title: Proliferation of rat small hepatocytes requires follistatin expression.
abstract: Small hepatocytes (SHs) are a subpopulation of hepatocytes that have high growth potential in culture and can differentiate into mature hepatocytes (MHs). The activin (Act)/follistatin (Fst) system critically contributes to homeostasis of cell growth in the normal liver. ActA and ActB consist of two disulfide-linked Inhibin (Inh)β subunits, InhβA and InhβB, respectively. Fst binds to Act and blocks its bioactivity. In the present study we carried out the experiments to clarify how Fst regulates the proliferation of SHs. The gene expression was analyzed using DNA microarray analysis, reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR, and protein expression was examined by western blots, immunocytochemistry, and enzyme-linked immunosorbent assay. RT-PCR showed that Fst expression was high in SHs and low in MHs. Although the ActA expression was opposite to that of Fst, ActB expression was high in SHs and low in MHs and increased with time in culture. Fst protein was detected in the cytoplasm of SHs and secreted into the culture medium. ActB protein was also secreted into the medium. Although the exogenous administration of ActA and ActB apparently suppressed the proliferation of SHs, apoptosis of SHs was not induced by treatment with ActA or ActB. On the other hand, Fst treatment did not affect the colony formation of SHs but prevented the inhibitory effect of ActA. Neutralization by the anti-Fst antibody resulted in the suppression of DNA synthesis in SHs, and small hairpin RNA against Fst suppressed the expansion of SH colonies. In conclusion, Fst expression is necessary for the proliferation of SHs.
authors.affiliation: Department of Tissue Development and Regeneration, Research Institute for Frontier Medicine, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Ooe
authors.forename: Qijie
authors.initials: Q
authors.lastname: Chen
authors.forename: Junko
authors.initials: J
authors.lastname: Kon
authors.forename: Kazunori
authors.initials: K
authors.lastname: Sasaki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Miyoshi
authors.forename: Norihisa
authors.initials: N
authors.lastname: Ichinohe
authors.forename: Naoki
authors.initials: N
authors.lastname: Tanimizu
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Mitaka
mesh_terms: D028341:Activins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002454:Cell Differentiation; D049109:Cell Proliferation; D048429:Cell Size; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000378:metabolism; D004261:DNA Replication; D004797:Enzyme-Linked Immunosorbent Assay; D038681:Follistatin / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling / Q000379:methods; D005786:Gene Expression Regulation; D022781:Hepatocytes / Q000378:metabolism*; D007150:Immunohistochemistry; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D034622:RNA Interference; D051381:Rats; D011916:Rats, Inbred F344; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014162:Transfection
chemical_list: D017077:Culture Media, Conditioned; C503233:FST protein, human; D038681:Follistatin; C422405:activin A; C044147:activin B; D028341:Activins