Name: development of an ethanol-induced fibrotic liver model in zebrafish to study progenitor cell-mediated hepatocyte regeneration
Uploaded: 2016-05-13T14:00:00
Description: Watch this Scientific Journal Video about Development of an Ethanol-induced Fibrotic Liver Model in Zebrafish to Study Progenitor Cell-mediated Hepatocyte Regeneration at JoVE.com

This work was supported in part by grants from the GTEC (2731336 and 1411318), the NIH (K01DK081351), and the NSF (1354837) to C. H. S. We thank Alem Giorgis for critical reading of the manuscript.

Zebrafish were raised and bred using a standard protocol that meets the criteria of the National Institutes of Health and approved by the Georgia Institute of Technology Institutional Animal Care and Use Committee.&#160;
1. Preparation of Solutions
<ol>
	<li>Prepare 20 L egg water (interchangeably used with &#8216;embryo medium&#8217;)&#160;&#160;to maintain embryonic/larval zebrafish. Dissolve 1.5 g CaSO4 and 6 g instant ocean sea salt in 250 ml distilled water. Pour into a carboy filled with 20 L di...

<ol>
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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+liver+fibrosis+in+rodents.">Modeling liver fibrosis in rodents.</a> Methods Mol Med. 117, 237-250 (2005).</li><li>Gabele, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+model+of+interactive+effects+of+alcohol+and+high-fat+diet+on+hepatic+fibrosis.">A new model of interactive effects of alcohol and high-fat diet on hepatic fibrosis.</a> Alcohol Clin Exp Res. 35 (7), 1361-1367 (2011).</li><li>Lieber, C. 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R., Saxena, M. T., Mumm, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+in+zebrafish+chemical+screening+technologies.">Advances in zebrafish chemical screening technologies.</a> Future Med Chem. 4 (14), 1811-1822 (2012).</li><li>Chen, C. H., Durand, E., Wang, J., Zon, L. I., Poss, K. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=zebraflash+transgenic+lines+for+in+vivo+bioluminescence+imaging+of+stem+cells+and+regeneration+in+adult+zebrafish.">zebraflash transgenic lines for in vivo bioluminescence imaging of stem cells and regeneration in adult zebrafish.</a> Development. 140 (24), 4988-4997 (2013).</li><li>Westhoff, J. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+an+automated+imaging+pipeline+for+the+analysis+of+the+zebrafish+larval+kidney.">Development of an automated imaging pipeline for the analysis of the zebrafish larval kidney.</a> PLoS One. 8 (12), e82137 (2013).</li><li>Perlman, Z. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multidimensional+drug+profiling+by+automated+microscopy.">Multidimensional drug profiling by automated microscopy.</a> Science. 306 (5699), 1194-1198 (2004).</li><li>Chu, J., Sadler, K. 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We observed HPC-mediated hepatocyte regeneration in the EtOH/MTZ-treated recovering livers, suggesting that even in the presence of substantial amount of ECM proteins including fibrillar type I collagen, the HPCs retain their competency to regenerate as hepatocytes. The MTZ only-treatment did not increase deposition of ECM proteins significantly, whereas the EtOH only-treatment did not induce HPC activation15. By utilizing the combined EtOH/MTZ treatment, we were able to investigate HPC-driven regeneration in ...

Despite the remarkable regeneration capacity of hepatocytes1, which are the major parenchymal cell type of the liver, chronic liver failure impairs this ability, leading to hepatic progenitor cell (HPC)-dependent regeneration2.
Chronic liver damage is mainly derived from alcohol abuse, chronic hepatitis C virus (HCV) infection3 and non-alcoholic fatty liver disease (NAFLD)4. It leads to sustained liver fibrosis, which is associated with the accumulation of extracellular matrix (ECM) proteins. Persisting ECM accumulation distorts intact hepatic architecture by forming a fibrous scar tissue5, subsequently resulting in cirrhosis with high morbidity and mortality. Many attempts have been made to mitigate the fibrotic response mainly by focusing on inhibiting profibrogenic cytokines and activated myofibroblasts6. The latter is primarily derived from hepatic stellate cells (HSCs), the principle hepatic non-parenchymal cells responsible for liver scar formation4. Nevertheless, regenerative therapies that stimulate endogenous cellular sources including HPCs to regenerate hepatocytes in the presence of sustained fibrogenic insults await further investigation.
Many experimental models of hepatic fibrosis have been described in mammals. Repetitive injection of carbon tetrachloride (CCl4) has been widely used to induce liver fibrosis in murine and rat models7. When combined with a high-fat (HF) diet, alcohol led to a substantial upregulation of profibrogenic gene expression and hepatic fibrosis8. While steatosis (lipid accumulation) results from acute alcohol exposure, it makes the liver susceptible to more severe hepatic injury9.
The zebrafish, Danio rerio, has emerged as an invaluable vertebrate model system for studying regeneration. Though other lower vertebrates such as newts and axolotls have a remarkable capacity for regeneration, the zebrafish has advantages over other model systems in regards to the gene manipulation and visualization strategies needed to manipulate potential regenerative factors10. The zebrafish also represents an attractive vertebrate model for studying alcoholic liver disease (ALD) by simply adding ethanol (EtOH) to their water. Acute EtOH exposure to larval and adult zebrafish caused hepatic steatosis11-13. When adult zebrafish received extended EtOH exposure, collagen deposition was observed with upregulation of fibrosis-related genes14. However, a need exists for developing models to study liver regeneration in response to EtOH as a fibrogenic stimulus.
Recently, we developed an EtOH-induced fibrotic liver model in zebrafish15. We combined a hepatocyte-specific genetic ablation system with EtOH treatment in larval and adult zebrafish. We generated two transgenic lines, Tg(fabp10a:CFP-NTR)gt1 and Tg(fabp10a:mCherry-NTR)gt2, in which E.coli nitroreductase (NTR) are fused to the cyan and mCherry fluorescent protein, respectively, under the control of the hepatocyte-specific fatty acid binding protein 10a, liver basic (fabp10a) promoter. In this system, NTR converts a nontoxic prodrug metronidazole (MTZ) into a DNA inter-strand cross-linking agent16, inducing explicit death of hepatocytes. Using this model, we demonstrated that a population of hepatic cells, which are responsive to Notch signaling, converted into hepatocytes in the near absence of hepatocytes and in the excess of ECM. We designated these cells as HPCs. Furthermore, through chemical screens, we identified small molecule activators of Wnt signaling and inhibitors of Notch signaling that augment hepatocyte regeneration in the fibrotic liver. Therefore, our fibrotic liver model in zebrafish represents a superb chemical screening system compared to cell culture- or mammalian-based screening system. It is an in vivo system with significant cost- and time-saving benefits. Here we describe the detailed procedures for establishing an EtOH-induced fibrotic liver model and for performing chemical screens using this model in zebrafish. Furthermore, time-course analyses were performed to investigate how hepatocyte regeneration occurs in the fibrotic liver. This protocol will provide an invaluable tool to study the mechanisms and strategies of enhancing hepatocyte regeneration in the fibrotic liver.

<table>
	<tbody>
		<tr>
			<td>Calcium sulfate hemihydrate (CaSO4)</td>
			<td>Acros</td>
			<td>AC385355000</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium sulfate (MgSO4)</td>
			<td>EMD</td>
			<td>MX0075</td>
			<td></td>
		</tr>
		<tr>
			<td>1,4-Piperazinediethanesulfonic acid (PIPES)</td>
			<td>Sigma-Aldrich</td>
			<td>P6757</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylene glycol-bis(2-aminoethylether)-N,N,N&#8242;,N&#8242;-tetraacetic acid (EGTA)</td>
			<td>Sigma-Aldrich</td>
			<td>E3889</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Sigma-Aldrich</td>
			<td>E7023</td>
			<td>200 proof</td>
		</tr>
		<tr>
			<td>Formaldehyde</td>
			<td>Fisher Scientific</td>
			<td>F79-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Metronidazole (MTZ)</td>
			<td>Sigma-Aldrich</td>
			<td>M3761</td>
			<td></td>
		</tr>
		<tr>
			<td>1-phenyl-2-thiourea (PTU)</td>
			<td>Sigma-Aldrich</td>
			<td>P7629</td>
			<td></td>
		</tr>
		<tr>
			<td>3-amino benzoic acid ethyl ester (Tricaine)</td>
			<td>Sigma-Aldrich</td>
			<td>A5040</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate-buffered saline (PBS) tablet</td>
			<td>Amresco</td>
			<td>E404</td>
			<td>Dissolve one tablet with 100 ml distilled water</td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide (DMSO)</td>
			<td>Sigma-Aldrich</td>
			<td>D2438</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine serum albumin</td>
			<td>Fisher Scientific</td>
			<td>BP1600</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Fisher Scientific</td>
			<td>BP151</td>
			<td></td>
		</tr>
		<tr>
			<td>Low-melting agarose&#160;</td>
			<td>Amresco</td>
			<td>BP165</td>
			<td></td>
		</tr>
		<tr>
			<td>Stem Cell Signaling Compound Library</td>
			<td>Selleck Chemicals</td>
			<td>L2100</td>
			<td>10mM stock in DMSO</td>
		</tr>
		<tr>
			<td>ActiProbe-1K Library</td>
			<td>Timtec</td>
			<td>ActiProbe-1K</td>
			<td>10mM stock in DMSO</td>
		</tr>
		<tr>
			<td>SB 415286</td>
			<td>Selleck Chemicals</td>
			<td>S2729</td>
			<td>Dissolve with DMSO to 10mM</td>
		</tr>
		<tr>
			<td>CHIR-99021</td>
			<td>Selleck Chemicals</td>
			<td>S2924</td>
			<td>Dissolve with DMSO to 10mM</td>
		</tr>
		<tr>
			<td>Anti-Collagen I antibody</td>
			<td>Abcam</td>
			<td>ab23730</td>
			<td>Use at 1:100 for immunostaining, reacts with fish</td>
		</tr>
		<tr>
			<td>AlexaFluor 647 Donkey anti-rabbit IgG (H+L)</td>
			<td>Molecular Probes</td>
			<td>A31573</td>
			<td>Use at 1:200 for immunostaining</td>
		</tr>
		<tr>
			<td>Mounting media (Vectorshield)</td>
			<td>Vector Laboratories</td>
			<td>H-1400</td>
			<td></td>
		</tr>
		<tr>
			<td>100 mm petri dish</td>
			<td>VWR</td>
			<td>25384-088</td>
			<td></td>
		</tr>
		<tr>
			<td>24-well plate</td>
			<td>VWR</td>
			<td>10062-896</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>Fine Science Tools</td>
			<td>11255-20</td>
			<td>Dumont #55</td>
		</tr>
		<tr>
			<td>Glass slide</td>
			<td>VWR</td>
			<td>48312-003</td>
			<td>75x25 mm</td>
		</tr>
		<tr>
			<td>Cover glass</td>
			<td>VWR</td>
			<td>48366-045</td>
			<td>18 mm</td>
		</tr>
		<tr>
			<td>Plastic wrap</td>
			<td>Fisher Scientific</td>
			<td>22305654</td>
			<td></td>
		</tr>
		<tr>
			<td>Aluminum foil</td>
			<td>Fisher Scientific</td>
			<td>1213100</td>
			<td></td>
		</tr>
		<tr>
			<td>Kimwipes</td>
			<td>Kimberly-Clark</td>
			<td>34155</td>
			<td></td>
		</tr>
		<tr>
			<td>Vibrotome</td>
			<td>Leica</td>
			<td>VT1000 S</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereo microscope</td>
			<td>Leica</td>
			<td>M80</td>
			<td></td>
		</tr>
		<tr>
			<td>Epifluoresent microscope</td>
			<td>Leica</td>
			<td>M205 FA</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocol microscope</td>
			<td>Zeiss</td>
			<td>LSM700</td>
			<td></td>
		</tr>
	</tbody>
</table>

development of an ethanol-induced fibrotic liver model in zebrafish to study progenitor cell-mediated hepatocyte regeneration

Sustained liver fibrosis with continuation of extracellular matrix (ECM) protein build-up results in the loss of cellular competency of the liver, leading to cirrhosis with hepatocellular dysfunction. Among multiple hepatic insults, alcohol abuse can lead to significant health problems including liver failure and hepatocellular carcinoma. Nonetheless, the identity of endogenous cellular sources that regenerate hepatocytes in response to alcohol has not been properly investigated. Moreover, few studies have effectively modeled hepatocyte regeneration upon alcohol-induced injury. We recently reported on establishing an ethanol (EtOH)-induced fibrotic liver model in zebrafish in which hepatic progenitor cells (HPCs) gave rise to hepatocytes upon near-complete hepatocyte loss in the presence of fibrogenic stimulus. Furthermore, through chemical screens using this model, we identified multiple small molecules that enhance hepatocyte regeneration. Here we describe in detail the procedures to develop an EtOH-induced fibrotic liver model and to perform chemical screens using this model in zebrafish. This protocol will be a critical tool to delineate the molecular and cellular mechanisms of how hepatocyte regenerates in the fibrotic liver. Furthermore, these methods will facilitate potential discovery of novel therapeutic strategies for chronic liver disease in vivo.

Figure 1 shows the development of an EtOH-induced fibrotic liver model in larval zebrafish. To optimize a protocol for exposing zebrafish larvae to EtOH, we first assessed EtOH toxicity. 2.5 days-post-fertilization (dpf) larvae were exposed to EtOH concentration 1%, 1.5%, or 2% for 24 hr followed by a concurrent 24 hr EtOH/MTZ treatment. Exposure to 2% EtOH caused high mortality, while nearly all larvae exposed to 1% EtOH or less showed minimal fibrogenic changes with rar...

Watch this Scientific Journal Video about Development of an Ethanol-induced Fibrotic Liver Model in Zebrafish to Study Progenitor Cell-mediated Hepatocyte Regeneration at JoVE.com

Development of an Ethanol-induced Fibrotic Liver Model in Zebrafish to Study Progenitor Cell-mediated Hepatocyte Regeneration

Sustained fibrosis with deposition of excessive extracellular matrix proteins leads to cirrhosis. Alcohol abuse is one of the main causes of severe liver disease. We established an ethanol-induced zebrafish fibrotic liver model to study the mechanisms and strategies of promoting hepatocyte regeneration upon alcohol-induced injury.

Sustained liver fibrosis with continuation of extracellular matrix (ECM) protein build-up results in the loss of cellular competency of the liver, leading ...

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JoVE Journal

Developmental Biology

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