Doctoral dissertation

Dissertation: Liver cells differentiated from stem cells offer a promising model for studying lipid metabolism

Doctoral dissertation of MSc. Mostafa Kiamehr will be publicly examined at the Faculty of Medicine and Health Technology on 8 February 2019 at 12 o'clock.

Liver cells differentiated from skin samples through induced pluripotent stem cell technology: A future personalised cell model for studying the lipid metabolism of the liver.

This thesis demonstrates that liver cells differentiated from induced pluripotent stem cells (iPSCs) provide a relevant and functional cell model for exploring human lipid homeostasis at both cellular and molecular levels.

Additionally, the thesis provides novel findings on the possible role of lipids, fatty acids, and miRNAs in the process of differentiation and/or de-differentiation. These findings could be applied in designing culture environments that would improve the maturity of HLCs.

Primary human hepatocytes (PHHs) are currently considered the “gold standard” cell model for investigating the liver physiology, toxicity, and lipid homeostasis. However, PHHs are scarce and functionally heterogeneous, and when cultured, they lose their liver-specific functions relatively fast within a few days.

Induced pluripotent stem cell-derived hepatocyte-like cells (iPSC-HLCs) provide a relevant alternative model for PHHs to study the lipid derangements of the liver. Unlike PHHs, the cell source to generate iPSC-HLCs is unlimited. They can be advantageously generated from selected individuals with different genetic backgrounds.

Since lipid defects play central roles in the pathogenesis of several common diseases, such as non-alcoholic fatty liver disease and atherosclerotic cardiovascular disease, iPSC-HLCs could serve as a novel platform for studying the basic mechanisms of lipid metabolism and its dysregulation in a truly patient-specific manner. This cell model could also be utilised in drug discovery and especially in studying drug induced hepatotoxicity. In order to maximise the utilisation of HLCs for such valuable purpose, it is critical to characterise their detailed lipid profile in relation to the human adult liver cells.

Lipids are a major class of molecules, which play critical roles in cellular structure, function, and signalling. It has been shown that certain fatty acids (FAs) promote neuronal and adipocyte differentiation. Therefore, in-depth knowledge of changes in the lipid and FA profile of the hepatocytes during differentiation and de-differentiation could assist the generation of matured target cells, which resemble the lipid profile of PHHs even closer. In addition, this knowledge can be utilised to optimise the culture environment according to the cellular need and subsequently prolong the life span and functionality of both the iPSC-HLCs and the PHHs in culture.

The major aims of this thesis were to first study the alterations in the lipid and FA profile of the cells during the hepatic differentiation in order to identify the lipid species that may play important roles in the differentiation and maturation of hepatocytes.

The second aim was to comprehensively characterise the lipid and FA profile of HLCs against current standard hepatic cell models. The third aim focused on the mechanisms behind the hepatic de-differentiation by studying the alterations in the lipid profile of the PHHs during their prolonged two-dimensional (2D) culture. In addition, the results from lipidomics were complemented with miRNA analysis to further identify the differentially expressed miRNAs that may regulate changes in the lipid profile of PHHs during the process of de-differentiation.

Mostafa Kiamehr comes from Iran. He earned a BSc. in Medical Laboratory Technology at Tehran University of Medical Sciences and an MSc. in Biotechnology at the University of Leeds, UK. He currently works as Doctoral Researcher at the Faculty of Medicine and Health Technology at Tampere University.

The doctoral dissertation of MSc. Mostafa Kiamehr in the field of Stem Cell and Tissue Engineering titled Induced Pluripotent Stem Cell-Derived Hepatocyte-Like Cells; The lipid status in differentiation, functionality, and de-differentiation of hepatic cells will be publicly examined at the Faculty of Medicine and Health Technology at Tampere University on 8 February 2019 at 12 o'clock.
The Opponent is Professor Edward A. Fisher from New York University (NYU). The Custos is Professor Katriina Aalto-Setälä from the Faculty of Medicine and Health Technology at Tampere University.

The dissertation is available online at http://urn.fi/URN:ISBN:978-952-03-0989-3