BMC Seminar Thursday 31st of January at 12:00 in room 343 Læknagarður

Speaker: Þóra Björg  Sigmarsdóttir ^1, Sarah McGarrity ^1,2, Óttar Rolfsson ^2,3, Ólafur Eysteinn Sigurjónsson ^1,4

1. School of Science and Engineering, University of Reykjavík, Reykjavík, Iceland
2. Center For Systems Biology, University of Iceland, Reykjavík, Iceland
3. Biomedical Center, University of Iceland, Reykjavík, Iceland
4. Blood bank, Landspitali University Hosptial of Iceland, Reykjavík, Iceland

Title: Proliferation & Osteogenic differentiation of human Mesenchymal Stem Cells: Metabolic model building

Abstract: Constraint based modelling (CBM) is a formaliswidely used to study cellular metabolism and the various metabolic pathways. It is a computational framework used to analyse various types of high throughput (HT) data in order to describe and predict metabolic phenotypes in any type of a micro-organism and make the relation between genotype and phenotype more clear. This kind of metabolic reconstruction involves the application of series of constraints involving stoichiometric, thermodynamic and enzymatic capacities constraints with the addition of regulatory and kinematic constraints when available and appropriate. A model subtype that can be made using the CBM formalism is a Genome-Scale Model (GEMs). This subtype applies the methods of CBM on the gene level instead of the reaction level and so takes into account the complex gene-protein reaction associations that exists. GEMs also offer a way of combining multiple types of -omics data in order to better understand and manipulate the features of a biological system.

Transplant of cells derived from human mesenchymal stem cells (hMSCs) to treat diseases such as osteoporosis is getting closer to being a reality. The production of cells for transplant requires further study and currently there is lack of knowledge on metabolomic changes that occur during proliferation and osteogenic differentiation (OD) of hMSCs. It has been shown that MSCs osteogenic differentiation is accompanied by metabolic shifts, especially in utilisation of glucose. In order to better understand this process and expand the knowledge of other metabolic pathways that interact with stem cell fate this project is building genome-scale metabolic models using the CBM formalism to integrate transcriptomic and metabolomics data.

Publically available transcriptomic data and new glucose and lactate measurements were combined in the CobraToolbox v3.0. This created initial models of the first stages of proliferation and osteogenic differentiation. Functional assays confirmed the process of osteogenesis in vitro.

Change point analysis performed on five metabolite measurements (glucose, lactate, glutamine, glutamate and ammonia) collected from five donors during osteogenic differentiation indicate multiple stages to the process. In total four change points were found over the 28 day period of osteogenic differentiation, indicating the possibilities of five metabolic stages and accompanying phenotypes.

The preliminary models created were able to recreate known metabolic features of mesenchymal stem cells during the first seven days during proliferation and osteogenesis. These include relative levels of oxidative phosphorylation to glycolysis and production of kynurenine from tryptophan. These models also suggest glycan production as well as more central metabolism as areas key to the shift from proliferation to osteogenic differentiation though further curation and work on the models is needed in order to have a better functioning comparable model pair.