Hedgehog-mediated epithelial-to-mesenchymal transition and fibrogenic repair in nonalcoholic fatty liver disease.
OBJECTIVE
Repair responses define the ultimate outcomes of liver disease. This study evaluated the hypothesis that fibrogenic repair in nonalcoholic fatty liver disease (NAFLD) is mediated by Hedgehog (Hh) pathway activation and consequent induction of epithelial-to-mesenchymal transitions (EMT) in ductular-type progenitors.


METHODS
Immature ductular cells were exposed to Sonic hedgehog (Shh) in the presence or absence of the Hh inhibitor cyclopamine to determine whether Hh-pathway activation directly modulates EMT in liver progenitors. Potential biologic correlates of progenitor cell EMT were assessed using mice fed methionine-choline-deficient + ethionine (MCDE) diets with or without cyclopamine. The effects of increased Hh signaling on EMT and fibrogenic repair during diet-induced NAFLD were also compared in wild-type (WT) and Patched haplo-insufficient (Ptc(+/-)) mice. Finally, evidence of Hh-pathway activation and EMT was examined in liver sections from patients with NAFLD.


RESULTS
In cultured progenitors, Shh repressed expression of epithelial genes and EMT inhibitors but induced genes that are expressed by myofibroblasts. Cyclopamine reversed these effects. In mouse NAFLD models, Hh-pathway activation, EMT, expansion of myofibroblastic populations, and liver fibrosis occurred. Cyclopamine inhibited Hh-pathway activation and induction of EMT. Ptc(+/-) mice, which have an overactive Hh pathway, exhibited sustained overinduction of Hh target genes and more EMT, myofibroblast accumulation, and fibrosis than WT mice. Numbers of Shh-producing cells and Hh-responsive ductular cells that expressed EMT markers increased in parallel with liver fibrosis in patients with NAFLD.


CONCLUSIONS
Hh-mediated EMT in ductular cells contributes to the pathogenesis of cirrhosis in NAFLD.
Syn
Wing-Kin
WK
Division of Gastroenterology, Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
Jung
Youngmi
Y
Omenetti
Alessia
A
Abdelmalek
Manal
M
Guy
Cynthia D
CD
Yang
Liu
L
Wang
Jiangbo
J
Witek
Rafal P
RP
Fearing
Caitlin M
CM
Pereira
Thiago A
TA
Teaberry
Vanessa
V
Choi
Steve S
SS
Conde-Vancells
J
J
Karaca
Gamze F
GF
Diehl
Anna Mae
AM
D000818:Animals; D016022:Case-Control Studies; D002460:Cell Line; D054338:Cell Transdifferentiation / Q000187:drug effects / Q000235:genetics; D002796:Choline Deficiency / Q000150:complications / Q000378:metabolism / Q000473:pathology; D018450:Disease Progression; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D005234:Fatty Liver / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D053823:Hedgehog Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D008106:Liver Cirrhosis, Experimental / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D008715:Methionine / Q000172:deficiency; D051379:Mice; D008810:Mice, Inbred C57BL; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014704:Veratrum Alkaloids / Q000494:pharmacology
D053823:Hedgehog Proteins; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; C000606240:Ptch1 protein, mouse; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; C509239:SHH protein, human; C465570:Shh protein, mouse; D014704:Veratrum Alkaloids; D008715:Methionine; C000541:cyclopamine