Liver regeneration biology: Implications for liver tumour therapies

Table 1 Hepatotoxins used in rodent models

Toxin	Mechanism	Necrosis pattern
Acetaminophen (paracetamol)[19,36,37]	Free radical enhancement and Kupffer cell activation	Pericentral
Carbon tetrachloride[19,30,37]	Free radical enhancement and Kupffer cell activation	Pericentral
Concanavalin A[37]	T-cell activation; cytokine release; ICAM-1 & VCAM-1 upregulation.	Centrilobular
D-Galactosamine[19,37]	Uridine metabolite deficiency	Random
Ethanol[19,31]	Increases production of reactive oxygen species and infiltration of inflammatory cells	None
Lipopolysaccharide[37]	Kupffer cell activation	Centrilobular
Thioacetamide[19,37,38]	Increases production of toxic metabolites and reactive oxygen species	Pericentral

ICAM-1: Intercellular adhesion molecule 1; VCAM-1: Vascular cell adhesion molecule 1.

Table 2 Studies of liver regeneration involving transgenic or knockout mice

Yr	First author	Gene product	Study title	Ref.
1994	Webber	TGF-α	“Overexpression of transforming growth factor-alpha causes liver enlargement and increased hepatocyte proliferation in transgenic mice”	[55]
1996	Cressman	IL-6	“Liver failure and defective hepatocyte regeneration in interleukin-6-deficient mice”	[56]
1997	Yamada	TNF	“Initiation of liver growth by tumor necrosis factor: deficient liver regeneration in mice lacking type I tumor necrosis factor receptor”	[57]
1998	Greenbaum	C/EBP-β	“CCAAT enhancer-binding protein beta is required for normal hepatocyte proliferation in mice after partial hepatectomy	[58]
1998	Rai	iNOS	“Impaired liver regeneration in inducible nitric oxide synthase-deficient mice”	[59]
1998	Roselli	uPA	“Liver regeneration is transiently impaired in urokinase-deficient mice”	[60]
1998	Yamada	TNFR-1TNFR-2	“Analysis of liver regeneration in mice lacking type 1 or type 2 tumor necrosis factor receptor: requirement for type 1 but not type 2 receptor”	[61]
2002	Anderson	PPAR-α	“Delayed liver regeneration in peroxisome proliferator-activated receptor-alpha-null mice”	[62]
2003	Leu	IGFBP-1	“Impaired hepatocyte DNA synthetic response posthepatectomy in insulin-like growth factor binding protein 1-deficient mice with defects in C/EBP beta and mitogen-activated protein kinase/extracellular signal-regulated kinase regulation”	[63]
2003	Strey	C3a/C5a	“The proinflammatory mediators C3a and C5a are essential for liver regeneration”	[64]
2004	Borowiak	Met	“Met provides essential signals for liver regeneration”	[65]
2004	Mohammed	TIMP3	“Abnormal TNF activity in Timp3(–/–) mice leads to chronic hepatic inflammation and failure of liver regeneration	[66]
2004	Nakamura	OSM	“Hepatocyte proliferation and tissue remodeling is impaired after liver injury in oncostatin M receptor knockout mice”	[67]
2004	Oe	TGF-β	“Intact signaling by transforming growth factor beta is not required for termination of liver regeneration in mice”	[68]
2005	Duffield	DTR	“Selective depletion of macrophages reveals distinct, opposing roles during liver injury and repair”	[69]
2005	Mitchell	HB-EGF	“Heparin-binding epidermal growth factor-like growth factor links hepatocyte priming with cell cycle progression during liver regeneration”	[70]
2005	Oliver	MT	“Impaired hepatic regeneration in metallothionein-I/II knockout mice”	[71]
2005	Seki	MyD88	“Contribution of Toll-like receptor/myeloid differentiation factor 88 signaling to murine liver regeneration”	[72]
2006	Fernández	Caveolin-1	“Caveolin-1 is essential for liver regeneration”	[73]
2006	Olle	MMP9	“Matrix metalloproteinase-9 is an important factor in hepatic regeneration after partial hepatectomy in mice”	[74]
2007	Mayoral	Caveolin-1	“Dispensability and dynamics of caveolin-1 during liver regeneration and in isolated hepatic Cells”	[75]
2009	Tumanov	Rag1LT	“T cell-derived lymphotoxin regulates liver regeneration”	[54]
2010	Erhardt	CCR5, CXCR3	“Tolerance induction in response to liver inflammation”	[47]
2010	Liu	GPC3	“Suppression of liver regeneration and hepatocyte proliferation in hepatocyte-targeted glypican 3 transgenic mice”	[76]
2012	Borude	FXR	“Hepatocyte-Specific Deletion of Farnesoid X Receptor Delays But Does Not Inhibit Liver Regeneration After Partial Hepatectomy in Mice”	[77]
2013	Bhave	GPC3	“Regulation of Liver Growth by Glypican 3, CD81, Hedgehog, and Hhex”	[78]
2014	Kong	FGF15	“Fibroblast growth factor 15 deficiency impairs liver regeneration in mice”	[79]
2014	Yang	Lrp5/6	“β-catenin signaling in murine liver zonation and regeneration: a Wnt-Wnt situation!”	[80]
2015	Lu	Mdm2	“Hepatic progenitor cells of biliary origin with liver repopulation capacity”	[81]
2016	Swiderska-Syn	Cre recombinase	“Hedgehog regulates yes-associated protein 1 in regenerating mouse liver”	[82]
2018	Tsagianni	MET	“Combined Systemic Disruption of MET and Epidermal Growth Factor Receptor Signaling Causes Liver Failure in Normal Mice”	[83]
2019	Asrud	Epac	“Mice depleted for Exchange Proteins Directly Activated by cAMP (Epac) exhibit irregular liver regeneration in response to partial hepatectomy”	[84]
2019	Fortier	p38α MAPK	“Hepatospecific ablation of p38α MAPK governs liver regeneration through modulation of inflammatory response to CCl 4-induced acute injury”	[85]
2019	Modares	IL-6R	“IL-6 Trans-signaling Controls Liver Regeneration After Partial Hepatectomy”	[86]
2019	Zhou	Rictor	“Mammalian Target of Rapamycin Complex 2 Signaling Is Required for Liver Regeneration in a Cholestatic Liver Injury Murine Model”	[87]
2020	Laschinger	CGRP-RAMP1	“The CGRP receptor component RAMP1 links sensory innervation with YAP activity in the regenerating liver”	[88]
2020	Seguin	Mfrn1, Mfrn2	“The mitochondrial metal transporters mitoferrin1 and mitoferrin2 are required for liver regeneration and cell proliferation in mice”	[89]
2020	Xue	GPC3	“Phosphorylated Ezrin (Thr567) Regulates Hippo Pathway and Yes-Associated Protein (Yap) in Liver”	[90]

Table 3 Advantages and disadvantages of zebrafish as a model for human liver pathophysiology

Advantages	Disadvantages
Vertebrate body plan	Partial genome duplication in teleosts
Ease of husbandry	Differences in microanatomy and liver architecture
Inexpensive to maintain	Less conserved physiology than mammalian models
Large numbers of embryos produced rapidly	Less conserved morphogenesis than mammals
External development	Less developed cell culture technology
Optical clarity during development	Poorly developed embryonic stem cell technology
Zebrafish liver not required for foetal haematopoiesis
Amenable to forward and reverse genetics
Molecular conservation of development
Amenable to high-throughput screening: (1) Phenotype assessment; and (2) Drug/chemical screening

Table 4 Examples of liver decellularization-repopulation studies

First author	Yr	Liver scaffold source	Cell source & type	Repopulation route	Outcomes	Ref.
Uygun	2010	Rat	Rat hepatocytes	Portal vein	Recellularised liver grafts implanted in rats, perfused in vivo for 8 h, explanted and assessed after 24 h, demonstrating hepatocyte survival, albumin secretion, urea synthesis and cytochrome P450 expression.	Uygun 2010[127]
Zhou	2011	Mouse	Human foetal hepatocytes	Portal vein	Recellularised liver matrix implanted in mice, achieving hepatocyte survival after 6 wk, with albumin secretion and cytochrome P450 expression.	Zhou 2011[131]
Ko	2014	Pig	Murine endothelial cells, after scaffold conjugation with rat anti-mouse CD31 antibodies	Portal veinHepatic arteryInferior vena cava	Recellularised liver grafts implanted in pigs, demonstrating good blood flow and patency throughout vascular network over 24 h after transplantation.	Ko 2015[130]
Navarro-Tableros	2015	Rat	Human liver stem-like cells	Portal vein	Loss of embryonic markers, expression of albumin, lactate dehydrogenase and cytochrome P450 subtypes. Production of urea and nitrogen.	Navarro-Tableros 2015[133]
Ogiso	2016	Rat	Mouse hepatocytes	Biliary tree; Portal vein	(1) > 80% of cells seeded via biliary tree entered the parenchyma; (2) Approximate 20% of cells seeded via portal vein entered the parenchyma; and (3) Increased gene expression of foetal hepatocyte albumin, glucose 6-phosphatase, transferrin, cytokeratin 19, and gamma-glutamyl transpeptidase, activation of liver detoxification enzymes, formation of biliary duct-like structures.	Ogiso 2016[132] [PMID 27767181]
Verstegen	2017	Human	Human umbilical vein endothelial cells.	-	Re-endothelialisation of vascular tree, demonstrated by luminal vimentin and von Willebrand Factor/F8 staining.	Verstegen 2017[138]
Butter	2018	Rat	Rat hepatocytes	Hepatic artery and portal vein	In vitro demonstration of hepatocyte spread to all liver lobes, with proliferation, and production of aminotransferases, lactate dehydrogenase and albumin.	Butter 2018[134]
Chen	2018	Rat	Rat hepatocytes	Portal vein	None (description of materials and methods).	Chen 2018[135]
Chen	2019	Rat	Rat cholangiocytes Rat hepatocytes	Common bile duct; Portal vein	In vitro viability and function demonstrated by albumin and urea secretion, and gene expression of functional proteins.	Chen 2019[136]
Harper	2020	Rat	Rat bone marrow cells	Portal vein	Stem cells engrafted in portal, sinusoidal and hepatic vein compartments, achieving expression of endothelial cell surface markers for up to 30 d.	Harper 2020[118]
Takeishi	2020	Rat	Human hepatocytes, biliary epithelial cells, and vascular endothelial cells derived from pluripotent stem cells, mesenchymal cells, and fibroblasts.	Biliary tree; Portal vein; Central veins	Auxiliary grafts implanted in rats, achieving in vivo functionality for 4 d.	Takeishi 2020[137]