Characterisation of the molecular events responsible for the

differentiation of liver stem cells.

Liver Immunbiology Laboratory

http://www.centenary.org.au/p/res/liver/rp/

Supervisors: Dr Nick Shackel and Dr Fiona Warner

Contact: Dr. Nick Shackel n.shackel@centenary.usyd.edu.au 95656286

Background: The promise of hepatic stem cells is impressive given their potential as therapy for a variety of liver diseases(1). There has been a recent explosion of research in the area of both general and liver stem cell biology and this has led to considerable debate about the origin and function of hepatic stem cells. Further, basic concepts surrounding stem cell biology including - “plasticity” and “transdifferentiation” has been introduced in an attempt to explain the role of resident and bone marrow derived stem cells in hepatocyte repopulation of the liver. The term, “plasticity” has been coined to emphasize the process in which pluripotent stem cells are able to differentiate into multiple cell lineages, and is supported by the finding of intrahepatic chimerism in transplant recipients as well as the apparent repopulation of injured livers with bone marrow derived cells. The term, “transdifferentiation”, is used to focus on differentiation of cells from one organ specific lineage to those of another organ. These concepts have an underlying assumption that is not proven, that there are distinct liver specific stem cell precursors that are important in liver regeneration following injury(1).

Hypothesis and aims: Our working hypothesis is that are pivotal events involved in the differentiation of stem cells into distinct lineages within the liver. We aim to address this hypothesis by studying the molecular events involved in the differentiation of a rodent stem cell line.

Methods: The initial phase of this project will compare the expression of stem cells (OV6, Thy1, AFP), hepatocyte (albumin) and cholangiocyte (cytokeratin 19, ACE2) markers on a rodent stem cell line using immunohistochemistry/immunofluoresence and flow cytometry. Further we plan to use conditioned media to study the events involved in the differentiation of the stem cell line into hepatocytes, or cholangiocyte cell lineages. The final part of this project will study the effects of the stem cells administered to rodents in models of liver injury.

Skills: This project will utilise real-time RT-PCR, cell isolation, immunofluorescence/ immunohistochemistry, confocal microscopy and flow cytometry techniques. It is envisaged that the student who undertakes this project will become proficient in all of these methods whilst being exposed to a number of other general laboratory techniques.

Conclusion and Significance: This project has great significance in determining the nature of the molecular events responsible for the differentiation of stem cells into liver cell lineages. The results will have widespread implications for the majority of human disease, as this is likely to be applicable to general stem cell responses in liver injury. Importantly, the project as outlined will be suitable for publication. This project embodies a number of techniques and builds on established knowledge and expertise with our laboratory. We look forward to attracting a student to what we believe is exciting and significant work!

1. N. A. Shackel and D. C. Rockey (2005) In pursuit of the "Holy Grail"- Stem cells, hepatic injury, fibrogenesis and repair. Hepatology 41(1) p16-8.