, the role of these cell cycle molecules during the development of liver cirrhosis remains to be examined. In the present study, liver cirrhosis was produced in rats by intraperitoneally administering dimethylnitrosamine (DMN). Proliferative capability of hepatocytes estimated immunohistochemically by proliferating cell nuclear antigen staining was markedly increased at an early stage of cirrhosis development. However, it was gradually decreased thereafter and suppressed substantially at the time of cirrhosis manifestation. Cyclin D1 expression estimated by a real-time reverse transcription-polymerase chain reaction (RT-PCR) method was also increased markedly at an early stage of cirrhosis development but decreased substantially thereafter. mRNA levels of catalytic subunits of cyclin D1, cyclin-dependent kinase 4 (Cdk4) and Cdk6, did not show significant changes during the development of liver cirrhosis. Among G1-specific Cdk inhibitors, expression of p15INK4b and p16INK4a estimated by an RT-PCR method was increased according to the progression of cirrhosis and reached a peak at the time of cirrhosis manifestation. Conversely, p18INK4c expression did not change significantly during the development of liver cirrhosis. These results suggest that cyclin D1 plays an essential role in hepatocyte proliferation in response to hepatic damage. However, with the decrease of cyclin D1 expression and increase of p15INK4b and p16INK4a expression, proliferative capability of hepatocytes is severely impaired and extracellular matrix components are deposited to retrieve space lost by the destruction of hepatic parenchyma, resulting in establishment of liver cirrhosis.
Funakoshi
Fumi
F
Third Department of Internal Medicine, Kagawa University School of Medicine, Miki-cho, Kita-gun, Kagawa 761-0793, Japan.
Masaki
Tsutomu
T
Kita
Yuko
Y
Hitomi
Misuzu
M
Kurokohchi
Kazutaka
K
Uchida
Naohito
N
Watanabe
Seishiro
S
Yoshiji
Hitoshi
H
Kuriyama
Shigeki
S
D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D019938:Cyclin D1 / Q000378:metabolism*; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D050763:Cyclin-Dependent Kinase Inhibitor p18; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004128:Dimethylnitrosamine / Q000633:toxicity; D005109:Extracellular Matrix / Q000378:metabolism; D016193:G1 Phase / Q000502:physiology*; D022781:Hepatocytes / Q000378:metabolism / Q000473:pathology*; D008099:Liver / Q000378:metabolism / Q000473:pathology*; D008103:Liver Cirrhosis / Q000139:chemically induced / Q000209:etiology / Q000378:metabolism*; D008297:Male; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D025521:Tumor Suppressor Proteins / Q000378:metabolism
C493969:Cdkn2b protein, rat; C493973:Cdkn2c protein, rat; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050763:Cyclin-Dependent Kinase Inhibitor p18; D018809:Proliferating Cell Nuclear Antigen; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; C495903:Cdk4 protein, rat; C495913:Cdk6 protein, rat; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases; D004128:Dimethylnitrosamine