Osteopontin is induced by hedgehog pathway activation and promotes fibrosis progression in nonalcoholic steatohepatitis.
Nonalcoholic steatohepatitis (NASH) is a leading cause of cirrhosis. Recently, we showed that NASH-related cirrhosis is associated with Hedgehog (Hh) pathway activation. The gene encoding osteopontin (OPN), a profibrogenic extracellular matrix protein and cytokine, is a direct transcriptional target of the Hh pathway. Thus, we hypothesize that Hh signaling induces OPN to promote liver fibrosis in NASH. Hepatic OPN expression and liver fibrosis were analyzed in wild-type (WT) mice, Patched-deficient (Ptc(+/-) ) (overly active Hh signaling) mice, and OPN-deficient mice before and after feeding methionine and choline-deficient (MCD) diets to induce NASH-related fibrosis. Hepatic OPN was also quantified in human NASH and nondiseased livers. Hh signaling was manipulated in cultured liver cells to assess direct effects on OPN expression, and hepatic stellate cells (HSCs) were cultured in medium with different OPN activities to determine effects on HSC phenotype. When fed MCD diets, Ptc(+/-) mice expressed more OPN and developed worse liver fibrosis (P < 0.05) than WT mice, whereas OPN-deficient mice exhibited reduced fibrosis (P < 0.05). In NASH patients, OPN was significantly up-regulated and correlated with Hh pathway activity and fibrosis stage. During NASH, ductular cells strongly expressed OPN. In cultured HSCs, SAG (an Hh agonist) up-regulated, whereas cyclopamine (an Hh antagonist) repressed OPN expression (P < 0.005). Cholangiocyte-derived OPN and recombinant OPN promoted fibrogenic responses in HSCs (P < 0.05); neutralizing OPN with RNA aptamers attenuated this (P < 0.05).


CONCLUSIONS
OPN is Hh-regulated and directly promotes profibrogenic responses. OPN induction correlates with Hh pathway activity and fibrosis stage. Therefore, OPN inhibition may be beneficial in NASH.
Division of Gastroenterology, Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
Wing-Kin
WK
Syn
Steve S
SS
Choi
Evaggelia
E
Liaskou
Gamze F
GF
Karaca
Kolade M
KM
Agboola
Ye Htun
YH
Oo
Zhiyong
Z
Mi
Thiago A
TA
Pereira
Marzena
M
Zdanowicz
Padmini
P
Malladi
Yuping
Y
Chen
Cynthia
C
Moylan
Youngmi
Y
Jung
Syamal D
SD
Bhattacharya
Vanessa
V
Teaberry
Alessia
A
Omenetti
Manal F
MF
Abdelmalek
Cynthia D
CD
Guy
David H
DH
Adams
Paul C
PC
Kuo
Gregory A
GA
Michelotti
Peter F
PF
Whitington
Anna Mae
AM
Diehl
D000818:Animals; D002460:Cell Line; D002796:Choline Deficiency; D004032:Diet; D005234:Fatty Liver / Q000503:physiopathology; D053823:Hedgehog Proteins / Q000502:physiology*; D055166:Hepatic Stellate Cells; D006801:Humans; D008103:Liver Cirrhosis / Q000209:etiology*; D008715:Methionine / Q000172:deficiency; D051379:Mice; D008810:Mice, Inbred C57BL; D065626:Non-alcoholic Fatty Liver Disease; D053495:Osteopontin / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics*; D015854:Up-Regulation; D014704:Veratrum Alkaloids / Q000494:pharmacology
D053823:Hedgehog Proteins; D014704:Veratrum Alkaloids; D053495:Osteopontin; D008715:Methionine; C000541:cyclopamine