(650e) Mathematical Modeling of Human Embryonic Stem Cell Differentiation During Endoderm Induction

Embryonic stem cells (ESC) have the potential to be used in many therapeutic applications due to their ability to differentiate into cells of any of the three primary germ layers (ectoderm, endoderm, and mesoderm) while maintaining the ability to proliferate and remain in an undifferentiated state if certain conditions are met. Whether or not these future medical applications are successful partly depends on the purity level of the germ cells and if a particular germ cell can be preferentially cultured with a low yield of the other germ layer cells.

While there have been several successful attempts in differentiating human embryonic stem cells (hESC) to endodermal germ layer, an understanding of the population dynamics involved during such induction has not been thoroughly analyzed. While the literature of hESC differentiation shows several growth factor cocktails as being important in endodermal induction, a proper understanding of the process would require help of mathematical modeling.

In the present study we have developed an integrated experimental and computational approach to analyze the differentiating population of hESC induced towards endodermal lineage. Endoderm induction was performed by culturing the cells in activin alone, activin + BMP4, and activin + PI3KI. The cell population was analyzed for differentiation, proliferation and apoptosis in these environments primarily by flow cytometry, which enables collection of single cell level information. An in silico stochastic model was developed based on earlier reports by Glauche et al. (2007) to capture the population dynamics of the differentiating cell population. The model employs the probabilistic nature of a cell's propensity to proliferate, differentiate to a particular lineage and apoptose. The primary objective of this investigation was to evaluate the difference in population dynamics and lineage commitment achieved by different combinations of growth factors and inducers. The primary assumption in the developed model is that the same phenomena are driving the process in all three cases investigated, the difference being in the model parameters. A detailed sensitivity analysis was performed on the model parameters to determine the most sensitive parameters, accurate estimation of which was performed in the subsequent step. Comparison of the model parameters for different combinations of growth factors allows a detailed evaluation of the differentiation dynamics predominant in the heterogeneous population of human embryonic stem cells.

Reference

Glauche, I., Cross, M., Loeffler, M., and Roeder, I. ?Lineage Specification of Hematopoietic Stem Cells: Mathematical Modeling and Biological Implications.? Stem Cells Vol. 25. pp. 1791-1799, 2007.