Manifestation of Novel Social Challenges of the European Unionin the Teaching Material ofMedical Biotechnology Master’s Programmesat the University of Pécs and at the University of DebrecenIdentification number: TÁMOP-4.1.2-08/1/A-2009-0011
LIVER REGENERATION FROM STEM CELLS
Dr. Péter Balogh and Dr. Péter EngelmannTransdifferentiation and regenerative medicine – Lecture 8
Manifestation of Novel Social Challenges of the European Unionin the Teaching Material ofMedical Biotechnology Master’s Programmesat the University of Pécs and at the University of DebrecenIdentification number: TÁMOP-4.1.2-08/1/A-2009-0011
TÁMOP-4.1.2-08/1/A-2009-0011
Glutamine synthetase +(1-3 cells)
Centrilobular(8-10 cells)Limiting plate
Periportal(6-8 cells)
Structure of the hepatic lobe
Portal tracts(triads)
Central vein
Bile duct
Bile canaliculi
Sinusoids
Branch portalvein
Branch hepaticartery
Central vein
Portal tract
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Clinical necessity of liver regeneration• Shortage of livers for orthotopic liver
transplantation• Liver cell transplantation – limited amount• Choice of stem cell candidates – variable
success in experimental conditions
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Stem cells(c-kit, c-met, CXCR4)
Main phases of liver regeneration
3 ClearanceGadolinium chloride/monocrotaline
Immunosuppression
EncapsulationCo-transplantation
Effector cells
Central veinKupffer cells(phagocytosis)
Dead cell
Central veinVasodilatatorsAlteration of blood flow
VEGFHGFTGFFGF
MMP-9MMP-2
MT1-MMP
Cell loss of 70-80%
2 Integration
Gap junctionsVariable in vivo cell phenotype
Organ damageSinus endothelpermeability
Central veinMMP-9SDF-1HGF(SCF)
Organ damage
Recruitment
1 Migration
Monocrotaline
DoxorubicinHepatic injuryVEGF
Physical/chemical/genetical stimulus
TÁMOP-4.1.2-08/1/A-2009-0011Developmental relationship between hepatic-pancreatic differentiation
Oval cell progenitor
Hepatic oval cell
Bile duct Hepatocyte
Pancreatic oval cell
Endocrine cell Acinar cellPancreatic duct
Pancreatic progenitor(s)?
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Transcriptional control of hepatoblast development
Hepatocyte maturation cords
HepatocyteCore transcription
factor network:
HNF-1
LRH-1HNF-6Foxa2
HNF-4
HNF-1
Jagged
Cholangiocyte
Parenchyma PeriportalHNF-1
Sox9
HNF-6/OC-2 TGF
Hex C/EBP
Hepatoblast
HNF-6
HNF-1
Notch2HNF-4
C/EBP
Tbx3
Albumin
HGF
Cholangiocyte maturation ducts
?
WntBMP+FGFFoxM1B
ECM
ECM
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Oval cells – adult liver stem/progenitor cells• Origin: debated (their precursors are
associated with the biliary tree)• Bipotential differentiation: hepatocyte and
cholangiocyte• Phenotype: shared markers with adult
hepatocytes (albumin, cytokeratins 8 and 18), bile duct cells (cytokeratins 7 and 19, OV-6, A6), fetal hepatoblasts (AFP), and haematopoietic stem cells (Thy -1, Sca-1, c-kit).
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Cellular targets for hepatic regeneration• Hepatocytes: metabolic activity of the liver• Cholangiocytes: formation of bile ducts• Both derive from embryonic endodermal
epithelium.
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Stages and forms of liver regeneration• Surgical partial hepatectomy – from hepatocytes
(often polyploid cells)• Possible sources: hepatocytes, oval cells and
extrahepatic stem cells (HSC?)• Assessment of lineage commitment: albumin,
glucose-6-phosphatase, transferrin and transthyretin (hepatic).
• Fibrotic regeneration: transformation of fibrocytes into myofibroblasts
• Parenchymal regeneration: regeneration of hepatocytes
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Sequence of parenchymal regeneration of the liver• Stem cell migration into the liver parenchyma is
directed by chemoattractive agents (as SDF-1, HGF and SCF) secreted by damaged liver cells
• Increased MMP-9 expression by host hepatocytes after injury, leading to ECM remodeling and increased vascular permeability
• Transformation of local microenvironment for the integration and proliferation of the transplanted cells, including local secretion of cytokines/growth factors (HGF, FGF, TGF). Dead cells will be phagocyted by Kupffer cells.
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Oval cell activation and expansion• Liver injury activates oval cells (their precursors in
the biliary tree?) AND other support cells (stellate cells, macrophages/Kupffer’s cells, NK cells, endothelium, etc)
• Homing/intrahepatic migration to the site of injury• Proliferation and bidirectional differentiation
(hepatocyte/cholangiocyte)
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Non-hepatic cells for liver regenerationAutologous: Bone marrow-derived/mesenchymal stem cells – fibroblastic regenerationAllogenic: Fetal-derived hepatocytes or embryonic stem cell-derived liver cells
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Differentiation of iPS cells into hepatocytes• Induction of iPS cells: transfection with TFs• Formation of embryoid bodies• Induction of endodermal commitment: treatment
with Activin A and bFGF• Differentiation into hepatocytes: treatment with
hepatocyte growth factor (HGF)• Assessment: gene expression, albumin secretion,
glycogen storage, urea production, and inducible cytochrome activity
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Summary
• Depending on the origin/type of liver damage, different regeneration processes operate, thus (a) in loss of liver mass, the regeneration is initiated from hepatocytes, whereas (b) in toxicity from hepato-cholangiocyte progenitors.
• Oval cells as adult-type hepatocyte/cholangiocyte progenitors are most likely to be facultative stem cells, although cells with stem cell activity from extrahepatic sources may also operate in liver regeneration.
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