Bone morphogenetic protein-4 modulates proliferation and terminal differentiation of fetal hepatic stem/progenitor cells.
Fetal hepatic stem/progenitor cells, called hepatoblasts, play central roles in liver organogenesis; however, molecular mechanisms regulating proliferation and terminal differentiation of such cells have not been completely elucidated. Bone morphogenetic protein-4 (BMP-4) is essential for the development of stem cells in various tissues, but its function in regulating the phenotype of hepatoblasts after the mid-gestational fetal stage remains unclear. The aim of this study is to clarify a functional role for BMP-4 in proliferation and terminal differentiation of murine hepatoblasts in mid-gestational fetal livers.


METHODS
A functional role for BMP-4 in proliferation and terminal differentiation of murine hepatoblasts was validated by assay of colony formation, biliary luminal formation, and hepatic maturation using primary hepatoblasts in vitro. Molecular mechanisms regulating such effects of BMP-4 on primary hepatoblasts were also analyzed.


RESULTS
Stimulation of BMP-4 upregulated phosphorylation of Smad1/5 in hepatoblasts. Bone morphogenetic protein-4 significantly suppressed colony formation of primary hepatoblasts in a dose-dependent manner, significantly suppressed cholangiocytic luminal formation of hepatoblasts, and promoted hepatic maturation of primary hepatoblasts. Stimulation of BMP-4 regulated the activation of several mitogen-activated protein kinases, such as extracellular signal-regulated kinase, Akt, p38 mitogen-activated protein kinase, and calcium/calmodulin-dependent protein kinase IIα in primary hepatoblasts. Moreover, Wnt5a, a molecule regulating cholangiocytic luminal formation, and BMP-4 coordinately suppressed proliferation and cholangiocytic luminal formation of hepatoblasts.


CONCLUSIONS
This study shows that BMP-4-mediated signaling controls proliferation and terminal differentiation of fetal hepatic stem/progenitor cells.
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Fumio
F
Goto
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.|Department for Liver Disease Control, Tokyo Medical and Dental University, Tokyo, Japan.
Sei
S
Kakinuma
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Masato
M
Miyoshi
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Tomoyuki
T
Tsunoda
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Shun
S
Kaneko
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Ayako
A
Sato
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Yu
Y
Asano
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Satoshi
S
Otani
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Seishin
S
Azuma
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Hiroko
H
Nagata
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Fukiko
F
Kawai-Kitahata
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Miyako
M
Murakawa
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Sayuri
S
Nitta
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Yasuhiro
Y
Itsui
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Mina
M
Nakagawa
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.|Department for Liver Disease Control, Tokyo Medical and Dental University, Tokyo, Japan.
Yasuhiro
Y
Asahina
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Mamoru
M
Watanabe
Wnt5a; calcium/calmodulin-dependent protein kinase II; cholangiocytic cyst; cyclinD1; hepatoblast