studies

HEPATOLOGY, VOLUME 62, NUMBER 1 (SUPPL) AASLD ABSTRACTS 259A
98
In vivo reprogramming of myofibroblasts into hepatocytes
as a therapy for liver fibrosis
Milad Rezvani 1 , Regina Español-Suñer 1 , Yann Malato 1 , Laure
Dumont 1 , Andrew A. Grimm 2 , Eike Kienle 3 , Julia Bindmann 1 , Ellen
Wiedtke 3 , Syed J. Naqvi 1 , S. C. Derderian 4 , Robert F. Schwabe 5 ,
Dirk Grimm 3 , Holger Willenbring 1,6 ; 1 Institute of Regeneration
Medicine, University of California San Francisco, San Francisco,
CA; 2 Department of Pediatrics, Division of Gastroenterology,
Hepatology, and Nutrition, University of California San Francisco,
San Francisco, CA; 3 Department of Infectious Diseases, Cluster of
Excellence CellNetworks, BioQuant BQ0030, Heidelberg University
Hospital, Heidelberg, Germany; 4 4Department of Surgery,
Division of Pediatric Surgery, University of California San Francisco,
San Francisco, CA; 5 Department of Medicine,, Columbia
University, New York, NC; 6 Department of Surgery, Division of
Transplantation, University of California San Francisco, San Francisco,
CA
Repeated hepatocyte loss in chronic liver injury can exceed
the regenerative capabilities of hepatocytes and lead to liver
fibrosis, a form of scarring characterized by replacement of
hepatocytes by collagen produced by myofibroblasts (MFs).
The structural and molecular changes associated with liver
fibrosis further impair liver function, leading to liver failure.
The only cure for advanced liver fibrosis is liver transplantation,
but donor organs are scarce. As a strategy to replenish
the hepatocyte mass and limit collagen deposition in the
chronically injured liver, we developed in vivo reprogramming
of MFs into hepatocytes by overexpression of hepatic transcription
factors. To facilitate clinical translation, we delivered
these genes to MFs using adeno-associated viral (AAV) vectors,
which are not toxic and do not integrate into the genome. We
first investigated the feasibility of generating induced hepatocytes
from primary MFs (MF-iHeps) using AAV vectors expressing
FOXA1, FOXA2, FOXA3, GATA4, HNF1α and HNF4α in
vitro. We found that AAV vectors were effective in generating
expandable MF-iHeps resembling previously reported iHeps
generated from fibroblasts with integrating retroviral or lentiviral
vectors. Specifically, MF-iHeps lost most of their original
cell identity and acquired hepatocyte gene and protein expression
and functions like low-density lipoprotein uptake, glycogen
storage and cytochrome P450 activity. Next, we established
hepatic reprogramming of MFs in vivo. For this we used a
lineage-tracing mouse model in which MFs and their progeny
are constitutively labeled. To induce liver fibrosis, we treated
these mice with carbon tetrachloride. After intravenous injection
of the AAV vectors we observed the formation of MF-iHeps
and reduced liver fibrosis. Like primary hepatocytes MF-iHeps
proliferated in response to liver injury in both CCl4-treated
and fumarylacetoacetate hydrolase-deficient mice. To assess
hepatocyte differentiation of MF-iHeps, we isolated them by
laser-capture microscopy and analyzed their gene expression
with microarrays. MF-iHeps closely resembled primary hepatocytes,
with the exception of minimal residual MF identity. We
confirmed these results using functional assays, including analysis
of hepatic glucose metabolism, and ascertained stability
of MF-iHep differentiation in mice followed for 6 months. Our
results establish repurposing of MFs as a potential new therapy
for liver fibrosis that not only reduces fibrosis but also increases
the functional hepatocyte mass. By using AAV vectors, which
proved effective and safe in liver-directed human gene therapy,
our strategy lends itself well to clinical translation.
Disclosures:
Robert F. Schwabe - Consulting: Merck
The following authors have nothing to disclose: Milad Rezvani, Regina Español-
Suñer, Yann Malato, Laure Dumont, Andrew A. Grimm, Eike Kienle, Julia Bindmann,
Ellen Wiedtke, Syed J. Naqvi, S. C. Derderian, Dirk Grimm, Holger
Willenbring
99
Protective role of miR-122 against acetaminophen toxicity
is due to suppression of Cyp2e1 and Cyp1a2
Vivek K. Chowdhary 3 , Huban Kutay 3 , Laura James 2 , William M.
Lee 1 , Kalpana Ghoshal 3 ; 1 UT Southwestern Medical Center, Dallas,
TX; 2 University of Arkansas for Medical Science, Little Rock,
AR; 3 Pathology, Comprehensive Cancer Center, The Ohio State
University College of Medicine, Columbus, OH
Approximately 2000 cases of acute liver failure occur annually
in the United States and acetaminophen (APAP) accounts for
nearly 50% of cases. miR-122 is the most abundant, conserved
liver-specific microRNA that maintains metabolic homeostasis
and functions as a tumor suppressor. Although circulating
miR-122 is a sensitive biomarker of APAP toxicity in humans
and rodents, its role in this injury has not been elucidated. To
investigate whether miR-122 has any protective role against
APAP toxicity, we gave APAP (500mg/Kg) intraperitoneally
to the Mir122 fl/fl (WT) and liver-specific miR-122 knockout
(Mir122 fl/fl ; Alb-Cre) (aka LKO) mice generated in our lab
(PMID: 22820288), and monitored their survival. Mortality
rate of LKO mice was significantly higher than that of WT mice
(P