A Global Sensitivity Approach for the Analysis of Intracellular PI3K/AKT Signaling Pathway during Definitive Endoderm Induction of Human Embryonic Stem Cells

Introduction: Differentiation of human embryonic stem cells (hESCs) to the definitive endoderm lineage is an important step towards important functional cell types of the pancreas and liver. In vitro differentiation efforts are directed towards the activation of cellular signaling pathways which are active during embryonic development in vertebrates. As an important step in the chemical induction of definitive endoderm, modulation of the growth factor mediated PI3K/AKT pathway has been implicated in the control of the outcome of other pathways by making early fate decisions between the maintenance of pluripotency and initiation of differentiation [1]. Specifically, PI3K/AKT pathway suppresses the differentiation signals and sustains the undifferentiated state, while inhibition of the pathway results in upregulation of Smad and Wnt signaling pathways [2]. Mathematical models can help in the formulation of informative experiments to identify the precise role of these interactions and the conditions under which the cell commits to a particular fate. However, by nature, stem cell systems exhibit intricate signaling pathways; and with the added uncertainty in physical parameters, mechanistic models are either incomplete or difficult to build. One possible solution to construct predictable models is to perform sensitivity analysis on models validated in other cellular contexts and identify regions of interest relating to an experimentally observed output. Given the multivariate nature of the problem, such a sensitivity analysis has to be global in approach to capture the nonlinear interactions between the system parameters. The goal of our study was the use of global sensitivity analysis to design experiments to analyze the role of PI3K/AKT pathway following the induction of hESCs towards definitive endoderm.