Defining the functional role of the progenitor cell-laminin interaction during liver regeneration
Lead Research Organisation:
University of Edinburgh
Department Name: MRC Centre for Inflammation Research
Abstract
Liver cirrhosis is the fifth most common cause of death in the UK. Any cause of chronic liver injury
(e.g. viruses, fat, alcohol, inherited disorders) can result in scarring and eventually lead to cirrhosis
and liver cancer. At present, the only effective treatment for cirrhosis is liver transplantation but many patients die whilst waiting for a new liver.
In the adult, many organs possess their own ‘stem cells‘ which are able to replenish stocks of cells
as they are depleted. As the cirrhotic liver‘s ‘stem cells‘, termed oval cells in rodents, proliferate to regenerate the injured liver, they are surrounded by a specific matrix component called laminin. We know from other organs (such as the brain) that the interactions between the adult stem cell and laminin are critical for regeneration.
I will examine the liver stem cell-laminin relationship using rodent models of liver injury and using cultured liver cells.
Understanding the regulation of liver stem cells will be essential to rationally design new
treatments for liver disease.
(e.g. viruses, fat, alcohol, inherited disorders) can result in scarring and eventually lead to cirrhosis
and liver cancer. At present, the only effective treatment for cirrhosis is liver transplantation but many patients die whilst waiting for a new liver.
In the adult, many organs possess their own ‘stem cells‘ which are able to replenish stocks of cells
as they are depleted. As the cirrhotic liver‘s ‘stem cells‘, termed oval cells in rodents, proliferate to regenerate the injured liver, they are surrounded by a specific matrix component called laminin. We know from other organs (such as the brain) that the interactions between the adult stem cell and laminin are critical for regeneration.
I will examine the liver stem cell-laminin relationship using rodent models of liver injury and using cultured liver cells.
Understanding the regulation of liver stem cells will be essential to rationally design new
treatments for liver disease.
Technical Summary
Background
Problems arise in the cirrhotic liver due to a lack of functional hepatocytes. The liver is usually able
to regenerate through division of mature hepatocytes. In cirrhosis, this mechanism is impaired
and hepatocyte replacement occurs through proliferation of hepatic progenitor cells, also termed
oval cells (OCs).
The pericellular microenvironment is a key regulator of stem cell behaviour in many organs. The progenitor cells in the regenerating liver are surrounded by an extracellular matrix, rich in laminins. Furthermore OCs express a laminin-binding receptor ( 6 1 integrin).
Hypotheses
We hypothesise that the liver progenitor cell response is regulated by changes in laminin isoforms within the extracellular matrix and changes in laminin receptor expression, and that 1-integrin-laminin interaction is a major mediator of the progenitor cell response.
Aims and objectives
The project aims to examine the role of laminins in the hepatic stem cell niche by:
(a) defining the laminin isoforms associated with the liver progenitor cell response in mouse liver
(b) describing the range of laminin receptors expressed on liver progenitor cells
(c) establishing the functional role of laminin-integrin signaling in regulating the liver progenitor cell response.
Design and methodology
The liver progenitor response will be assessed in 3 independent mouse models of liver injury: the choline-deficient, ethionine-supplemented (CDE) diet, recovery from chronic carbon tetrachloride injury, and the Mdm2/flox mouse. Using antibodies to specific laminin isoforms and cell surface receptors, confocal microscopy will localize the changes at key time points in the progenitor cell response. The source of laminin production will be confirmed using in situ hybridization with riboprobes, and confirmed by quantitative PCR on sorted cell populations. Similarly, changes in receptor expression will be confirmed by FACS on sorted cells.
The role of 1-integrin in regulating oval cell behaviour will be assessed in vitro, using siRNA-mediated 1-integrin knock-down in cultured OCs. The role of 1-integrin will also be assessed in vivo using a transgenic mouse model that allows conditional 1-integrin knock-down.
Scientific and medical opportunities
In my opinion, understanding the regulation of the liver progenitor cell response is key to developing rational stem cell therapies for a wide range of liver diseases.
Problems arise in the cirrhotic liver due to a lack of functional hepatocytes. The liver is usually able
to regenerate through division of mature hepatocytes. In cirrhosis, this mechanism is impaired
and hepatocyte replacement occurs through proliferation of hepatic progenitor cells, also termed
oval cells (OCs).
The pericellular microenvironment is a key regulator of stem cell behaviour in many organs. The progenitor cells in the regenerating liver are surrounded by an extracellular matrix, rich in laminins. Furthermore OCs express a laminin-binding receptor ( 6 1 integrin).
Hypotheses
We hypothesise that the liver progenitor cell response is regulated by changes in laminin isoforms within the extracellular matrix and changes in laminin receptor expression, and that 1-integrin-laminin interaction is a major mediator of the progenitor cell response.
Aims and objectives
The project aims to examine the role of laminins in the hepatic stem cell niche by:
(a) defining the laminin isoforms associated with the liver progenitor cell response in mouse liver
(b) describing the range of laminin receptors expressed on liver progenitor cells
(c) establishing the functional role of laminin-integrin signaling in regulating the liver progenitor cell response.
Design and methodology
The liver progenitor response will be assessed in 3 independent mouse models of liver injury: the choline-deficient, ethionine-supplemented (CDE) diet, recovery from chronic carbon tetrachloride injury, and the Mdm2/flox mouse. Using antibodies to specific laminin isoforms and cell surface receptors, confocal microscopy will localize the changes at key time points in the progenitor cell response. The source of laminin production will be confirmed using in situ hybridization with riboprobes, and confirmed by quantitative PCR on sorted cell populations. Similarly, changes in receptor expression will be confirmed by FACS on sorted cells.
The role of 1-integrin in regulating oval cell behaviour will be assessed in vitro, using siRNA-mediated 1-integrin knock-down in cultured OCs. The role of 1-integrin will also be assessed in vivo using a transgenic mouse model that allows conditional 1-integrin knock-down.
Scientific and medical opportunities
In my opinion, understanding the regulation of the liver progenitor cell response is key to developing rational stem cell therapies for a wide range of liver diseases.
