Mesenchymal stem cell homing to the chronically injured liver.
Lead Research Organisation:
University of Birmingham
Department Name: Sch of Biosciences
Abstract
Chronic liver disease is an increasing cause of morbidity & mortality in the UK, for which stem cell therapy has been suggested as a possible treatment. Stem cells within our bone marrow have the ability to change into different tissue types, and it is thought, that during liver injury, these cells migrate to the liver and promote repair. Alarmingly, recent data suggest that a population of bone marrow stem cells, called mesenchymal stem cells (MSCs), may be harmful by increasing liver scarring.
We propose to determine the molecules which control the migration of MSCs to the injured liver. We will firstly explore the mechanisms which control the migration of such cells to chronically damaged liver using a complex tissue culture model which recreates the interaction between MSCs and the cells in the liver. Having identified relevant molecules in this setting we will test their role in whole animal models of chronic liver injury. In this setting we will block the previously identified molecules on the MSCs, so as to reduce their liver-directed migration and hence their contribution to liver scarring.
This work will provide key insights into the contribution and future manipulation of mesenchymal stem cells in chronic liver injury.
We propose to determine the molecules which control the migration of MSCs to the injured liver. We will firstly explore the mechanisms which control the migration of such cells to chronically damaged liver using a complex tissue culture model which recreates the interaction between MSCs and the cells in the liver. Having identified relevant molecules in this setting we will test their role in whole animal models of chronic liver injury. In this setting we will block the previously identified molecules on the MSCs, so as to reduce their liver-directed migration and hence their contribution to liver scarring.
This work will provide key insights into the contribution and future manipulation of mesenchymal stem cells in chronic liver injury.
Technical Summary
The progression of hepatic inflammation to fibrosis and cirrhosis represents a common pathway for chronic liver diseases regardless of aetiology. Cirrhosis and its related morbidity place a significant burden on healthcare worldwide. Although liver transplantation is effective for patients with end-stage liver disease, it is an insufficient resource. Reports of unexpected bone marrow stem cell (BMSC) plasticity have generated hope for cellular based regenerative therapy in patients with liver disease. Reports of the effects of BMSCs in rodent models of liver injury are conflicting however, with some suggesting benefit and others not.
Furthermore, some investigators have demonstrated that mesenchymal stem cells (MSCs) make a significant contribution to cells such as fibroblasts and myofibroblasts which are responsible for much of the scar production within the liver. These observations raise concerns that BMSC therapy may be deleterious to the patient. Migration of MSCs from BM into injured liver tissue is poorly understood. Understanding the molecular mechanisms regulating MSC migration to the liver and their subsequent functional contribution to liver fibrosis will potentially lead to the identification of new therapeutic targets.
We hypothesise that MSCs home to the chronically injured liver by a tissue specific interaction and contribute functionally to liver fibrosis.
We will identify the molecular mechanisms which regulate the adhesion of MSCs within liver sinusoids using in vitro methods such as our flow-based adhesion assays as well as in vivo methods such as intravital microscopy. These experiments are unique in that they are able to analyse the mechanisms involved in MSC homing in a step-wise manner from in vitro models through to in vivo models. Thus, the results have biological relevance and reduce unnecessary animal work.
We will then examine the effects of blockade of these molecular pathways, by lentiviral knock-down, to identify the most important candidate molecules involved in this process. Having confirmed the effects of this knock-down on adhesion in vitro we will test the effects in vivo to determine the effect of MSC adhesion molecule knock-down/blockade on generation of liver fibrosis.
Either wild type RFP+ MSCs or adhesion molecule knockdown RFP+ MSCs (which are also GFP+ as the result of successful lentiviral transduction), will be transplanted into mice prior to the establishment of chronic liver injury. The contribution to liver fibrosis will be quantified and compared between the two groups.
We predict that disabling the hepatic migration of MSCs will lead to reduced liver fibrosis.
Furthermore, some investigators have demonstrated that mesenchymal stem cells (MSCs) make a significant contribution to cells such as fibroblasts and myofibroblasts which are responsible for much of the scar production within the liver. These observations raise concerns that BMSC therapy may be deleterious to the patient. Migration of MSCs from BM into injured liver tissue is poorly understood. Understanding the molecular mechanisms regulating MSC migration to the liver and their subsequent functional contribution to liver fibrosis will potentially lead to the identification of new therapeutic targets.
We hypothesise that MSCs home to the chronically injured liver by a tissue specific interaction and contribute functionally to liver fibrosis.
We will identify the molecular mechanisms which regulate the adhesion of MSCs within liver sinusoids using in vitro methods such as our flow-based adhesion assays as well as in vivo methods such as intravital microscopy. These experiments are unique in that they are able to analyse the mechanisms involved in MSC homing in a step-wise manner from in vitro models through to in vivo models. Thus, the results have biological relevance and reduce unnecessary animal work.
We will then examine the effects of blockade of these molecular pathways, by lentiviral knock-down, to identify the most important candidate molecules involved in this process. Having confirmed the effects of this knock-down on adhesion in vitro we will test the effects in vivo to determine the effect of MSC adhesion molecule knock-down/blockade on generation of liver fibrosis.
Either wild type RFP+ MSCs or adhesion molecule knockdown RFP+ MSCs (which are also GFP+ as the result of successful lentiviral transduction), will be transplanted into mice prior to the establishment of chronic liver injury. The contribution to liver fibrosis will be quantified and compared between the two groups.
We predict that disabling the hepatic migration of MSCs will lead to reduced liver fibrosis.